GB2163532A - Flow control valve - Google Patents

Abstract

In the flow control valve comprising a valve seat 8 and a valve member 10 movable between a closed flow position on the valve seat substantially to prevent flow through the valve and an open flow position spaced from the valve seat, a leakage path is provided between the seating surfaces of the valve member and valve seat in the closed position. Alternatively a flow control valve has a valve chamber 5 min an a valve plate longitudinally movable within the valve chamber, the cross- sectional area of the valve plate being less than the coplanar cross-section area of the chamber; the valve chamber wall or protrusions 20 therefrom about points on the plate periphery substantially to prevent lateral movement thereof. <IMAGE>

Description

SPECIFICATION Flow control valve This invention relates to a flow control valve, more particularly but not exclusively for use as a non-return valve in pumps primarily for firefighting purposes.

In the use of pumps for fire-fighting purposes a common requirement is to discharge at low flow rates through a hose reel holding reinforced rubber hose of, say, 2.5 cm diameter. When fire pumps are being fed with water from a hydrant connected to the public water supply system, it is required by some authorities to feed into the pump through a non-return valve in a collecting head to avoid any possibility of water being forced back into the water main.

When subjected to the high operating pressures which are now being used by fire services the hose expands somewhat and the resulting increase in diameter over the whole length of the hose retains a substantial volume of water at the operating pressure. When the discharge nozzle at the downstream end of the hose is closed, the flow ceases and the non-return valve in the collecting head closes.

If the pump is now shut down, it is no longer developing the pressure to retain the charge of pressurized water in the hose, and this feeds back into the pump and collecting head.

Since the non-return valve is closed the retained pressure cannot dissipate and may result in failure of the collecting head.

It is known to fit to the high pressure fire pump a valve to bypass a small flow of water to the fire engine water tank, the purpose of which is to allow heat dissipation when the pump is operated against closed discharge.

This bypass flow can be used to dissipate the pressurized water stored in the expanded hose provided that the rate of feed back of this water is reduced to a low level. However, when fighting fires, a fire hydrant connected to the water main may not be available and it may be necessary to use whatever water is available. Often this water contains solid matter such as sand or grit and conventional relief valves are subject to sticking or blockage as a result of such particulate material getting into the valve.

It is an object to provide a flow control valve capable of dissipating the retained water pressure but which at the same time is less prone to sticking or blockage as a result of particulates in the water supply.

In accordance with one aspect of the present invention a flow control valve comprises a valve seat and a valve member movable between a closed flow position on the valve seat substantially to prevent flow through the valve and an open flow position spaced from the valve seat, in which a leakage path is provided between the seating surfaces of the valve member and valve seat in the closed position.

The leakage path is preferably provided by a surface discontinuity of the seating surface of the valve seat and/or the seating surface of the valve member. By surface discontinuity is meant that one or other or both surfaces are provided with an area over which the surfaces do not fully meet in the closed position. The seating surfaces of the valve member and valve seat may be spaced from one another over part of their area to provide the said leakage path. The spacing formed by the discontinuity may for example be a groove or a notch in one or other member across the seating surfaces.

In a preferred form of the invention the valve seat is substantially planar (and for example annular) and the valve member is a substantially planar plate, the leakage path in this form of the invention being provided by a notch or groove across the seating surface of the valve plate and/or the valve seat. With both valve seat and the valve plate having substantially planar seating surfaces, those surfaces when engaged in the closed position prevent flow through the valve. The leakage path permits a small flow. If the leakage path becomes blocked during leakage flow through it, for example by particulate material, as soon as the valve member is lifted from the valve seat to allow flow through the valve, the flow will remove the particulate matter from the leakage path.

In accordance with a further aspect of the present invention a flow control valve comprises a valve chamber provided with a first and second ducts opening into the chamber, the first duct terminating in the chamber in a substantially planar annular seating and, within the chamber, a closure member in the form of a plate which is arranged to be forced off the seating and to allow comparatively unimpeded liquid flow from the first duct through the chamber around the edge of the closure member and out of the second duct when the pressure in the first duct is greater than that in the second duct, but which, when the pressure in the second duct is greater than that in the first duct, rests on the seating, a groove or notch being provided between the seating and the plate such that the liquid flow from the chamber into the first duct is limited essentially to that which can pass between the seating and the plate through the notch or groove.

