IL96024A - Cross-section apparatus - Google Patents

Description

a s-.-na*-n nanyn CROSS 30NNECTIGN APPARATUS FIELD OF THE INVENTION The present invention relates to cross-connection apparatus in general and, in particular, to a combination fluid meter and backflow preventer.

BACKGROUND OF THE INVENTION A variety of backflow preventing devices are known in the literature and on the market. Such devices are conventionally installed in water distribution systems to prevent backflow of contaminated water, particularly from institutions such as hospitals, factories, irrigation systems, fire protection sprinkler systems etc. The junction of this installation with the main water, line, or the junction of two different kinds of water, is known as a cross-connection. A cross-connection generally also includes a water meter for measuring the quantity of water flowing through the lines.

Conventional backflow preventing devices fall into two general categories, those suitable for use with contaminated water which presents health hazards and those suitable only for those materials which are objectionable but not toxic.

Generally these devices include an upstream and a downstream check valve with upstream and downstream shut-off valves, and four test cocks, one upstream and one downstream of each of the check valves. Those devices used to protect potable water supplies against hazardous materials in cross-connections generally operate on the reduced pressure principle. These devices include an intermediate or reduced pressure zone between the two check valves to provide drainage to the atmosphere through a relief valve if the second check valve fails to seal when the upstream supply pressure is suddenly reduced or the upstream is entirely drained.

A disadvantage of many of these devices is that, although they are required, they aire often so expensive to purchase and maintain and require such a large quantity of energy (pressure or head loss) that their use is limited.

In the same locations that a backflow preventer is required, generally a compound meter is also mounted, such as in hotels and other locations mentioned above. Compound meters are also expensive to purchase and maintain and they also require upstream and downstream manual:' valves to stop the flow through the line. Furthermore, compound meters includes a change-over valve which is, in effect, a type of non-return or check valve . . ^ In certain locations, such as sprinkler systems for fire detection and prevention, generally a main backflow preventer of large diameter is used which is opened only in case of fire (i.e., large water supply). In addition, a second backflow preventer of small diameter with a more sensitive meter is mounted in parallel in order to permit leakage detection in the system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a simplified cross-connection device including a compoud water meter whose valve serves as a part of backflow preventer and whose bypass meter acts as a leakage detector.

There is thus provided in accordance with the present invention cross-connection apparatus including an upstream check valve, a downstream check valve, an upstream shut-off valve disposed upstream of the upstream check valve and a downstream shut-off valve disposed downstream of the downstream check valve characterized in that the upstream check valve consists of the change-over valve of a compound fluid meter and the bypass meter of the compound meter includes a conduit from the inlet of the upstream check valve to the outlet of the downstream check valve.

According to a preferred embodiment, the compound fluid meter includes a main meter including an hydraulic valve having an upper pressure chamber and a bypass meter including a flow passage through the upper pressure chamber of the main hydraulic valve-, and a more sensitive metering unit than the main metering unit.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further understood from the following detailed description taken in conjunction with the drawings in which: Fig. A is a schematic sectional view of backflow preventer apparatus constructed and operative in accordance with one embodiment of the present invention; Fig. 2 is a side sectional view of backflow preventer apparatus according to a preferred embodiment of the invention; and Fig. 3 is a side view in partial cross section of backflow preventer apparatus constructed in accordance with an alternate embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a simplified cross-connection device consisting of two check valves. One of the check valves constitutes the changeover valve of a compound meter with a bulk meter in the main line to measure the fluid flow. A second, bypass line includes the sensitive meter of the combined meter (a flow meter of higher sensitivity than the main meter to measure flows beneath the threshold of the main meter) and a small-size backflow preventer. This device, therefore, provides both backflow prevention and accurate compound metering.

By means of a few changes in conventional compound meters, it is possible to utilize their change-over valves as one of the check valves required in the backflow preventer. By combining the two devices into one, great savings in purchase and maintenance costs can be gained, the cross-connection can be simplified and great savings in energy can be achieved.

According to the invention, the cross-connection includes a compound fluid meter whose change-over valve serves as the first check valve and whose bypass meter is coupled between the inlet of the change-over valve and the outlet of the second check valve. It will be appreciated that the bypass meter also provides leakage determination.

The invention is illustrated in Fig. 1 which is a schematic sectional view of cross-connection apparatus constructed and operative in accordance with one embodiment of the present invention and comprising an upstream gate or shut-off valve 10 and a downstream gate valve 12. Coupled to upstream gate valve 10 is the main meter 14 of a compound fluid meter. The main meter comprises a metering device 16 and a change-over valve 18. Change-over valve 18 may comprise any spring loaded check valve having a pre-determined threshold flow below which is remains closed tight and above which it rapidly opens to its full extent.

