GB1592540A - Gas fired heating apparatus - Google Patents

Description

(54) GAS FIRED HEATING APPARATUS (71) We, COOPERHEAT, a Company organised under the laws of Great Britain of 164 Lord Street, Southport, Merseyside, PR9 OQH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a gas fired heating apparatus for heat treating circumferentially welded pipes of a given diameter.

Our copending British Patent Application No. 38006/76 (Serial No. 1,585,467) describes a tangentially gas fired muffle comprising a housing which is provided with inlet ports in the form of tangentially directed immersion tubes which locate atmospheric gas burners, and outlet ports located adjacent the immersion tubes for discharging the products of combustion of the gas burners in previous tubes. The housing is divided internally by a ring of perforate or expanded heat resistant material into first and second annular chambers. The first chamber is provided with the inlet and outlet ports whereby the ring contains the combustion processes within the first chamber and acts as a radiant for dissipating heat uniformly onto the surface of pipe sections bounded, in use, by the second annular chamber.Thus, the combustion products do not pass through the ring of perforate or expanded heat resistant material.

The present invention provides a gas fired heating apparatus for heat treating circumferentially welded pipe sections of a given cross-sectional dimension, the apparatus comprising a housing having two or more sections which can be arranged opposite respective surfaces of said pipe sections, each housing section having at least one inlet port in which an atmospheric gas burner is supported so that combustion takes place outside the housing, a perforate or expanded screen made of heat resistant material and which divides said housing section internally, said division providing one or more first chambers communicating with the respective inlet ports, each of said first chambers being lined internally with heat resistant material and receiving the flame and the products of combustion of the respective atmospheric gas burner whereby the heat resistant material, forming said screen and lining said first chamber, acts as a radiant, said division also forming at least one second chamber which is bounded by said screen, by wall portions of the housing section and by the surfaces of said pipe sections when the apparatus is applied thereto, a region of the latter wall portions being dimensioned so as to terminate short of said surfaces of said pipe sections to provide an axial flue-way for the products of combustion of said burner passing from said first chamber, through said screen and to said second chamber.

The housing may be annular whereby the screen is in the form of a ring of perforate or expanded heat resistant material, the apparatus being provided for heat treating pipe sections of circular diameter. Such an arrangement provides first and second annular chambers for respectively receiving the flame and products of combustion of atmospheric gas burners arranged in tubes directed tangentially into first annular chamber. The products of combustion exit at an annular flue-way or flue-ways provided by gaps between the redially innermost edges or wall portions of the housing adjacent the pipe sections. The housing may be divided into arcuate sections, for example, semi-circular sections which are hinged together or provided with fasteners so that they may be split and assembled about the welded pipe sections.

The housing may also have a rectangular cross-section, each housing section being in the form of an open-sided box, the open side being arranged to confront respective surfaces of the pipe sections. The atmospheric gas burners are then supported at one end of each housing section so as to discharge their flame and products of combustion axially, with respect to the pipe sections, into respective first chambers. Each first chamber is terminated by an end wall, opposite the respective burner, whereby the products of combustion are caused to flow through the screen and into the second chamber bounded by the pipe surfaces. If the burner is fitted to one axial end portion of a box section, the main axial flue-way may be provided at the opposite axial end of the box section by a gap between the respective pipe surface and the radially innermost wall portion of the housing.A series of box sections may be circumferentially arranged about a pipe of large circular diameter, each burner discharging into a respective first chamber and the second chambers communicating via radial gaps between adjacent box sections.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Fig. I schematically illustrates a single box section forming a housing of apparatus according to one embodiment of the invention, Figs. 2 and 3 schematically illustrate a pair of box sections, each according to Fig. 1, arranged about a pipe and connected to a gas supply, Figs. 4 and 5 schematically illustrate annular apparatus according to another embodiment of the invention, Figs. 6 and 7 each schematically illustrate a range of sizes of apparatus in accordance with the first two embodiments of the invention respectively, Fig. 8 schematically illustrates how a series of box sections may be arranged circumferentially about a pipe to provide apparatus of larger dimensions, Fig. 9 is a section through similar annular apparatus, and Figs. 10 and 11 are respective longitudinal and end sections of the box housing section forming part of the apparatus.

Referring generally to the drawings, Figs.

1-3, 6, 8, 10 and 11 illustrate box housing sections forming part of, or used as heating apparatus with axially fired burners. In such an arrangement, the burners discharge their flame and products of combustion axially of welded pipe sections as illustrated, for example, in Fig. 3. Figs. 4, 5, 7 and 9 illustrate an annular form of apparatus with tangentially fired burners. In this case, the flames and products of combustion are directed tangentially to the welded pipe sections as shown, o r- A for example, in Fig. 9.

