Increasing the speed of centrifugal pump
Increasing the speed of centrifugal pump
(OP)
I have a Worthington centrifugal pump running at 1200 RPM moving sea water. I have a electric motor that will mount up perfectly that turns at 1800 RPM. I want more flow, without changing the pump what will changing the speed do? The Worthington manuals pump curves are set up for a specific RPM, so they are no help.





RE: Increasing the speed of centrifugal pump
for example, at same inlet conditions, the discharge pressure will be higher at the higher rpm. is the piping system rated for the higher pressures? relief valve settings/capacities?
before increasing speed, i'd have the mfg evaluate the pump's performance at the higher rpms for the design/actual process conditions.
good luck!
-pmover
RE: Increasing the speed of centrifugal pump
Is the motor capable to handle a 1.53 times greater HP demand ?
RE: Increasing the speed of centrifugal pump
Q is proportional to N*D^3
H is proportional to N^2*D^2
P is proportional to rho*N^3*D^5
So for your pump, Q (flow) will be 1.5 times original Q. H (differential head) will be 1.5^2=2.25 times original H. P (power) will be 1.5^3=3.375 times original power.
RE: Increasing the speed of centrifugal pump
The question is, can the pump handle this power? Also, can the pump run at the higher speed?
What is the model and size of the pump?
RE: Increasing the speed of centrifugal pump
RE: Increasing the speed of centrifugal pump
All the info you have provide points that my 1800 RPm motor will handle the load. Original in service motor is 15 HP the 1800 is 25 HP. These Worthington LRV type pumps are built like a tank to take the neglect that only sailors can dish out.
RE: Increasing the speed of centrifugal pump
(1800/1200)^3 X 12 = 40HP (minimum)
However, this will depend largely on the head imposed on the pump by the pipe work configuration and the static head - you also need to review the NPSHr versus the NPSHa --- this is NOT a function of them being built like a tank but a matter of physics and wishful thinking will not overcome an NPSH problem.
You need a proper review of this installation by someone who understands pumps and the ramifications of increasing the speed by 50%.
RE: Increasing the speed of centrifugal pump
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Increasing the speed of centrifugal pump
My previous comment stands - contact the manufacturer.
RE: Increasing the speed of centrifugal pump
Higher flow can result in flow-induced vibration in systems not designed for it. This has caused cracks in piping, espectially small instrument lines, and occasionally valves and even large components (such as a steam dryer). Higher velocity (than originally designed) will also wear out heat exchanger tubes and throttle valves. And, of course, there is flow accelerated corrosion, especially downstream of elbows.
Increased flow is not always a good thing.
Patricia Lougheed
Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.
RE: Increasing the speed of centrifugal pump
You have to remember that, impeller can be modified to keep power consumption under 25 Hp.
From 1996 I was modifying impellers for Kocak to fix Goulds pumps operating away from BEP and breaking the shafts.
The same can be done in your case of replacing motor.
The similar problem happens, when companies are buying European ships and converting from 50 HZ to 60 HZ.
Best Regards.
RE: Increasing the speed of centrifugal pump
"You need a proper review of this installation by someone who understands pumps and the ramifications of increasing the speed by 50%."
This means a complete study of the pipe work and anticipated flow rate, pump performance and power limitations for the speed / flow / impeller diameter etc.
RE: Increasing the speed of centrifugal pump
I think you've gotten plenty of replies that should lead you to the correct conclusion that you should not willy-nilly replace the motor with a higher speed motor. Despite its build and reputation, the pump and/or other components of the system may not do well at the revised conditions that will occur. Decide what you want in terms of new flowrate and head and determine the NPSH you have available. Armed with that information you should be able to predict using the pump affinity laws how the existing pump will perform at the new speed. Now with help from the pump vendor, determine if you should trim the impeller to achieve the desired performance.
Doug