WO2000006947A1 - Air inlets for gas water heaters - Google Patents
Air inlets for gas water heaters Download PDFInfo
- Publication number
- WO2000006947A1 WO2000006947A1 PCT/AU1998/000585 AU9800585W WO0006947A1 WO 2000006947 A1 WO2000006947 A1 WO 2000006947A1 AU 9800585 W AU9800585 W AU 9800585W WO 0006947 A1 WO0006947 A1 WO 0006947A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- water heater
- ports
- combustion chamber
- flame
- inlet
- Prior art date
Links
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23D—BURNERS
- F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
- F23D14/46—Details, e.g. noise reduction means
- F23D14/72—Safety devices, e.g. operative in case of failure of gas supply
- F23D14/82—Preventing flashback or blowback
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/18—Water-storage heaters
- F24H1/20—Water-storage heaters with immersed heating elements, e.g. electric elements or furnace tubes
- F24H1/205—Water-storage heaters with immersed heating elements, e.g. electric elements or furnace tubes with furnace tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N2231/00—Fail safe
- F23N2231/16—Fail safe using melting materials or shape memory alloys
Definitions
- the present invention relates to air inlets gas fired water heaters, particularly to improvements to gas fired water heaters adapted to render them safer for use
- the present invention also relates to ignition inhibiting water heaters Background of the invention
- the most commonly used gas-fired water heater is the storage type, generally including an assembly of a water tank, a gas burner to provide heat to the tank, a pilot burner to initiate the main burner on demand, an air inlet adjacent the burner near the base of the jacket, an exhaust flue and a jacket to cover these components
- Another type of gas-fired water heater is the instantaneous type which has a water flow path through a heat exchanger heated, again, by a main burner initiated from a pilot burner flame
- water container water containment and flow means
- water flow paths such as pipes, tubes, conduits, heat exchangers and the like in gas-fired water heaters of the instantaneous type
- locations for water heaters are also used for storage of other equipment such as lawn mowers, trimmers, snow blowers and the like It is common for such machinery to be refuelled in such locations
- Vapours from spilled or escaping flammable liquid or gaseous substances in a space in which an ignition source is present provides for ignition potential
- the expression "fumes,” “extraneous gases” or “extraneous fumes” is sometimes hereinafter used to encompass gases, vapours or fumes generated by a wide variety of liquid volatile or semi-volatile substances such as gasoline, kerosene, turpentine, alcohol, insect repellent, weed killer, solvents and the like as well as non-liquid substances such as propane, methane, butane and the like
- Many inter-related factors influence whether a particular fuel spillage leads to ignition These factors include, among other things, the quantity, nature and physical properties of the particular type of spilled liquid fuel Also influential is whether air currents in the room, either natural or artificially created, are sufficient to accelerate the spread of fumes, both laterally and in height, from the spillage point to an ignition point yet not so strong as to ventilate such fumes harmlessly, that is, such that air
- One surrounding circumstance is the relative density of the fumes
- a spilled liquid fuel spreads on a floor normal evaporation occurs and fumes from the liquid form a mixture with the surrounding air that may, at some time and at some locations, be within the range that will ignite
- the range for common gasoline vapour is between about 3% and 8% gasoline with air, for butane between about 1 % and 10%
- Such mixtures form and spread by a combination of processes including natural diffusion, forced convection due to air current drafts and by gravitationally affected upward displacement ot molecules of one less dense gas or vapour by those ot another more dense
- Most common fuels stored in households are, as used either gases with densities relatively close to that of air (e g . propane and butane) or liquids which torm fumes having a density close to that of air, (e g gasoline which may contain butane and pentane among other components is very typical ot such a liquid fuel)
- the present invention provides a water heater including a water container, a combustion chamber located adjacent said container, a burner located inside said combustion chamber, at least one inlet positioned at an opening said combustion chamber, said inlet permitting ingress of admit air and extraneous fume species into said combustion chamber and prevent egress of flames from said water heater
- the air inlet is or includes a flame arrestor positioned at said opening in said combustion chamber to block ingress of admit air and extraneous fume species when the temperature in said combustion chamber adjacent said flame trap exceeds a predetermined temperature
- a blocking plate can be positioned within said combustion chamber and spaced above said opening
- the water heater can further include a heat sensor positioned within said combustion chamber and adjacent said flame trap and capable of shutting off fuel to said burner when said the temperature in said combustion chamber adjacent said flame trap exceeds said predetermined temperature
- the flame arrestor can also include a blocking plate supported by at least one leg formed from a temperature sensitive fusible mate ⁇ al adapted to melt when said predetermined temperature is exceeded, thereby permitting said blocking plate to move toward and over said opening
- the temperature sensitive fusible mate ⁇ al is a thermoplastic, and more specifically low density polyethylene having a melting temperature of about 100 °C to 200 °C
- the air inlet can be formed from a ceramic mate ⁇ al having a thickness of about 12 mm or more and having openings of about 36 5 to 73 openings per square centimetre and wherein said openings include about 64% to 80% of the surfaces of said air inlet
- the openings are square and the ceramic matenal is extruded
- the air inlet can alternatively be formed from two layers of woven metal mesh arranged to be in contact with each other over substantially all of their respective contacting surfaces and being formed in a non-planar o ⁇ entation to facilitate substantially even layer contact du ⁇ ng expansion and contraction
- the layers of woven metal mesh can be dome-shaped if desired
- the water heater can include a flame arrestor positioned at said opening and adapted to direct a flame extinguishing substance toward a surface of said flame trap in said combustion chamber
- the flame arrestor can include a container having at least one nozzle and contains said flame extinguishing substance
- the at least one nozzle can contains a plug made from a fusible mate ⁇ al. having mate ⁇ al has a melting temperature of about 150 °C to 300°C, that maintains said flame extinguishing substance inside said container unless the temperature in said combustion chamber adjacent said flame trap exceeds a predetermined temperature
- the flame extinguishing substance is selected from the group consisting of sodium bicarbonate and fire blanketing foams mixed with a propellant
- fire blanketing foams are mixed with a propellant are activated when the temperature adjacent said flame trap is 300 °C -500°C
- the container preferably has two nozzles extending from opposite end portions thereof, each nozzle being directed to opposing edge portions of said at least one inlet
- the at least one inlet can have a plurality of ports, each port having a limiting dimension less than a minimum quenching distance applicable to said extraneous fume species, thereby confining ignition and combustion of said extraneous fume species within said combustion chamber
- said at least one inlet is constructed such that peak natural frequencies of vibration of said at least one inlet, in combination with said combustion chamber structure, are different from peak frequencies generated by an extraneous fume combustion process on the inlet within the combustion chamber
- a surface of said at least one inlet located outside of said combustion chamber remains sufficiently cool so as to prevent heating the extraneous fume species and air with it before it passes through said at least one inlet to a temperature above an ignition temperature of said extraneous fumes species and air
- the ports of said at least one inlet can be spaced apart on said at least one inlet by a distance which enables the temperature of mixtures of extraneous fume species with air adjacent to the surface of the walls of said ports to remain below the ignition temperature of said mixtures
- the ports of said at lest one inlet can be spaced apart from each other so that a closest point between bounda ⁇ es of adjacent ports is a distance of no less than about 1 1 mm
- the shortest distance between adjacent ports can be substantially the same
- At least one of said ports of said at least one inlet is adjacent a pilot burner associated with said combustion chamber to ignite said extraneous fume species as the fume species passes into said combustion chamber and before there is a potentially explosive accumulation of fumes in said combustion chamber
- the ports of said at least one inlet include slots and wherein said limiting dimension is the width of said slots
- said ports include slots which have an L/W ratio of between about 2 to about 15, wherein L is the length of said slots and W is the width of said slots
- ports of said at least one inlet are arranged in rows It is preferable that a first port in every alternate row has its location offset with respect to a port of an adjacent row Alternatively the ports of said at least one inlet are slots arranged in rows, with at least one peripheral row of said at least one inlet including slots arranged parallel to each other and which have their longitudinal axes at an angle of about 90" the o ⁇ entation of each of the longitudinal axes of slots in other rows
- At least one of said rows of ports of said at least one mlet is a pe ⁇ pheral row having a larger mterport spacing than others of said rows
- the at least one inlet is constructed from a sheet mate ⁇ al with ports that are elongated and spaced apart said ports being arranged so that there are at least two regions of ports, an inner region which is included ot a group of said ports, and an outer region which is comp ⁇ sed of the remainder of said ports, said outer region having an mterport spacing between adjacent ports which is greater than the lnterpo ⁇ spacing of said ports in said inner region
- ports include slots about 0 5 mm in width and if said ports include circular holes, the circular holes are 0 5 mm in diameter
- the water heater can emit an audible signal when said extraneous fumes pass through said at least one inlet and are burning inside said combustion chamber
- the audible signal can be produced by the action of the burning of said extraneous fumes near to said at least one inlet, inside of said combustion chamber
- the ports of said alt least one inlet can be formed in a metal plate by photochemical machining
- the water heater combustion chamber can be formed with a surrounding skirt having an end cap joined at one end thereof, with another end of said surrounding skirt being a surface of said combustion chamber
- An enclosure can be provided which encloses said container and which also forms both of said surrounding skirt and said end cap
- said surrounding start and said end cap are formed separate from the enclosure which encloses said container and said combustion chamber
- the water heater will include an outlet spaced apart from said at least one inlet allowing products of combustion to exit said combustion chamber
- Thew at least one inlet preferably includes a plate having a plurality of ports
- the plate is preferably made of metal
- the at least one inlet can have a heat dissipation region at its pe ⁇ phery
- the heat dissipation region can include a metal to metal overlap portion between a pe ⁇ pheral edge of a plate forming said at least one inlet and a pe ⁇ pheral edge of an opening in the combustion chamber
- the plate can include a skirt, while said combustion chamber has an opening which seahngly receives said plate said opening having a surrounding skirt, and said skirts are sized so that inwardly facing surfaces of said skirt ot said plate engage outwardly facing surfaces of said surrounding skirt
- the plate can alternatively include a skirt, while said combustion chamber has an opening which seahngly receives said plate, said opening having a surrounding skirt, and said skirts are sized so that outwardly facing surfaces of said skirt of said plate engage inwardly facing surfaces of said surrounding start
- the heat dissipation region can include an additional surface area in the form of at least one fin extending from the inlet
- the heat dissipation region can include an increased interport spacing ad j acent its pe ⁇ phery
- the plate is a ferrous based mate ⁇ al about 0 5 mm thick
- the interport spacing of the ports of said at least one inlet adjacent a pe ⁇ pheral portion of the ports in said plate is in the range of about 2 mm to 4 mm and the interport spacing of remaining ports is in the range of about 1 mm to 1 5 mm
- the plate can be a ceramic plate having a thickness in the range about 9 mm to 12 mm and ports in the range of about 1 1 mm to 1 3 mm diameter
