Has NASH been in? What did the representative say?

Nope. They were not aware of this problem.

I did not consult NASH directly. NASH do have sales representative here in Malaysia but so far no feedback from them yet. We did purchased a new similar vacuum pump from them last year but the problem still happened for the new vacuum pump.

Consider there is a 5 years gap between the old vacuum pump and the new one in the plant, I'm sure that there will be an improvement for packing when I purchased the new pump last year; sadly there were none.

I would be appreciate any good recommendation from your guys on how to solve the leaking problem. Thanks.

NASH has a reputation to protect in the marketplace. Get a technical representative to visit site at the earliest opportunity. The manufacturer has seen all the problems before elsewhere and needs to be given an opportunity to put this one right too.

I thought that packing glands are supposed to leak a few drops per minute. Does the leakage prevent the pump from producing adequate vacuum?

I agree with Tornado. We had Nashes aboard many ships and there was always a weep-age of sealing water out of the packing gland. We used graphite impregnated asbestos back then but later used Teflon braided packing.Is your source of sealing water clean? Could you be getting rust or sediment into the water and gland? A little rust can tear up a packing. Is so, install a Y strainer with a fine mesh in the seal water line and check after a while for contamination.

I also agree with tornado. We have water ring compressors and using similar packings (graphite impregnated asbestos or Teflon braided packing).

See if it can be modified to use a rotary seal, as you're using it to suck liquids it will stay lubricated. Get an engineer to look at it.

Bazzer

I am not familiar with this specific application but in general packing should not be over tightened to the point it does not leak. Doing so causes premature wear and failure. Double check with NASH on the proper install procedure.

These kinds of pumps always leak at those seals. I have four Dekker pumps that use oil instead of water, and they started leaking within a few months of being new. Dekker replaced one set of seals, but it made no difference. I finally went to cheaper oil and premium seals after the warranty ended, and I just live with it. Having used this kind of pump in different companies, mostly using water, I can safely say they all leak. That is the main reason they put the bearings outside of the seals and insure any leaking doesn't get to the bearings.

One problem I have been having lately is the radiators clogging up. I think it may be varnish, but I do change the oil frequently and it is good turbine grade oil. Does anyone have any ideas on what I could add to the oil to clean up the varnish?

Thanks

Here's a thought for you. Can you run a vacuum line from the pump to the seal area to suck the leaking water back into the pump? You may need to design a drip pan, but this would solve any problems with the water getting on the floor.

Have you checked the condition of the shafts at the seal area? I have discovered abnormal wear in the past that interfered with the packing. That all said they should leak a bit of water to provide lubrication of the packing riding on the shaft.

Best option would be replacing packing arrangement to mechanical seal. You may consider retrofitting towards upgrading to mechanical seal arrangement.

A comparison of compression packing with mechanical seal states:

Those days NASH and GARO were pioneer liquid ring vacuum pump/compressor manufactures. NASH models have BB - Between Bearing type and GARO have OH - Over Hung type. I think NASH and GARO have now merged, I am not sure.

Is your model type BB or type OH? If OH type, retrofit would be relatively easier.

If this discussion is relevant, I can discuss more, since have quite an experience on such retrofit.

Dekker uses the mechanical seals in their pumps. The pumps are actually made by Travini, so I should be saying Travini uses them. Either way, when the rubber boot on the seal breaks, it's a real mess to clean up. I've only had that happen once, and replaced it with a higher grade seal.

Guys,

I have already contacted the sales representatives of NASH to ask for technical assistance. Still waiting for their feedback.

Currently we were using SEPCO Multi Lok Braid Packing ( which i assume that it is the same with Teflon-Braided Packing judging from the appearance of it). Source of water is clean but we do get some fines from the gas that went in the liquid vacuum pump. The packing is still in a good shape when we took it out. There was a time when we took it out the shaft condition was in a bad shape due to the Aramid type of Packing (which now we do not use anymore).

What do you mean from rotary seals? Is it the same type with Chesterton type of seals?

I will double check the proper installation procedure for the packing but for the mean time I am sure that we do not over-tightened it during the 1st installation.

FYI the application of the mechanical seal in the vacuum pump is not suitable for the plant since we need to run the liquid vacuum pump 24/7 every year until the annual shutdown.

Thanks alot for the comments guys BTW.

BTW there is some confusion on the packing that should be used on the pump. I just recently ordered the Repair Kit for the pump. The packing that comes in the kit is SEPCO Treated PTFE Yarn Packing which is used commonly in static application such as valves (as indicated in SEPCO product catalogue).

This make me skeptical about NASH technical capablities. Why do they provide us this kind of packing for the pump? Of course I didn't use that packing as I afraid it will damage my pump.

BTW the repair kit was not bought directly from NASH but from the agent who liase with them.

Any comment guys?

You have indicated, "The packing in the stuffing box always leak within 1 month after replacing the new one." Also, "there is a 5 years gap between the old vacuum pump and the new one in the plant".
After replacing the packing rings, do both new and old starts leaking after just one month? Or the new machine gives better life?
What was the experience, the same from the beginning, since 5 years?
The shaft packing area comes with (SS) sleeves, have you ever changed them, why?
Have these machines overhauled after installation?
Tell about the vassal these pumps are effecting vacuum. Are the just sucking plain air or with acidic gas?
What is the pressure of gland cooling liquid/water?
I've maintained vacuum pumps for several years, including the Chlorine service where concentrated Sulfuric acid was the sealing liquid. I think I this problem could be sorted out by proper diagnosis. Your answers might help our analysis.

That's a nice list of root cause investigating criteria there.

OP seems to be on the ball...should be interesting.

OP, call NASH again. Don't wait for their response. Squeaky wheel gets the oil....