Patent Application
20070204916
The present invention generally relates to a backflow prevention device and, in particular, to a removable cartridge housing check valves, a relief valve cartridge, and/or a self cleaning check valve for a backflow prevention device.
Backflow prevention devices are used to protect potable water supplies from contamination. Backflow prevention devices are typically installed in pipelines between a main water supply and service lines that feed users such as industrial or commercial sites or residences. Many localities legally mandate their use.
Backflow is caused by abnormalities in the water distribution system such as backpressure or backsiphonage. Backpressure occurs when the water pressure is higher in the downstream system than in the water supply. Backsiphonage can occur when the water supply pressure drops, such as when a water main breaks or severe demands are placed on the water supply. Either condition could lead to backflow, the flow of water from the downstream system back into the water supply. Backflow is undesirable because it may cause contamination of the potable water supply.
Two common types of assemblies are the double check (DC) and the reduced pressure (RP) backflow prevention devices. The double check devices, commonly used with non-health hazards, have two check valves between two shut-off valves. The reduced pressure devices, commonly used to prevent health hazard, have two check valves, with a relief valve located between them, and two shut-off valves.
Backflow prevention devices commonly include two independently acting check valves, internally loaded to a closed position. Each check valve permits water flow in only a single direction, from the main water supply toward the service line. If the pressure drop across a check valve falls below a predetermined threshold, typically about 1 psi, the loading of the check valve should cause it to close, thereby preventing the flow of water backwards through the device. The first check valve (in the direction of flow) provides redundancy in case of failure of the second check valve.
Some backflow prevention devices further include a hydraulically operated relief valve to vent the zone between the two check valves to atmosphere. The relief valve is configured so that if the pressure in the zone between the two check valves gets within a predetermined threshold of the supply pressure, typically about 2 psi, the relief valve will open and dump water from the zone. The relief valve is usually installed over a drain or plumbed to a drain with an appropriate air gap.
Ball valves are provided upstream and downstream of backflow prevention devices, allowing isolation of the device. Test cocks provide the ability to measure pressure at various points in the backflow prevention device and to supply water at desired pressures for purposes of testing the functionality of the check valves to insure proper operation of the device without removing the device from the water line. Test cocks are typically located at four sites: on the upstream side of the inlet ball valve; between the inlet ball valve and the first check valve; between the two check valves; and between the second check valve and the outlet ball valve.
It is desirable to access the check valves or the relief valve (when present) from time to time for purposes of inspection, maintenance, repair, or replacement. With current backflow prevention devices, this generally requires either removing the device from the water line or accessing the valves through ports provided on the device.
In
An inlet ball valve 26 and an outlet ball valve 28 make it possible to isolate the backflow prevention device 2 from the water system to which it is connected. The inlet ball valve 26 is mounted in a ball valve housing 30 which is mounted to the main body 4, preferably by means of a threaded engagement. The ball valve housing 30 may comprise a mounting portion 36 and a valve containment portion 38, each defining a fluid flow passage 40, 42 respectively. A test port 14 is in fluid communication with the fluid flow passage 40 of the valve containment portion 38 via a test port channel 44. A test port valve 46 is attached to the test port 14. The upstream end 48 of the ball valve housing 30 is configured for connection to a source of water, preferably via internal threads 50.
The outlet ball valve 28 is mounted in a second ball valve housing 52 which is mounted to the main body 4, preferably by means of a threaded engagement. The second ball valve housing 52 may comprise a mounting portion 58 and a valve containment portion 60, each defining a fluid flow passage 62, 64. The downstream end 56 of the second ball valve housing 52 is configured for connection to a downstream system, preferably via internal threads 66.
Referring now to
Referring again to
A first check valve 94 is located in the slider receiver 70. A ridge 96 on the inside surface of the slider receiver 70 helps to fix the check valve 94 in position against the main body 4 when the removable cartridge 68 is mounted in the main body 4. The check valve 94 is of a standard type well known in the industry and is biased to a normally closed position. The check valve allows flow through the valve in only one direction, downstream.
