When centrifugal pumps feed into empty or partially full pipelines, the pumps will produce a high flow to fill the pipeline until the pressure has increased sufficiently to operate at its duty point. However, before that is achieved, the pump may damage the balance disc or trip-out due to excessive power demand.
Upwey Valve & Engineering presents a range of pump control valves from Hydro Power Equipment designed to maintain sufficient back pressure on the pump to prevent pump overload and flow surging in the pipeline during filling.
Pump control valves fulfil all the requirements of pump control in starting and stopping, additionally offering protection against pipeline failure.
When centrifugal pumps are switched off, the water in the pipeline rapidly slows down and may reverse, causing pressure surges (water hammer) in the line, which can on occasion result in pipe failure.
The underground pump control valve systems minimise pressure surges on closing by throttling the flow rate to a low value a few seconds before cutting power to the motor, protecting the pump from possible damage due to any low downstream pressure condition.
The pressure control valves consist of an isolation valve with a manual handwheel and a two-stage opening/ closing pilot control pistons. The pre-opening piston opens the valve fractionally to ensure that the valve will sustain upstream pressure by throttling the flow.
The second stage opens the valve fully from the pre-opening position. This valve is a standard two stage pilot controlled (WIP type) isolation valve. A system incorporating a solenoid valve, a downstream pressure sensing valve together with strainers, hoses, check valves, ball isolation valves and a sub-plate controls the main isolation valve.
Key features of HPE underground pump control valve systems:
- Designed to conform with ANSI B16.34
- Available in straight through (Y-body) or 90-degree angle pattern body
- Cast steel body to ANSI class 1500 or 25 MPa working pressure
- Flanges or taper hub and clamp connections
- All working parts made from stainless steel
- Proven erosion resistant labyrinth long seal poppet and seat
- Robust, well guided poppet and cage design
- Isolates and throttles in the operating direction
- Throttles and maintains the pump pressure when the downstream column is empty or partially full
- Opens fully when the downstream column is full
- Throttles the pump outlet when the pump is to be stopped to prevent water hammer
- Operates with only one electrical signal to the valve: no PLC or auxiliary compressed air is required
- Electrically allows selection of one line ‘operating’ and the other line ‘isolated’
- Electrical signal must be on whilst the pump is operational
- Closes to the pre-open position to reduce flow, and does not damage the pump if the electrical signal is lost
- Resorts to safe operating condition if installed from new, and self-primes if started full of air
- Manual ball valve to over-ride automatic operation of solenoid valve
Hydro Power Equipment is based in South Africa and represented in Australia by Upwey Valve & Engineering.