POWER DROP
POWER DROP
(OP)
What is the design characteristics in a pump that decides the power drop point? During testing of pump after the 150 % flow the power keep on increasing to a point after which either the power drops or stabilizes. How to bring down the point(not below 150 % flow )?
can anyone help me out?
can anyone help me out?





RE: POWER DROP
All will become apparent by looking at the head generated and the efficiency curves
For centrifugal pumps ( you don't say which one you are looking at)
As you increase in power past the duty point the efficiency is normally quite high or drops a bit, but flow increases and head stays more or less the same hence power goes up.
As you increase flow, the efficiency goes down, which means more power, but the head starts to drop off faster than the drop in efficiency which although you have more flow overall the power levels off or drops a bit.
All this is HIGHLY pump dependant, which is why pump vendors issue pump curves
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: POWER DROP
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: POWER DROP
RE: POWER DROP
E.g. in the curve below, if your duty point on say the top curve was say 600 GPM then there is a large rise in power as flow increases.
If on the other hand you had specified 1000 or 1100GPM as your duty point on the same pump, you would only have up to 1300GPM before you went off the curve, but max power would only increase by ~20% compared to rated power. Like I said - it's all down to the individual pump curve and why you're trying to limit max power. It's all down to good pump selection. Vendors will often try and give you a pump which matches their models, but alternatives are available.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: POWER DROP
RE: POWER DROP
The only time power might reduce is if NPSHr greatly exceeds NPSHa, but then the pump will be suffering cavitation and may even hunt up and down its performance curve. Neither of which is recommended.
If you need to limit power input you should consider fitting an orifice plate in the discharge.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: POWER DROP
Please explain why.
You size and choose a pump based on a duty requirement. It's all about matching pump duty and service. if you choose a bigger pump than you need "to be on the safe side", but do nothing about the system then you will flow more fluid and use more power.
Please describe your system and provide more data if you want this thread to go much further
If you flow more fluid through it than rated flow then you use more power.
If you want to limit power, limit the flow
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: POWER DROP
A soft start feature on the pump motor may or may not work in this application with this concern.
RE: POWER DROP
RE: POWER DROP
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: POWER DROP
Please see the table attched.
This pump (340 m3/hr rated flow,511m3/hr is the 150 per flow point)was tested with a motor of 185 rated KW.
You can see that after 511 m3/hr we kept on increasing the flow and we got the power drop at 576 m3/hr at 266kw . Where the power dropped from 266 kw to 261 kw.
What i am trying to achive is to bring this value some where close to 150 per flow , like say 530 m3/hr or so.
RE: POWER DROP
You are running round in circles, time to involve someone who knows what they are doing for your particular application.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: POWER DROP
At 266kw that 185 kW motor would be running pretty hot(!)
You need a bigger motor. I would go for 275kW.
Or a smaller pump.
End of story.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: POWER DROP
RE: POWER DROP
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: POWER DROP