GB2380771A

GB2380771A - A valve or hydrant

Info

Publication number: GB2380771A
Application number: GB0216553A
Authority: GB
Inventors: Bryan Sanderson; Shaun Thomas Sharp
Original assignee: Saint Gobain Pipelines PLC
Current assignee: Saint Gobain PAM UK Ltd
Priority date: 2001-07-18
Filing date: 2002-07-17
Publication date: 2003-04-16
Anticipated expiration: 2022-07-17
Also published as: GB0216553D0; IE20020520A1; GB2380771B; GB0117454D0

Abstract

A valve or hydrant 100 comprises a housing 2 to define a chamber 3 the hydrant further comprises a valve cover plate 22 and an outlet cover plate 20. The cover plates are sealingly attachable to the housing 2 preferably by means of bayonet fittings and also by means of an interlocking engagement between the two cover plates. This engagement may take the form of a tooth 24 and tooth receiving recess (26 figure 3). The hydrant 1 further comprises a ball valve 40 for regulating drainage of water from the hydrant when the hydrant is not in use.

Description

A HYDRANT This invention relates to an apparatus for providing an outlet from a water supply such as but not limited to a mains supply. The invention relates particularly but not exclusively to a water valve or to a fire hydrant for enabling fire appliances and other machinery to tap water from a mains water supply.

A known valve and a known fire hydrant each comprise a housing, defining a chamber, a valve member contained within the housing associated with an inlet passage, an outlet passage and a drainage passage. The valve member controls the flow of water from the mains water supply into the valve or fire hydrant via the inlet passage.

For convenience hereinafter the term"fire hydrant"is used to mean a fire hydrant proper or a valve as aforesaid.

Water in a mains water supply is typically held under pressure, and therefore water entering the fire hydrant from the mains water supply will be pressurised.

The valve member, when open, allows water to flow under pressure from the water mains supply via the inlet passage, and prevents water from escaping from the mains supply into the hydrant when closed.

Thus water entering the fire hydrant from the mains water supply enters via the inlet passage into the chamber and exits via the outlet passage. The outlet passage is connectable to, for example, a fire hose for enabling the water to be used to assist in extinguishing a fire.

A valve cover plate is sealingly attached to both the valve and the housing.

An outlet cover plate defines the outlet passage and is also sealingly attachable to the housing. The valve cover plate and the outlet cover plate are formed separately from the housing and from one another in order to allow easy and safe access to the interior of the fire hydrant during assembly and for maintenance purposes.

In addition, by forming the valve cover plate and the outlet cover plate separately from the housing it is possible to design different outlets to suit customer requirements, whilst using a standard housing design. This reduces the costs of design variants.

Because the water within the hydrant is under pressure, it is necessary to ensure that the cover plates are sealingly attached to the housing of the fire hydrant in order to define a sealed chamber.

In a known fire hydrant, the cover plates are bolted to the housing. Whilst this method of attaching the cover plates to the housing results in the formation of a sealed chamber, it can be time consuming and therefore expensive to manufacture the components of the fire hydrant with the required tolerances to ensure accurate location of the cover plates relative to the housing. In addition it can be a labour intensive operation to bolt the cover plates to the housing during assembly of the fire hydrant, further adding to the expense.

In a second known fire hydrant the valve cover plate and the outlet cover plate are each sealingly attached to the housing by means of a bayonet fitting. A problem with this known fire hydrant is that in use, the act of opening and closing the valve tends to cause the valve cover plate to turn within the bayonet fitting relative to the housing and thus to detach itself from the housing. Because water flowing from the mains water supply into the chamber of the fire hydrant is under pressure, once the valve cover plate

becomes insecurely attached to the housing, the pressure of the water will force the cover plate completely away from the housing of the fire hydrant thus rendering the fire hydrant inoperable, and unsafe.

It is important for operational efficiency as well as from a safety point of view to prevent one or both of the cover plates from detaching from the housing during operation. It is known to try and prevent the cover plates from detaching through use of separate securing devices associated with each cover plate.

According to a first aspect of the present invention there is provided a water valve or a hydrant comprising: a housing comprising : an inlet passage attachable to a water supply; a chamber; an outlet passage; an inlet valve operatively associated with the inlet passage for controlling pressurised flow of water from a water supply to the hydrant; and a valve cover plate and an outlet cover plate each formed separately from the housing, and each being sealingly attachable to the housing, characterised in that the valve cover plate and the outlet cover plate are engageable with one another such that, in use, each of the cover plates resists any tendency of the other cover plate to detach from the housing.

