Don't know what happen on motor that use for pump 1

[amphan]

I have some problem in water pump group motor in my factory. I must be change a motor's bearing every 1-2 month because the shock pulse value exceed standard value
(~35db). I check everything and found
1. The grease (type shell R3) in Brearing non-drive change to liquid status
temperature on flange ~80 C.
2. Electric Current on ground's cable has ~16 Amps(150 Hz). We not connect this cable to ground system but we connect this cable to the copper ground rod.
3. My group motor has 10 motors (200 , 90 , 132 Kw).

 

[jbartos]

Do you happen to have connected the motor stator to the motor rotor, for example a copper jumper from the motor stator to the shaft slip rings, additionally installed? There may be an electrical current flowing from the motor stator to the motor rotor via the motor bearings. Large electrical rotating machines have this grounding feature designed and installed. A possible measurement by an ammeter between the motor stator and motor rotor shaft could reveal an approximate amount of current flowing from the motor stator to the motor rotor via bearings under assumption that the copper connection has much lower resistance than the electrical path via the motor bearings.

 

[BJC]

If these are driven by VFDs you have induced bearing current. Check ou thease people.

http://www.teleport.com/~sgsi/

 

[don01]

amphan
Jbartos and bjc have highlight most probable cause. If these are not the case decouple the motor from the pump and run, measure voltage and currents and spm again without the pump (or intermediate transmision bearing) connected.
Is it just one motor on the skid or the whole group giving problems?
are the pumps allowed to "cavitate" this can cause you some strange spm readings.
Also consider that if your ground connection resistance is up a little and you are pumping sea water or such then a real good earth will be the process via bearings and pump rotor

keep us posted
regards Don

 

[work]

Amphan.
I send you a little cuestions that probably help you.
1- begin easy.
¿It´s only one motor that have the problem?
in case "yes"- The other motors have the same grease???
Discard lubrication problem.
Check the geometric line between the motor and the pump ;and the torque adjust of the mounting bolts .
Try to get an acelerometer and send us the values.

2- The electric problems leave in the bearing a very little holes, if you measure this you found a high frecuency. this is cause of the bearing balls beating in front of the hole edges.

3- low frecuency it´s a typical response from desbalance it might be mechanical or electric, in the electric case c ould be that any bars of the squirrel rotor are broken.

4- if you have the same problems in all motors change the grase i recomend you "LE" lubrication enginers monolec type.

keep au posted
Regards.