Pump Shaft Seal

[LVFD301]

On a smaller pump, 500/750 GPM or so, PTO. What is the general feeling about a mechanical seal as opposed to plain old packing?

I was warned off mechanical due to the water we often use, lakes, creeks, etc. Very dirty at times, sand and grit. Hydrants are only something we see when we go to the city.

Waterous most likely for the pump.

[FIREMECH1]

I'd recommend using the gland packings over the mechanical seals. Since you've noted your using "dirty" water, packings will take better abuse than a mechanical seal. Replacement sucks for both, but the packing style lasts quite a bit longer.

FM1

[kuh shise]

For either type of seal, it is important not to turn the shaft for long periods without water. Reading between the lines, I suspect that your F.C. does a lot of drafting. This in itself results in extended prime times while water is brought up the hard sleeve. Ceramics, be they Carbon, Aluminum Oxide or Silicon Carbide, do not like rapid changes in temperature, especially when applied to only one side of the ceramic. To others who may be reading this post... Minimize the rpm and time that a ceramic seal is operated without water. When water contacts a ceramic, the part exposed to the water contracts rapidly due to cooling. This change in size creates stress in the ceramic that can cause failure of the ceramic due to internal stress from having one hot side and one cold side. Actually the ceramic will hold up better to dirty (sand or clay particles) water than the chrome plated pump shaft under the packing rings. Packing rings can be adjusted, but a cracked ceramic seal must be replaced.

[LVFD301]

Thanks both of you. Sort of what I remembered, but wanted to make sure that I was correct.

[westofd1]

I would not reccommend mechanical seals to anybody. We've had nothing but troubles with our 2003 Tanker with a Hale ap50. 3 times in5 years is not a good average. The last time in crapped out while pumping from creek. Go with a gland style. stay safe

[FIREMECH1]

I would not reccommend mechanical seals to anybody. We've had nothing but troubles with our 2003 Tanker with a Hale ap50. 3 times in5 years is not a good average. The last time in crapped out while pumping from creek. Go with a gland style. stay safe

Missed this one.

There is a place for everything, including the mechanical seals. 90% of our stations will run off of hydrants. With that, I have no problems with rigs in those areas running mechanical seals. We have them on 16 rigs, and have only replaced 3 to date on waterous pumps('97-'09). The ones that will run MA get spec'd with gland packings. Reason being is they are more apt to run off a draft instead of a hydrant. Pumps are always kept wet.

FM1

[Stuart]

We purchased a Darley rear-mount pump in 2003. So far (knock wood) we've had NO problems with the mechanical seal. It doesn't leak a drop and while it doesn't draft very often, we've had a few operators heat the heck out of it already.