How to prime a booster pump?
How to prime a booster pump?
(OP)
Hello, I have a project that will be installing a set of centrifugal booster pumps in the middle of a feed train. These pumps will take suction from the first set of pumps after the fluid goes through several heat exchangers. My question pertains to the start up sequence of the new booster pumps. I currently foresee starting up the upstream pumps and establishing flow through the first half of the system. What needs to happen when I get to the booster pumps?
Is it advisable to leave the suction and discharge valves open to allow liquid to flow through it before starting the motors?
How else can I ensure that I have a sufficient liquid source to the booster pumps to avoid running them dry?
Thank you,
Is it advisable to leave the suction and discharge valves open to allow liquid to flow through it before starting the motors?
How else can I ensure that I have a sufficient liquid source to the booster pumps to avoid running them dry?
Thank you,





RE: How to prime a booster pump?
Normal procedure is to start the pump against a closed outlet valve with the inlet valve open.
How you control start-up pressure and flow is down to you and your system to gradually introduce the higher pressure at such a speed that the rest of the system can adjust accordingly until you reach steady state.
It is far from unknown for no one to properly think this through and hence when you start a booster pump with a high inlet pressure, the pump trips either on high outlet pressure, excess flow / amps or low inlet pressure /flow. It often needs some sort of control valve or similar downstream the booster pump to prevent this. A recirculation valve is also sometimes used.
You provide virtually zero data so it's not possible to see what levels of protection this pump has or what is possible / going to happen when you start the pump.
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RE: How to prime a booster pump?
A PHA has yet to be completed, so pump protections have not yet been defined.
Thanks for the comments so far.
RE: How to prime a booster pump?
Then you usually introduce a no return valve around the booster pump to let flow through then simply start the pump when flow is developed with a set point higher than the flow established by the upstream pump
With your plan I would start the booster pump first against a closed valve then open the discharge valve.
I would fill the system first before turning the pumps on. Where is the vapour going to go?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: How to prime a booster pump?
I am curious about your statement to set the booster pump flow setpoint "higher than the flow established by the upstream pump"? Wouldn't this create a flow imbalance? This is why we plan to maintain a discharge pressure setpoint on the first pump, and flow setpoint on the second pump. As the booster pump calls for more flow, the upstream pressure will drop until the first pump catches up and reaches its previous pressure target.
Thanks,
RE: How to prime a booster pump?
Doing it slowly with a VFD is the best way to avoid shocks and trips. You could always stick in a manual control into a low selector block and simply manually or automatically ramp the booster pump up which the flow controller then automatically takes over as the flow gets up to your set point.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: How to prime a booster pump?
RE: How to prime a booster pump?
RE: How to prime a booster pump?
RE: How to prime a booster pump?
Just to confirm my understanding, would the min flow recycle take off from the discharge of the booster pump and go back to the suction of the upstream pumps? Also, how would the pumps be able to start simultaneously, as there would be some lag time to fill the system up to the booster pump?
The level control for V-1002 is accomplished by a control valve on its inlet. This stream is fed from upstream storage tank pumps.
T1 is a set of internal condensing coils at the top of a tower. We pre-heat our feed in this pump system. At T1 we are generating internal reflux with this heat recovery.
Thanks,
RE: How to prime a booster pump?
RE: How to prime a booster pump?
If the vapor pressure of the fluid is less the pressure at the 65ft elevation point, then there would be no risk of vapor breakout on the suction line to the boosters on startup, and it should be acceptable (but not ideal) to start both pumps simultaneously, since pressure and temp to the boosters should normalise in a short while.
Alternatively, you could delay the booster pump startup and run an automated bypass across the boosters on a timer to allow pressure and temperature to stabilise somewhat, and then close off this bypass/ autostart the boosters at min speed.
Whether you start the boosters simultaneously or delay it ( by using this startup booster bypass) will depend on the volatility at the 65ft point / and or viscosity of this fluid without much preheat.
Though this is not the topic of discussion here, also check that the shaft seal cooling system for each of these pump sets will work okay when the 2 pump sets are at min speed, especially if you are relying on an internal pumping ring to keep seal fluid circulation going - often overlooked.