Multiple pumps - start up against closed butterfly control valves
Multiple pumps - start up against closed butterfly control valves
(OP)
Good Morning,
Are there any recommended opening / closing procedures for bringing a pump on line or closing one down by utilising the pump control calve located in the discharge pipe for each pump prior to joining the manifold?
We have 9 pumps, 7 of which are on line at any one time (2 dedicated standby units)
The pumps are all FIXED SPEED submersible canister type. (motor is with pump and not above floor level - the whole pump is lowered to the bottom of the 1100mm canister)
Diameter is 800mm and the manifold is 1400mm.
Fluid: Raw water
Would like to know if there are recommendations for the start-up procedures and any advice for correct installation considerations would be very much appreciated. Cavitation, surge, duration of closed head etc.
Best Regards
John
Are there any recommended opening / closing procedures for bringing a pump on line or closing one down by utilising the pump control calve located in the discharge pipe for each pump prior to joining the manifold?
We have 9 pumps, 7 of which are on line at any one time (2 dedicated standby units)
The pumps are all FIXED SPEED submersible canister type. (motor is with pump and not above floor level - the whole pump is lowered to the bottom of the 1100mm canister)
Diameter is 800mm and the manifold is 1400mm.
Fluid: Raw water
Would like to know if there are recommendations for the start-up procedures and any advice for correct installation considerations would be very much appreciated. Cavitation, surge, duration of closed head etc.
Best Regards
John





RE: Multiple pumps - start up against closed butterfly control valves
Unless there is some process reason why the pumps need to be started up against a pinched or closed discharge valve, I would start them up with the valves open in this situation. Possible process drivers for pinching on the valve could include the need to have all changes in flow and pressure occur gradually. Some processes are prone to upset or unit trip if the flow or pressure changes quickly. If that is not the case, I don’t see a need to close a valve for start-up.
You described a situation where each pump has an individual control valve of a butterfly configuration. I assume that each pump also has an individual check valve (non-return valve). Please confirm that is the case.
Johnny Pellin
RE: Multiple pumps - start up against closed butterfly control valves
YEs we have NRVs in the discharge line. Agree the 'back pressure' on the downstream side of the NRV is at the common manifold pressure agree, unless the flow / pressure is equivalent, ie reaches the duty point then the NRV doesn't open. I guess it is more of a problem say on an individual well pump if it is an independent system and the rising main may have a low pressure or indeed be empty. But in that case we have small bypass valves fitted to the mainline valves to control pipe filling rate.
Regards
John
RE: Multiple pumps - start up against closed butterfly control valves
A leak in the check/control valve could be spilling flow back through a pump. If it is turning fast it may cause damage if started.
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P.E. Metallurgy, Plymouth Tube
RE: Multiple pumps - start up against closed butterfly control valves
1. Starting a Pump
2. Stopping a Pump
3. What Happens in the middle of a Power Failure?
RE: Multiple pumps - start up against closed butterfly control valves
QualityTime, for 3b, why is the valve manually closed? Is it not a case of witing for the power to be resumed and the valve closes prior to pump energizing? Or is it to ensure no backflow? (Even with an NRV before it). Ie no pump can start unless its control valve is fully closed.
And with sensors to confirm no backward rotation.
RE: Multiple pumps - start up against closed butterfly control valves
I am not sure how a voltage sensor will work if the motor is turbining due to backwards flow. As long as you have a check valve I would not worry about water running backwards through the pump. I have done a lot of big pumps and I think this concept might be a bit overboard. Remember that for water to flow backwards BOTH the motorized valve and the check valve must be having problems. This is highly unlikely. Even if does happen, remember there is always maintenance program that has to be done on pumps. An operator can easily determine from sound if there is a leak. That is what an operator is for. Time to fix the problem.
Motor contacts or a current sensor is all you need to determine if a pump is running or not.