The cover plates may be sealingly attached to the housing by any appropriate means, but preferably each cover plate is sealingly attached to the housing by means of a bayonet fitting.

A bayonet fitting is a simple method of coupling two components together. This is achieved by inserting one component axially into another, and

rotating to a fixed position. Axial removal is then prevented by the action of lugs on one of the rotatable components acting on the underside of corresponding shoulders on the other component. Thus removal can be achieved only by contra-rotation.

Because the cover plates are engageable with one another as well as being attached to the housing by means of a bayonet fitting, when the valve is opened any tendency for the valve cover plate to rotate (as a consequence of the opening of the valve) will be resisted by the outlet cover plate to which the valve cover plate is attached.

By means of the present invention therefore each of the valve and outlet cover plates are not only secured relative to the housing of the fire hydrant, but are also located and locked relative to one another.

Preferably, each of the cover plates comprises locking means, the locking means of the respective cover plates being engageable with one another which engagement results in an interlocking arrangement between the two cover plates.

Because of the interlocking arrangement the act of opening the valve is unlikely to result in the unlocking of the valve cover plate from the housing of the hydrant since the outlet cover plate will serve to further anchor the valve cover plate and prevent relative movement between the valve cover plate and the housing of the fire hydrant within the bayonet fitting.

In the invention, the interlocking bayonet arrangement between the valve cover plate, the outlet cover plate and the housing prevents anti-rotation of either cover plate when the cover plates are assembled in the housing. At the same time, by means of the present invention, the cover plates are not permanently joined to the housing, or to each other. The interlocking

arrangement, together with the locking means, results in two independent means for locking the cover plates relative to the housing.

Preferably, one of the locking means of one of the cover plates comprises a tooth extending from the plate, and the locking means of the other cover plate comprises tooth receiving means within which the tooth is locatable.

Advantageously, the tooth is formed on the valve cover plate and the tooth receiving means is formed on the outlet cover plate.

Alternatively, each cover plate comprises one or more teeth, and one or more tooth receiving means. Thus a tooth in each cover plate is locatable within a tooth receiving means formed in the other cover plate.

Preferably, the locking means further comprises at least one pin receiving means in each of the valve cover plate and the outlet cover plate and corresponding pin receiving means in the housing. Each of the pin receiving means allows a pin to be inserted into the housing through a respective cover plate thus providing further anchoring of the cover plates.

Alternatively, only one of the cover plates comprises a pin receiving means.

The principle of the interlocking device is very similar to a gear tooth arrangement, having protrusions on both cover plates that mesh together when the bayonet fittings associated with each cover plate are rotated simultaneously into position. A pin is then secured to or through each cover plate into the housing. The combination of the bayonet fitting, the interlocking device and the pins will provide two independent and functionally different means of securing both cover plates to the housing.

Alternatively, a bolt may be used in place of each pin to secure the cover

plates to the housing.

Although the valve could be any suitable valve, preferably the valve comprises a stem threadedly engageable with a stem nut. The stem nut is held securely within a gate, and the valve as a whole is positioned within the inlet passage of the hydrant. The underside of the gate comprises a resilient seat. When the valve is in a closed position, the stem nut and gate are positioned towards the lower end of the stem, such that the underside of the gate presses against the inlet passage thus forming a seal between the gate and the inlet passage.

Alternatively, the stem nut may be integrally formed with the gate.

In order to open the valve, the stem is rotated causing the gate and nut to travel up the stem and away from the inlet passage thus allowing water to enter the hydrant by the inlet passage.

When it is required to close the valve the stem is rotated in the opposite sense causing the stem nut and gate to travel down the nut and to again move into sealing contact with the inlet passage.

In order to allow drainage of water from the housing when the fire hydrant is not in use, the hydrant further comprises a drainage passage through which water may drain away into the surroundings of the fire hydrant.

In a known fire hydrant, a valve is positioned within the drainage passage.

When the hydrant is in operation, the pressure of water entering the housing forces the valve onto the valve seat within the drainage passage and holds the valve in a closed position, sealing the drainage passage. This prevents water from draining away from the fire hydrant when the hydrant is in use.

When operation of the fire hydrant ceases, the pressure within the housing falls, and a resilient means such as a spring holds the valve off its seat when the fire hydrant is not in use, thus allowing water to drain away from the hydrant.

