Bore Pump - which oil?

[Gecko]

Slightly OT question.
The background is that I put in a bore with a solar powered pump two years ago and it's been running well until now. Diagnostics said the controller had failed, but after getting first one then a second controller, the salesman admitted the problem probably wasn't the controller and told me the problem had to be in the pump (must have got water in it and seized the bearings - he said). Apart from having chinese bearings that were rough after only two years, there was nothing wrong with the motor, so I moved onto the "wet end" and discovered the case had burst internally.

Neither a new wet-end or complete pump was available locally, but I found an Italian wet-end on fleabay for a good price, counted the splines and took a punt the chinese had copied rather than designed - I got lucky and the fit is perfect.
The bearings and seals are off the shelf, so I'll replace everything before sending it back down the hole.

To the question: The pump runs 100% full of oil (it has an expansion bladder), so the bearings and armature are fully immersed.
I'm thinking the lightest hydraulic oil I can get (with anti corrosion and anti wear additives) would be suitable (I'm thinking an ISO 22 or even an ISO 15).

Any opinions/ experience?

 

[DaveDCB]

Dad had to get a new one last year.. sure he said it was £800 odd… then ran dry and buggered that one up

 

[Gecko]

Dad had to get a new one last year.. sure he said it was £800 odd… then ran dry and buggered that one up

There is a very wide price range on these. In Oz, they range from £250~3000. I paid about £500 for mine and once it had proven it's self, I intended to buy a second to have a spare on site, but seeing how this one has failed, I'll look for something better made.
My controller somehow detects the pump has gone dry and shuts it down (the damage caused running dry is in the wet end, not the motor). I tested this several times when I had the motor/wet end separated (at least that works!).

 

[Gecko]

as an update, I've bought a liter of "transformer oil" whatever that is - high dielectric obviously but no info on other properties. I guess that'll do the job.

 

[V8Druid]

as an update, I've bought a liter of "transformer oil" whatever that is - high dielectric obviously but no info on other properties. I guess that'll do the job.

very thin viscosity usually

 

[Canal Navvy]

Isn't transformer oil quite toxic ?

 

[Gecko]

Isn't transformer oil quite toxic ?

Yeah, the old stuff was nasty - contained PCB's (Polychlorinated biphenyls), but have been banned since the '70's.
I'm rather hoping what I've bought isn't old stock!

 

[Gecko]

very thin viscosity usually

Yep - needs to be as the armature and bearings are fully submersed - which leads to another question.
Bering are normally grease lubricated or partially oil immersed, but in this application, the bearings are fully submersed.
When I stripped the motor, the bearings had a mix of open and shielded sides (two bearing side by side at the bottom, one bearing at the top).
My feeling is the bearings are better running without shields, but open to arguments.

 

[Left hooker]

Isn't transformer oil kerosene

 

[Gecko]

Transformer oil should have a very high flash point and very low flammability.
Some oils mix easily with water (eg. machining coolant) - another property that must be avoided particularly as the voltage rises

Transformer oil - Wikipedia

en.wikipedia.org

The oil that was in the motor had a viscosity similar to ISO15 or 5W (fork oil for those that ride)

 

[V8Druid]

Transformer oil should have a very high flash point and very low flammability.
Some oils mix easily with water (eg. machining coolant) - another property that must be avoided particularly as the voltage rises

Transformer oil - Wikipedia

en.wikipedia.org

The oil that was in the motor had a viscosity similar to ISO15 or 5W (fork oil for those that ride)

tranny oil is a cooling oil to conduct heat away from the windings NOT a lubricating oil, per se .. is there no where you can get a spec. for the required oil in a subby well pump? ... 'bout the right viscosity though I'd guess

 

[Gecko]

tranny oil is a cooling oil to conduct heat away from the windings NOT a lubricating oil, per se .. is there no where you can get a spec. for the required oil in a subby well pump? ... 'bout the right viscosity though I'd guess

yeah, my thoughts too. My voltage is not high enough to cause most of the problems transformer oil is designed to cope with (except water resistance).
My plan at this stage is to filter the oil that came out and top it off with the new stuff.

 

[Gecko]

Update

Pump back in service today.
After only one year in service, the chinese bearings were running rough, so the they got replaced ( Bearings - 1 deep groove at the top and a deep groove plus an angular contact at the bottom - guess which one I didn't have).
In place of the original 14 stage wetend I'd sourced italian 10 and 20 stage wetends - then had to choose which to use. The '20' won and down the whole it went.
When all was assembled and connected, I only had 5min before sunset - not ideal for a solar (only) pump, but it still managed 1000 rpm (max. 4k rpm) and brought water to the surface.