GB2439338A

GB2439338A - Valve

Info

Publication number: GB2439338A
Application number: GB0612272A
Authority: GB
Inventors: David Laurence Melton
Original assignee: Firetrace Ltd
Current assignee: Firetrace Ltd
Priority date: 2006-06-21
Filing date: 2006-06-21
Publication date: 2007-12-27
Anticipated expiration: 2026-06-21
Also published as: GB2439338B; GB0612272D0

Abstract

A valve for controlling a high pressure circuit in dependence on the pressure in a low pressure reservoir has a valve member in the form of a stepped piston working in a stepped cylinder. The low pressure acts on the larger diameter piston step and the high pressure acts on the smaller piston step, with the pressure and the piston dimensions being such that the low pressure normally maintains the valve member in a position where the high pressure circuit is closed. A retraced bypass passage is opened to allow limited flow from the high pressure circuit to the low pressure reservoir when there is a slight pressure drop in the low pressure reservoir, to replenish the low pressure. However if there is a catastrophic drop in the pressure of the low pressure reservoir, the high pressure will move the valve member to open the high pressure circuit.

Description

BACKGROUND

a. Field of the Invention

This invention relates to a valve, and in particular to a pressure-controlled valve for controlling flow through a high pressure conduit by using a relatively low pressure circuit to control the valve.

b. Related Art EP 0 888 152 discloses a fire-extinguishing valve in which a low pressure circuit controls a high pressure circuit from which extinguishant will be discharged in the event of a fire. If pressure is lost in the low pressure circuit, the valve will open to allow high pressure extinguishant to be discharged. In this disclosure, the high pressure circuit has a restricted bleed passage by means of which high pressure is continuously in communication with a piston chamber, to bias the piston to close a high pressure discharge passage.

This valve is difficult to manufacture and does not cope well with large variations of pressure while the system is in a static state.

SUMMARY OF THE INVENTION

According to the invention, there is provided a valve having a body with a high pressure inlet port and a high pressure outlet port, a valve member movable within the body for opening and closing communication between the inlet and outlet ports and a low pressure chamber with a low pressure port for connection to a low pressure reservoir, wherein the pressure in the low pressure reservoir determines whether communication is opened between the inlet and outlet ports and wherein the valve member has two parts which are movable relative to one another, a first part being adapted to open and close communication between the inlet and outlet ports and the second part being exposed to pressure in the low pressure reservoir, the first and second parts being relatively movable between a first position where there is no communication between the high pressure inlet port and the low pressure reservoir, a second position where there is a restricted communication between the high pressure inlet port and the low pressure reservoir, and a third position where communication is opened between the inlet and outlet ports.

The body preferably has two cylinder portions of differing diameters, the first part of the valve member being in the form of a piston having a small diameter portion working in the smaller diameter cylinder and the second part of the valve member being also in the form of a piston, with a large diameter portion working in the large diameter cylinder. The first part of the valve member preferably has a bore, and a shank of the second part slides in the bore.

A gas-tight seal preferably exists in the bore when the first and second valve parts are in the first position and in the second position, the shank moves in the bore to allow a restricted passage to open between the high pressure inlet port and the low pressure chamber. The gas-tight seal can be formed by an 0-ring between the bore and the shank, and the restricted passage can takes the form of relieved portions of the shank surface which, in the second position, extend on either side of the 0-ring to allow flow past the 0-ring.

The restricted passage can include transverse and longitudinal passages in the bore of the second valve member part, communicating with the low pressure space.

The bore of the first part of the valve member can have a cap with an aperture through which the shank of the second part of the valve member passes, and the shank can have a shoulder which engages behind the cap when the second part of the valve member moves out of the first part, so that the shoulder makes contact with the cap to entrain the first part with the second part.

The second part of the valve member can be biased by a spring in the direction of the low pressure reservoir.

A snifting valve in the valve body allows the space behind the large diameter piston portion to vent to atmosphere during normal operation, but to close when the valve member parts are in the third position.