However, due to weather conditions such as frost typically experienced by a fire hydrant, the spring is likely to rust and become damaged. It then becomes unable to hold the valve off its seat. This in turn means that complete drainage of the hydrant cannot be achieved. Any water remaining in the housing after the main valve is closed exposes the housing to the risk of damage caused by freezing. In addition on subsequent opening of the valve any remaining water may be drawn back into the water mains thus contaminating the water supply.

According to a second aspect of the present invention there is provided a water valve or a hydrant comprising: a housing comprising : an inlet passage attachable to a water supply; a chamber; an outlet passage; an inlet valve for controlling pressurised flow of water from a water supply to the hydrant, the valve having an open position in which water may flow from the water supply via the inlet passage into the chamber, and a closed position in which water is prevented from entering the chamber via the inlet passage; and a drainage passage, characterised in that the hydrant further comprises a ball valve operatively associated with the drainage passage allowing drainage of water from the chamber when the valve or fire hydrant is not in use.

Advantageously, the ball is made from a plastics material, and the ball valve

further comprises a seal, and a retainer for retaining the ball within the valve.

The seal may be in the form of an 0-ring, gasket, lip seal, cup seal or any other available seal.

Because the ball is made of a plastics material it will float in water. However when the hydrant is in use, and water is within the chamber, the ball will be forced onto the valve seat within the drainage outlet passage due to the pressure of water within the chamber thus sealing the housing. When the pressure in the chamber is removed, i. e. when the main valve is closed preventing further water from the water mains from entering the housing, the ball will float above the outlet passage allowing water to exit the chamber.

The retainer prevents the ball from floating out of the drainage passage, and thus retains the ball within the passage.

The retainer comprises a plurality of notches or perforations allowing drainage from the housing when the ball is in contact with the retainer.

Preferably, the retainer comprises a plurality of notches or perforations allowing continued drainage from the housing even when the ball is positioned on the seat of the valve.

Preferably the ball is made from a plastics material that will not deteriorate under very cold temperatures.

Embodiments of the invention will now be further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic representation of a known fire hydrant in which the valve cover plate and the outlet cover plate are bolted to the housing of the fire hydrant; Figure 2 is a schematic representation of a fire hydrant according to an embodiment of the present invention; Figure 3 is a schematic and partly cut away representation of a fire hydrant according to the present invention showing outlet plates according to the first aspect of the invention, and the ball valve according to the second aspect of the invention; Figure 4 is a schematic representation of a part of the housing of a fire hydrant according to a second embodiment of the invention incorporating a ball valve.

Referring to Figure 1 a known fire hydrant is designated generally by the reference numeral 1. The fire hydrant comprises a housing 2 defining a chamber 3. The hydrant further comprises an inlet passage 4 which is connected to a mains water supply (not shown) and an outlet passage 5.

The inlet passage is opened and closed by means of valve 6. The valve 6 is in the form of a valve stem positioned within a gate 7 which in turn is sealingly connected to the inlet passage 4 by means of gate seal 8. The valve is contained within a cover plate 9 which is sealingly attached to the housing 2 by means of bolt 10.

The outlet passage 5 is defined by cover plate 11 which cover plate is sealingly attached to the housing 2 by means of bolts 12. The outlet is covered by a cap 13 when not in use.

The valve is moved between an open position and a closed position by rotating the valve in an anticlockwise or clockwise direction as appropriate. The valve stem is threaded and moves in a stem nut 14 which is also

threaded.

A fire hydrant 100 according to the present invention will now be described with reference to Figures 2 to 4.

Parts of the fire hydrant that correspond to parts of the known fire hydrant shown in Figure 1 have corresponding reference numerals for ease of reference.

The hydrant 100 comprises a valve cover plate 20 and an outlet cover plate 22. The outlet cover plate 22 comprises a tooth 24 extending from the periphery thereof towards valve cover plate 20. The valve cover plate 20 comprises a tooth receiving means in the form of a recess 26 that is formed in its peripheral edge and shaped to receive the tooth 24. Mutually spaced teeth 28a and 28b define the recess 26 and in use of the hydrant 100 hold the tooth 24 in position within the recess 26. Tooth 28b formed in valve cover plate 20 is receivable within a further recess 26b formed in the peripheral edge of outlet cover plate 22.

The housing 2 comprises outlet cover plate receiving portion 32 and a valve cover plate receiving portion 34. Each of the receiving portions 32, 34 is in the form of a bayonet fitting and comprises slots 36, into which lugs are engageable.

