electric motor lubricant

[Yogibear]

I have taken apart an electic motor that has a circuit board in it. Little did I know that there was also some type of oil inside it. I thought it was water at first since it wasn't working, that's why I took it apart, and by the time I realized it was some type of lubricant/coolant it was empty. I was wondering if someone might have an idea of what kind of fluid that might have been. It has to be heavier than water since this motor is in an underwater pump and has to be safe for a circuit board to be submurged in it.

Thanks for the help in advance.

 

[Skogsgurra]

Best advise is to ask the manufacturer.

Also, it isn't cooling/isolant in the first place. It is to keep water out. Probably not heavier than water.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

If the cavities are filled with an incompressible liquid then the water won't want to enter a 'lower' pressure area as skogs sez.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[stardelta]

Assuming you have a submersible pump of standard vertical shaft design and not a fishtank or pond-pump! Submersible pumps are usualy cooled by the surrounding water, I have never seen one totaly full of oil that depends on it just for cooling and sealing purposes, but just because I havent seen one doesnt mean they dont exist! Again assuming its a standard design sub`pump I believe the oil is there to lubricate and cool the mechanical seals. Most designs of submersible pump have an oil chamber at the bottom of the pump between the stator winding and volute that the shaft passes through, there are 2 seals on the shaft, the top one prevents oil getting into the stator. It could be an ordinary lip-seal or a light duty mechanical seal, the other being the main mechanical-seal behind the impeller. Flygt and KSB are the 2 most popular makes we see although there are others. The amount of oil, its grade and how its filled differ from make and model to model, some have external filler/drain plugs and some have to be dismantled to be drained/filled. We always check with the maker if we can regarding oil grade and quantity, but if its not possible to obtain the information we have always used ISO-32 hydraulic oil as makers always seems to spec` a similar grade and fill the pump with enough to totaly cover the lower mech-seal when the pump is in the vertical.
First thing to do is check if there is a nameplate if there is one and contact the makers or service agents in the hope they will give you the information you require, otherwise you need to involve a pump repair company. Some questions in return...why did you dismantle it in the first place, did it have a problem? Are you sure all the seals and gaskets etc are reusable and undamaged after dismantling it? What is the purpose of the PCB, is it part of a water ingress detection system?

 

[Yogibear]

Here is some more info. that I probably should have previously included.
What this is is a Aquabot. An Aquabot is a motorized pool cleaning machine. It has electric propeller pump and seperately has another box that contains the circuitboard with some drive gears. The propeller pump pulls water thru a mesh bag that captures the debris in the pool. The bot will go forward for a period of time then stop and back the other way.
I took apart to box that contains the CB because the machine quite working (come to find out that I have a short in the power cable) Should have tried the simplier things first. I have talked to the company and they said they would refill it for a $$$ charge. I was hoping that there was a fluid that I could buy over the counter that would work.

 

[ScottyUK]

If it is solely for the purposes of cooling, and not lubrication, silicone transformer fluid will be a pretty safe bet. It is expensive in small quantities if you buy it prom the likes of Dow and their distributors, but a transformer rewind or maintenance shop will probably either sell you a pint for a couple of pounds, or just give it to you. Some companies have combined transformer and motor service divisions: you could be honest and ask them to do the refill as a paying job so they make a little out of it.

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I don't suffer from insanity. I enjoy it...

 

[SteveKW]

Electric motor shops that service submersibles will also carry that type of oil.