According to a further aspect of the invention, there is provided a valve having a housing with a high pressure inlet port, a high pressure outlet port, a low pressure port and a valve member working in the housing, wherein the housing has two concentric bores of different diameter and the valve member has a large diameter piston working in the large diameter bore and a small diameter piston working in the small diameter bore, wherein the low pressure port communicates with the large diameter bore and the large diameter piston, the high pressure inlet port communicates with the small diameter bore and the small diameter piston, and the valve member is movable between a first position where there is no communication between the high pressure inlet port and the low pressure bore, a second position where there is a restricted communication between the high pressure inlet port and the low pressure bore, and a third position where communication is opened between the high pressure inlet and outlet ports.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic cross-section through a valve forming a first embodiment of the invention; Figures 2 to 4 show the embodiment of Figure 1 in three different operating states; Figure 5 is a schematic cross-section through a valve forming a second embodiment of the invention; Figure 6 is a schematic cross-section through a valve forming a third embodiment of the invention.; Figure 7 is a schematic cross-section through a valve forming a fourth embodiment of the invention; and Figures 8 and 9 show the embodiment of Figure 7 in two different operating states.

DETAILED DESCRIPTION

The valve shown schematically in Figures 1 to 6 has a housing 10 with a high pressure inlet port 12 and a high pressure outlet port 14. The housing also has a low pressure port 16. The terms high pressure and low pressure are intended to be relative and do not relate to any absolute pressure values.

The valve can typically be used in a fire extinguisher system. In this application, the high pressure ports are part of a fire extinguishant circuit with the port 12 being connected to a cylinder containing, for example CO2 at a pressure of 60 to 100 bar, and the outlet port being connected to a system of disperser nozzles so that when the valve is open, CO2 from the cylinder is passed to the nozzles to extinguish a fire.

The inlet port 12 is shown in Figures 1 to 6 as a simple threaded spigot, but the connection can take any appropriate form to enable it to be attached to any desired pressure cylinder or pressure circuit. For example, this port could be a tapered fitting as shown at 100 in Figures 7 to 9.

The low pressure port in this case can be connected to a thermoplastic tube 18 which contains a gas under pressure, for example at 10 bar, the tube being adapted to burst and release the pressure when it is exposed to excessive heat.

Such tubes are sold under the Registered Trade Mark FIRETRACE. Effectively, the pressure in the tube 18 watches for the occurrence of a fire and bursts when a fire (or an imminent fire) is in the vicinity of the tube, and the release of the pressure in the tube causes the valve to open to dispense fire extinguishant.

The embodiment of Figure 1 will now be described, and the manner of operation will become more apparent from Figures 2 to 4.

Within the housing is a valve member 20 which has a large diameter piston 22 working in a large diameter cylinder 24 and a small diameter piston 26 working in a small diameter cylinder 28. Both pistons are formed in the valve member 20 which is a single component. The piston 22 is provided with sealing 0-rings 30 to seal against the walls of the cylinders 24. The piston 26 is provided with sealing 0-rings 32a and 32b which are axially spaced apart, for reasons which will become apparent. The valve member also has an axial passage 34 which extends between the low pressure chamber 36 and the space between the 0-rings 32a and 32b. A one-way valve 40 is fitted in this passage to permit flow only in the direction towards the low pressure chamber 36.

A compression coil spring 38 acts between an end of the housing 10 and the large diameter piston 22.

In use, in the position shown in Figures 1 and 2, the system is commissioned by charging the tube 18 and the chamber 36 with a gas at an appropriate pressure.

This causes the cylinder 22 to be biased to the left (as seen in the Figures) and to compress the spring 38. The piston will come to rest against the end of the cylinder 28. In this position, the 0-ring 32a will close the high pressure inset port 12.

When high pressure is applied at the inlet port, the pressure which it exerts on the valve member 20, against the small diameter piston 26, will be insufficient to move the valve member to the right, so the inlet port will stay closed. Clearly the operating pressures and the piston sizes will have to be designed with a knowledge of the operating pressures at which the valve will be used.

Figure 2 therefore shows the normal position, when the system in which the valve is installed is active, ie is monitoring a space ready to detect a fire or an imminent fire.

Figure 3 shows the situation where there is a slight leak of pressure from the tube 18. As the tube 18 connected to the chamber 36 is a closed system, there may be a small drop of pressure in that system over a period of time, as the low pressure system will often be static for a period of many years. The pressure may drop unavoidably by very slow leakage of gas through the tube walls, for example.