- Flame lift promoters can be provided at edge portions of the ports
- the flame lift promoters can be sharp edges at upstream extremities of the ports
- the flame lift promoters can be undercut cross-sectional profiles wherein the intersection ot the ports with at least an inside surface of the plate is an angle of less than 90'
- the flame lift promoters are interport spacmgs of at least about 3 mm
- the ports of said at least one inlet can be constructed so that in cross-section, said ports have substantially parallel sides
- the ports can be constructed so that in cross-section said ports have sides which converge
- the ports can converge in an upstream direction, and may terminate with substantially parallel sides
- the ports are slot shaped and not more than about 0 6 mm wide and spaced apart from each other at least about 1 1 mm
- the ports can include pe ⁇ pheral extrusions extending inwardly into the combustion chamber to act as flame lift promoters
- the ports can be formed in a plate in a pattern, said pattern acting as a flame lift promoter
- the ports can be arranged in a pattern comp ⁇ sing solely apertures in the form of an aligned and spaced array of slots
- a first pattern of slots can be located in a centre portion of said inlet and a second pattern of slots at a pe ⁇ pheral portion, with said second pattern comp ⁇ sing a larger interport distance than said first pattern
- the ports can be arranged in a radial pattern or alternatively in a circumferential pattern
- the water heater can include a cooling mechanism in cooperating with said at least one inlet
- the cooling mechanism can include a water applicator for said inlet
- Preferably the water applicator directs water to a face of the inlet external to the combustion chamber
- the at least one inlet is preferably constructed such that the peak resonant frequencies of said inlet are different from peak resonant frequencies of a combination of said combustion chamber and an exhaust gas flow path when extraneous fumes are being combusted at the inlet
- the heat dissipation region includes an additional surface area in the form of at least one fin extending from the combustion chamber
- the ports can be formed with cross-sections which, within a single port, both converge and diverge
- the said at least one inlet can be formed from a metal plate which is deformed from a flat form to include stiffening members extending across at least a portion containing said plurality of ports Preferably said stiffening members intersect with ports Alternatively stiffening members are provided extending across unported portions which subdivide said plurality of ports into an integral number of sub-portions
- the invention also provides a control valve for supplying fuel to a water heater containing a ma burner and a pilot burner including a fuel inlet adapted to connect to a supply of fuel, at least one fuel outlet adapted to connect to the main burner, a conduit for fuel flow between the inlet and outlet, a closure associated with the conduit to control flow of fuel from the inlet to the outlet, a circuit associated with the valve and including a thermally actuated device associated with the closure said device, when heated by the pilot burner providing a signal to the closure to open or close the closure, and a combustion sensitive fuse connected to the circuit and positioned to be exposed to extraneous sources of flame and/or heat
- the control valve can further include an externally accessible socket in the circuit into which the fuse is removably insertable Alternatively the socket is adapted to receive the fuse independently separate from the thermallv actuated device Preferably the socket is accessible from an underside of the valve while the fuse is positioned at an underside of the valve
- the closure of the control valve includes a member located in a portion of the conduit and is normally resihently biased in a closed position
- the circuit further includes a solenoid associated with the closure, the solenoid being capable of receiving an elect ⁇ cal signal from the thermally actuated device and opening said closure in response
- the fuse is temperature sensitive and the circuit further includes an over temperature energy cut out switch associated with a temperature sensitive thermostat probe, said energy cut out switch being capable of interrupting gas flow through said control valve to the main burner and the pilot burner
- the thermally actuated device is a thermocouple
- the circuit can further include a manual switch connected to the thermally actuated device and having on, off and pilot positions, said pilot position causing the closure to open until such time as the thermally actuated device is capable of providing a signal to open the closure
- the closure can include a member located in a portion of the conduit and which is normally resihently biased in a closed position
- said circuit associated with the valve includes a solenoid associated with the closure, the solenoid being capable of receiving output from the thermocouple and maintaining open said closure m response to output indicative of a flame at said pilot burner
- the control valve can include an energy cut out switch associated with a temperature sensitive thermostat, the energy cut out switch being associated with a temperature sensitive thermostat probe, said energy cut out switch being capable of interrupting gas flow through said control valve to the mam burner and the pilot burner
- control valve includes a combustion sensitive fuse connected to the control valve circuit and positioned to be exposed to extraneous sources of flame and/or heat external to and ad j acent the control valve
- the invention further provides a water heater as desc ⁇ bed above having a control valve as also described above
- Said at least one inlet can be positioned below and adjacent said pilot burner and with said water heater further including a ventu ⁇ extending into said combustion chamber to supply combustion air to said main burner
- the water heater further includes a lint trap positioned exte ⁇ orly of said at least one inlet and across said opening
- the invention provides a gas water heater including a water container adapted to be heated by a gas burner An enclosure surrounds the burner and the water container The water heater has at least one opening adapted to allow air for combustion or extraneous fumes to enter the enclosure without igniting flammable extraneous fumes outside of the enclosure
- the invention encompasses a water heater including a water container and a combustion chamber located adjacent the container
- the combustion chamber has a floor portion with an opening
- An upwardly extending conduit is substantially air tightly sealed to the edge of the opening
- a burner is located inside the combustion chamber and a flame trap is positioned across the conduit, the flame trap permitting ingress of air and extraneous gases, if present into the combustion chamber and prevent egress of flames from the structure
- a flame arrestor is positioned at the opening and is actuated when the temperature in the combustion chamber ad j acent the flame trap exceeds a predetermined temperature
- the water heater includes specially constructed flame traps
- One is a ceramic material having a thickness of about 12 mm or more and having openings of about 36 6 to 73 openings per square centimetre (opemngs/cm 2) and wherein the openings are about 64% to 80% of the surface of the flame trap
- Another has two layers of woven mesh arranged to be in contact with each other over substantially all of their respective contacting surfaces and in formed in a non-planar o ⁇ entation to facilitate substantially even layer contact du ⁇ ng expansion and contraction
- the invention also provides a water heater including a water container, adjacent which is, a combustion chamber having one or more inlets to admit air and any extraneous flammable fume species which may have escaped in the vicinity of the water heater into its combustion chamber
- a water container adjacent which is, a combustion chamber having one or more inlets to admit air and any extraneous flammable fume species which may have escaped in the vicinity of the water heater into its combustion chamber
- an inlet comp ⁇ ses a metal plate of thickness about 0 4 to 0 6 millimetres and through which pass many ports, each of which has a quenching distance as will be defined within 10% of the thickness of the plate Because of choice of the quenching distance approp ⁇ ate to several types of inlet plate the water heater is able to confine ignition and combustion of extraneous fume species within the combustion chamber, despite the presence of a burner(s) in the combustion chamber to combust fuel to heat the water in container
- the inlet can take the form of a ceramic plate having a thickness in the range about 9 mm to 12 mm through which passes many ports each having a quenching distance of 1 1 to 1 3mm which can likewise confine ignition and combustion of extraneous fumes to the combustion chamber
- Figure 1 is a schematic partial cross-sectional view of a gas water heater embodying aspects of the invention
- Figure 2 is a schematic partial cross-sectional view of a gas water heater similar to Figure 1 , with additional safety features
- Figure 3 is a cross-sectional view of the water heater of Figure 2 taken through the line III-III
- Figure 3A is a cross-sectional view of the base region of the water heater of Figure 1
- Figure 4 is a schematic partial cross-sectional view of a gas water heater similar to that of Figure 2
- FIG. 5 is a cross-sectional view of the water heater of Figure 4 taken through line V-V
- Figure 6 is a schematic partial cross-sectional view of a gas water heater with a safety feature in accordance with aspects of the invention
- Figure 7 is a schematic partial cross-sectional view of a gas water heater of another embodiment of the invention
- Figure 8 is a schematic partial cross-sectional view of a gas water heater of yet another embodiment of the invention
- Figure 9 is a schematic partial cross-sectional view of still another embodiment of the invention.
- Figure 10 is a cross-sectional view of the water heater of Figure 9 taken through the line X-X
- Figure 1 1 is an up ⁇ ght elevational view taken from the rear of a gas valve according to the aspects of invention
- Figure 12 is an up ⁇ ght elevational showing the left side of the gas valve shown in Figure 1 1
- Figure 13 is an up ⁇ ght perspective view of the valve of Figure 1 1 and Figure 12
- Figure 14 is a schematic partial cross-sectional view of a water heater with the gas valve as shown in Figure 1 1 to Figure 13
- Figure 15 is an elect ⁇ cal circuit embodied m the gas valve shown in Figure 1 1 to Figure 13
- Figure 16 is a cross-sectional view of the gas valve shown in Figure 1 1 to Figure 13
- Figure 17 is a schematic elevation, taken partly in section, of a portion of the bottom end of a water heater of the type shown in Figure 14 including further means for dampening combustion
- Figure 18 show the first extinguishing means of Figure 17 following actuation in the event of combustion on the flame trap illustrated
- Figure 19 is a further embodiment of a means for extinguishing fire similar to that shown in Figure 17
- Figure 20 shows the first extinguishing means of Figure 19 following actuation in the event of combustion on the flame trap
- Figure 21 is a detailed schematic elevation, taken partly in section, of a bottom end portion of a water heater of the type shown in Figure 14 substituting a different type of flame trap
- Figure 22 is a detailed schematic elevation, taken partly in section, including a heat actuated chemical fire extinguishing means operative with the flame trap
- Figure 23 is a detailed schematic elevation, taken in section and similar to Figure 22, including an embodiment of flame trap mate ⁇ al arranged in two contacting layers
- Figure 24 is a schematic partial cross-sectional view of a gas-fuelled water heater having a single large air inlet according to the invention
- Figure 25 is a cross-sectional view of a water heater of Figure 24 taken through the line II-II in Figure 24
- Figure 26 is a schematic plan view depicting a portion of the base of a combustion chamber of a water heater including an air inlet
- Figure 27 is a schematic plan view of an air inlet according to the invention of a type which could be included in the Figure 26 arrangement
- Figure 28 is a schematic plan view depicting a portion of the base of a combustion chamber of a water heater substituting an air inlet of different shape and hole pattern
- Figure 29 is a schematic plan view of an air inlet according to the invention of a type which could be included in the Figure 28 arrangement
- Figure 30 is a plan view of an inlet plate showing a hole pattern applicable to an air inlet of the type shown in Figure 29
- Figure 31 is a plan view of an inlet plate showing a further hole pattern applicable to an air inlet of the type shown in Figure 29
- Figure 32 is a plan view of ports on an inlet plate according to the invention of the embodiment shown in Figure 26
- Figure 33 to Figure 41 are each a further plan view of additional alternative patterns of ports on an inlet plate according to the invention of the embodiment shown m Figure 26
- Figure 42 illustrates a plan view of a single port as shown in Figure 33 to Figure 41
- Figure 43 and Figure 44 are each a detail view of the spacing of part of the arrangement of ports on the inlet plate of Figure 33 and Figure 34 respectively
- Figure 45 is a cross-section of an embodiment of a port in an air inlet according to the invention.