A second check valve 20 is coupled between changeover valve 18 and downstream gate valve 12. Check valve 20 may comprise any suitable spring-loaded check valve, such as a poppet valve, toggle switch valve, hydraulic valve, etc. While it is convenient for change-over valve 18 and second check valve 20 to be of the same type, it is not necessary.

As known, main metering device 16 has a relatively high measuring threshold and thus the change-over valve 18 remains tightly closed when there are low rates of flow through the system. In order to measure these low flow rates, a bypass 22 is installed coupling the inlet of the main meter 14 with the outlet of the second check valve 20. Bypass 22 includes a secondary metering unit 24 of higher sensitivity than main metering unit 16 and, is also provided with two check valves 26 and 28 downstream of the metering unit 24 to prevent backflow through the bypass line. Upstream and downstream gate valves 30 may also be provided on the bypass meter.

Operation of the cross-connection of Fig. 1 is as follows. When gate valves 10 and 12 are open and there is a demand for water downstream, the pressure at gate valve 12 is substantaially reduced relative to the pressure at gate valve 10, causing the inflow of fluid through bypass 22. As long as the rate of fluid flow is below the threshold of main meter 14, the fluid flows only through the bypass. Check valves 26 and 28 serve to provide some resistance in the flow line and to prevent the back flow of fluid in the bypass 22.

As the rate of flow increases, it reaches the threshold of main meter 14 and change-over valve 18 opens to permit fluid flow therethrough. Metering unit 16 begins to register the flow. A reduced pressure chamber 32 is formed between the two check valves, as known. The flow passess through second check valve 20 to downstream gate valve 12 which is at still lower pressure than chamber 32. Stop cocks 34 may be provided upstream and downstream of each check valve to permit the testing of the pressure differential in the system.

When there is reduced flow through the cross-connection device, the pressure at gate valve 12 rises, causing the change-over valves 18 and 20 to close, and the entire flow is measured by the meter in bypass 22.

When it is desired to test the system for leakage, the downstream fluid demand is turned off. If there is flow through the cross-connection device caused by leakage in the system, it will be seen and measured by metering unit 24 of bypass 22.

Referring now to Fig. 2 there is shown a side sectional view of cross-connection apparatus according to a preferred embodiment of the invention comprising upstream and downstream gate valves 40 and 42. In this embodiment of the invention, the main meter of the compound meter includes an hydraulic change-over valve 44. Hydraulic valve 44 includes a metering device 46, a flexible closure assembly 47 and defines an upper pressure chamber 48. Bypass 50 includes a first conduit 52 coupling the inlet 54 of the hydraulic valve 44 to the inlet of the upper pressure chamber 48 . A metering unit 56 is disposed i conduit 52 , as known. Metering unit 56 may comprise a positive displacement or inferential or velocity meter or any other metering unit of higher sensitivity (lower threshold) than main metering unit 1 8 . < ■' ' A second conduit 60 couples the outlet of upper pressure chamber 48 with the outlet 58 of the second check valve. Disposed in conduit 60 are " two spring loaded check valves 62 and 63 , defining a backflow preventer, and on/off control means 64 for stopping the flow in the downstream section of the bypass. This on/off control means can comprise a solenoid or other two-way actuated pilot valve or a manual tap or any other on/off control means disposed in conduit 60 adjacent the outlet from upper chamber 48 .

It will be appreciated that, in this embodiment, the bypass acts as a two-way control loop to control the opening and closing of the main meter. Thus, the bypass conduit acts as an on/off control pilot to stop the flow throughout both the main meter and the bypass meter. This capability is desirable if an on/off valve is needed at the meter location for anti-burst closure, remote control closing, etc.

According to a most preferred embodiment , a flow reducing element 66 is provided in bypass conduit 52 at the inlet to the upper chamber 4,8 . Flow reducing element 66 preferably comprises a rubber plug which is coupled by a positive connection to closure assembly 47 of the main meter. In this preferred embodiment, flow reducing element 66 is physically affixed as by a plate 48 to closure assembly 47. Alternatively, closure assembly 47 can be arranged to push flow reducing element 66 or can be provided with remote means for triggering its movement. It is merely required that the valve of main meter 44 and the valve of bypass 50 are operated in inverse or reciprocal relationship, such that the more one is open to permit fluid flow, the more the other is closed.