When the low pressure drops (indicated in Figure 3 by a small gas escape at 44), the opposing pressure from the high pressure acting on the piston 26, together with the pressure of the spring 38 will move the valve member to the right. When this happens, the 0-ring 32a moves into a region 42 of the cylinder 28 where the cylinder wall is slightly relieved. For example, there could be a small scratch or groove in the cylinder wall which would allow high pressure gas to leak past the 0-ring 32a into the space between the 0-rings 32a and 32b. The high pressure can then enter the passage 34 and pass through that passage into the low pressure chamber 36, where it adds to the pressure acting on the piston 22 which is then urged back to the position of Figure 2.

However if there is a large and catastrophic drop in pressure in the low pressure system, as would be the case if the tube 18 burst (indicated in Figure 4 by a large gas escape at 46), then all pressure would immediately be lost in the chamber 36 and the valve member would move all the way to the right (see Figure 4), the high pressure would enter the interior of the housing 10 and would be able to flow freely through the outlet 14.

The valve as described will therefore, under normal operating conditions, keep the low pressure system topped up. If the pressure drops, the valve member will move to the Figure 3 position, pressure from the high pressure system will enter the low pressure system to top it up, and the valve member will then move back to the Figure 2 position. The relieved portion 40 of the cylinder 28 needs only to allow a very small flow past the first 0-ring 32a, for this mode of action to be effective. It will also be seen that the relieved portion 42 has a tapered configuration, such that as the 0-ring 32a first begins to overlap with the relieved portion, only a small passage will open around the edge of the 0-ring, but as the piston moves further to the right, the cross-sectional area of this passage will increase. As a result, the movement of the piston will be smooth and not jerky.

This valve is simple to manufacture, as the two cylinder bores can each be machined in separate components without any steps, shoulders or cross bores, with a seal between the components being necessary only at the interface 44.

Figure 5 shows how additional high pressure inlet ports 50 can be added, upstream of the valve, to both feed in to the same, common outlet port 14. This enables a larger volume of high pressure gas to be controlled by one and the same valve, and may be necessary when the system potentially requires a large volume of extinguishant in the event of a fire.

In Figure 5, the low pressure chamber also has a pressure relief valve 52.

Figure 6 shows a modification in which the high pressure gas, when the valve opens, flows not only through an outlet pipe 60, but also back through the plastic tube 18 (which now has a burst in it). Normally, the tube 18 would not be able to handle the high pressure gas without failing. However once the tube has failed, the high pressure gas can flow along the tube, to exit at the burst which is the point at which the tube has sensed the most heat, ie where the fire or the seat of the fire is located.

In this case, a manifold 62 is fitted at the outlet port 14. This manifold allows flow into an outlet pipe 60 and also, through a one-way valve 64, into a connecting tube 66 which connects, through a second manifold 68, into the tube 18. A one-way valve 70 prevents flow back into the low pressure chamber 36. The one-way valve may be of the type which allows controlled flow into the chamber 36, so as to allow the chamber to be charged with pressure on commissioning, but prevents uncontrolled flow such as would occur when the high pressure system feeds into thetubel8.

The pressure in the high pressure system (typically connected to a pressurised gas bottle) can vary over time, in particular with varying climatic conditions.

The spring 38 is not essential, but offers the advantage that its presence allows the valve to operate in the same manner over a wider range of climatic conditions than would otherwise be the case.

The operation of the valve described here relies on the difference in the exposed areas of the pistons 22 and 26. Where the pressure differences between the low and high pressure sides of the system are high, it may be necessary with the previous embodiments to make the piston 22 rather large. To avoid this, an alternative embodiment is shown in Figures 7 to 9.

The valve shown in Figures 7, 8 and 9 has a high pressure inlet port 100 and a high pressure outlet port 102. In the closed position shown in Figure 7 the passage from the inlet port 100 to the outlet port 102 is closed by a valve member 104 which sits on a valve seat 106. The valve seat 106 would normally be a compliant rubber or similar surface.

The valve member 104 is one end of a multi-part piston arrangement, the other end of which carries a piston head 108 which works within a low pressure space 110. The low pressure space is connected to an external space, typically a FIRETRACE tube (FIRETRACE is a Registered Trade Mark), which contains a fixed volume of gas at a (relatively) low pressure. The tube will be connected through the port 109. In the closed position shown in Figure 7 (which is the position in which the valve is to be found practically all of the time in operation) the low pressure in the space 110 biases the piston head 108 to the left.