- Figure 46 is a schematic cross-section of a water heater having a ported inlet connected to a remotely positioned clean-in-place lint filter, according to the invention
- Figure 47 and Figure 48 illustrate alternative forms of attachments according to the invention of two shapes of inlet to a wall of a combustion chamber of a water heater
- Figure 49 a plan view of one version of an air inlet plate and its attachment to a combustion chamber
- Figure 50 is a side view of the air inlet plate of Figure 49
- Figure 51 is a partial cross of the air inlet plate of Figure 49 at the lines LI-LI
- Figure 52 is an attachment detail cross section of the air inlet plate of Figure 49 and its attachment to a combustion chamber
- Figure 53 is a perspective view of a version of an embodiment of an air inlet plate
- Figure 54 is a perspective view of a version of another embodiment of an air inlet plate
- Figure 55 is a cross-sectional view of the version of air inlet plate shown in Figure 54
- Figure 33 to Figure 35 are schematic cross-section views of three embodiments of water heaters showing relative positions of air inlet plates to other components including the combustion chamber walls
- Figure 59 is a detail of an inlet in cross section
- Figure 60 is a perspective view of one port in the inlet as shown in Fig 36
- Figure 61 is a perspective view of one port of an inlet with an adjacent bead of solder
- Figure 62 is a cross section of an air inlet plate coated with an intumescent coating
- Figure 63 is a cross section identical with Figure 62 with the addition of combustion of extraneous fumes on one surface
- Figure 64 is a cross section showing the aftermath of the combustion shown in Figure 63
- Figure 65 is a perspective schematic view of an inlet plate with a sliding mechanism to occlude ports in an inlet plate
- Figure 66 is a cross section along the line A-A through the arrangement of Figure 65 with ports aligned
- Figure 67 is the same cross section of Figure 65 when the ports are occluded
- Figure 68 is a perspective schematic view of an inlet plate with a rotary mechanism to occlude ports in an inlet plate
- Figure 69 is a cross section along the line B-B through the arrangement of Figure 68 with ports aligned
- Figure 70 is the same cross section of Figure 68 when the ports are occluded
- Figure 71 is a partial cross section of the lower portion of a water heater with a spray nozzle at an air inlet according to the invention and including an audible alarm
- Figure 72 to Figure 75 are partial cross-sections of ports in inlet plates
- Figure 76 is a plan view of an air mlet plate stiffened by cross broken diagonal folds
- Figure 77 is front elevation of the air inlet plate of Figure 76
- Figure 78 is a side elevation of the air inlet plate of Figure 76
- Figure 79 is a plan view of an air inlet plate stiffened and divided into separate perforated portions with stiffening formations between those separate portions
- Figure 80 is a front elevation of the air inlet plate of Figure 79
- Figure 81 is a side elevation of the air mlet plate of Figure 79
- Figure 82 is a schematic elevation of a bottom half of a water heater with an inlet plate mounted in the base of the combustion chamber, the base being dampened by contact with resilient damping mate ⁇ als sandwiched between the external surface of the combustion chamber and a pan forming the base of the water heater s protective jacket
- Figure 83 is a plan view of an air inlet in the base of a water heater enclosure
- Figure 84 is a side view of the base of Figure 83
- Figure 85 is a detail cross sectional view of a portion of Figure 84
- FIG. 1 illustrates a storage type gas water heater 2 including jacket 4 which surrounds a water tank 6, a main burner 14 m a combustion chamber 15
- Water tank 6 is preferably of mains pressure capability and capable of holding heated water
- Water tank 6 is preferably insulated by foam insulation 8
- Alternative insulation may include fibreglass or other types of fibrous insulation and the like
- main burner 14 which preferably uses natural gas or other gases such as LPG, for example Mam burner 14 combusts a gas and air mixture and the hot products of combustion resulting ⁇ se up through flue 10 Flue 10, in this instance, contains a se ⁇ es of baffles 12 to better transfer heat generated by main burner 14
- Near pilot burner 49 is a sheath 52, preferably made of copper, containing wires from a flame detecting thermocouple 51 which is a known safety measure to ensure that in the absence of a flame at pilot burner 49 the gas control valve 48 shuts off the gas supply
- Duct 22 is preferably constructed from sheet metal 20 In a non-illustrated alternative construction, a part or all of duct 22 may be inside the external cyhnd ⁇ cal envelope of j acket 4
- Water heater 2 is preferably mounted on legs 24 to raise the base 26 off the floor
- a flame trap device 30 which operates on a flame quenching p ⁇ nciple Flame trap 30 is preferably made from two substantially parallel sheets of mesh each about 0 010 inch diameter metal wire strands woven into mesh having about 30 to 40 strands per inch
- mlet could be a woven metal mesh having transverse wires of thickness about 0 2 to 0 5 millimetres defining a plurality of ports, so that each port has a quenching distance equal to the greater of the side lengths of four-sided open areas between the woven wires and in a range of about 03 to 05 mm, being thereby able to confine ignition and combustion of said extraneous fume species within said combustion chamber
- Mild steel or stainless steel wire are suitable
- a ported ceramic tile of the SCHWANK ® type can be utilised although the recognised flame quenching ability of metallic woven or knitted mesh together with its robustness and ease of forming generally commends its use
- a ported ceramic tile functions as a flame quenching trap as long as the porosity is suitable
- a ported ceramic tile is used, preferably it has a thickness in the range about 9 mm to 12 mm and having openings of about 36 5 to 73 openings per square centimetre
- the openings include about 64% to 80% of the surfaces of the tile or aperture which the tile will cover
- the tile is made of extruded ceramic mate ⁇ al and can have openings which are square, or alternatively the openings can be slots having an length to width ratio (L/W) of between about 3 to about 20 Circular holes could also be used but preferably these will have a quenching distance which is a diameter of about 1 1 mm to 1 3mm
- a single layer of mesh or a porous ceramic tile may be susceptible to clogging by lint or other 'blocking' mate ⁇ als such as dust or the like Lint caught in the openings of a single mesh or a tile might act as a wick which may allow flame, which would not otherwise pass through the flame trap, to do so In this situation the flame trap device would tend not to function as efficiently
- the flame trap is preferably constructed with either two layers of mesh or a layer of mesh and a tile The mesh layers are most preferably in contact with one another In this way the layer of mesh further from the source of fumes acts as a flame trap and the layer closer to the source of fumes acts as a lint trap
- mating surfaces 32 can be sealed thoroughly to prevent ingress of air or flammable gas or vapour
- mating surfaces 32 extend upwardly from base 26 around jacket 4
- the cyhnd ⁇ cal wall of jacket 4 (the majo ⁇ ty of gas water heaters are cyhnd ⁇ cal, however, a cubic or other shaped jacket 4 may be utilised) can be sealed gas tightly so no openings or breaks remain upon assembly and installation
- gas, water, elect ⁇ cal, control or other connections, fittings or plumbing, wherever they pass through jacket 4 or base 26 to jacket 4 and all service ent ⁇ es or exits to jacket 4 or duct 22 need not be sealed airtight providing they are designed and constructed to have only minor surface to surface clearances or gaps, each of which is capable of acting as flame quenching traps
- the structure of such service ent ⁇ es or exits are known in the art and not desc ⁇ bed herein It is preferred, however, that the space around the burner be substantially air
- Pilot flame establishment can be achieved by a piezoelectric igniter
- a pilot flame observation window sealed to the jacket 4 can be provided Alternatively, if the pilot 49 is to be lit by removing or opening an access, safety interlocks (not illustrated) are included to ensure complete closure against unprotected fume access du ⁇ ng water heater operation
- water heater 2 operates in the same fashion as conventional water heaters except that most air for combustion enters at air inlet 18 and a small proportion through flame trap 30
- flame trap 30 allows the combustible gas or vapour and air to enter but prevents flame escaping jacket 4 or duct 22
- the spilled fuel is bumed within combustion chamber 15 and exhausted either through flue 10 via outlet 16 and duct 19 or through duct 22 and inlet 18 (which m this case will act as an outlet) Because flame is rest ⁇ cted from passing outwardly through flame trap 30 spilled fuel external to water heater 2 will not be ignited
- the embodiment of illustrated could, as in Figure 3A, include a flame sensitive switch 50A located near to the flame trap 30 so that it can detect the existence of flame on the flame trap 30 and subsequently close valve 48 to shut down the gas supply to the burner 14 and pilot 49
- the flame sensitive switch 50A may be substituted by a light detector or a heat detector, or a gas, fume or vapour detection switch, or an oxygen depletion sensor, so as to close off gas control valve 48 when either a flammable fume or a flame is detected
- FIG. 2 and Figure 3 show an embodiment similar to that of Figure 1 Like parts use the same reference numbers as those of Figure 1
- gas control valve 48 there is adjacent gas control valve 48, a flame sensitive switch 50 which may be inserted in the same circuit as pilot flame detecting thermocouple 51 and located close thereto
- duct 22 contains gas control valve 48 and flame trap 30 is shown forming a bottom end of the duct 22
- flame trap 30 can be arranged and installed spanning the bottom end of duct 22 and an adjacent portion of base 26
- An advantage from such a positioning of flame trap 30, including that shown in Figure 2 and Figure 3, by compa ⁇ son with the centre position of base 26 shown in Figure 1 is that it permits positioning of flame sensitive switch 50 (Figure 2) directly below gas control valve 48 which is also an ideal position to detect flame spillage from combustion chamber 15 which can occur if, for example, flue 16, or exhaust duct becomes blocked Similarly, it is ideally positioned to detect flame spillage such as would occur due to air starvation if inlet 18 were inadvertently blocked
- opening 28 and flame trap 30 are at the base of duct 22 below gas control valve 48 and flame detecting switch 51 (see Figure 2)
- gas control valve 48 actuates the gas control valve 48 to shut off the gas supply, thus removing it as a continuing source of ignition
- any vapours of spilled fuel continuing to enter through flame trap 30 may continue to burn because of the initial ignition and resulting suction of air (which may also be due to how water in tank 6) and may continue to burn until there is insufficient flammable vapour remaining to be drawn in from the vicinity of water heater 2
- the path for air entry to main burner 14 is provided by a combined air inlet and duct 54 fab ⁇ cated of metallic mesh 21
- This arrangement provides that combustion air passes through the air inlet which is constructed from a flame quenching surface 21 and the height of duct 54 need not be as high as jacket 4 nor need it necessa ⁇ ly extend upwardly
- it is preferably composed of separated layers 21a and 21b of metallic mesh
- This two layer construction avoids a layer of lint, deposited externally, providing a possible combustion path through the mesh, as previously explained Lint deposition in the openings of the mesh may be a cause of gradual blockage In due course such linting may cause starvation of combustion air Therefore, an extended surface area (along the full height of water heater 2 as depicted for instance) of the combined air inlet and air duct 54 may be of advantage for prolonging the time taken tor duct 54 to become occluded with lint and for providing an adequate path for free induction of
- gas valve 48 outside duct 54
- gas pipe and thermocouple sheath can enter water heater 2 via an opening in jacket 4, completely bypassing duct 54 This opening can then be sealed or if a gap is left, the gap is sized to act as a flame trap
- flame sensitive switch 50 or other sensor is located in relation to the position of flame trap 30 so that the relative positions co-operate in the event that a flame from spilled fuel forms on the flame trap
- FIG. 6 Illustrated in Figure 6 is another embodiment of the present invention, similar to that of Figure 1 , with like parts like numbered
- This embodiment includes an anchor 34 which anchors a nylon line 36 which is a heat sensitive frangible member
- the nylon line 36 passes close to the upper surface of flame trap 30 and around a lower pulley 38 then continues on to an upper pulley 40 around which it passes though 180 degrees, to make connection with a flap 42
- Flap 42 is connected by hinge 44 either to the inside of passage 22 or to a flange 46
