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Mechanical seals vs packing

Mechanical seals vs packing

(OP)
We have numerous jacketwater pumps at our "emergency only" power generation (diesel engines) plant.

One of our operators has suggested replacing the existing packing type of seals for mechanical type. The pumps in question are 50+ year old Allis Chalmers type, with nameplate info: model 21306, size 8X8, dia. imp 8 5/8 FV, 1750 rpm, 1450 gpm serial #810-144-2. (see attachment for a picture of one of the pumps)

I am curious about this process. Is it advisable to do this?

Can you recommend a company who could come in to evaluate our setup, in order to obtain a price for conversion?

We are located in southeastern Colorado.

Thanks in advance for any help.

Rick Miell

RE: Mechanical seals vs packing

That's a clean facility.

Do you have room for the seals? Do you really feel like taking the bearing bracket off every time you have to change one? I'm guessing the "operator" is not the maintenance technician.

It will change the support on the rotor (seals will have less support than packing) so it will have a longer span between supports, this lowers the first critical speed and will bring it closer to the operating range. Hopefully still well above and won't cause problems, but if it ain't broke...

RE: Mechanical seals vs packing

The biggest thing I find is what mounting surface will be used for the seal, and whether there is room for them.

Reliability of packing and mechanical seals is simply different. I suggest converting a few in the beginning to get to know the best mechanical seal solution before a full deployment.

RE: Mechanical seals vs packing

If this is an emergency diesel engine driven gen set, there would be no mains power when you this set gets the start command. And I would presume one of the permissives for this unit to start would be that these jacket water pumps are already running.

So do you have a battery bank to kick start the jacket water pumps ?

If so, whatever seal plan you use for these pumps, if it involves additional seal fans or pumps, the total incremental power demand should be within the capacity of this battery bank. If there is monitoring instrumentation for these seals at 110V DC, you may need a new local seal system control panel ?

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