The piston assembly comprises an outer sleeve 112, an inner sleeve 114 and a piston shank 116 fixed to the piston head 108.

The outer sleeve 112 has a narrow bore 118 leading from the high pressure inlet into the interior space of the sleeve 114. This space carries reference numeral 120. The shank 116 is sealed against the internal bore of the sleeve 112 by 0-rings 122, 124, such that, in the closed position shown in Figure 7, the chamber 120 is closed. The forces acting on opposite ends of the piston and shank 108, 116 are such that the pressure exerted by the low pressure gas in the chamber 110, acting on a large area of piston head 108 is greater than the force exerted by the high pressure acting on this smaller diameter left-hand end of the shank 116, and thus the closed position shown in Figure 7 is maintained under normal operation.

However, if the pressure in the chamber 110 drops, the valve member moves.

In a first scenario, the pressure in the chamber 110 drops by only a small amount.

This situation may occur over the lifetime of the system in which the valve is incorporated, for example by very minor leakage of the pressure either through joints in the system or through the walls of a tube attached to the low pressure space 110.

In this situation, the position shown in Figure 8 is taken up temporanly. When the pressure in the chamber 110 drops, the pressure in the space 120 is sufficient to begin to move the piston to the right. It will be seen that the left-hand end of the piston has longitudinal grooves 128 in the piston surface. In a position shown in Figure 7, these grooves do not communicate with any other space, but once the grooves overlap the 0-ring 122, the high pressure from the space 120 can pass along the grooves 128 into an intermediate space 130. From their the pressure passes into a transverse bore 132, and a long longitudinal bore 134 into the low pressure space 110, where the low pressure space is "topped-up" with pressure from the high pressure inlet. The result of this is that the pressure acting on the piston head 108 will increase, and the piston head and shank will move back to the left to reoccupy the position shown in Figure 7, and this movement takes place without the high pressure passage becoming open.

Effectively, in the Figure 8 position there is a trickle recharging of the space 110 to replace the pressure lost through minor leakage in the system.

It will be noted that the space 130 into which high pressure gas can penetrate through the grooves 128 is bounded on the right-hand side by the 0-ring 124, so that the high pressure gas is forced to enter the transverse bore 132 which communicates with the longitudinal bore 134, but cannot reach the part of the space 110 behind the piston head 108.

The second scenario is where there is a catastrophic loss of pressure in the low pressure circuit, and when this happens it leads to a full opening of the high pressure passage as shown in Figure 9. This situation typically applies when a FIRETRACE tube connected to the port 109 bursts after sensing the presence of excessive temperatures.

In this case when all pressure is suddenly lost in the low pressure space 110, the high pressure passing through the bleed passage 118 and acting on the left-hand end of the shank 116 has no opposing pressure in the chamber 110 to work against and therefore this drives the shank 116 and the piston 108 fully to the right. In doing so, a shoulder 136 on the shank 116 makes contact with an opposing shoulder 138 at the end of the sleeve 114, to entrain the sleeve 114 -11 -which then moves to the right, thus opening the high pressure circuit. The force exerted by the high pressure on the left-hand end of the shank 116 wilt be greater than the pressure exerted on the annulus 140 behind the valve member 104, the annulus being part of the sleeve 114 and which will normally assist in keeping the high pressure circuit closed. In this position, which can arise, for example, if the FIRETRACE tube bursts, the high pressure circuit will open to allow fire extinguishant to be released to extinguish a fire.

It will be noted that the housing 142 includes a snifter valve 144 to ensure that any pressure which builds up behind the piston head 108 does not build up to oppose the low pressure in the chamber 110. The snifter valve (shown schematically in the figures) has a ball 146 which normally drops down under the influence of gravity so that the space 151 behind the piston 108 is unpressurised. It will be noted that this space is sealed from the low pressure space by peripheral seals 148 around the piston head 108 and by 0-rings 150 between the housing 142 and the valve outer sleeve 112. However when the high pressure circuit is opened, in the position of Figure 9, high pressure can reach the space 151 behind the piston head 108, through the bleed passage 118, the chamber 120 and around the outside of the shank 116. When high pressure is thus present in the space behind the piston head 108, the valve ball 146 is urged upwards to close the snifter valve 144.