Figs. 10 and 11 show a box housing section in greater detail. It comprises a stainless steel casing 1 with an inlet port 2 and a main axial flue-way 3. The inlet 2 is located opposite a holder 4 having a collar portion 4' with a clamping screw 4" to secure the body of an atmospheric gas burner (not shown). The holder 4 is spaced by a gap 5 from the casing 1 by arms 6 welded to the holder and the housing. The casing 1 is open at the end adjacent gap 5. When the gas burner is fitted to holder 4, it directs its flame and products of combustion axially in the direction of the arrow 7.

The main flue-way 3 is formed by making a cut-out in an end wall 8 of casing 1 and by folding a lip 9 inwardly to locate one end of a perforate or expanded metal screen or mesh 10. The screen 10 is made of heat resistant material, such as Inconel (Registered Trade Mark) and it has a substantially U-shaped cross-section with sidewalls 11 and outwardly directed flanges 12 as shown in Fig.

11. Fig. I I also shows inwardly directed flanges 13 of housing I which provides support for the flanges 12 of the screen 10.

The screen 10 divides the casing 1 into an upper chamber 14 and a lower chamber 15 (bounded, in use, by the surfaces of welded pipe sections to be heat treated by the muffle). The chamber 14 is lined internally with heat resistant or insulating material 16 such as ceramic fibre blanket. The material 16 is applied with an adhesive to the outer wall 17 and end wall 8 as shown in Fig. 10 and to sidewalls 18, as shown in Fig. 11, the sidewall insulation extending below the level of the screen 10 at the sides of the chamber 15.

Fig. 11, which is a section on the line YY of Fig. 10, best illustrates the main axial flueway 3 at the remote end of the box housing section.

Fig. 1 schematically illustrates the box housing section of Figs. 10 and 11 fitted with an atmospheric gas burner 20. A flame failure device 21, of known construction, controls the supply of gas in a pipe 22 in response to a temperature sensor 23. A primary air inlet 20' is controlled by axially sliding a hose clip 20" relative thereto. A series of secondary air inlets 19 are arranged in an annulus 19'. Although the end of casing 1 adjacent the burner is open to the atmosphere, both above and below the screen 10, the velocity of combustion products escaping from the end of the burner 20 tends to draw further secondary air into the upper chamber 14 rather that act as a second axial flueway.

However, some products of combustion will escape from the 'burner' end of chamber 15 and this assists a more even spread of heat on the pipe sections (not shown) to be heat treated. The arrows 24 indicate the longitudinal extent of the gap between the end of the burner 20 and the inlet port 2. Axial movement of the burner 20 in holder 4 will vary this gap to assist in controlling the inflow of secondary air and hence the heat input to the pipe sections to be treated by the muffle.

Fig. 2 shows how the box housing sections are secured together, by hinges 25 with withdrawable pins 26. The open sides of the box sections (i.e. chamber portions 15) face each other and surround welded pipe sections 27.

Fig. 3 shows another aspect of the apparatus of Fig. 2 and illustrates, by arrows 28, the main axial outflow of combustion products. The pipe sections 27 have a weld 29 which is located centrally of the apparatus generally indicated by reference 30. A gas supply pipe 31, branching to each burner is connected to a quick release coupling 32 which is one of several attached to respective regulators 33 in a manifold 34 connected to a gas supply cylinder 35. The gas supply tubing 31 may be in the form of hose having thermocouple extension leads attached thereto and which can be run off of a supply reel for attachment to gas burners as required.

The thermocouple wire is flash-welded to the surfaces of the pipe sections to provide a temperature signal for use with recorders and hence the control of the heat treatment.

Fig. 6 is a series of schematic end views of differently sized apparatus having a generally similar construction to those shown in Figs. 2 and 3 but drawn on a different scale.

The size of the apparatus is selected with regard to the size of the welded pipe sections to be treated to ensure a uniform supply of heat to the pipe surfaces for adequately treating the weld.

Fig. 8 schematically exemplifies an arrangement which employs a plurality of box housing sections 37, each of which are generally similar in construction to the individual box sections shown in Figs. 2 and 3 but drawn on a different scale. The housing sections 37 are circumferentially connected by means of hinges and pins 25, 26 to surround pipe sections 38 of a larger diameter. As can be seen from the drawing, the chambers 15 communicate via gaps between respective box housing 37 and the surfaces of the pipe sections 38. An appropriate number of gas channels and thermocouple connections, generally indicated by reference 39, are connected between burners 20 and the gas supply and temperature recorder (not shown).