- Flange 46 if it is utilised, can have a sealing medium (not illustrated) around it so that when flap 42 makes contact with it, an air tight seal or a flame trap is formed If flange 46 is not utilised, flap 42 can carry a seal so that, when released to move to a closed position, it will seal the inside of duct 22 to air tight quality, or, in the alternative to form a flame trap Flap 42 can be biased towards the closed position by a sp ⁇ ng, which is a preferred method, or alternatively the biasing can be by other means If desired, flap 42 can be constructed from mesh, as desc ⁇ bed above to act as a flame trap
- FIG. 7 and Figure 8 are illustrated a gas water heater 2 constructed similarly to that illustrated in Figure 1 , and illustrated with like parts being numbered
- Water heater 2 includes a base 26 and jacket 4 which are either completely sealed (not illustrated) to air tight and flammable gas or vapour tight quality or, alternatively, unsealed gas paths are fine (small) enough to act as flame traps
- the embodiments shown in Figure 7 and Figure 8 have no flame trap 30 or opening 28
- an appreciable time delay will occur before gases or vapours from spilled fuel ⁇ se to the elevated level of air inlet 18 Only once the gases or vapours from spilled fuel ⁇ se to the level of air mlet 18 could the gases or vapours be drawn down passage 22 to main burner 14
- base 26 and jacket 4 has small gaps or openings limited in their size to act as flame traps, then its operation will be similar to the embodiment of Figure 1
- the features of Figure 6 can be inco ⁇ orated also with the embodiments desc ⁇ bed in Figure 7 and Figure 8 when base 26 and jacket 4 are sealed
- the water heater now includes a heat sensitive frangible member 36 located in an air passage in the vicinity of the main burner 14, if gases or vapours ignite having flowed down the passage 22 (which would indicate that the volume of gases or fumes had ⁇ sen to the level of air entry of the air inlet 18), the resulting flame would melt a frangible member such as nylon line 36 in the vicinity of main burner 14
- Nylon line 36 can be connected in turn to a non-flammable and non-frangible section which in turn makes connection with a sp ⁇ ng biased flap similar to flap 42 capable of sealing passage 22
- the distance between nylon line 36 and flap 42 is sufficiently long to close passage 22 before a flame travelling back up passage 22 reaches flap 42 If flap 42
- thermocouple 51 is preferably located just inside of the flame trap 30 where ever it appears Flame sensitive switches may also be used in circuit with the thermocouple (e g , thermocouple 51 of Figure 1 ) provided for confirming the establishment and retention of a pilot flame by raising an elect ⁇ c current flow to a level capable of keeping open a gas supply to the pilot burner
- Flame sensitive switches may also be used to reduce fire hazards in circumstances where flame of the burner can "spill" through an air access opening adjacent the main and pilot burners
- the heat sensor is externally positioned and in some embodiments of the invention a flame sensitive switch is positioned above flame trap 30 to sense flame heat input resulting from spilled flammable vapour burning on the inside of flame trap 30 after having entered the combustion chamber through a possible entry path
- the preferred position of the flame sensitive switch 50A is immediately above the flame trap and it is preferred that a small heat shield (not shown) be placed above the flame sensitive switch to shield it from the normal radiant heat associated with the main burner 14
- the flame sensitive switch 50 is positioned a short way above flame trap 30
- pilot air duct has an air intake external to the remainder of the water heater assembly, preferably low to floor level where water heaters are generally installed, standing up ⁇ ght on a floor
- a flame quenching insert composed of one or more of a va ⁇ ety of high thermal capacity gas porous heat resistant mate ⁇ als such as desc ⁇ bed in relation to flame trap 30 Locating the flame quenching insert at or near the air intake end is advantageous to make it accessible for cleaning ot lint or dust that may accumulate in it
- An element sensitive to oxygen depletion is also located in the pilot air duct
- oxygen depletion sensor reduces the risk of ignition of flammable vapour in particular when pilot burner 49 is alight but main burner 14 is not, by sensing oxygen depletion in the incoming pilot air supply if a flammable component ignites in which case it would cause a gas control valve 48 of the type referred to in Figures 1 to Figure 7 to shut down gas flow to the pilot burner
- the shut down provides a time pe ⁇ od for flammable vapour to safely ventilate Resumption of normal operation of the water heater requires human intervention but, even if done lll-advisedly, in any event the oxygen depletion sensor would continue to deny pilot burner 49 of gas and the arrangement would behave safely even with extraneous flammable fumes remaining near water heater 2
- An oxygen depletion sensor can be used alternatively in place of or in conjunction with the previously desc ⁇ bed flame sensitive switch 50, and can be located similarly
- the invention thus far desc ⁇ bed can function at three levels of safety
- the first level is illustrated in relation to Figure 7 and Figure 8, wherein there is added height and distance so that fumes from spilled fuel must travel to reach main burner 14 or pilot burner 49
- the second level as illustrated in Figure 1 , Figure 2.
- Figure 3 and Figure 6 adds not only height and distance but also allows some, and advantageously all, the extraneous fumes to enter the base of water heater 2 and be consumed safely, conceivably until all residual ⁇ sk of fire and explosion is avoided by dissipation of the spillage
- the third level adds a further level of confidence by protecting all air entry with a flame arrestor, recognising that high levels of airborne lint or other dust may tend to block the air intake and starve the burner of air for combustion if the air entry were not pe ⁇ odically cleared of that lint or other dust
- the embodiment of Figure 4 and Figure 5 can be constructed to protect against ignition of flammable gases and vapours outside of the enclosure or jacket regardless of the density of those gases and vapours relative to air
- the water heater 2 contains at least some of the following features the opening includes an aperture which is covered by a flame trap, which prevents the burner from igniting extraneous fumes outside of the enclosure, and an air inlet through which air for combustion purposes is drawn, the opening is remote from the burner and includes a duct for passage of air to the burner, the opening and the aperture are collocated or are a single item, the at least one opening is covered by a flame trap, the aperture is in the enclosure, the aperture is positioned close to a lower end of the enclosure, the aperture is positioned in a lower end of the enclosure, the aperture is positioned below the burner, the aperture is positioned to allow air and fumes outside of the water heater to enter into an air passage leading to the burner, the aperture is positioned to allow air and fumes outside of the water heater to enter into an air passage leading to the burner, the aperture allows air and fumes to enter the lowest point of the air passage, one of or a combination of a light detection or sensitive device, a flame
- One advantage provided by the invention is the provision of a bar ⁇ er to unprotected entry, at the lower end of the jacket or enclosure, of flammable extraneous fumes
- it provides a protected entry means for such fumes near or at the base of the enclosure in which case these extraneous fumes are consumed in a controlled manner
- the protected entry is, in the most preferred form, an air inlet or a flame trap preventing ignition of the remaining fumes in the surrounding atmosphere or of any liquid remaining nearby
- An advantage of locating the air intake for combustion pu ⁇ oses above the midpoint of the gas water system is that it reduces the chance of extraneous fumes entenng the heater via the air intake because generally such flammables are heavier than air, which in the mam do not attain dangerous levels at the air intake level
- the use of air close-off means and gas shut-off means activated by a t ⁇ gger provides the advantage of suffocating any flame in the heater, or switching off the gas supply, or preventing uncontrolled or undirected ignition of gases or vapours from exiting the heater environment
- Figure 9 and Figure 10 show water heater 2 wherein aperture 28 having flame trap 30 across its mouth and positioned below pilot burner 49, pilot burner 49 being located adjacent one edge of main burner 14 Aperture 28 is positioned immediately underneath pilot burner 49, preferably the closer the better to assist m achieving smooth and or early ignition Aperture 28 is connected to the lower end of the enclosure by an upwardly extending tube 70, the upwardly extending portion of tube 70 being preferably impermeable to air, gas or fumes
- Tube 70 is preferably constructed of sheet metal, although other suitable mate ⁇ als may be substituted It is also possible that tube 70 as shown in Figure 9 can be made either partially or completely from flame trap mate ⁇ als, especially the upper portion
- Locating flame trap 30 above base 26 minimises the possibility of water condensate occluding the pores or openings in flame trap 30 or water splashing from, for example, hosing the floor near base 26 of water heater 2
- the length of tube 70 is not especially c ⁇ tical so long as it performs the function of preventing pore or port occlusion
- a ho ⁇ zontal blocking plate 74 is located above flame trap 28 to prevent water condensate or particulate matter such as steel scale flakes falling on the flame trap, thereby reducing the chance of occluding it
- FIG. 9 illustrates a lint filter 72 in addition to a double layer flame trap 30
- Filter 72 may be a different mate ⁇ al trom flame trap 30
- the potential for accumulation of lint over time has been a concern
- structure such as that shown in Figure 9 and Figure 10 is su ⁇ singly free of lint accumulation problems
- the ho ⁇ zontal and very close positioning of flame trap 30 to main burner 14 results in small pressure pulses associated with mam burner 14 igniting on each occasion Apparentlv, the pulses blow away anv lint from the face of flame trap 30 This appears to provide a repeating self-cleaning effect
- thermocouple and over- temperature fuse have been inconveniently located in an integrated structure sheathed in a copper capillary tube with significant thermal inertia If either the thermocouple or the temperature fuse require replacement then it is not immediately apparent which one has failed and, because both are replaced as an integrated unit, unnecessary cost is involved
- the thermal fuse is a relatively low cost item compared to the entire integrated structure and, therefore, it is advantageous to be able to test the circuit by merely removing the suspect fuse and replacing it This test does not involve removal of the thermocouple which requires awkward access into the water heater combustion chamber
- Inco ⁇ orated in valve 48 is an elect ⁇ cal circuit 128 such as shown in Figure 15 and 16, including thermocouple 51 connected to a solenoid 132
- Thermocouple 51 provides an elect ⁇ cal potential, sometimes hereinafter referred to as "signal ', when heated by a flame established at pilot burner 49, typically 12 to 15 mV, to solenoid 132 which is sufficient to maintain solenoid 132 open against the normally closing bias of a sp ⁇ ng 156 associated with closure 154
- the elect ⁇ cal potential is provided to solenoid 32, creating a magnetic force which, via an armature connected to closure 154, maintains closure 154 open
- the elect ⁇ cal potential is not sufficient to open closure 154 from its closed position except when valve passage 127 is first opened by manual switch 142 being manually position in the "pilot" or ' on ' positions and the potential is adequate to maintain closure 154 in its open position
- valve 48 When a flame is absent at pilot burner 49, valve 48 remains shut except du ⁇ ng a start up procedure
- the circuit has a manual switch 142 with three positions, “off, "pilot” and ' on' In the “pilot” position the switch may be depressed to hold open valve 48 while thermocouple 51 heats sufficiently to power circuit 128
- Manual switch 142 is depressed in the "pilot” and “on” positions to lift closure 154 off its seat against the closing bias force of sp ⁇ ng 156
- an elect ⁇ cal current passing through the coil of solenoid 158 generated by the thermocouple 51 when heated by the flame of the pilot burner 49 ( Figure 4) is adequate to maintain closure 154 in the open position du ⁇ ng normal use of water heater 2
- Normal use of water heater 2 involves pilot burner 49 being alight at all times
- An over-temperature energy cut out 144 is installed mside a temperature sensitive thermostat probe 146 (shown in Figure 12) which interrupts all gas flow through the valve in the event that an unsafe temperature develops inside the tank
- valve 48 has a fuse 134 connected in elect ⁇ cal circuit 128 and exposed at the bottom surface of valve 48 to be sensitive to extraneous sources ot flame and heat external to and in the region of the valve, particularly underneath it
- Valve 48 features an externally accessible socket 136 in elect ⁇ cal circuit 128 in which thermal fuse 134 is removably inserted Socket 136 is positioned to receive thermal fuse 134 independently and separate trom thermocouple 51