In order to assemble the fire hydrant 100, the cover plates 20, 22 and the housing 2 are held in a predetermined position relative to one another by a mechanical aid. The cover plates 20, 22 are then pushed down into the housing 20 and twisted in opposite directions so as to allow the teeth 24, 28a, 28b to interlock. The lugs 38 will also have moved into position so that they are engaged within slots 36. Rotation is limited by the use of a mechanical stop (not shown) within the housing 2. The mechanical stop

may be formed integrally with the housing or may formed separately from the housing and secured thereto.

Each of the cover plates 20,22 has protruding from its peripheral edge an essentially laminar lug 25. Each lug 25 is spaced a short circumferential distance from the teeth 24,28a and 28b.

The seatings (defined by housing 2) on which the respective cover plates 20,22 sit in use are each of essentially the same peripheral shape as the associated cover plate 20,22. Consequently each of the seatings includes projecting from its periphery a further lug 25a that is of complementary shape to the lugs 25.

The lugs 25a are so located that on rotation of the cover plates 20,22 as aforesaid to cause engagement of the teeth 24 in the recess 26 each lug 25 overlies a respective lug 25a.

The four lugs 25,25a are perforated as shown. Consequently a pin 60 or a similar device such as a bolt is insertable into each pair of lugs when they occupy the positions visible in Figure 3. As a result of insertion of the pins 60 unintentional back-rotation, tending to cause releasing of the cover plates 20,22, is prevented.

In an alternative arrangement only one of the pairs 25,25a of lugs is capable of receiving a said pin 60.

Although each of the pins 60 serves to hold a respective cover plate 20,22 in position within the bayonet fitting 32,34, the interlocking device comprising teeth 24,28a, 28b provides an independent, additional means of preventing the cover plates 20,22 from detaching from the housing.

If either or both of the pins 60 should become damaged or removed for whatever reason, the interlocking mechanism will transmit any rotational force to the teeth.

For a given size of hydrant 100 made from the materials set out below, it is possible to calculate the required width of each tooth, 24,28a, 28b and also the width of tab 25 in order to withstand the applied torque. The specified torques are applied to either the valve cover plate 20 or the outlet cover plate 22 but not both.

Where Ultimate tensile strength of Spheroidal Graphite Cast Iron, Grade 500 = Rm SG = 500 N/mm2 Ultimate tensile strength of Nylon = Rm~nylon = 65 N/mm2 Ultimate tensile strength of Gunmetal, Grade LG2-RmLG2 = 200 N/mm Factor of Safety = FOS = 3 Maximum allowable stress in Spheroidal Graphite Cast Iron = osG Maximum allowable stress in Spheroidal Nylon (nylon Maximum allowable stress in Gunmetal, Grade LG2 = GLG2 The outlet passage 5 and cover plate 2 may be made from nylon, cast iron or gun metal. Since nylon is the weakest of these materials, the stresses are calculated for nylon only. Since the calculations show that nylon could stand appropriate levels of stresses, then the components will be strong

enough to withstand such stresses due to the presence of other materials which are stronger than nylon.

The stress within the teeth 28a, 28b and 24 may be calculated as follows : Radius of valve cover plate RB = 76. 75 mm Radius of outlet cover plate Ro = 59. 25 mm Torque Applied to valve cover plate Te = 303Nm Torque Applied to outlet cover plate To = 303Nm Tooth Form 20 deg involute Number of Teeth on valve cover plate nB = 20

Circular Pitch p=L n.

Resultant load on outlet teeth = Wto, Resultant load on cover teeth = Wtb

T T Resultant load on teeth n = - = to-- 0 B

This gives

Maximum Load W, = M !. c (, ) Wt = 5. 114 x 103N

These calculations determine the maximum load that the teeth 24, 28a, 28b are subjected to and therefore have to be capable of resisting. By limiting the stress in the teeth to an acceptable level the force exerted by the maximum load is used to determine the required size of the teeth.

To calculate the stress in one of the teeth 24, 28a, 28b, it is assumed that P = Trp, and Y-Try, where P = diametric pitch, p = circulate pitch, Y = Form Factor, y = Lewis Form Factor.

The term "pitch diameter" refers to the diameter of a theoretical circle upon which all calculations are usually based. The pitch circles of two mating gears are tangential to each other.

The term"diametric pitch"refers to the ratio of the number of teeth on a gear to the pitch diameter.

