Mechanical seal failures

[MedicineEng]

Hi all:

In our property We have been having mechanical seal failures that in my opinion are excessive.
Since most of the systems are still under DLP, I'm arguing that given the high rate of failure, the contractor assumes the cost of an entire full replacement before DLP expires to be validated by pump manufacturer, which he is trying not to do due to the costs involved.
I was trying to find some indications on expected life expectancy on mechanical seals, but I can't find anything definitive. What I know is that given that these pumps are basically pumping water for HVAC and compared with my past experience in chemical industry, these mechanical seals are presenting an abnormal rate of failure.

Let me give you some numbers:
From 5 condensing water pumps, 4 had its mechanical seal replaced between 10-14 months after put into service
Chilled water: 1 out 5 in 14 months of service
Evaporator side on the heat pump: 2 out of 3 in 9 months of service
Hot water @80C 6 out of 8 failed within 9 months
Hot water @60C: no mechanical seal failure up to now out of 10 pumps

All pumps are from the same manufacturer (Grundfos)

I know that the life expectancy of a mechanical seal depends on a lot of factors namely type, fluid, pressure, temperature, etc. but I was hoping to find some industry rules of thumb (or ideally something more concrete) that I can nail the contractor with or else I'm seeing myself having him walking away in a couple of months when DLP expires and I stay with all the lemons to make a big sour lemonade...

Thanks a lot for your feedback.

 

[Artisi]

Contact Grundfos.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

That looks like a lot of seals, but finding anything definite will be very difficult. If you're getting no joy from the pump vendor or seal supplier then type going to need am expert to deal with the court case it sounds like you're aiming for.

Only am organisation who see hundreds of pumps per year will have the statistics you're looking for.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rotw]

Have the seals been supplied from the same/common manufacturer - across your project / plant ?
Has the contractor set up and applied a selection process for the procurement of the seals or was it left up to the pump manufacturer?
Has the contractor prepared a technical specification for the selection of the mechanical seals? and/or has the end user put some project requirement on the selection of the seals?

 

[mk3223]

Instead of relying on the pump vendor, the vendor, such as John Crane specialized in the pump seal, may be helpful to your pump issue.

 

[rotw]

by the way, DLP stands for?

 

[LittleInch]

Defects Liability Period, but I had to go look it up. ....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rotw]

ok thanks. Sort of "guarantee period" (the contractor is subject to).

 

[MedicineEng]

Thank you all for your feedback.
As far as I know, since I'm part of the operations team, and not the construction, all pumps and mechanical seals were supplied by Grundfos but I'll try to get some more information about it.
Of course at this stage of the game, I doubt that the contractor will be very forthcoming on sharing information with me.
Let's see where this takes us.

 

[Artisi]

"Let's see where this takes us." around in circles if you don't do anything positive.
Return a few of the failed seals to Grundfos for comment.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[rotw]

This is a technical article related to the topic. Maybe it can help to get a "feel" in general on failure rates, MTBF figures etc...

http://turbolab.tamu.edu/proc/pumpproc/P17/P17171-186.pdf

 

[MedicineEng]

Artisi:
That's what we are doing. We are requesting Grundfos to step in and give us a technical assessment of the root causes for premature seal failures.

rotw:
Thanks for the article I scrolled it quickly and it gives some nice information. I'll read it more carefully tonight at home when everybody is asleep and I can dig deeper on those calculations.