- Socket 136 and fuse 134 are accessible from the underside of valve 48 as shown in Figure 1 1 and Figure 14 wherein valve 48 is mounted on an external vertical wall of water heater 2
- valve 48 is mounted on an external vertical wall of water heater 2
- valve 48 is also vertically above access point 138 to mam burner 14 and pilot burner 49 such as for lighting, inspection and combustion air entry
- Extraneous flame and heat within water heater 2 may result from accidental combustion of a flammable substance near water heater 2, the flame being likely to establish itself firstly adjacent to access point 138
- fuse 134 Another advantage of mounting fuse 134 to be accessible at a downward facing surface of valve 48 is that fuse 134 would not be as noticeable upon a casual inspection of water heater 2 and valve 48 and, therefore, not so likely to invite removal by personnel unaware of its safety-motivated pu ⁇ ose Water heater 2 will not continue to function if it were removed and not replaced
- Fuse 134 has minimal thermal inertia and to that end involves minimal mass and is not enclosed in a copper or similar sheath
- a preferred fuse 134 is one encapsulated only in a small quantity of organic polymer resin
- One presently preferred form of thermal fuse 134 is manufactured by Therm-O-Dis, Inc , Mansfield, Ohio, USA
- the radial lead type is the most suitable for insertion into a socket 136 and a model available with a maximum rated opening temperature of 102 °C has a suitably rapid response time
- the first such strategy involves mechanical devices t ⁇ ggered to operate by the heat of the flame burning on the face of the flame trap in the combustion chamber The devices operate to starve flames of air for continuing combustion which flames are established on the flame trap surface
- the second strategy is to extinguish flames established on the flame trap quickly by a combined chemical and physical reaction to the heat o the flame trap by generating, releasing and propelling a flame extinguishment substance into the intake ot the flame upstream of the flame trap
- the third strategy involves selecting specific flame trap mate ⁇ als and coating them with an ablative or intumescent substance that when subjected to heat of combustion of split flammable vapours on the "downstream' surface of the flame trap, expands to occlude the pores of the flames trap thereby extinguishing the flame
- the fourth strategy is to select a thick, low heat conductive flame trap mate ⁇ al such that heating at the downstream surface of the flame trap results in a much longer or infinite pe ⁇ od before the temperature on the upstream face of the flame trap could reach a temperature able to cause ignition of the spilled vapours upstream of the flame trap entry
- base 226 of the water heater has an aperture to which an upstanding tube 270 is joined, the tube terminating approximately 5 cms above the base 270 to create a hole spanned by a flame trap 229
- a substantially ho ⁇ zontal blocking plate 274 ad j acent combustion chamber 2B which may be conical or curved so as to be able to deflect any condensation water falling upon its upper surface outwardly beyond the flame trap area
- Fixed to the underside of ho ⁇ zontal blocking plate 274 is a temperature sensitive fuse 234 connected to the gas valve 48 (see, for example Figure 1) arranged to enable flow of gas through the gas valve to be shut off in the event of fuse 234 being open circuited by formation of a flame on the upper surface of the flame trap
- a drop tube 302 is provided to create a smooth sliding fit inside the tube 270 Drop tube
- Fusible sealant 304 which acts as a hot melt adhesive to support tube 302 for normal operation in an upward position Fusible sealant 304 most preferably has a melting temperature of about 100 °C to 200 °C
- Opening 271 in the drop tube 302 may be spanned by a lint filter 272 if desired As shown in Figure 18 in the event of a flame forming on flame trap 229 the fusible sealant 304 melts allowing drop tube 302 to fall until it reaches a flat surface such as a floor or mating stop 303 upon which the heater is installed The distance between the floor
- FIG. 19 A different arrangement performing a similar function to that shown m Figure 17 and Figure 18 is provided in Figure 19 and Figure 20
- a ho ⁇ zontal blocking plate 274 is supported above flame trap 229 (Figure 19) by three legs 320 made from readily fusible mate ⁇ al, preferably a thermoplastic mate ⁇ al such as low density polyethylene
- the readily fusible mate ⁇ al most preferably has a melting temperature of 100 °C to 200 °C
- other readily fusible mate ⁇ als may be substituted
- legs 320 melt as shown in Figure 20 so that ho ⁇ zontal blocking plate 274 falls onto the top of tube 270, thus blocking the flow of further vapour or fumes and air to continue combustion, thereby extinguishing combustion
- the flame trap 329 may be in a number of forms, the common feature of which is a much greater dimension in the direction of through flow of air or fumes than previously disclosed in the illustrated embodiments
- the main pu ⁇ ose of the thicker flame trap material 329 is to delay and/or reduce the conduction of heat from the top surface of flame trap 329 to the underside of flame trap 329 in the event of combustion being established due to flammable fumes and vapour igniting on the upper surface of flame trap 329
- One type of flame trap is constructed of stainless steel foil, which is corrugated and joined to an uncorrugated st ⁇ p of stainless steel foil of similar thickness and the first and second tapes joined together and spirally wound as disclosed in Hayakawa et al U S Patent 5,588,822 Then, the time taken for the inlet side of the flame trap to become heated to a temperature sufficient to ignite flammable vapours external to the water heater is considerably increased This configuration can be
- Flame trap mate ⁇ al 329 is constructed of ceramic materials such as Celcor (registered trade mark of Corning Inco ⁇ orated of Houghton Part, Coming, NY 14831 ) extruded ceramic having a thickness of about 12 mm or greater being preferred It is preferably provided with an open frontal area between about 64% and 80% and with between about 36 ⁇ square openings/cm 2 and 73 square openings/cm" Flame trap 329 may be in any desired shape and may be built up to a total required area by using smaller modules of the ceramic mate ⁇ al Adjacent modules of ceramic can be sealed to each other using a flexible sealant 330 or the like as required With reference to Figure 22, an alternative means of extinguishing flames on flame trap 229 is shown Upstanding tube 270, water heater base 226 and optional lint filter 272 are as previously illustrated as in Figure 23 Flame trap 229 may be made from any of the mate ⁇ als as herein mentioned Additional structure in Figure 22 includes a container 306 charged with Celcor (registered trade mark
- an alternatively shaped flame trap 332 is shown Support tube 270, water heater base 226 and optional lint filter 272 are as previously illustrated, for example as in Figure 23
- this includes a double layer of woven metal mesh as previously desc ⁇ bed except that in Figure 23 the two component layers are formed in a non-planar upwardly domed shape (for a circular aperture tube or an upwardly corrugated shape for a square or rectangular aperture at the top of tube 270)
- the advantage of the flame trap 332 over flat woven mesh constructions is that the two layers can be reliably manufactured substantially in contact and will remain substantially in contact because of the way they expand when so curved and do not form localised areas of contact between the two layers of mesh
- a disadvantage obtained with localised contact is that hot spots form quickly at such areas of contact and these might initiate ignition of unburned flammable fuels on the outside of the flame trap structure
- the flame trap illustrated in Figure 23 can sustain combustion on its upper surface for a greater length of time than a similar
- the flame trap or air inlet may be located at va ⁇ ous positions other than those shown in the drawings and desc ⁇ bed above One alternative position is in the side of the combustion chamber opposite the gas supply In such a construction the flame trap or air inlet would be located in an opening in the skirt below the water tank and extending through the corresponding portion of insulation
- the flame trap is positioned above the height of entry to the combustion chamber and a flame sensitive switch is positioned above that height of entry in the flow path of combustion air toward the burner
- the aperture covered by the flame trap is in radiant heat communication with a flame sensitive switch also positioned to be sensitive to flame roll out from flue blockage or combustion air starvation
- the flame trap may be made from a va ⁇ ety of mate ⁇ als such as those desc ⁇ bed above, but can be fabncated from others not specifically identified so long as they permit passage of air and fumes in one direction but prevent flames from travelling in the opposite direction
- Suitable flame trap mate ⁇ als include those being porous, gas permeable and possessing sufficiently high thermal capacity to quench flame under typical conditions of use
- Metallic structures having holes of sizes desc ⁇ bed below, made from, for example, mild steel, stainless steel, copper or aluminium as desc ⁇ bed below are suitable and porous ceramics including glass or mineral wool woven or non-woven constructions are also suitable Fibre mat ⁇ x ceramic is suitable as is flexible or ⁇ gid constructions
- the air passage for combustion air can be located between water tank 6 and jacket 4
- the passageway can be of a va ⁇ ety of shapes and sizes and can be formed in and bounded by the insulation or can be formed by tubes, pipes conduits and the like
- thermocouples 51 providing elect ⁇ cal potentials may be employed so long as they are capable of converting heat energy to assist in actuating closure 154 Heat to mechanical, heat to optical, heat to magnetic and the like types of conversions are all within the scope of the invention Accordingly, "signal" as used in the claims refers not only to ' elect ⁇ cal potential” but to any means whereby closure 154 is actuated/deactuated as a result of detection of heat energy
- Main burner 14 and combustion chamber 15 can have different constructions such as those desc ⁇ bed in U S patents 4,924,816, 5,240,41 1 , 4,355,841 , for example, the subject matter of which is inco ⁇ orated herein by reference
- Duct 270 may be made from a number of heat and corrosion resistant mate ⁇ als, may be shaped and sized in different configurations, and can have flame trap 229 placed in any number of relative position, including ho ⁇ zontal, vertical and at va ⁇ ous angles Finally, it is possible that container 306 shown in Figure 22 may be located in alternative positions within combustion chamber 215 or even exte ⁇ orly of the water heater so long as fusible mate ⁇ al 310 and nozzles 312 are located adjacent flame trap 229, either above or below it
- a thin sheet metallic plate having many ports of closely specified size formed, cut, punched, perforated, etched, punctured and or deformed through it at a specific spacing provides an excellent balance of performance, reliability and ease of accurate manufacture
- the plate provides damage resistance p ⁇ or to sale and delivery of a fuel burning appliance such as a water heater having such an air intake and du ⁇ ng any subsequent installation ot the appliance in a user's premises
- An excessive ⁇ sing temperature of the perforated plate in contact with the flame can transfer heat by conduction through the relatively thin metal plate to the extent that it can reach a sufficiently high temperature (of the order of 1250"F or 675"C) such that a failure might possibly occur under some conditions caused by hot surface ignition of the spilled fumes on the outside of the combustion chamber
- Du ⁇ ng expe ⁇ mentation which was designed to create potential ignition conditions not likely to occur under normal operating conditions and, with a video camera filming the mside of the combustion chamber, a potential mode of failure was observed in some instances to involve flame retention more closely to the pe ⁇ phery of the inlet plate than in the centre Where the flames are closely retained the inlet plate becomes visibly hotter such as by becoming red which indicates a temperature in excess of 1250°F and which was confirmed by thermocouple based temperature measurement
- the embodiments attempt to address ways ot meeting extreme conditions and keeping the overall temperature of the inlet plate to a level that will not encourage external ignition by excessive heating of any portion ot the mlet plate
- the invention also addresses wavs of avoiding detonation wave type ignition that we discovered propagates from the inside to the outside of the combustion chamber through the inlet plate under certain circumstances by minimising the amount of flammable fumes which may enter the combustion chamber before initial ignition inside the combustion chamber occurs, and, also, du ⁇ ng prolonged combustion incidents, in controlling thermally induced resonance within the combustion chamber
- the inventors found that the shape and the pattern of the ports in an air intake plate having the required air flow rate can be su ⁇ singly significant in preventing detonation ignition and delaying or preventing temperature ⁇ se of the plate du ⁇ ng prolonged combustion testing resulting from a spill Furthermore, the inter-port spacing in the plate can be specified to minimise flash-through ignition, all other parameters being in a satisfactory range