The term"circulate pitch"refers to the distance measured on the pitch circle from one point on one tooth to a corresponding point on an adjacent tooth.

The value Y is taken from Table 11-3 in Mechanical Engineering Design by Joseph E Shigley published by McGraw Hill Kogakusha Limited, Third Edition, 1988, the contents of which are incorporated herein by reference.

Lewis Form Factor y = 0. 322 P = np Stress in a tooth a Where F = Width of tooth FRY FPY Therefore F --'-Fnyton =9. 7 mm nylon Let Fnylon = 10mm

The stress within area (Ltab) of the tab 62 may be calculated as follows :

w IV Failure in Shear , , =---- < T, ,,, = 25. 6-- 2Ltab F ylon mm Failure by crushing dpm= 12mm

Where d pin is the diameter of the pin In practice, if the area of the tab 62 near the pin 60 starts to deform, due to excessive loading, the surplus load will be transmitted to the interlocking mechanism which will provide additional support.

The fire hydrant according to the present invention further comprises a drainage passage 42 to allow water to drain away from the hydrant 100 when not in use.

The hydrant 100 comprises a ball valve 40 positioned within the drainage passage 42 located adjacent to inlet passage 4. The ball valve 40 comprises a ball 44 made of a plastics material, a sealing ring 46 and a retainer 48 for retaining the ball 44 within the drainage passage 42.

In use, when the inlet passage 4 is closed by means of valve 6, there will be no or very little water contained within the chamber 3 of the fire hydrant.

When the valve 6 is opened water will enter the chamber 3 via the inlet passage 4 and will also enter the drainage passage 42. The water is under pressure and will force the ball 44 down onto the sealing ring 46 thus preventing water from escaping via the drainage passage during use of the hydrant.

When the valve is closed, the pressure within the chamber will fall, and because the ball 44 is made of a plastics material it will float in water. The ball will therefore float up towards the retainer 48, opening the drainage passage.

The retainer 48 comprises a plurality of holes or notches (not shown) which allow water to drain from the chamber 3 to the outside of the valve when the hydrant is not in use.

Claims

CLAIMS 1. A water valve or a hydrant comprising: a housing comprising: an inlet passage attachable to a water supply; a chamber; an outlet passage; an inlet valve operatively associated with the inlet passage for controlling pressurised flow of water from a water supply to the hydrant; and a valve cover plate and an outlet cover plate each formed separately from the housing, and each being sealingly attachable to the housing, characterised in that the valve cover plate and the outlet cover plate are engageable with one another such that, in use, each of the cover plates resists any tendency of the other cover plate to detach from the housing.
2. A valve or hydrant according to Claim 1 characterised in that each cover plate is sealingly attached to the housing by means of a bayonet fitting.
3. A valve or hydrant according to Claim 1 or Claim 2 wherein each of the cover plates comprises locking means, the locking means of the respective cover plates being engageable with one another.
4. A valve or hydrant according to Claim 3 wherein one of the locking means of one of the cover plates comprises a tooth extending from the plate, and the locking means of the other cover plate comprises tooth receiving means within which the tooth is locatable.
5. A valve or hydrant according to Claim 4 wherein the tooth is formed on the outlet cover plate and the tooth receiving means is formed on the

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valve cover plate.
6. A valve or hydrant according to any one of Claims 3 to 5 wherein the locking means further comprises at least one pin receiving means in each of the valve cover plate and the outlet cover plate, and corresponding pin receiving means in the housing.
7. A water valve or a hydrant comprising: a housing comprising : an inlet passage attachable to a water supply; a chamber; an outlet passage; a drainage passage an inlet valve for controlling pressurised flow of water from a water supply to the hydrant, the valve having an open position in which water may flow from the water supply via the inlet passage into the chamber, and a closed position in which water is prevented from entering the chamber via the inlet passage; and a drainage passage, characterised in that the hydrant further comprises a ball valve operatively associated with the drainage passage for allowing drainage of water from the chamber when the valve or fire hydrant is not in use.
8. A valve or hydrant according to Claim 7 wherein the ball of the ball valve is made from a plastics material, and the valve further comprises a seal, and a retainer for retaining the ball within the valve.
9. A valve or hydrant according to Claim 7 or Claim 8 wherein the retainer comprises a plurality of notches or perforations.

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10. A valve or hydrant substantially as herein before described with reference to Figures 2 to 4 of the accompanying drawings.