Better seal for pumps

[HiriseBuilding]

Which is the better seal for condenser water pumps in A/C plant. Mechanical seal or packing gland type seal?

 

[MikeHalloran]

Packing glands have to leak a little in order to survive. Can you deal with that?



Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

Probably mech seal in this case as plants like this are never well maintained and packed glands need some attention, and as pointed out by Mike - can gland leakage be handled.

 

[HiriseBuilding]

In my building, pumps are packing glands type. What we usually do when there's a leakage in packing glands was we were just re-tightened the nuts and the leaks stop. My only problem here after 2-3 days the leaks was there again. Is it possible to convert packing glands to mechanical seal? Any disadvantages for mechanical seal type based on your experience guys?

 

[Artisi]

Packed glands need to leak a little - this lubricates the packing and the shaft or shaft sleeve if fitted, depending on the pump size 2 - 4 drops a minute is probably sufficient lubrication.
Over-tightening will destroy the shaft / shaft sleeve and reduce packing life - once you have burnt the packing or damaged the shaft/ sleeve a good seal become impossible.

Most pumps can be converted to mech. seal - the best idea is to contact the supplier or a reputable seal supplier for advice - there are far too many variables to make a seal selection from here.

 

[CJD1984]

HiriseBuilding-

Depending on the type of pump that you are using, you may be able to retrofit the existing packing to mechanical seals.

It depends on the internal dimensions, but you may be able to utilize an "off the shelf" seal. If your pump does not easily fit a standard, mass-produced seal, custom seals are available.

You will need to have a vendor help you with this. We engineer seals all the time and the only negative in my mind is intial cost. Mechanical seals will be more money than packing most of the time. But, if you can look at the money situation long-term, you will save maintenance costs by not having to concern yourself with re-tightening the packing. When designed correctly and with no signinficant process upsets, a seal can last up to 10 years with no maintenance.

 

[MJCronin]

This is a good question to post on the "Pump Engineering" forum...

I know that there is no one clear answer to the question...and that a lot depends on the particular pump in consideration.

Another issue, as I understand it, is pump vibration.

Mechanical seals are more sensitive to damage in service where there may be vibration.....packing, as I understand is more forgiving.

-MJC