PTFE Gland Packing

[Malcolm]

Has anyone in the group used woven PTFE packing for steam cylinder glands? What was your experience of it? Is there a supplier of small quantities of one-eighth square? I don't want to buy a box of about fifty feet at some horrendous price.

[chris vine]

Hi,
I have never tried it for packing glands but I use it for making valve seats etc.

You could buy a stick of it, say half inch diameter from GLR Distributors Ltd, and machine a bit like a square O ring on the end of the stick, part it off, and split it with a sharp knife so that you can get it over the piston rod.

How long it will last will depend on the smoothness of your piston rod.....
Chris.

[waggy]

Malcolm,
I have used PTFE for piston and valve rod glands on my 5" B1 since I built it ten years ago. I used PTFE string which used to be available from RS components. It is approx 1mm diameter and is wrapped around the rod and then tamped into the gland, secured by the gland nut. I have never changed any of the seals, nor suffered leakage. When the PTFE is "squeezed up" in the gland it forms a ring seal without using much force. All the gland nuts on the loco can be turned by hand! Polish your rods longitudinally and all will be well! If string not available, you could try twisting the readily available PTFE tape into a string, might work! Good luck.

Dave.

[NigelMuskett]

I use ptfe tape as a heating engineer every day and I would agree with Dave in suggesting its use. There are two thicknesses of tape 0.7mm and 0.02 mm. Get the thicker tape tear off a strip, hold one end and roll it around - instant ptfe string certainly holds mains water pressure up to 5bar locally.

Nigel

[Malcolm]

Thanks for the replies. What I had in mind was the proper square packing, like graphite asbestos valve packing but PTFE. However it doesn't seem to be available in small quantities, so I might try the string or tape.

[rtownsend]

Hi
I used to overhaul boilers here in Oz for their annual inspection. the boilers were made in Andover (Hants)(super economic , Presha Engineering) and used to run at 100 psi. I found that the ptfe packing on the glands would extrude when under full pressure and a much superior packing was the graphited asbestos square stuff from J Walker. I know the mention of asbestos makes everyone wary but this stuff had a really graphitey greasy feel and there was no chance of any asbestos fibres escaping or being breathed in.
Hope this information is of use to you
Regards Reg Townsend

[Malcolm]

Thanks, Reg. I agree with you. I would love to use graphited asbestos, but it has been totally banned here. There have been several nasty accidents with steam boilers due to the inferior asbestos replacements blowing out.