In the preferred form of the invention the notch or groove is provided across the seating surface of the valve seat. There may be a single notch or groove provided around the periphery of the valve seat. However in a more preferred form of the invention two such notches or grooves will be provided thereby reducing the chances of blockage of the leakage path in the first place. More than two grooves or notches may be provided. However it must be borne in mind that the crosssectional area of the leakage path or paths must be tailored to the leakage rate required, and an increase in the number of notches or grooves will require the notches or grooves to be smaller for a given leakage flow rate with consequent machining and accuracy difficulties and increase the likelihood of blockage.

The notch or groove, whether it be in the valve seat surface or the valve member/plate surface may be of any configuration for example radial. The notch or groove may be U-shaped, V-shaped or whatever may be appropriate having regard to the need for the notch or groove itself not to retain particulate matter when the valve member/plate is removed from the valve seat.

In accordance with a further aspect of the invention a flow control valve having a valve chamber and a valve plage longitudinally movable within the valve chamber and in which the cross-sectional area of the valve plate is less than the coplanar cross-sectional area of the chamber provides for the valve chamber walls or protrusions therefrom to abut points on the plate periphery substantially to prevent lateral movement thereof.

The chamber walls and the valve plate may preferably be substantially circular in crosssection and be provided with three or more longitudinal protrusions, such as ribs, from the chamber wall to abut the plate for lateral location thereof.

The valve of this last aspect of the invention may preferably be a valve as defined above in relation to any of the preceding aspects of the invention. The greater area of the valve chamber as against the area of the valve plate permits passage of fluid between the valve plate and the chamber when the valve plate is spaced from the valve seat. The abutment of the chamber walls or protrusions with points on the plate periphery in effect spaciously locate the plate within the chamber.

Maintaining the contact between the locating points and the plate periphery as small as possible reduces frictional factors between the plate and the chamber and moreover minimises the possibility of inhibiting the longitudinal movement of the valve plate due to the entrained particulates in the fluid flowing through the valve.

In this aspect of the invention the term "longitudinal" is used to refer to the general direction of flow of fluid through the valve, the term lateral referring to the planes substantially at right angles thereto.

In accordance with a final aspect of the invention a fire pump comprises a fluid control valve as set out in any of the above defined aspects of the invention.

The fire pump arrangement preferably includes some form of non-return valve which may or may not be within a collecting head located between the pump inlet and the fluid source, the valve the subject of the present invention being placed between the pump high pressure outlet and the hose.

A valve of this construction may be cheap and simple, not least because a comparatively poor fit when the plate is resting on the seating is acceptable. There is little danger of the small flow control being impeded by particulate matter since the flow control passage is essetially through the notch or groove, and any other slight gap between the seating and plate, and the notch or groove, will be flushed out each time the plate lifts off the seating upon discharge through the valve.

It is equally important for there to be some loose guidance of the plate closure member within the chamber towards and away from the seating, but for the edge of the plate to be spaced sufficiently from the chamber wall for there to be substantially uninterrupted flow between the chamber wall and the plate around the edge of the plate. One simple solution is to provide the inner surface of the chamber wall as a cylinder, coaxial with the seating, and to provide the closure member plate in the shape of a regular polygon, such as a hexagon, pentagon, or preferably square.

The corners of the plate will then abut the chamber wall with a working clearance to centre the plate in the chamber and relatively to the seating but there will be adequate passage between the circular wall of the chamber and the flats on the edge of the plate for unimpeded flow.

A further solution, as discussed above, is to provide for longitudinal protrusions from the valve wall to make point contact with sufficient points on the periphery of the valve plate to prevent lateral movement to the valve plate.

The second duct is preferably provided opposite to and substantially coaxial with the first duct and also terminates in the chamber in an annular seating, so that the plate is movable between the two seatings depending upon the pressure differential in the two ducts. However, since there must be substantially unimpeded flow from the chamber into the second duct when the plate closure member is seated on the seating at the end of the second duct, the second duct may be provided with a ring of apertures opening through an end portion of the second duct which projects into the chamber, behind the respective seating.

