[PSUBS-MAILIST] motor seal

[Alan James via Personal_Submersibles]

Hank,is it a simple diaphragm or rolling diaphragm?There are rolling diaphragm compensators with switches to show low oil,that look easy to make.Below are some from Silvercrest. Note that they start at 270cc in size which isreasonably small.AlanOil Compensator Units.Silvercrest / Submersible Motor Engineering supply oil compensator units for subsea vehicles, to suit manned submersibles, ROVs, submarines,  subsea trenchers and  subsea ploughs, and subsea equipment.We can offer a range of oil compensation unit sizes, including a 2.7L Compensator.  7 x 1/4" NPT (BSPT). SA-HC-0745-MAS.  This is a rolling diaphragm, positive pressure compensator (2700cc capacity), manufactured in corrosion resistant plastic suitable for ROV and tooling applications.These units are particularly suitable for compensating thrusters, compensating oil filled junction boxes, compensating valve packs, and other subsea applications   
   - Size - 270cc, 2700 cc, and 13.5L
   - Delrin Plastic Construction
   - Grade 316 Stainless Steel Spring
   - Adjustable Pressure Relief Valve
   - Mounting Feet
   - Low Level Proximity Sensor Option
 

 

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Thursday, December 15, 2016 4:46 AM
 Subject: Re: [PSUBS-MAILIST] motor seal
   
One more detail I forgot to mention, there is a spring loaded diaphragm at the bottom of the oil filled motor that would create a small internal pressure that would help the seal.  Alan mentioned there is a 4 psi internal pressure on purpose built thrusters, that would coincide with the pump arrangement.Hank 

    On Wednesday, December 14, 2016 8:28 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 Alec,There must be a reason the seal in the pump motor is backward to the Minn Kota.  The pump motor is designed to be oil filled under water and the Minn Kota is designed to be air filled under water.  If we want the Minn Kota to act the same as the pump motor, it may be beneficial to copy the pump arrangement.I don't know, this is above my pay grade ;-)Hank 

    On Wednesday, December 14, 2016 7:57 AM, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 Hi Hank,
I don't know anything about submersible pumps, but might it just be that the high pressure is on the inside in that application? For oil compensation I did not reverse the seals. If the pressure differential is less than what the seal can tolerate, I really see no reason to change anything or to provide positive pressure (which could blow a seal out). I would just fill the space between the double seals with grease and that's it.
Best,
Alec
On Wed, Dec 14, 2016 at 8:16 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hi All,I took a submersible pump apart to find that it has one seal and it is backwards compared to the Minn Kota.  Maybe the trick is to reverse the seal when the motor is oil filled.Alec, is that what you did, I remember you and Cliff talking about that.Hank
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