GB2243667A - Reversible check valve - Google Patents

Abstract

A check valve 8 is mounted in a through passage of the ball 9 of a shut-off valve. The ball may be positioned such that (a) fluid may pass from an inlet to an outlet but may not pass from the outlet to the inlet (fig 3a) or, (b) no fluid may pass through the valve (fig 3b) or, (c) fluid may pass from the outlet to the inlet but may not pass from the inlet to the outlet (fig 3c). <IMAGE>

Description

IMPROVEMENTS RELATING TO THE PREVENTION OF CONTAMINATION OF FLUID OR WATER SUPPLIES BY BACKSIPHONAGE OR BACKFLOW Short Title: Reversible Check Valve The invention relates to the prevention of backsiphonage backs low or backsuction in fluid or water supplies conveyed by closed pipe systems to and within premises and the testing and verification of the operation and efficiency of such devices. In essence the invention is a check valve otherwise known as a non-return valve which can be readily, rapidly and temporarily reversed in the direction of fluid flow in a pipework system in order to verify that the device is operating correctly and then relocated in its normal operating mode. The following description of the invention commonly refers to potable water supplies as this is the situation where backsiphonage is of most concern to the public health.

Backsiphonage occurs under circumstances where there is either complete or partial pressure loss in systems conveying water under pressure to taps or outlets on premises such that a suction or vacuum or siphonage occurs which can reverse the normal direction of fluid flow such that extraneous fluid or water or substances are drawn into the pipework system causing contamination thereof. Devices for the prevention of such contaminations are well known as non-return valves or check-valves which are inserted serially in the pipework system and are so arranged to close to provide a substantially fluid-tight seal under conditions of potential reversal of flow.

One of the main problems with such check valves used to prevent backsiphonage in water supplies is that their fluid tightness under conditions of flow reversal can not be tested satisfactorily in situ. Recognising this problem, water undertakers commonly stipulate an assembly of two check valves in series in the water flow including a test drain valve or drain plug interposed between them. This assumes that two serial check valves are inherently more reliable than one; if one valve fails it is assumed that the other one still functions, but no rapid and positive verification procedure has hitherto been available.

To test the present typical double check valve assembly, the supply has to be isolated and a back pressure applied to an outlet downstream of the double check valve assembly; if water emerges from the opened drain valve between the two check valves then a fault is assumed. However, this procedure is time consuming, difficult in practice and only tests the fluid tightness of the downstream check valve. The test is also unreliable as the check valve can not be tested under full working pressure.

The present invention provides a method whereby a non-return valve, check-valve or any assembly of more than one of the aforementioned can be arranged such that it is possible readily and temporarily to reverse the valve(s) against the direction of flow of fluid in the system such that fluid tightness can be tested at full working pressure without the need to apply a back pressure downstream of the valve or to incorporate any test drain valves upstream of the check valve to be tested. The test can be conducted in a matter of seconds by simply opening an outlet downstream of the check valve and reversing the valve temporarily against the direction of flow by the means later to be described in this specification. If any significant amount of fluid continues to emerge from the opened outlet then a fault is assumed.If all fluid flow substantially ceases then the valve is deemed satisfactory in function and on turning the check valve back to its original direction normal operation of the system is resumed.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings (Figures 1 to 3) Referring to Figure 1., a typical ball-plug type of stopvalve or shut-off valve is shown. This type of valve is well known for the control of fluid flow in liquid or gas systems and its use is becoming increasingly common in the control of water supplies.

Its usual form for the control of water supply consists of a spherical polished metal plug, or plastics plug (1) bored through as shown. This plug is mounted in a metal or plastics body (2) such that it can be rotated within the body by means of a control lever (3). Seals are provided (4) to ensure fluid tightness whilst allowing free rotation of the ball-plug within the body.

The body is provided with inlet and outlet ports (5). In operation, the valve is open to allow free flow of fluid when the bore of the plug lies parallel with the axis of the body as shown in Figure 1. Rotation of the ball-plug through one quarter turn closes the valve to fluid flow when the bore of the plug lies perpendicular to the axis of the body.

Referring to Figure 2., a typical non-return valve or check valve is shown. This type of valve is well known for the prevention or limitation of reverse flow in fluid systems as previously explained. Its typical form consists of a housing (1) surrounding a sliding plug (2) which when moved in one direction by fluid movement within the pipe in which it is located forms a substantially fluid tight seal preventing further flow of fluid within the system. When the sliding plug is moved in the opposite direction by fluid movement within the pipe, the valve opens and free flow of fluid within the system is allowed.

Figure 2a. shows the valve in the open position and Figure 2b in the closed position.

Referring to Figure 3a., the invention herein described consists of a typical check valve assembly (1) such as described previously by reference to Figure 2 mounted within the bore of the ball-plug (2) of a typical ball-plug stopvalve such as previously described by reference to Figure 1. The invention thus combines the functions of both check valve and plug-ball stopvalve in a single integrated device. In addition to the prevention of backs low by means of the check valve and the control of fluid flow by means of the ball-plug valve, the invention provides the facility rapidly to verify the function and fluid tightness of the integral check valve at full working pressure without the need to isolate the supply upstream of the device and without the requirement for a test point drain plug or drain valve upstream of the device.

Referring again to Figure 3., the operation of the invention in practice is explained. In the 'open' position the bore axis of the ball-plug valve is parallel to the direction of fluid flow and the integral check valve held open so that fluid passes freely through the device (Figure 3a). If the ball-plug is turned through 90 degrees by means of the control arm its bore axis lies perpendicular to the direction of fluid flow such that no fluid passes the internal seals. This is the 'closed' position (Figure 3b). If the ball-plug is again turned through a further 90 degrees from the 'closed' position, its axis again lies parallel to the direction of fluid flow but the integral check valve now faces the opposite direction and should therefore automatically close against the flow of fluid within the system as would be its normal action when acting as a non-return valve.

This is the 'test' position (Figure 3c). If a outlet is now opened downstream of the device, little or no fluid should emerge if the check valve is functioning normally and thus its correct functioning can be quickly verified or the device shown to be faulty, when it replacement would be considered. By turning the ball-plug through 180 degrees to the 'open' position, normal operation of the fluid system may be resumed.

Claims (5)

1. A reversible check valve comprising a valve housing having two ports, and a non-return valve positioned within the valve housing between the two ports, wherein the non-return valve is moveable between a first position in which it allows fluid to flow through the valve housing from a first one of the ports to a second one of the ports but prevents flow from the second port to the first, and a second position in which it allows fluid to flow through the valve housing from the second port to the first but prevents flow from the first port to the second.

2. A reversible check valve as claimed in claim 1, wherein a ball plug is rotatably housed within the valve housing, the said ball plug defining a bore extending therethrough in which the said non-return valve is mounted.

3. A reversible check valve as claimed in claim 2, wherein the said ball plug can be rotated through 180 degrees within the valve housing.

4. A reversible check valve as claimed in claim 2 or claim 3, wherein the said ball plug is connected to a lever extending from the valve housing.

5. A reversible check valve substantially as hereinbefore described with reference to Figures 2a, 2b, 3a, 3b and 3c of the accompanying drawings.