- a storage type gas water heater 462 including jacket 464 which surrounds a water tank 466 and a main burner 474 in an enclosed chamber 475
- Water tank 466 is preferably capable of holding heated water at mains pressure and is insulated preferably by foam insulation 468
- Alternative insulation may include fibreglass or other types of fibrous insulation and the like Fibreglass insulation surrounds chamber 475 at the lowermost portion of water tank 466
- a foam dam 465 separates foam insulation 468 and the fibreglass insulation
- Located underneath water tank 466 is a pilot burner 473 and mam burner 474 which preferably use natural gas as their fuel or other gases such as LPG, for example
- Other suitable fuels may be substituted
- Burners 473 and 474 combust gas admixed with air and the hot products of combustion resulting rise up through flue 470 possibly with heated air creating a suction that draws ambient air into the combustion chamber 475, as will be further desc ⁇
- the fuel gas is supplied to both burners (473,474) through a gas valve 469
- Flue 470 in this instance, contains a se ⁇ es of baffles 472 to better transfer heat generated by main burner 474 to water within tank 466
- Near pilot burner 473 is a flame detecting thermocouple 480 which is a known safety measure to ensure that in the absence of a flame at pilot burner 473 the gas control valve 469 shuts off the gas supply
- the water temperature sensor 467 preferably located inside the tank 466, co-operates also with the gas control valve 469 to supply gas to the main burner 474 on demand
- the products of combustion pass by natural convection upwardly and out the top of j acket 464 via flue outlet 476 after heat has been transferred from the products of combustion Flue outlet 476 discharges conventionally into a draught diverter 477 which in turn connects to an exhaust duct 478 leading outdoors
- Water heater 462 is mounted preferably on legs 484 to raise the base 486 of the combustion chamber 475 off the floor
- In base 486 is an aperture 487 which is closed gas tightly by an air inlet plate 490 which admits all required air for the combustion of the fuel gas combusted through the main burner 474 and pilot burner 473 regardless ot the relative proportions of p ⁇ mary and secondary combustion air used by each burner
- Air mlet plate 490 is preferablv made from a thin metallic perforated sheet of stainless steel Copper or brass sheet metal can be used to take advantage of its supe ⁇ or heat conducting properties Stainless steel when used mav be surface treated by dipping in molten sodium and/or potassium dichromate, to blacken it and raise its emissivity Preferably the metal plate has a thickness of about 0 4mm to 1 mm Alternatively, a ported ceramic tile of the SCHWANK ® type (registered trade mark) can be utilised although the robustness of thm perforated metal when compared to its good flow capacity commends its use The ceramic tile type functions adequately as long as the porosity is suitable and it does not become damaged du ⁇ ng assembly, transit, installation or use
- adjoining surfaces can be either one piece or alternatively sealed thoroughly to prevent ingress of air or flammable extraneous fumes Gas, water, elect ⁇ cal control or other connections, fittings or plumbing, wherever they pass through combustion chamber wall 479 are sealed
- the combustion chamber 475 is air/gas tight except for means to supply combustion air and to exhaust combustion products through flue 470
- Some alternative structure of the combustion chamber is shown schematically in Figure 56 to Figure 58, which is discussed later
- Pilot flame establishment can be achieved by a piezoelect ⁇ c igniter
- a pilot flame observation window can be provided which is sealed Cold water is introduced at a low level of the tank 466 and withdrawn from a high level in any manner as already well known
- water heater 462 operates in substantially the same fashion as conventional water heaters except that all air for combustion enters through air mlet plate 490
- all air for combustion enters through air mlet plate 490
- Air mlet 490 allows the combustible extraneous fumes and air to enter but confines combustion inside the combustion chamber 475
- quenching distance of a port in an inlet plate in a combustion chamber of a water heater or similar appliance to account for a wide va ⁇ ety of suitable shape of port
- the quenching distance in this context is that distance measured in the plane of the port area below which a flame formed by a combustible mixture of a fume species and air passing or having passed through the port in a forward direction will not propagate through the port in a reverse direction, whether as a result of detonation or deflagration type initiation of combustion or as a result of prolonged steady combustion at the inlet plate within the combustion chamber
- the quenching distance of such a port For shapes of ports such as may be catego ⁇ sed as geometrically regular such as circular holes or straight slots or l ⁇ egular such as curved or wavy slots, we define the quenching distance of such a port by first defining an axis of the open area of that port as the longer or longest line, which may be straight or curved, which divides that open area in half exactly or approximately The quenching distance of that port, is then the length of the longest straight line which passes pe ⁇ endicularly through the defined axis to meet the boundary of the open area
- the quenching distance according to this definition for a straight slot is its width and, for a circle, its diameter
- complex patterns may be formed by supe ⁇ mposing shapes where axes may cross or intersect, in many ways, one example being wavy slots intersecting pe ⁇ endicularly
- the blocking plate 492 if used is the same or slightly larger size and shape as the inlet plate and has the pu ⁇ ose of stopping conden
- the size of air let plate 90 is dependent upon the air consumption requirement for proper combustion to meet mandated specifications to ensure low pollution burning of the gas fuel
- the air mlet plate of Fig 1 should be conveniently about 3700 square mm in perforated area when fitted to a water heater having between 35,000 and 50,000 BTU/hr (approximate) energy consumption rating to meet US requirements for overload combustion
- Figure 26 shows schematically an air inlet 490 to a sealed combustion chamber including an aperture 487 in a portion of the lower wall 486 of the combustion chamber and, overlapping the aperture 487, a thin sheet metal air inlet plate 490 having a perforated area 500 and an unperforated border 501
- Holes in the perforated area 500 of plate 490 can be circular or other shape although slotted holes have certain advantages as will be explained, the following desc ⁇ ption generally refer ⁇ ng to slots
- Figure 27 to Figure 41 show in each case an air inlet plate 490 of va ⁇ ous configurations as will be desc ⁇ bed to admit air to the combustion chamber 475
- the air inlet plate 490 is a thin sheet metal plate having many small slots 504 passing through it
- the metal may be stainless steel having a nominal thickness of about 0 5 mm although other metals such as copper, brass, mild steel and aluminium and a thickness in the range about 0 3 mm to about 1 mm as an indication, are suitable Depending on the metal and its mechanical properties, the thickness can be adjusted within the suggested range Grade 409, 430 and 316 stainless steel, having a thickness of 0 45 mm to 0 55 mm are preferred
- Figure 27 is a plan view of an air inlet plate 490 having a se ⁇ es of ports in the shape of slots 504 aligned in rows All such slots 504 have their longitudinal axes parallel The ports are arranged in a rectangular pattern formed by the aligned rows The plate is about 0 5 millimetres thick This provides mlet plate 490 with adequate damage resistance and, in all other respects, operates effectively The total cross-sectional area of the slots 504 is selected on the basis of the flow rate of air required to pass through the inlet plate 490 du ⁇ ng normal combustion For example, a gas fired water heater rated at 50,000 BTU/hour requires at least 3,500 to 4,000 square millimetres of port space in plates of nominal thickness of approximately 0 5 mm
- Figure 47, Figure 48 and Figure 49 show numerous va ⁇ ations in the pattern of slots 504 in the perforated area 500, each va ⁇ ation representing one of many patterns which is suitable in the practice of this invention
- a pattern of slots 504 and the size and shape of them constitutes an important consideration for optimum function in the event that extraneous flammable fumes accidentally enter with the air ente ⁇ ng the combustion chamber 475, thereby creating a ⁇ sk of accidental and dangerous ignition of a substantial or significant quantity of such spilled flammable volatile substance, such as gasoline, external to the combustion chamber
- Figure 33 shows one particularly suitable pattern with longitudinal axes of the edge slots 507 at ⁇ ght angles to those of the ports 504 in the remaining perforated area 505
- the slots 504 are provided to allow sufficient combustion air through the mlet plate 490 and there is no exact rest ⁇ ction on the total number of slots 504 or total area of the plate, both of which are determined by the capacity of a chosen gas (or fuel) burner to generate heat by combustion of a suitable quantity of gas with the required quantity of air to ensure complete combustion in the combustion chamber and the size and spacing of the slots 504
- the air for combustion passes through the slots 504 and not through any larger inlet air passage or passages to the combustion chamber, no such larger inlet or air inlet being provided
- Figure 27 to Figure 45 and Figure 54 illustrate ports which are elongated in shape the present invention is applicable to inlet plates formed with circular shaped ports as is illustrated in Figure 53, or alternatively the sloi ports of the other figures can be replaced by circular ports preferably no bigger than 0 5 mm or 06 mm
- one of several manufactu ⁇ ng operations are approp ⁇ ate Such operations include laser cutting, etching, photochemical machining, stamping, punching, blanking or piercing
- a process of piercing and bending can be used to produce a slot formed as shown in cross section in Figure 45
- a tool punctures a line in a plate and a portion of the plate to one side of the line is then displaced laterally to create a slot of desired length and width W as shown
- Figure 42 shows a single slot 504 having a length L, width W and curved ends
- the slots 504 are formed having at least about three times the length L as the width W and are preferably at least about twelve times as wide Length to width (L W) ratios outside these limits are also effective
- L W Length to width
- slots are more effective in controlling accidental detonation wave ignition than circular holes although beneficial effect can be observed with L/W ratios in slots as low as about 3
- L/W ratios of about 15 there can be a disadvantage in that in a plate 490 of thin flexible metal possible distortion of one or more slots 504 may be possible as would tend to allow opening at the centre of the slots creating a loss of dimensional control of the width W
- reinforcement of a thin inlet plate by some form of stiffening, such as cross-breaking can assist adoption of greater L/W ratios L/W ratios greater than about 15 are otherwise useful to maximise air flow
- the slots 504 perform in respect of any species of extraneous flammable fumes which may reasonably be expected to be involved in a possible spillage external to the combustion chamber 475 of which the air inlet plate 490 of the invention forms an integral part or an appendage
- the quenching distance adopted for the slots 504 or other port 502 needs to be modified downwards to allow for preheating of the unburnt extraneous fume/air mixture which inevitably obtains, although its intensity is va ⁇ able depending on specific water heater design parameters and other va ⁇ ables associated with particular incidents
- flame speed increases with preheat of the unburnt mixture and have read that for a mixture of butane ( as a convenient example of an extraneous fume species) with air that the maximum flame temperature achievable occurs with a slightly lean mix (about 103% air) and is about 1900°C
- Computer modelling of unburnt gas passing through our highly preferred 0 5mm by 6mm long slots indicated a temperature of the unburnt gases reaching 375°C
- preheating causes the flame temperature (1900°C) to be increased by about the same amount as the preheat temperature, l e , to about 2275°C Using relationships familiar to those stalled in combustion enginee ⁇ ng
- a quenching distance can best be determined with the assistance of some expe ⁇ mental observations for a given design of air inlet plate 490 in a water heater 462 having a combustion chamber 475
- Our defined quenching distance is affected by one or more of the following factors the incoming air and extraneous fume temperature, as affected by preheating, the ratio between extraneous fumes and air, the nature of the extraneous fumes m relation to its flame speed and flammability limits in combination with air as an oxidant, appliance design related va ⁇ ables, including flue length and therefore the velocity of input air and extraneous fume mixtures and pressure difference across the air inlet plate 490 the depth and shape of the chosen air inlet ports 502.
