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View Full Version : Oil filled submersible pump. Which oil?



mickeyf
04-26-2015, 07:10 PM
So I seem to have acquired this elderly, rusty horizontal bandsaw project which I hope to bring back from the dead, and it came with a Little Giant coolant pump (Model 2E-NT, apparently now obsolete). The pump does not look like it needs more than a cleaning and a new power cord - the old one was worn / broken off 1/2 an inch from where it entered the pump. However, I also discovered to my messy surprise that it was oil filled, and now I'm wondering what the correct type of oil will be to refill it with after I replace the cord. (And the seal around the cord, and what I take to be the oil fill plug...)

I have not called Little Giant (yet) but I thought perhaps someone here knew what these things are filled with? (And please don't tell me PCB oil!)

Rosco-P
04-26-2015, 08:08 PM
Dielectric oil like Mobil Univolt.

mickeyf
04-26-2015, 11:28 PM
Thanks! That was the magic search term I needed. I now know what I need and have some leads on where to find it.

Black_Moons
04-27-2015, 04:51 AM
Dielectric oil like Mobil Univolt.

Cool, I had always wondered what kind of oil spilled out of my shopvac and submerseable pump onto my basement floor. (Yes, Both let go at the same time. Because one was inside the other, running unattended for 4 days straight.. Loss of water pumping didn't help the shopvac any)

wtrueman
05-02-2015, 04:21 AM
Hi Mickey: can this type of motor NOT run free in the atmosphere?

MaxHeadRoom
05-02-2015, 10:14 AM
Thanks! That was the magic search term I needed. I now know what I need and have some leads on where to find it.

Also known by some as Transformer oil, try motor winding shops or local electrical supply house may offer a lead.
Max.

camdigger
05-02-2015, 02:53 PM
Hi Mickey: can this type of motor NOT run free in the atmosphere?

Dunno about his in particular, but some rely on immersion in fluid for cooling.

Some time ago, I worked at a place that used oil filled assemblies that were submerged in use and routinely subjected to very high external pressures ( 3000 psi not uncommon). These units were filled with oil, then submerged in oil and a high vacuum drawn over the oil surface to make sure all air was removed. Complicated process to make sure the unit didn't flood in service.

macona
05-02-2015, 09:05 PM
Any pure mineral oil will be fine.

mickeyf
05-03-2015, 02:37 PM
Hi Mickey: can this type of motor NOT run free in the atmosphere?

I have no idea, this is the first one I've encountered. My working assumption is that the oil was there because it was part of the original design and that they wouldn't have gone to the expense if it didn't need it. I plan to replace it rather than run the pump without it. In any case, it won't be free in the atmosphere, but submerged in coolant.

Actually, I think that explains it. If there were no oil the motor would be inside a small sealed container with no way to lose heat except via the non-circulating air inside that box. The oil is able to transfer the heat to the walls of the die-cast aluminium box, and thus to the surrounding coolant, keeping the pump from overheating.

macona
05-03-2015, 03:11 PM
The oil serves many purposes. Like mentioned, heat conduction. Since these pumps are shaft drive if the pump was full of air it would build pressure as it heated up and air might get past the shaft seal and when it cools it could suck in water. The oil also keeps the water out by being incompressible. Also it keeps the internal bearing and seals lubricated.

mickeyf
05-03-2015, 06:13 PM
I suppose this implies that when refilling - which obviously was not intended by the manufacturer to be done by me the end user - as little air as possible should be left in. I don't have any way to vacuum seal this thing, but I suspect that what I am able to do will be "good enough".

macona
05-03-2015, 06:29 PM
I tried working on one of these pumps before and gave up and just bought another due to the oil issues. I am guessing they are assembled under oil or something.

mickeyf
05-03-2015, 10:19 PM
Did the pump fail after working on it, or were you just unable to reassemble it filled and sealed to your satisfaction?

I have nothing to lose but a bit of my time. I could even (manually, and messily) assemble it under oil, but I don't think that's the first thing i'll try. Since I had to destroy the original plug and power cord gasket to disassemble it I figured I'd re-tap for pipe plugs, adapt one for the sealed cord egress, fill through the other, then "cork in the bottle" at the fill hole.

