Seal design for submersible motor

[vcolella]

Hello all,

I'm trying to design the casing for a submersible motor, which will then power a submersible slurry pump. My concern right now is with sealing the casing with a IP68 rating.

For the endbells sealing I believe some well dimensioned o-rings should do the trick. Now regarding the shaft, I thought about using the so called "Bearing Isolators", but from what I found those doesn't seem to be intended for continuous submerged duty. Another possibility that I've found in similar products is a double mechanical seal configuration with an oil chamber, the later being used to "track" the mechanical seal wear by measuring how much of the external fluid is leaking to the insides of the chamber.

Would you say the double seal is the best approach ? And if so, do you have any special advice that I should pay attention when selecting the mechanical seals for this type of application ?

I've been trying to learn about the API plans, but there are so many that I feel kinda lost. Should I go for one of them ? Should I combine them ? How are they supposed to be used ?

Thank you in advance !

 

[gerhardl]

What is your requirement for maintenance free operation time? Continuous? Cost if failure? Submerged 1 meter or 1500 meter? Dimensions? Why not seal the whole shaft?

 

[vcolella]

Hi gerhardl, thanks for replying !

Desired maintenance free operation time would something around 120 days of non-continuous operation. Let's assume for now the max depth is 20m, and the shaft has ~Ø45mm.

I'm not exactly sure what you mean by 'seal the whole shaft'. As I've explained, we'll probably be using an oil chamber for the leakage sensor, so at some point I think the shaft will have to be in contact at least with the oil, right ? Or are you suggesting something like a cartridge seal ?

 

[gerhardl]

Sketch?