Second check valve 68 of the backflow preventer in the cross-connection device may comprise a mechanical valve or any other check valve .

Operation of this embodiment is substantially the same as that of Fig. 1, except with regard to the operation of the compound meter in the most preferred embodiment illustrated. When the flow through the cross-connection reaches the threshold of main meter 44, closure assembly 47 begins to open. As closure assembly 47 opens, flow reducing element 66 moves a corresponding distance into the conduit 52 at the inlet to chamber 48. This serves to block part of the flow of fluid, thereby reducing the pressure in chamber 48 and making fluid flow easier (less restricted) through the main meter than through the bypass.

As pressure in chamber 48 is reduced, the higher pressure at inlet 54 causes greater opening of closure assembly 47 until it is fully opened. As closure assembly 47 opens further, flow reducing element 66 is inserted farther into conduit 42, thereby substantially closing the inlet to chamber 48 and reducing the flow through bypass 50 to a minimum. In this respect, flow reducing element 66 acts like a needle valve in the bypass to increase the opening of the huydraulic valve above that necessitated by the pressure differential alone.

Since the closure of conduit 52 is simultaneous with the opening of closure assembly 47 which causes continued rapid reduction of pressure in upper chamber 48, this transition from flow only through the bypass meter to flow substantially through the main meter occurs very rapidly. This is due to the fact that once the main hydraulic valve begins to open, it must open all the way, and cannot open only slightly and then close again .

The reverse process occurs when the fluid flow to the meter is stopped or slowed significantly. As the flow is reduced in the inlet 54, the pressure is reduced and the relative pressure in chamber 48 acts together with the spring in closure assembly 47 to urge the closure assembly to close. As closure assembly 47 is urged towards its valve seat, flow reducing element 66 gradually is removed from conduit 42, thereby reducing the restriction and permitting the inflow of more fluid into chamber 48. It also acts like a needle valve, whose opening causes closing of the valve. As fluid flow into chamber 48 and the pressure therein rises, the closure assembly 47 is urged faster and faster into the closed position.

Fig. 3 shows yet another embodiment of cross-connection apparatus conastructed and oeprative in accordance with the present invention wherein both check valves are mounted at an angle relative to the flow.

It will be appreciated by those skilled in the art that the present invention is not limited to what has been shown and described hereinabove by way of example. Rather, the scope of the invention is limited solely by the claims which follow.

Claims (8)

1. Cross-connection apparatus comprising: a compound meter including a change-over valve serving as an upstream check valve; a downstream check valve; said upstream and downstream check valves defining a main line backflow preventer; and a bypass of the compound meter extending from the inlet of the upstream check valve to the outlet of the downstream check valve and including a more sensitive meter and a backflow preventer.

2. Cross-connection apparatus according to claim 1 and wherein the compound fluid meter comprises a main meter comprising an hydraulic valve having an upper pressure chamber and a bypass comprising a flow passage through said upper pressure chamber and a more sensitive metering unit than the main metering unit.

3. Cross-connection apparatus comprising: an upstream gate valve; a downstream gate valve; a main meter coupling said upstream gate valve with said downstream gate valve and comprising: a metering unit; a change-over valve operative as a check valve ; and a bypass of the compound meter extending from the inlet of the upstream check valve to the outlet of the downstream check valve, said bypass comprising: a metering unit of higher sensitivity than the main metering unit disposed in said conduit; and two check valves disposed downstream of said metering unit.

4. Cross-connection apparatus according to any of the preceding claims and wherein said change-over valve comprises an hydraulic pilot-operated control valve.

5. Cross-connection apparatus according to claim 3 and wherein: the check valve in said main meter comprises an hydraulic valve having an upper pressure chamber; and said bypass defines a flow path through the upper pressure chamber of the main meter, said bypass further comprising: flow control means disposed in said conduit adjacent the flow path inlet to the upper chamber and coupled to said hydraulic valve for reciprocal movement therewith for opening said bypass when said main meter is closing and vice versa.

6.' Cross-connection apparatus according to claim 5 and wherein said bypass further comprises ori/qff control means disposed downstream of the metering unit in the bypass in order to control the closing of the hydraulic check and change-over valve.

7. Cross-connection apparatus according to any claims 3 to 6 and wherein said main metering unit and said hydraulic valve are integrated into a single unit.

8. Cross-connection apparatus substantially as shown and, described hereinabove or as shown in any of the drawings . AGENT FOR APPLICANT