Minimum Flow in pump

[Rafael Dos Santos]

Greeting everyone...

There is a case where our pump running below minimum flow, but all parameters are in good condition. The vibrations are good, the temp and so the discharge pressure. My question is, do we need to increase the flow to above minimum flow or is okay if all parameters are good??

Pump details:
Minimum flow: 69m3/h
Running flow at site: 29~33 m3/h
Type: OH2 Pump
Allowable flow: 69 to 256 m3/h
FLC: 50/ 135 amp

 

[nondimensional]

At higher head on an OH pump, bearing life may change.

 

[Artisi]

Rafael:
So what is your problem?
How long has the pump been in operation?

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.)

 

[JJPellin]

The pump manufacturer tests on water to establish minimum flow. What fluid are you pumping?

Johnny Pellin

 

[Rafael Dos Santos]

Im confused cause most pumps when running below minimum flow, it will show abnomalities but this pump doesnt. This pump runs half from what it should be and already runs for 3 days.


JJpelin, it runs with main frac reflux..

 

[Artisi]

Is the data you are using correct, are you using the wrong pump curve - - for instance, you think it's 4 pole speed but it's actually 6 pole or 2 pole but actually 4 pole?
Check data against the site operation.




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.)

 

[LittleInch]

First we have to ask why are you trying to run a pump at about 10% of its max rated duty??

This is nonsensical.

However if it seems to run ok then let it, but it will be suffering somewhere.

Basically when it fails prematurely (seals, bearings, impellor wear / clearences) you won't get any joy from the vendor if you operate it outside the recommended limits.

Even 69 m3 is quite low for such a pump.

Efficiency must be horrible. You're doing 11% of full flow for 37% of FLC...


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

When you lose the pump due to one of the many reasons listed above, will Management go ballistic on you due to the outage/additional cost ?

Will the operators stand by you or just shrug and say "hey, it's his fault ....he let us do it !!!!"

Did the guy who had your job just before you only last a short time, but no one will tell you why ????

Lather, rinse, repeat .....

MJCronin
Sr. Process Engineer

 

[georgeverghese]

Agreed, pls check the Q-h-P curve for this pump. You will probably get the min flow of 69m3/hr at little or no increase in power draw? If so, what is the point in running below min flow ?
What do you mean by vibrations are good at this low flow of 30m3/hr? Most small and medium size pumps dont have an onboard vibration monitor. When installed, it would be from a inbuilt vibration probe sitting in a port right next to the shaft bearing. How did you get this reading?

 

[JJPellin]

The testing on water can produce a very conservative value for minimum flow. Running on light hydrocarbon it is possible to see good performance at very low flow. But it is still not recommended. What is the pump speed?

Johnny Pellin

 

[JJPellin]

What is the service? Main Frac Reflux doesn't tell me anything. The main fractionator in crude unit is much different than the main fractionator in a HF-Alky unit. What is the specific gravity of the fluid being pumped?

Johnny Pellin