Generally speaking, the axially fired apparatus is useful in heat treating pipe sections which are inaccessible to an annular type of gas muffle, for example, where the pipe sections to be treated form a continuous pipe which is one of a series of pipes extending adjacent one another in the same direction.

In the latter case, the adjacent pipes would prevent the "wrap-round" installation of the annular apparatus. However, the annular apparatus is generally prefered with regard to an even heat distribution around pipesections of circular cross-section.

Referring now to Fig. 9 which illustrates an annular and tangentially fired apparatus, a stainless steel and annular housing 41 has a pair of tangentially directed immersion tubes, 42,42' for receiving atmospheric gas burners (not shown). Tube 42' is shown fitted with a collar portion 43 and fixing screw 44 for securing the body of the burner, the collar portion 43 being welded to tube 42' by arm portions 45 which extend alongside a gap for admitting secondary air. Tube 42 is similarly equipped, but tubes 42,42' may be provided with alternative forms of holder for securing the gas burner.It will be convenient here, having described the immersion tubes 42 and 42', to note that immersion tubes are not provided in the axially fired apparatus described in the previous embodiment, whereby the "stand-off" dimension (i.e. the radial projection) of the box housing sections is kept to a minimum. Immersion tubes may, however, be used in such apparatus if the "stand-off' dimension can be increased without causing any disadvantage.

As shown in Fig. 9, the housing 41 is lined with insulating material 47 and it supports a perforate or expanded Inconel (Registered Trade Mark) screen 48. The screen 48 divides the housing 41 into a first annular chamber 49 and a second annular chamber 50 which is bounded by the surfaces of the welded pipe sections 51.

Referring to Fig. 4, the arrows 52 indicate the outflow of combustion products from burners 53, the products passing through annular and axial flue-ways 54 adjacent the pipe sections 50.

Fig. 5 shows semi-circular housing sections 55, 55' hinged together at 56 and secured by a toggle fastener 57.

Fig. 7 shows a range of sizes of tangentially fired apparatus.

Generally speaking, the preferred embodiments of the invention were developed so as to provide apparatus fired by miniature gas burners which are small and flexible enough to cover a range of duties in sometimes difficult and inaccessible places. These duties would be carried out with a minimum of preparation of labour compared with similar duties carried out electrically with resistance elements. The burners may be hand operated, as often preferred by the users, as this avoids the expense and noise of a high/low gas rate burner. Another advantage of apparaus according to the preferred embodiments is that the flame of each burner is not visible due to the use of axial flue-ways. Moreover, at least with the axial fired apparatus, there is substantially no flame impingement on the surfaces of the welded pipe sections.The apparatus could also be used for the rapid pre-heating of heavy wall pipe-work as well as for heat-treating circumferential welds.

The atmospheric burners are of known construction and incorporate an integral injector which induces air for combustion as described above. The number of burners used depends on the size of the apparatus which is selected with regard to the size of the pipe and the width of the hot band required.

The principle of operation is that combustion takes place at each gas burner outside the apparatus housing, the flame and products of combustion being directed into the open end of a stainless steel or Inconel (Registered Trade Mark) housing to heat up the ceramic fibre lining and the dividing screen so that they act as a radiant to the surfaces of the pipe sections. The products pass through the screen and out of the main axial flue-ways on one or both sides of the apparatus.

The individual burners require a pressure of 1.4 2.0 atmospheres (20 -30 Ib/sq. in.) of propane gas. Each burner has a typical rating of 10,000 k. cal/hr and is fitted with an adjustable air shutter to control primary aeration, and a push button thermo-magnetic flame failure device and a wind deflector for adverse conditions. The gas is supplied to the individual burners through combination rubber/stainless steel hoses manufactured to the desired length, the final 1.5 metres being as standard in convoluted stainless steel for thermal protection in hot zones. All connections in the system are preferably of the push-pull, plug-in, quickrelease variety with integral valves.

A suitable manual control system may have 24 separate channels consisting of a gas supply hose and compensating cable partnership, which can be quickly run out from a reel on a supply vehicle to the pipe sections to be treated, for example, within a i O0 metre radius. Manual control of the outgoing pressure (via a regulator) is by an opeiator who watches a recorder chart r provide the control required.