Various aspects of the invention may be performed in various ways. Two particular embodiments will now be described, by way of example, with reference to the accompanying drawings in which: Figures 1 and 2 are axial sections of a valve showing the closure member plate in its two different operative positions; Figure 3 is a section taken on the line A-A in Fig. 2, Figure 4 is a perspective view of part of the valve which has been cut on the line A-A in Fig. 2, and with the plate closure member having been removed; Figure 5 is a section corresponding to that as shown in Fig. 3 of a further chamber and plate arrangement, and Figure 6 is a schematic representation of a typical arrangement of the valve of Fig. 1 in relation to a fire pump.

Referring the drawings, the illustrated valve 4 has a cylindrical chamber 5, through the end walls of which extend first and second ducts 6 and 7, which are externally screw threaded outside the housing, for connection to other plumbing. The two ducts extend into the housing and terminate in annular seatings 8 and 9 respectively, between which a square plate closure member 10 may move. The seating 8 is provided with a notch 11. Behind the seating 9 the part of the duct 7 projecting into the chamber is provided with a ring of ports 12. Fig. 1 shows the position in which comparatively unimpeded flow is provided through the valve from the duct 6 around the plate 19 and through the ports 12 to the duct 7. Fig. 2 shows the alternative position in which the return flow is limited essentially to that which can pass between the plate 10 and seating 8 through the notch 11.

Thus in operation the ducts 6 and 7 will function respectively as inlet and outlet. The duct 7 will be connected to a pressure hose.

When the discharge end of the pressure hose is closed down a return pressure from the outlet 7 to the inlet 6 will manifest itself. That will cause the plate 10 to seat on the valve seat 8. Excess pressure on the outlet side of the plate 10 will be allowed dissipate through the leakage path provided between the notch 11 and plate 10. If that notch 11 is obstructed for example by grit or dirt carried into the valve by the water, then that may in that cycle of operation prevent dissipation of excess pressure through the leakage path. However when next pressure is generated in the inlet side 6 as against the outlet side 7 of the valve, the plate 10 will lift from the seat 8.

As the notch or groove 11 is open to flow from the duct 6 to the duct 7 around the plate 10 any blockage will tend to be cleared therefrom by that flow. The valve of the invention is therefore self cleaning.

A preferred location of a notch 11 is shown in Fig. 4. In a further embodiment not shown a further notch 11 may be provided diametrically opposed to that shown on the other side of the seat 8.

Referring now to Fig. 3 it will be seen that the valve plate in this embodiment of the invention is substantially square in cross-section. An exaggerated clearance is shown in drawing between the four corner points 15 and the inner wall 18 of the valve chamber 5.

Idealy knife edged abutting contact between the points 15 and the chamber wall 18 would be provided. However that may cause difficulties both of manufacture and wear and in a further form of the invention (not shown), the corners 16 may be chamfered or rebated.

This will result in a loss of some of the advantages of point contact but may be of benefit in terms of manufacturing and wear.

Referring now to Fig. 5 the chamber 5' is provided with four longitudinally extending protrusions or ribs 20. Each of the ribs has an innermost point 25. The four points 25 lie on a circle substantially coaxial with the inner wall 18' of the chamber. The valve plate used in this aspect of the invention is not shown but is a substantially flat circular disc of diameter a distance very slightly less than the distance between diametrically opposed points 25. In this form of the invention the valve plate (not shown) is located and prevented from lateral movement by the four points 25 although at the same time being permitted longitudinal movement (in and out of the plane of the paper in Fig. 5).This contrasts with the arrangement of Fig. 3 where it is the abutment of points 15 with the inner wall 18 of the valve chamber 5 which prevents lateral movement of the valve plate 10 but allows longitudinal movement (again into and out of the plane of the paper in Fig. 3).

