Sewer Pump Name Plate DUTY Meaning/ Power Factor

[Rich S.]

I am working with a Sewer Lift station that has recently Installed Two out of Four New Dry pit submersible pumps. They are installed in a dry pit application. Our problem is the new pumps are getting super hot you can fry an egg on the motor. They can run from 3 to 4 hours at a time due to the volume coming into the station. The pump name plate says:
DUTY continuous/submerged
15 min. per hr./Air
The other issue Issue is these two pumps have a VFD drive and which we don't use them for this application so we have them switched to By-Pass mode. I was told that by having these in a by pass mode does something with the power factor which calculates I believe around .68 and should be closer to 1.0. By installing a capacitor this will bring the PF closer to 1.0 and the pumps will run cooler and by having the PF at that number of .68, the pumps are running under voltage creating them to heat up. We also checked the volt readings on the pumps with and with out a load and they are in the normal range. Could I have two problems. PF and wrong pump application. The older pumps. No VFD, No Heat, No problem. Any help?:?

 

[Joethemechanic]

Why are these pumps in a dry pit?

Submersibles need water around them to cool.

Total wrong pump for the application

I don't care what you do, you are never going to get them to cool without water around them

I've used large submersibles for emergency pumping, and all you can do once you get the water level down to where the motor is sticking out of the water is spray them down with a hose

 

[jim dungar]

The nameplate specifically says only 3-4minutes when not submerged. As Joe said, you have the wrong motors.

Adding PF correction capacitors will not make the motors run cooler.

 

[Rich S.]

Sewer pump name plate.

Sewer pump name plate.

I agree, this is the wrong application. We were told this pumps would work in both applications. I cant see how someone over looked this. The name plate says it all. I was not sure on the Power Factor. I will be looking for two new sewer close coupled pumps in the future like Monday Morning.
Thank you Joe and Jim.
Rich S.

 

[kwired]

Why are these pumps in a dry pit?

Submersibles need water around them to cool.

Total wrong pump for the application

I don't care what you do, you are never going to get them to cool without water around them

I've used large submersibles for emergency pumping, and all you can do once you get the water level down to where the motor is sticking out of the water is spray them down with a hose

Just don't spray them with more water than they are pumping or you will never get it all pumped

 

[Joethemechanic]

Just don't spray them with more water than they are pumping or you will never get it all pumped

I had some that I made up couplings for, that bolted to the discharge flange. They had a 3/4" and 1" pipe thread in them so I could hook up a cooling flow for the motor housings. We were talking 6" , 8", 10" and 12" pumps here.

What do you think people said about them ?????????

 

[Rich S.]

These pumps are 4" inlet and 4" out. Built by Flowserve in the USA. I"m wondering if the factory could reconfigure them to a close coupled style. I can check on Monday Also.

 

[Joethemechanic]

Something you want to be sure of when you go over to air cooled motors is you want to be sure there is adequate air flow in the dry well for cooling. The dry well pretty much needs to be ventilated to outside air.

Also in a retrofit, there are many mistakes in suction piping that can lead to cavitation and early pump failure. One big one is to stay away from concentric reducers mounted horizontally.

You want to use eccentric reducers in suction piping kinda like in the picture below

 

[Rich S.]

Thanks, this will help a bunch. I will keep everyone updated on my progress.

 

[Joethemechanic]

Little better diagram. This is a big big big deal., when designing suction (intake) piping

 

[kwired]

I had some that I made up couplings for, that bolted to the discharge flange. They had a 3/4" and 1" pipe thread in them so I could hook up a cooling flow for the motor housings. We were talking 6" , 8", 10" and 12" pumps here.

What do you think people said about them ?????????

12" pump - they probably mentioned something about how heavy it was at some point. You are talking diameter of discharge line I assume.

 

[Joethemechanic]

12" pump - they probably mentioned something about how heavy it was at some point. You are talking diameter of discharge line I assume.

Yeah diameter of discharge,

Well I had to take the ball valves off the cooling spray pipes, because idiots would shut them down. Like the flow from a 1" piece of pipe was signigicant.

And yeah I'm thinking a 12" Flygt had to be close to 5,000 pounds and about 150 HP