Referring now to
It is desirable that the plunger 158 not stick within the central bore 160 lest the check valve 94 jam in an open position. Under reverse flow conditions, contaminated water will flow into the valve cage 152 from the normally downstream direction. Spiral grooves 164 are provided in the central bore 160 in order to assist the plunger 158 in flushing any particulate matter that might have flowed into the central bore and reducing the chance of the particulate matter wedging between the plunger 158 and the central bore 160 and causing the check valve 94 to stick.
The downstream end of the slider 72, best seen in
Under normal operating conditions, if the water flow through the backflow prevention device 2 reduces to the point that the pressure drop across the second check valve 100 is less than 1.0 psi, the second check valve 100 would close, preventing flow in the reverse direction. If the second check valve 100 fails, the first check valve 94 would close, providing backup protection.
A geared or knurled exterior surface 106 allows for manual rotation of the slider 72 relative to the slider receiver 70 and the main body 4. Rotating the slider 72 in one direction causes the slider 72 to telescopically screw into the slider receiver 70, thereby reducing the overall length of the removable cartridge 68 and facilitating the removal of the cartridge 68 from the main body 4.
Removing the cartridge 68 makes it possible to inspect, maintain, repair, or replace the check valves 94100. After inspecting or servicing the check valves 94, 100 the cartridge 68 can be replaced by inserting either end of the cartridge 68 into the main body 4 and then unscrewing the slider 72 from the slider receiver 70 until the two ends of the cartridge 68 seat against the main body 4.
Many localities and several industry organizations mandate the location of the fourtest ports 10, 12, 14, 16 as described herein. The test ports 10, 12, 14, 16 allow testing of the functionality of the backflow prevention device 2 without removing the device 2 from the water supply system. For example, pressure sensors can be attached to the test ports 10, 12, 14, 16 and the various pressure readings compared. Under normal operating conditions, the pressure should drop as we move from each test port to the next downstream and the static pressure drop across each check valve 94, 100 should be at least 1.0 psi. If the pressure downstream of a check valve 94, 100 is greater than the pressure upstream of the check valve 94, 100, or if the downstream pressure is within 1.0 psi of the upstream pressure, the check valve 94, 100 should close and prevent flow back through the check valve 94, 100.
Alternatively, the backflow prevention device 2 can be isolated from the water supply system by closing both of the ball valves 26, 28 by rotating the ball valve handles 108, 110 (
As best seen in
When the supply water pressure is greater than the pressure in the zone between the two check valves 94, 100, by more than a predetermined threshold, typically about 2 psi, the pressure in the supply pressure chamber 224 is sufficient to overcome the force of the water in the control pressure chamber 236 and the biasing force of the spring 242. If the pressure in the zone between the two check valves 94, 100 should approach within 2 psi of the supply pressure, the relief valve 210 opens and water from the zone is vented to atmosphere.
Under normal operating conditions, if water flow through the backflow prevention device 200 reduces to the point that the pressure drop across the second check valve 218 is less than 1.0 psi, the second check valve 218 should close, preventing flow in the reverse direction. If the second check valve 218 fails, the first check valve 216 should close, providing backup protection. If the second check valve fails 218, or if it does not seal tightly, leakage back through the valve 218 will cause the pressure in the zone between the two check valves 216, 218 to increase. If the pressure in the zone between the two check valves 216, 218 gets within a predetermined threshold of the supply pressure, typically about 2 psig, the relief valve 210 will open, dumping water from the zone between the two check valves 216, 218 out to atmosphere through the exit port 222, thereby reducing the possibility of contaminated water flowing back through the device 200 to the water supply system. Ordinarily, the relief valve 210 should be installed over a drain or plumbed to a drain with an appropriate air gap.
The foregoing relates to preferred exemplary embodiments of the invention. It is understood that other embodiments and variants are possible which lie within the spirit and scope of the invention as set forth in the following claims.