- combustion chamber 475 relative to the main burner 474 positioning and the air inlet plate 490 positioning including effects of back radiation from the burner to the air inlet plate4 90 and any other internal or external rest ⁇ ctions to air flow through the air inlet plate 490, the mate ⁇ al of the flame trap including its thermal conductivity, the emissivity of its surface and the effect of any catalytic substance having combustion influence applied to its surface, and the effect of any combustion d ⁇ ven oscillation of the system as a whole, this can be a factor depending on the natural frequency of the structure as constructed by compa ⁇ son with the natural frequency and amplitude of any combustion process occur ⁇ ng inside the combustion chamber 475
- Figure 42 to Figure 44 show slot and inter-port spacing dimensions adopted in the embodiments depicted in Figure 27 to Figure 41 generally, Figure 43 and Figure 44 particularly refer ⁇ ng to Figure 33 and Figure 34
- the dimensions of the ports are equal and have a length L of 6 mm and a width W of 0 5 mm
- the ends of each slot are semicircular but more squarely ended slots are suitable
- the chosen manufactu ⁇ ng process can influence the actual plan view shape of the slot
- metal blanking such large numbers of holes can be difficult as regards maintaining good condition of such small punches if the corner radii are not rounded
- the photochemical machining process of manufacture of plates 490 with slots 504 is adapted to also produce radiused cornered slots
- the discussion has so far assumed ports 502 that are either circular 503 or slot shaped 504 There is no reason that the invention be rest ⁇ cted to such shapes Slots 504 may in fact, be formed as lines which can be curved or wavy The quenching distance of such non straight lines fits our definition and thus
- the inlet plate 490 having the dimensions and spacing of slots 504 as indicated above and the pattern shown in Fig 33, du ⁇ ng one testing procedure, allowed passage of fumes of spilled gasoline through the inlet plate 490 where they ignited inside the combustion chamber 475 and burned until 1 U S gallon was consumed This was done without the outside surface temperature of the inlet plate 490 increasing at any point such as to ignite fumes which had not yet passed through the inlet plate, the test concluding when no more gasoline remained to be consumed after more than one hour of continuous burning on the plate 490
- Figure 46 depicts schematically an outline of a lower portion of a water heater 462 having an air mlet leading to a combustion chamber 475 including a plate 490 of the type or similar to those depicted in Figure 27 to Figure 41 Because of the small size of the ports 502 in plate 490 they could, in certain circumstances, be prone to block up or become clogged with lint or other foreign mate ⁇ als Furthermore, being at a relatively inaccessible part of a water heater 462, an accumulation of lint may not be noticed since water heaters in general are usually not serviced regularly
- the inlet plate 490 is connected to an air entry duct 510 which turns at ⁇ ght angles and extends substantially ho ⁇ zontally to the front of a water heater 462 whereupon it again turns at ⁇ ght angles to extend upwardly to terminate any convenient distance above the floor level, about 60 cm to 100 cm or higher being suitable Higher levels are preferred because generally airborne lint levels decrease with increasing height above floor level
- the air entry duct 510 is nominally gas-tight (this term is amplified below) where it is terminated by the inlet plate 490 at one end portion and by a non-removable lint filter 512 facing the front of the heater 462 at an accessible height above floor level
- the lint filter 512 has many accessible small holes which can be circular, slotted or other shape, with no hole individually substantially larger in dimensions than the limiting distance as above defined of the ports (502,504) chosen in the particular air inlet plate 490 adopted
- the total open area must at least exceed the total open area of the air inlet plate 490 so as not to add greater rest ⁇ ction to air flow than the inlet plate 490 itself
- Most of the lint filtenng holes are positioned ideally as far above the floor as possible to face the front of the heater so as to be accessible for cleaning routinely, ideally with a vacuum cleaner
- the duct 1 10 was above desc ⁇ bed as nominally gas tight - it is not required to be fully gas tightly sealed, so long as its connection to the combustion chamber wall 86 meets the c ⁇ te ⁇ on of having no gap or crack exceeding the defined quenching distance for any feasible extraneous fume species (ente ⁇ ng the air inlet) which is desired to be confined if ignited, within the combustion chamber 75
- Fig 29 shows m schematic cross-section one suitable connection between an air inlet plate 90 and lower wall 86 of a combustion chamber 75
- a relatively large quantity of extraneous fumes on the inside surface of the plate 90 e g such as would vapo ⁇ se from the spill of one US gallon of gasoline
- heating to maximum incandescence of the plates 90 particularly correlates to extraneous fumes to air ratios close to the stoichiometnc value for the particular extraneous fumes
- the air inlet plate 90 in such circumstances acts like some types of perforated metal gas burners which function at red heat such as for broiling or gnlling but, unlike any such burner of that type, the air mlet plate in this invention must be able to provide reliable confinement operation despite an uncontrollable and uncontrolled spectrum of flow rates of flammable fumes relative concentration in a mixture of air and the
- FIG. 47 and Figure 48 shows two va ⁇ ants in which separated from its assembled position, an inlet plate 490 which has an unperforated border 501 which is assembled downwardly (as indicated by the dashed lines) in highly thermally conductive contact with a combustion chamber opening 487 formed, such as by piercing and extruding, a flanged border 514 defining an inwardly opening hole 487 into the combustion chamber 475
- the compressive contact can be achieved by metal to metal f ⁇ ctional contact involving mating flanges 514 and 501 or may include some form of gasket between the contacting faces of those flanges
- Figure 47 shows a circular plate 490 which fits tightly inside the flanged border 514 around the extruded hole 487 in the combustion chamber wall 486
- Figure 48 shows a rectangular plate 490 which fits tightly on the outside of the flanged border 514 around the mating hole 487 in the combustion chamber wall 486 It is optional whether either the circular or the four-sided va ⁇ ant mates inside
- Figure 47 and Figure 48 show one method of affixing the air let plate 490 to the combustion chamber wall 486, a second method is illustrated in Figure 83, Figure 84 and Figure 85 which show another arrangement to suitably fix or seal the two components It is intended that the air mlet 490 be substantially sealed against combustion chamber wall 486 to prevent air and or extraneous fumes passing between the surfaces of air inlet 490 and combustion chamber wall 486
- Air mlet plate 490 has an outer flange 601 that extends beyond the edge of the opening in combustion chamber wall 486 pe ⁇ odically, along flange 601 , mechanical c ⁇ mps 602 are pressed into flange 601 and corresponding portion of combustion chamber wall 486
- Such c ⁇ mps 603 are well known in the sheet metal art as TOG-L-LOC ® being a particular preferred example
- Other means of secu ⁇ ng or fixing air mlet plate 490 to combustion chamber wall 486 are possible, spot welding being one of them
- Figure 49 to Figure 52 illustrate a rectangular inlet plate 490 including a perforated central portion 505 bounded by a non-perforated portion 501 which is formed to include a penpheral channel 516
- the pe ⁇ pheral channel 516 is shaped to enable the inlet plate 490 tightly engage, or otherwise to snap into a mating connection 518 ( Figure 52) formed around an opening 487 in the base 486 of the combustion chamber 475
- the combustion chamber 475 with inlet plate 490 fitted is enclosed at the top by a mating connection to or ad j acent the outside pe ⁇ phery of the curved base of the tank 466 of a water heater 462 and so forms a closed combustion chamber 475
- Those potential sources of ignition of extraneous fumes forming part of a water heater burners 473 and 474 are enclosed by location in the combustion chamber 475
- the combustion chamber walls 479 support the mass of a water tank 466
- Figure 53 to Figure 55 schematically show alternative forms of profiled ports on a portion of air inlet plate
- the ports slots in Figure 54
- the ports can provide a more streamlined flow profile through them and can provide a convenient valley" mat ⁇ x in which to position viscous form(s) of intumescent swellable coating 536
- the application of intumescent swellable coating 536 to this invention will be desc ⁇ bed subsequently in relation to Figure 62 to Figure 64
- inlet plate 490 In relation to all the forms of inlet plate 490 so far illustrated it is ot concern that an initial ignition of flammable extraneous fumes inside the combustion chamber 475 as a sudden energetic detonation be minimised Otherwise, there might theoretically be a ⁇ sk of blowing a flame front back through the ports 502, 504 of the inlet plate 490 Forms of water heater 462 shown schematically in Figure 56 to Figure 58 particularly address this concern
- the entire base 486 of the combustion chamber is positioned at the top of a drawn wall 525 of the combustion chamber 475, the lowest pe ⁇ meter of the combustion chamber providing a support which rests on a support pan 528 which in turn is supported above floor level on feet 484
- the base 486 of the combustion chamber 475 and the inlet plate 490 are co-planar or approximately so and, by virtue of the desc ⁇ bed structure position the inlet plate 490 as close as possible to the burners 473, 474
- the mam burner 474 is conventionally positioned but the pilot burner 473 is positioned immediately above the inlet plate 490 upper surface This provides opportunity for a more immediate ignition of extraneous fumes ente ⁇ ng the combustion chamber 475 through the inlet plate ports 502, 504 and, thereby, substantially increases the probability that only a very small quantity of extraneous fumes would be in the combustion chamber 475 when ignition first occurs Such a small volume of extraneous fumes, if ignited, is likely to bum
- va ⁇ ous predeterrrunable design parameters can be chosen or operating conditions influenced to minimise undesirable effects If a design is prone to excessive sound level generation, then changes to that design to lessen the tendency include the reduction of temperature of the plate 490, changes to the length of the flue pipe 470, the spacing of ports 502 and the thickness of the air inlet plate 490, embossments to stiffen the air inlet plate 490 and gasket placement between the plate 90 and combustion chamber lower wall 486, as will be desc ⁇ bed
- Figure 59 to Figure 61 show arrangements to terminate prolonged combustion on a plate 490 for use in those instances in which it is desirable to extinguish that combustion quickly rather than allow it to draw remaining spilled extraneous fumes to consume them by combustion
- Figure 59 depicts a portion of air inlet plate 490 covered by a thm layer 532 of solder which has matching ports 533 to those in the plate 490
- this layer 532 is heated by extraneous fumes burning on the inside of the combustion chamber 475, the heated solder layer 532 liquefies and spreads to block or tend to block the adjacent slot or slots 504
- the plate 490 may be also formed with surfaces converging toward each slot 504, allowing the liquefied solder to more readily block each slot
- a fluxing agent such as widely known in solde ⁇ ng techniques
- Suitable lntumescent/ablative coatings include "FIRETEX” "M70/71 " (basecoat top seal intumescent fire retardant coating, manufactured by Fyreguard), and "FIRED AM 2000” intumescent coating supplied by 3M A coating thickness of about 200 ⁇ m on a SCHWANK ® tile or plate of the types shown in
- Figure 65 to Figure 70 show a se ⁇ es of devices in which a prolonged combustion incident inside a combustion chamber 475 can be more quickly extinguished
- Mounted to the inlet plate 540 is a sliding plate 541 which has ports 502 of corresponding size, patterns and o ⁇ entation to the ports 502 in the fixed mlet plate 540
- Figure 66 shows alignment of the ports 502 to provide a through passage for air and extraneous fumes to pass
- the sliding plate 541 is biased to the position shown in Figure 66 by one or more sp ⁇ ng(s) 543. which as depicted in Figure 65 can be tension sp ⁇ ng(s) 543
- the sliding plate 541 is locked into one location by a solder or thermoplastics pm 544.
