water hammer in sewer force main
water hammer in sewer force main
(OP)
I am dealing with a recurring problem on a pressurized pvc sewer pipe, which breaks due to water hammering on a regular base. The high pressures/subpressures are caused by immediate pump starts/stops between pump and a 90' bend. Anybody experienced in how to solve such problem enduring and reasonable? Thanks!





RE: water hammer in sewer force main
Search on "water hammer".
RE: water hammer in sewer force main
Changing the rundown time of the pump or closure rate of the downstream valve will improve the situation. A minimum flow recycle loop around the pump (with control valve) will allow the gradual ramp up or down of the pump without having to change the pump motor. However this will involve some additional control logic.
Also consider the installation of a surge vessel or pulsation damper i.e. a vessel pressurised with nitrogen (or similar inert gas) and a diaphragm isolating it from the process fluid. This will only really cope with small fluctuations in volume (how big is the pipe and how dramatic are the pressure fluctuations?).
I hope that this is of use to you.
RE: water hammer in sewer force main
RE: water hammer in sewer force main
A VSD can be fitted to the pump to control stopping and starting then you are only concerned with power failure. I fhtis is a regular occurrence you may need to consideration surge chamber.
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RE: water hammer in sewer force main
Do you mean VSD (variable speed drive) or VFD (variable frequency drive)? How does a VSD work? Without power?
RE: water hammer in sewer force main
Check out www.ventomat.com for the most modern technology in air valves.
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RE: water hammer in sewer force main
"Soft hydraulic start/stop" options:
Replace the pipe with stronger material.
Install motorized valve bypass system.*
Install a surge tank.
Use a "soft starter" aka, "solid state starter" to ramp start/stop. You are out of luck on power fail**.
Use a VFD to ramp the motor speed up /down (does not start a motor). You are out of luck on power fail**.
* A hydraulic actuator system with enengy storage system to handle a power failure
** Engineer a fly wheel to store energy in the event of a power failure.
The bottom line is your budget.
RE: water hammer in sewer force main
RE: water hammer in sewer force main
You need a waterhammer analysis to ensure that the working pressure plus surge pressure is within the de-rated pressure rating. Soft start and stop may solve your problem.
Brian
RE: water hammer in sewer force main