Mechanical Seal Problems - ECoat Paint and Ultrafiltrate as Barrier Fluid.

[DONLORIMER]

thread819-109062

Hi All

I have been reading a previous post (Sealing of Water Based Paint, Again) and I am having similar issues with mechanical seal leakage.
Did anyone ever get a good solution?

Long coupled end suction centrifugal pump with a double cartridge mechanical seal (double balanced). Plan 53 thermosyphon vessel with Ultrafiltrate as barrier fluid. Running at approx. 4 bar positive pressure differential.
We are suffering outboard seal face leakage of the UF - after 4 weeks operation.
A cooling coil was fitted to the vessel to keep barrier fluid nice and cool (25 degrees C) but this hasn't helped.

I would love to know if anyone has managed to achieve success using thermosyphon vessels as plan 53 on paint applications. I have been involved in numerous over the years (Jaguar, Honda, Citroen) and this type of sealing arrangement has always seemed more trouble than the traditional route which used back-to-back component seals with UF continually circulated through the seals.

Your help will be much appreciated.

Don. (UK)

 

[CHoff07]

Don,
I have more questions before I can help give answers.
I'm in O&G and not familiar with paint application but RCFA's are still RCFA's

Can you provide some more information regarding the seal failures you are experiencing?
What do the outboard seal faces look like after the failure?
Are they still showing thermal distortion?
What kind of leak are you seeing (Major failure after 4 weeks or small drips all the time that are just finally getting written up for work orders ever few weeks)?

I am not familiar with the barrier fluid, can you provide the physical properties for the barrier fluid?
When you say thermosyphon, does that mean that your dual, pressurized, seal does not have a pumping ring?
Without a pumping ring you may not be getting enough circulation at the outboard seal faces to utilize the cooling coils you recently installed.

Also since the outboard seal sees the higher differential pressure that face will generate the most heat and is more likely to experience a seal failure. Are you comfortable reducing the barrier fluid pressure to something closer to 2 bar.

Have you consulted the mechanical seal vendor?
Can they provide predicted seal face temperatures and estimated leakage rates?