Powerflex 753 Drive & Pump Settings/Selection

[careythibodeau]

Hey all,
I wanted to discuss an issue with achieving a constant flow rate of around 10 GPM on a glycol circulation pumps in a 1200-1300 PSI system. I have been experiencing pump failures and are unable to maintain a stable flow rate, which fluctuates between 1-3 GPM. Despite my attempts to adjust the control loop's PID settings, I haven't been able to find the ideal configuration due to mechanical breakdown and wear and tear of the PD pumps. They are constantly swapping the pumps out, a fresh pump runs around 20-28 Hz.



Currently, we are using 480V Powerflex 753 drives in Normal Duty 34 Amp cat# 20F11ND034AA0NNNNN. These drives are powering 460V, 29.5 Amp, 1765 RPM, Inverter Duty Motors (you can find more details about the motors here: [https://www.weg.net/catalog/weg/US/e...ted/p/12424790]). These motors are connected to smaller Rotor-Tech Positive displacement gear pumps (refer to the manual for Model GS 3312 EP).


In light of the situation, I see two possible options: either replacing the pump with a smaller size or up-sizing the drive and utilizing HD mode to accommodate the gear pumps. I have also included a communication I sent to operations expressing my belief that the current pump might be undersized. Operations wants us to further investigate if up-sizing the drives will resolve their issues.


Anyone got any tricks up their sleeve?! Thanks in Advance!

[JTCat]

Ah yes, operations just throwing darts and hoping they get it right. See it all the time.

Gear pumps can wear out faster than most other types of pumps. Especially if ambient air temperature and the process liquid are of significant difference. And pumping a coolant, that's more or less a guarantee.

What is your fluctuation on a brand new pump? Brand new pumps should be so close in tolerances that an 8hz swing in motor speed is a pretty big deal if that's required to get the same flow between one brand new pump and another one.

Are these pumps being rebuilt in house or are they new?
How are you metering flow rate? Do you have flow meters? Pulse counters? V/HZ/A monitoring?

[careythibodeau]

Thanks for the prompt reply JTCat.

As per a fresh install of Gpm fluctuations... I can't say cause I'm never on site for those events.

Worn pumps are around 50 Hz and new pumps run quiet and smooth at 20 ish Hz I believe.

Supposedly they are being sent new. However good question, I'll have to follow up with mechanical.

As per monitoring flow rate, we are just using an orifice plate with a Rosemount DP transmitter. (not the most accurate)

[James Mcquade]

one of the things that i have run into is product incompatibility with the pump.
you need to see the reactivity chart for the pump, gears, seals and see if your glycol solution eats at the material.
james

[JTCat]

You are basing your PID on the pressure differential transmitter?