Fire Pump Packings

[javhmgs]

I can't find any information on changing pump packings from graphite to teflon. I heard that teflon is harder and can damage shaft sleeves in as short a a weak of operation but i can't really find any information. The question arises because my company was replacing an inboard bearing of an horizontal split case fire pump that had been damaged because water got into it. During the repair we needed 1/2 inch graphite packings but they were not available to buy and we were fixing the pump in an emergency basis. We got teflon packings or 5/8 graphite packings. I decided to use the 5/8 graphite packings using them sideways in order to align the water seal properly. The pump performed as required until I could replace the packings to the correct size but still the question lingers. Do teflon packings damage a pump designed for graphite packings? All fire pumps i have worked with are manufactured in bronce.

 

[NGLENGR]

*Puts operator hat on*

"There's a difference? It's just water!"

*Takes off operator hat*

In all seriousness, I don't think there will be a major problem with teflon if you don't tighten it more than necessary.

Unfortunately, our firewater pumps rarely last much longer than the packing; our water is more brine than anything!

 

[TenPenny]

I would think that the graphite would be harder on the sleeve than the teflon impregnated packing. Can't see that it will have any major effect.

 

[4JawChuck]

Teflon packings do not conduct heat like a graphite packing does so overheat of the shaft is common when switching over, usually some leakage is required to use a teflon packing which is typically objectionable in the common service fire pumps are required to work under (no leakage while idle which is 99% of the service life).

Stay with graphite, save yourself the hassle of warped shafts and ruined impellers from high point contact when the shaft overheats.

This is the good reason why fire pumps use graphite impregnated packings.