The component is a two-stage centrifugal drip pump driven by a 3000 HP 4 pole motor. The process fluid is 370 degF water at 170 psia. The OB pump mechanical seal has developed a 2 gpm leak. The pump location is in a pit with limited access and escape. We are collecting additional oil samples from a tap that is real close to the leaking seal, as well as routine vibration surveys. Escape from that area, should it be necessary, would have to pass an area radial from the leaking seal.

So...to my point...is this dangerous? Our engineering staff has evaluated it as OK...but with little detail of explanation. I'm looking for 1st or 2nd hand knowledge of what such a seal failure would look like...how dangerous could it be to somebody performing a vibe survey at the pump? I suspect that the leakage would increase as a result of tripping the pump or otherwise taking it out of service due to additional delta-P across the seal? Comments?

Thanks in advance,
George

George, you state that the "process fluid is 370 degF water at 170 psia". This of course means it flashes to steam upon exiting to atmospheric pressure. I'm no safety engineer, but I would be concerned that someone would be present in the immediate area when the seal could perhaps totally blow out. Depending on the proximity of the person to the seal area, serious burns could be the result.

John from PA

About the only thing I know for sure about mechanical seals is that I don't know much. I'm pretty sure there is one style where the seal flow is fed from pump discharge through an orifice. The orifice would limit leakage in event of a complete seal failure and the max flow can be computed knowing the orifice size and the dp. But I am pretty sure there are a wide variety of seals and failure modes.

I would recommend to keep asking the question until you are satisfied that it is safe.

It is NOT ok. Burns are painful, slow to heal and can be disfiguring. It's not worth it chancing getting someone burned or maybe even worse. If your engineering staff still says it's ok, hand THEM the data collector and oil sample bottle and tell them to go in the pit. What does your safety department say about this? They should have the final and legal say so.

"in pit" is this an enclosed space? Limited access what rescue plans are in place in case of an accident?

Is this your own site or a customer, has a risk assessment and method statement been carried out.
what are your/customer control measures?

Any doubt fit sensors and hard wire for safety

Have you checked OSHA regulations on Confined Space? California is even tougher than many Federal Regulations, so check to see if there are any State Regs preempting the Federal Regs.

It doesn’t have to be very deep to be classified as confined space. There’s also some definition around one escape route and ease of escape. Check it out for your own good. Company Safety Departments don’t truly have final legal say so if they are wrong. If company decisions don’t match regulations, CHALLENGE AUTHORITY!

I believe that if it does meet the definition of Confined Space, there must be a published Rescue Plan in place at the Company Level.

This message has been edited. Last edited by: Wally,

quote:

process fluid is 370 degF water at 170 psia. The OB pump mechanical seal has developed a 2 gpm leak

So I assume the leakage rate has been measured? That implies the leakage is in a fluid state, right? The leakage is not flashing to steam, at present....correct?

This suggests the seal does not directly "see" process fluid. Your engineers may be correct. It all depends on how the seal is arranged. I suggest that you research this. Why not just call the pump manufacturer. I'm sure they have seen seals "fail" on this type pump before.