Currently we have some problems with our new changed pump(Progressive Cavity Pump). When it is in high speed (max about 1356RPM/M, 50 Hz electricity), it make a unpleasant noise. And I found a frequency of 152-153Hz dominant in the spectrum. It should come from the gearbox (reduction rate is 4.114).But the amplitude is higher in the pump. Is there any chance that the frequency is from the rubber inside the pump casing? We have history of all 5 pumps damaged rubber. Please see the picture of the pump and spectrum attached.

Progressive_Cavity_Pump.doc (854 KB, 63 downloads)

Can you provide some more information. A quick check of the math 1356 rpm is approx 22hz pump speed. With a 4:1 reduction gearbox, I take pump speed times 4 and that equals 88hz motor speed?
Some manufactures of these style pumps use a complex gear style coupling shaped like a "round ball" to drive the pump.
Pump running 22hz and vibration of 152hz equals about 7 times pump speed, highly unlikely there is a 7 tooth gear. How many curves on the rotor?
Cavitation, wrong material of construction, high speed operation all kill progressive cavity pumps. The 22hz pump speed is quite fast for this style of pump. Typical speed is 50-250 rpm for this style of pump
Hope this helps
Dave

Sorry! I mean the max speed for the motor is 1356（So max for the pump is 330 rpm）.Normal not exceed that speed. Between 1000-1356 pm for the motor. The frequency for the motor is normal in 1X2X, and not other frequency in the motor spectrum.

is there a 27 or 28 tooth gear in the reduction box?
motor speed 1356 rpm or 22.6 hz. divided by ratio 4.114 = output speed of 5.5hz. 152hz/5.5= 27.6
and what is the frequency of those sidebands? you may have a gear problem, and the fact you are wearing out pumps may just mean they are unsuitable for the application.
have the other pumps returned readings like this before they failed?

just thinking out loud.

Hi
I agree with jonesy, i think you have a planetry gear train which may include three planet gears(between sun gear and ring gear) and every planet gear involves 9 tooth
9*3=27 tooth rotate about the ring gear driving the sun gear and so the pump rotor generating vibration of 5.5 * 27 = 148.5 Hz at the gearbox and you can see on the spectrum the frequency of 144 and 148.55 have larger amplitude than 152 at the most cases.

I hope that you have planetry gear train and three planet gears with 9 tooth each, haven't you?

regards neger

This message has been edited. Last edited by: Mahmood El.Nagar,