- the sliding plate 541 can move by sliding relative to the fixed plate 540, guided in a restncted path by sealed ⁇ vets 542 which are secured leak tightly to the fixed plate 540 and which are a sliding fit into a pair of guide slots in the sliding plate 541
- the extraneous fumes with an approp ⁇ ate air mixture would be ignited by either the pilot 473 or main burner 474 of the water heater 462 Following a short penod of burning, the sliding plate 541 would heat to a temperature sufficient to melt the solder or thermoplastics pin 544 whereupon the force applied by the sp ⁇ ng 543 would move the sliding plate 541 in the direction of the arrow
- the guide slot(s) can only be long enough to allow unperforated parts of sliding plate 541 to align with the ports 502 in fixed plate 540 or, as an alternative, the slots 502 can be longer but two stops 146 can be provided to limit the travel of the sliding plate 541 over the fixed plate 540 and, either way, as shown in Figure 67, result in the closure of all the ports 502 thus extinguishing any further combustion
- the sliding plate 541 is held against the bias provided by the sp ⁇ ng 543 while placing a replacement solder or thermoplastics pin 544 into the aligned holes provided for the pu ⁇ ose through the plates 540, 541
- the air inlet 490 would then be functional again to allow normal combustion air flow but to cut off air and extraneous fumes if needed
- the solder or thermoplastics pin can be replaced by a thin layer of solder between the plates This layer of solder creates a laminate of the two metal plates sandwiching the solder, being also provided with ports aligned initially through all three layers of the laminate Connection of the sliding plate to a sp ⁇ ng could be provided as shown in Figure 65 or equivalent
- This variation has advantages including that the solder facilitates relative sliding between the plates once the solder liquefies due to heat input Moreover, its ability to exclude extraneous
- Figure 68 to Figure 70 show a similar occluding mechanism to those of Figure 65 to Figure 67, although in this case the cut-off of air entry is by relative rotation between the plates rather than linear movement
- Figure 68 shows a circular mlet plate like that illustrated in Figure 25
- a rotary plate 541 Overlying the fixed plate 540 is a rotary plate 541 with ports 545 aligning with ports 502 in fixed plate du ⁇ ng normal use, as shown in the cross section of Figure 69
- Secured to the fixed plate 540 is one end of a spindle 149 which car ⁇ es, at its other end, one end of a bimetallic torsion sp ⁇ ng 548 which in turn, at its other end, is attached to the rotary plate, by a pin 550
- Approp ⁇ ate stops between the two plates 540, 541 are provided to enable the respective ports 502 and 547 to remain out of mutual alignment, as shown in Figure 70
- the rotating plate 541 Upon cooling of the bimetallic torsion sp ⁇ ng 548, the rotating plate 541 returns to its original position bnnging the ports 502, 545 in both plates into alignment again, ready to allow air to pass through to enable combustion and to allow extraneous fumes if present, to pass through
- Figure 68 to Figure 70 features can be combined, such as the bimetallic torsion spnng 548 being replaced by a coil sp ⁇ ng or other sp ⁇ ng, and the plates 540, 541 being held in register (to allow air to pass) by a solder or thermoplastics plug 544 or a layer of solder between them, in each case relying on heat to melt the solder or thermoplastics, so allowing the spnng force to rotate the rotating plate 541 relative to the fixed plate 540 to shut off combustion of extraneous fumes in the combustion chamber 475
- Inlet plates of the invention which have ports solely in the shape of slots 504 allow flames burning extraneous tumes inside the combustion chamber 475 to lift further off the air mlet plate 490 and thereby reduce the operating temperature of the air inlet plate 490 as compared to a plate of the same mate ⁇ al and thickness having circular holes 503 Therefore, a plate 490 with slots 504 can consume more spilled substance over a longer combustion period, than can a plate 490 with holes 503 having an equivalent Quenching distance Also, slots 104 enable lint passage more readily than holes of equivalent quenching distance
- Figure 71 shows two additional provisions possible to inco ⁇ orate, so enhancing the likelihood of a safe outcome following a flammable substance spillage incident near a gas water heater having an air inlet 490 according to the invention Either provision may be included separately or together
- the first provision is an audible alarm 558 which operates in the event of a flame becoming established in the combustion chamber 475 at or adjacent the inside surface of the air mlet plate 490
- the alarm 558 can be actuated by a number of energy sources, one being an enclosed metallic bulb 555 containing a volatile substance which expands when heated, the bulb 555 being connected to the alarm by a small bore tube
- the tube is sealed bv a frangible diaphragm that bursts to vent the volatile substance through a whistle or similar audible device included m the alarm 558
- the second provision is a cooling device including a spray nozzle 556 positioned and aligned capable ot directing a fine spray of water 557 at the perforated area of the air inlet plate 490
- the water 557 is sourced from the mams pressu ⁇ sed cold water supplied to the tank through a pipe 551 , diverted therefrom by a branch pipe 552 through a valve 553, the outlet of which is connected to the spray nozzle 556
- the valve 553 is biased in a normally closed position and is opened to allow passage of water through the valve by lateral admission of a pressu ⁇ sed fluid via a small bore tube 154
- the pressu ⁇ sed fluid is in turn sourced from the temperature sensitive element 555 on any such occasion that it is heated by flame a ⁇ sing from combustion of extraneous fumes on the inside surface of the air inlet plate 490
- Other flame extinguishing substances such as compressed carbon dioxide may be suitable and can be released using generated heat to similarly open an approp ⁇ ate escape path
- Figure 73 to Figure 75 shows the possibility of forming the ports 502 in plates 490 of the invention having not only a parallel sided cross-section, as shown in Figure 72, which can be readily formed by any of the processes previously mentioned Ports 502 can be used, which in cross-section have both convergent and divergent shapes
- the photochemical machining process lends itself to forming holes with convergent or divergent shapes as illustrated in Figure 473, Figure 74 and Figure 75
- Figure 73 shows a hole 563 or slot 565 which converges from a larger dimension at the upstream face (I e the lower side, as illustrated) of the air mlet plate 490 Air and, if present, extraneous fumes, passes through the tapenng hole 563 or tape ⁇ ng slot 565 in a downstream direction indicated by the two vertical arrows into the combustion chamber 475
- the hole 563 or slot 565 as illustrated in Figure 73 converges in an upstream direction firstly but then terminates with substantially parallel sides
- Figure 74 shows a tapered hole 567 or tapered slot 569 which converges to a throat of minimum cross-sectional area between the upstream and downstream faces of the air mlet plate 490 which tends to provide minimum drag for a given limiting dimension of the port 567, 569
- the air mlet plate 490 can provide an optimised combination of maintaining rest ⁇ ction to air flow within workable bounds with ability to confine combustion inside the combustion chamber 475 for as long a time as necessary
- Figure 75 shows a tape ⁇ ng hole 571 or tape ⁇ ng slot 573 in which air for combustion passing through the air inlet plate 490 in the direction of the vertical arrows into the combustion chamber 475 first passes through a divergent portion which then converges such that the intersection of the port 571, 573 intersects with the inside (upper) surface of the plate 490 at an angle somewhat less than 490°
- the very sha ⁇ edged o ⁇ fice so formed at the inside surface of the air inlet plate 490 may function as a flame lift promoter so that combustion of extraneous fumes occur ⁇ ng near the inside surface of the plate 490 is encouraged to lift flames away from that surface, with the effect of causing the plate to remain cooler du ⁇ ng prolonged burning or, even more preferably, to cause the flame to liftoff entirely and extinguish
- the tapered ports of Figure 73, Figure 74 or Figure 75 can be formed by applying higher concentration of etchant solution to one side of the metal sheet from which the air inlet plate 490 is constructed, until the ports
- the air inlet plate 490 with perforations 504 is provided with diagonal cross-breaking lines 580 which can provide the plate 490 with additional stiffness in order to change the natural frequency of the combination of the combustion chamber 475 and connected air inlet plate 490 to move that natural frequency away from a frequency of combustion process which may occur if extraneous fumes ente ⁇ ng the air mlet chamber become ignited inside the combustion chamber 475
- the stiffened structure shown in Figure 77 may be even more efficient than a corresponding flat air inlet plate 490 as illustrated in Figure 58
- an air inlet plate 490 having slots 504 is shown having stiffening members extending at 90" to each edge of the plate 490
- the central perforated area as shown in Fig 35 is altered by deleting a suitable number of rows of slots followed by the forming of one or more rounded channels 582 extending in one or more directions across the unperforated portions of
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN98814252A CN1310791A (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
AU84262/98A AU747008B2 (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
MXPA01000808A MXPA01000808A (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters. |
PCT/AU1998/000585 WO2000006947A1 (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
CA002338078A CA2338078C (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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PCT/AU1998/000585 WO2000006947A1 (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
Publications (1)
Publication Number | Publication Date |
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WO2000006947A1 true WO2000006947A1 (en) | 2000-02-10 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/AU1998/000585 WO2000006947A1 (en) | 1998-07-24 | 1998-07-24 | Air inlets for gas water heaters |
Country Status (5)
Country | Link |
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CN (1) | CN1310791A (en) |
AU (1) | AU747008B2 (en) |
CA (1) | CA2338078C (en) |
MX (1) | MXPA01000808A (en) |
WO (1) | WO2000006947A1 (en) |
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US6622661B1 (en) | 2003-01-16 | 2003-09-23 | The Water Heater Industry Joint Research And Development Consortium | Fuel-fired heating appliance with dilution air/flammable vapor bypass tube and elevated combustion air inlet |
US6994056B1 (en) | 2004-09-03 | 2006-02-07 | Rheem Manufacturing Company | Water heater having a low NOx burner integrated with FVIR platform |
DE102004034138A1 (en) * | 2004-07-15 | 2006-02-09 | Schott Ag | Gas-fired heating device |
CN103343820A (en) * | 2013-07-30 | 2013-10-09 | 南京凯盛国际工程有限公司 | Sealing device used between kiln combustor and wicket interface |
CN108853847A (en) * | 2018-08-17 | 2018-11-23 | 广东万家乐燃气具有限公司 | A kind of device and electric heater with fire-extinguishing function concurrently |
CN112013037A (en) * | 2020-08-31 | 2020-12-01 | 东风商用车有限公司 | Heat radiation structure of clutch housing |
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CN1833200B (en) | 2003-06-02 | 2010-12-08 | 精工爱普生株式会社 | Etched vent screens |
CN102200285A (en) * | 2011-03-22 | 2011-09-28 | 创新工程方案有限公司 | Dynamic oxidation of industrial waste gas |
US20160123580A1 (en) * | 2013-07-02 | 2016-05-05 | Bekaert Combustion Technology B.V. | Gas premix burner |
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1998
- 1998-07-24 WO PCT/AU1998/000585 patent/WO2000006947A1/en active IP Right Grant
- 1998-07-24 CA CA002338078A patent/CA2338078C/en not_active Expired - Fee Related
- 1998-07-24 AU AU84262/98A patent/AU747008B2/en not_active Ceased
- 1998-07-24 MX MXPA01000808A patent/MXPA01000808A/en unknown
- 1998-07-24 CN CN98814252A patent/CN1310791A/en active Pending
Patent Citations (5)
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GB2226124A (en) * | 1988-12-08 | 1990-06-20 | Frymaster Corp | Flashback resistant infrared gas burner apparatus |
EP0530945A1 (en) * | 1991-06-24 | 1993-03-10 | BS & B SAFETY SYSTEMS, INC. | Flash gas venting and flame arresting apparatus |
WO1994001722A1 (en) * | 1992-07-13 | 1994-01-20 | Joseph Patric Brown | Fail-safe valve responsive to flame failure and flaring |
US5520536A (en) * | 1995-05-05 | 1996-05-28 | Burner Systems International, Inc. | Premixed gas burner |
US5765547A (en) * | 1996-11-13 | 1998-06-16 | La Plante; Thomas E. | Heater fire prevention device, system and method |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6622661B1 (en) | 2003-01-16 | 2003-09-23 | The Water Heater Industry Joint Research And Development Consortium | Fuel-fired heating appliance with dilution air/flammable vapor bypass tube and elevated combustion air inlet |
DE102004034138A1 (en) * | 2004-07-15 | 2006-02-09 | Schott Ag | Gas-fired heating device |
US7341448B2 (en) | 2004-07-15 | 2008-03-11 | Ceramat, S.Coop. | Gas-fired heating apparatus |
DE102004034138B4 (en) * | 2004-07-15 | 2008-04-03 | Ceramat, S. Coop., Asteasu | Gas-fired heating device |
US6994056B1 (en) | 2004-09-03 | 2006-02-07 | Rheem Manufacturing Company | Water heater having a low NOx burner integrated with FVIR platform |
CN103343820A (en) * | 2013-07-30 | 2013-10-09 | 南京凯盛国际工程有限公司 | Sealing device used between kiln combustor and wicket interface |
CN108853847A (en) * | 2018-08-17 | 2018-11-23 | 广东万家乐燃气具有限公司 | A kind of device and electric heater with fire-extinguishing function concurrently |
CN112013037A (en) * | 2020-08-31 | 2020-12-01 | 东风商用车有限公司 | Heat radiation structure of clutch housing |
Also Published As
Publication number | Publication date |
---|---|
AU8426298A (en) | 2000-02-21 |
MXPA01000808A (en) | 2002-04-08 |
CA2338078A1 (en) | 2000-02-10 |
CA2338078C (en) | 2008-09-30 |
CN1310791A (en) | 2001-08-29 |
AU747008B2 (en) | 2002-05-09 |
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