It will also be seen in all the Figures that a helical spring is provided in the chamber 120. This spring 150 normally provides a force acting with the high pressure gas on the left-hand end of the shank 116. Under normal operating conditions, the forces acting on the piston head 108 through the pressure in the low pressure space 110 are sufficient to overcome both the high pressure acting on the left-hand end of the shank 116 and the force of the spring 150. The spring is present to compensate for variations in the magnitude of the high pressure acting through the inlet 100. This pressure can vary quite substantially according to climatic conditions. If the high pressure reservoir should be at a lower than normal pressure at the time when the valve needs to move, the spring 150 will -12-assist the "lower than normal' high pressure so that the valve functioning is assured, if the valve needs to move to effect a trickle refilling of the low pressure space 110.

It will be seen from Figures 7 to 9 that the housing 142 is closed by an end plate 142a. The internal bores in the housing can all be formed by milling out the appropriate diameters from one end (or both ends), before the end plate is fitted.

Claims

CLAIMS

1. A valve having a body with a high pressure inlet port and a high pressure outlet port, a valve member movable within the body for opening and closing communication between the inlet and outlet ports and a low pressure chamber with a low pressure port for connection to a low pressure reservoir, wherein the pressure in the low pressure reservoir determines whether communication is opened between the inlet and outlet ports and wherein the valve member has two parts which are movable relative to one another, a first part being adapted to open and close communication between the inlet and outlet ports and the second part being exposed to pressure in the low pressure reservoir, the first and second parts being relatively movable between a first position where there is no communication between the high pressure inlet port and the low pressure reservoir, a second position where there is a restricted communication between the high pressure inlet port and the low pressure reservoir, and a third position where communication is opened between the inlet and outlet ports.

2. A valve as claimed in Claim 1, wherein the body has two cylinder portions of differing diameters, the first part of the valve member is in the form of a piston having a small diameter portion working in the smaller diameter cylinder and the second part of the valve member is also in the form of a piston, with a large diameter portion working in the large diameter cylinder.

3. A valve as claimed in Claim 2, wherein the first part of the valve member has a bore, and a shank of the second part slides in the bore.

4. A valve as claimed in Claim 3, wherein a gas-tight seal exists in the bore when the first and second valve parts are in the first position and in the second position, the shank moves in the bore to allow a restricted passage to open between the high pressure inlet port and the low pressure chamber.

5. A valve as claimed in Claim 4, wherein the gas-tight seal is formed by an 0-ring between the bore and the shank, and the restricted passage takes the form of relieved portions of the shank surface which, in the second position, extend on either side of the 0-ring to allow flow past the 0-ring.

6. A valve as claimed in Claim 4 or Claim 5, wherein the restricted passage includes transverse and longitudinal passages in the bore of the second valve member part, communicating with the low pressure space.

7. A valve as claimed in any one of Claims 3 to 6, wherein the bore of the first part of the valve member has a cap with an aperture through which the shank of the second part of the valve member passes, and wherein the shank has a shoulder which engages behind the cap when the second part of the valve member moves out of the first part, so that the shoulder makes contact with the cap to entrain the first part with the second part.

8. A valve as claimed in any preceding claim, wherein the second part of the valve member is biased by a spring in the direction of the low pressure reservoir.

9. A valve as claimed in any preceding claim, wherein a valve in the valve body allows the space behind the large diameter piston portion to vent to atmosphere during normal operation, but to close when the valve member parts are in the third position.

10. A valve having a housing with a high pressure inlet port, a high pressure outlet port, a low pressure port and a valve member working in the housing, wherein the housing has two concentric bores of different diameter and the valve member has a large diameter piston working in the large diameter bore and a small diameter piston working in the small diameter bore, wherein the low pressure port communicates with the large diameter bore and the large diameter piston, the high pressure inlet port communicates with the small diameter bore and the small diameter piston, and the valve member is movable between a first position where there is no communication between the high pressure inlet port and the low pressure bore, a second position where there is a restricted communication between the high pressure inlet port and the low pressure bore, and a third position where communication is opened between the high pressure inlet and outlet ports.

11. A valve substantially as herein described with reference to Figures 1 to 4 or Figure 5 or Figure 6 or Figures 7 to 9 of the accompanying drawings.