Pipe-work of a 12 inc1-: diameter and above demands two gas control channels to provide good top to bottom control. Below this size, it is advantageous to use one gas supply line and one thermocouple for cconomic reasons.

On very small sizes of pipe-work, satisfactory top to bottom control can be achieved by adequate positioning of the box housing sections on the pipe sections to be treated. On the intermediate pipe sizes, the same effect can be achieved by adequate positioning of the box housing sections and variation in the graduated jet sizes of the burners. When a common gas supply is regulated, top to bottom control can be effected by using different sizes of gas jets, the largest in the bottom burner or burners, the smallest in the top; the system is then balanced by natural thermal effects. With experience and established data, the top to bottom heat input can be controlled by a single pressure variation at the source of supply, to provide acceptable post-heat treatments within the relevant code of practice.Some degree of control can be achieved by axially positioning the burners to regulate the amount of secondary air entrainment for combustion. However, bad combustion should be avoided with regard to excessive flame lengths.

The gas supply may consist of a double group of interconnected bottles with full emergency change-over equipment and mains pressure regulating equipment to provide a steady 2.0 atmospheres (30 Ib/sq. in.) supply. The system would include an in-line filter to trap solid particles (in view of the number of small gas jets involved), individ tidal gas pressure regulators to each control channel, individual pressure indicating gauges and excess flow valves to protect against a cut or damaged hose. The latter feature is not practical with an on/of, high/low control system". However. without the excess flow valve, a muffle according to the present invention could be readily controlled in an automatic high/low mode.

Whilst the above embodiments employ one atmospheric gas burner in each housing section, larger apparatus may have two or more gas burners in each housing section.

WHAT WE CLAIM IS: 1. A gas fired heating apparatus for heat treating circumferentially welded pipe sections of a given cross-sectional dimension, the apparatus comprising a housing having two or more sections which can be arranged opposite respective surfaces of said pipe sections, each housing section having at least one inlet port in which an atmospheric gas burner is supported so that combustion takes place outside the housing. a perforate oF expanded screen made of heat resistant material and which divides said housing section internally, said division providing one or more first chambers communicating with the respective inlet ports, each of said first chambers being lined internally with heat resistant material and receiving the flame and the products of combustion of the respective atmospheric gas burner whereby the heat resistant material, forming said screen and lining said first chamber, acts as a radiant, said division also forming at least one second chamber which is bounded by said screen, by wall portions of the housing section and by the surfaces of said pipe sections when the apparatus is applied thereto, a region of the latter wall portions being dimensioned so as to terminate short of said surfaces of said pipe sections to provide an axial flue-way for the products of combustion of said burner passing from said first chamber, through said screen and to said second chamber.

2. Apparatus according to claim 1 wherein the housing is annular and the first and second chambers are divided into respective annular chambers by a screen in the form of a ring of perforate or expanded heat resistant material.

3. Apparatus according to claim 2 wherein a plurality of said atmospheric gas burners are arranged in respective tubes

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (14)

**WARNING** start of CLMS field may overlap end of DESC **. the apparatus housing, the flame and products of combustion being directed into the open end of a stainless steel or Inconel (Registered Trade Mark) housing to heat up the ceramic fibre lining and the dividing screen so that they act as a radiant to the surfaces of the pipe sections. The products pass through the screen and out of the main axial flue-ways on one or both sides of the apparatus. The individual burners require a pressure of 1.4 2.0 atmospheres (20 -30 Ib/sq. in.) of propane gas. Each burner has a typical rating of 10,000 k. cal/hr and is fitted with an adjustable air shutter to control primary aeration, and a push button thermo-magnetic flame failure device and a wind deflector for adverse conditions. The gas is supplied to the individual burners through combination rubber/stainless steel hoses manufactured to the desired length, the final 1.5 metres being as standard in convoluted stainless steel for thermal protection in hot zones. All connections in the system are preferably of the push-pull, plug-in, quickrelease variety with integral valves. A suitable manual control system may have 24 separate channels consisting of a gas supply hose and compensating cable partnership, which can be quickly run out from a reel on a supply vehicle to the pipe sections to be treated, for example, within a i O0 metre radius. Manual control of the outgoing pressure (via a regulator) is by an opeiator who watches a recorder chart r provide the control required. Pipe-work of a 12 inc1-: diameter and above demands two gas control channels to provide good top to bottom control. Below this size, it is advantageous to use one gas supply line and one thermocouple for cconomic reasons. On very small sizes of pipe-work, satisfactory top to bottom control can be achieved by adequate positioning of the box housing sections on the pipe sections to be treated. On the intermediate pipe sizes, the same effect can be achieved by adequate positioning of the box housing sections and variation in the graduated jet sizes of the burners. When a common gas supply is regulated, top to bottom control can be effected by using different sizes of gas jets, the largest in the bottom burner or burners, the smallest in the top; the system is then balanced by natural thermal effects. With experience and established data, the top to bottom heat input can be controlled by a single pressure variation at the source of supply, to provide acceptable post-heat treatments within the relevant code of practice.Some degree of control can be achieved by axially positioning the burners to regulate the amount of secondary air entrainment for combustion. However, bad combustion should be avoided with regard to excessive flame lengths. The gas supply may consist of a double group of interconnected bottles with full emergency change-over equipment and mains pressure regulating equipment to provide a steady 2.0 atmospheres (30 Ib/sq. in.) supply. The system would include an in-line filter to trap solid particles (in view of the number of small gas jets involved), individ tidal gas pressure regulators to each control channel, individual pressure indicating gauges and excess flow valves to protect against a cut or damaged hose. The latter feature is not practical with an on/of, high/low control system". However. without the excess flow valve, a muffle according to the present invention could be readily controlled in an automatic high/low mode. Whilst the above embodiments employ one atmospheric gas burner in each housing section, larger apparatus may have two or more gas burners in each housing section. WHAT WE CLAIM IS:

1. A gas fired heating apparatus for heat treating circumferentially welded pipe sections of a given cross-sectional dimension, the apparatus comprising a housing having two or more sections which can be arranged opposite respective surfaces of said pipe sections, each housing section having at least one inlet port in which an atmospheric gas burner is supported so that combustion takes place outside the housing. a perforate oF expanded screen made of heat resistant material and which divides said housing section internally, said division providing one or more first chambers communicating with the respective inlet ports, each of said first chambers being lined internally with heat resistant material and receiving the flame and the products of combustion of the respective atmospheric gas burner whereby the heat resistant material, forming said screen and lining said first chamber, acts as a radiant, said division also forming at least one second chamber which is bounded by said screen, by wall portions of the housing section and by the surfaces of said pipe sections when the apparatus is applied thereto, a region of the latter wall portions being dimensioned so as to terminate short of said surfaces of said pipe sections to provide an axial flue-way for the products of combustion of said burner passing from said first chamber, through said screen and to said second chamber.

2. Apparatus according to claim 1 wherein the housing is annular and the first and second chambers are divided into respective annular chambers by a screen in the form of a ring of perforate or expanded heat resistant material.

3. Apparatus according to claim 2 wherein a plurality of said atmospheric gas burners are arranged in respective tubes

directed tangentially into the first annular chamber.

4. Apparatus according to claim 2 or 3 wherein the products of combustion exit at an annular flue-way or flue-ways provided by gaps between the radially innermost edges or wall portions of the housing which, in use, are adjacent the pipe sections.

5. Apparatus according to any one of claims 2 4 wherein the housing is divided into arcutate sections which can be split or secured together by fasteners.

6. Apparatus according to claim 1 wherein each housing section is in the form of an open-sided box, the open side being provided for arrangement to confront respective surfaces of the pipe sections.

7. Apparatus according to claim 6 wherein each of the atmospheric gas burners is supported at one end of the respective box housing section so as to discharge its flame and products of combustion axially, with respect to the pipe sections, into the respective first chamber; each first chamber being terminated by an end wall, opposite the respective burner, whereby the products of combustion are caused to flow through the screen and into the second chamber bounded, in use, by the pipe section surfaces.

8. Apparatus according to claim 7 wherein the main axial flue-way for each box housing section is provided in the end wall opposite the end wall which supports the respective atmospheric gas burner.

9. Apparatus according to any one of claims 6 8 wherein a series of said box sections are arranged circumferentially to receive the welded pipe sections, each burner discharging into a respective first chamber and the second chambers communicating via radial gaps between adjacent box sections.

10. Apparatus according to claim 9 wherein the adjacent box sections are secured by releasable fasteners.

11. Apparatus according to claim I wherein the housing is annular and substantially as herein described with reference to Fig. 9 of the accompanying drawings.

12. Apparatus according to claim 1 wherein the muffle comprises a series of box sections each substantially as herein described with reference to Figs. 10 and 11 of the accompanying drawings.

13. Apparatus according to claim 12 and substantially as herein described with reference to Figs. 1--3 of the accompanying drawings.

14. Apparatus according to claim 12 and substantially as herein described with reference to Fig. 8 of the accompanying drawings.