Referring now to Fig. 6 there will be seen a schematic diagram showing the arrangements of the various integers of a fire pump including a valve 4 as described above. The arrangement comprises a pump 30 and a collecting head 32 along with a hose 34. The collecting head 32 has within it a non-return valve to prevent return of water through the collecting head 32 back to the water source A. The pump 30 has a high pressure outlet connected to the valve 4 and a lower pressure outlet 36 not relevant for the purposes of the present invention. The valve 4 is interposed between the high pressure outlet of the pump 30 and the hose 34. If required the valve 4 may be connected directly to the pump 30 as indeed the collecting head 32 may be connected directly to the pump 30.

In operation the pump 30 will draw water from the source A through the collecting head 32 with the collecting non-return valve in the open position. It will deliver water through the valve 4 with the valve plate 10 in the condition shown in Fig. 1. The hose 34 may be provided with a shutdown valve at its discharge nozzle 35. When that is closed the flow through the hose 34 ceases and the nonreturn valve in the collecting head 32 closes.

If the pump 4 is now shutdown any pressure retained in the hose 34 by expansion of the hose will force the valve 4 into the condition shown in Fig. 2. The leakage path in the valve will permit slow dissipation of the excess pressure in the hose 34 back into the pump.

The pump is provided with a by-pass 31 the principle purpose of which is to allow heat dissipation when the pump is operated against a closed discharge. However that by-pass 31 will here function also to dissipate the leakage pressure from the hose 34 through the valve 4.

By this mechanism the valve 4 prevents a sudden surge of back pressure from the hose 34 to the pump. The leakage path through the valve 4 enables the excess pressure in the hose 34 to dissipate back into the pump at a sufficiently slow rate that the existing by-pass 31 may cope with that dissipation thereby avoiding the cause of failure of the non-return valve in the collecting head to which previous arrangements have been prone.

Claims (12)

1. A flow control valve comprising a valve seat and a valve member movable between a closed flow position on the valve seat substantially to prevent flow through the valve and an open flow position spaced from the valve seat, in which a leakage path is provided between the seating surfaces of the valve member and valve seat in the closed position.

2. A valve as claimed in Claim 1 in which the leakage path is provided by a surface discontinuity of the seating surface of the valve seat and/or the seating surface of the valve member.

3. A valve as claimed in Claim 1 or Claim 2 in which the seating surfaces of the valve member and the valve seat are spaced from one another over a part of their area to provide the said leakage path.

4. A valve as claimed in any of Claims 1 to 3 in which the leakage path is provided by a groove or notch across the seating surface of the valve member and/or valve seat.

5. A valve as claimed in any of Claims 1 to 4 in which the valve seat is substantially planar and the valve member is a substantially planar plate, and in which the leakage path is provided by a notch or groove across the seating surface of the valve plate and/or valve seat.

6. A flow control valve comprising a valve chamber provided with a first and second ducts opening into the chamber, the first duct terminating in the chamber in a substantially planar annular seating and, within the chamber, a closure member in the form of a plate which is arranged to be forced off the seating and to allow comparatively unimpeded liquid flow from the first duct through the chamber around the edge of the closure member and out of the second duct when the pressure in the first duct is greater than that in the second duct but which, when the pressure in the second duct is greater than that in the first duct, rests on the seating, a groove or notch being provided between the seating and the plate such that the liquid flow from the chamber into the first duct is limited essentially to that which can pass between the seating and the plate through the notch or groove.

7. A flow control valve as claimed in Claim 1 and substantially as described herein with reference to the accompanying drawings.

8. A flow control valve having a valve chamber and a valve plate longitudinally movable within the valve chamber, the cross-sectional area of the valve plate being less than the coplanar cross-sectional area of the chamber, in which the valve chamber wall or protrusions therefrom abut points on the plate periphery substantially to prevent lateral movement thereof.

9. A valve as claimed in Claim 8 in which the chamber walls and the valve plate are substantially circular in cross-section and in which three or more longitudinal protrusions from the chamber wall abut the plate for lateral location thereof.

10. A flow control valve as claimed in Claim 8 and substantially as described herein with reference to the accompanying drawings.

11. A valve as claimed in any of Claims 8 to 10 further comprising the claimed features of any of Claims 1 to 7.

12. A fire pump comprising a fluid control valve as claimed in any of the preceding claims.