Duffy
05-03-2015, 11:01 PM
I worked with the superintendent of utilities for the Cowichan Regional District many years ago. In a discussion on submersible pumps, he had these gems to offer:- when dealing with sewage pumps, ALWAYS replace the seals annually or be prepared to replace the pumps. When servicing these pumps, ALWAYS refill them with vegetable oil, (did not really matter which kind, canola would do.) The reason for the vegetable oil was IF a seal failed, it was not recognized as a contaminant in the waste stream, while a mineral oil would cause all sorts of regulatory grief. At the voltages encountered, (maximum 575 3 phase,) and the temperatures involved, ANY oil would work. This of course was just an opinion based on several years of successful application. but what the hell would an old techy know?:rolleyes:

macona
05-04-2015, 12:23 AM
It was mostly along the lines of "ugh. what a mess. aww, screw it."

Get another used one off ebay and forget it. Or better yet get a real coolant pump and use that.

wtrueman
05-04-2015, 03:09 AM
I worked with the superintendent of utilities for the Cowichan Regional District many years ago. In a discussion on submersible pumps, he had these gems to offer:- when dealing with sewage pumps, ALWAYS replace the seals annually or be prepared to replace the pumps. When servicing these pumps, ALWAYS refill them with vegetable oil, (did not really matter which kind, canola would do.) The reason for the vegetable oil was IF a seal failed, it was not recognized as a contaminant in the waste stream, while a mineral oil would cause all sorts of regulatory grief. At the voltages encountered, (maximum 575 3 phase,) and the temperatures involved, ANY oil would work. This of course was just an opinion based on several years of successful application. but what the hell would an old techy know?:rolleyes:

When were you in Duncan? I was born and raised there in the 60's. Lived out in Glenora, Deerhome. Wayne

wtrueman
05-04-2015, 03:13 AM
The reason I was asking about the necessity to run in oil is, was, because the motor runs fine without being surrounded by oil but was wondering how long without being submerged. Thanks all for your time, wayne.

Rosco-P
05-04-2015, 06:57 AM
The reason I was asking about the necessity to run in oil is, was, because the motor runs fine without being surrounded by oil but was wondering how long without being submerged. Thanks all for your time, wayne.

The oil provides for heat transfer from the winding to the case and ultimately the fluid the motor is immersed in. Probably some lubrication of the bearing as well. I'd expect it to have a short life with the oil.

mickeyf
05-04-2015, 09:07 PM
It was mostly along the lines of "ugh. what a mess. aww, screw it."

Ah, yes. I think we all can relate to that!

Duffy
05-04-2015, 11:09 PM
Wtrueman, I never LIVED in Duncan. I was the Public Health Engineer for, at different times, all three Vancouver Island Health Districts. I spent a lot of time in each of them, but I lived in Colwood and Saanich. I met the supt when he and I both joined a consulting engineering firm for a CIDA water supply job in Kenya.This all happened between 1970 and 1981.

Quadra
05-05-2015, 01:47 AM
I was looking for this information for my little giant as well- thank you all!! The manufacturer did not want to share any information .. or sell me a replacement cord set.. no help at all. the cord on mine had hardened up over the years from exposure to chemicals used in cleaning and sanitizing our hot tub. and did have a very small air space ( approx 1oz volume ) in the top of the pump when I broke the seal.
I grew up on the Island and Have family in Duncan and Maple Bay.... and have visited the Lunenburg Foundry last summer :) :)

wtrueman
05-05-2015, 04:39 AM
Thanks Duffy, Wayne

wtrueman
05-05-2015, 04:42 AM
Quadra: I'm now in Gold River and may have some pump parts.

Quadra
05-05-2015, 12:08 PM
Quadra: I'm now in Gold River and may have some pump parts.

I have everything I need thanks, I was just unsure what to use for oil as what I have looks cloudy and I thought I may as well replace it while changing the cord.