Valve Packing Material

[JonRiley56]

Howdy all,

What do I use to pack the valve/gland where my connecting rod enters the steam chest ? Also, is there anyting special I need to know in re-doing it ? The nut came off this summer while I had steam on it and I chewed the packing up a bit getting it put back on. I would like to re-do it for ths next season. Do I oile it or anything ?

jon

[Oilking]

Jon,
Three things govern a packing selection: temperature, surfce feet/min, & pressure.
After rulling out flax/petroleum "Marine" packings that won't stand up to the temp, just about anthing else will work. Any PTFE(teflon) combination will top out at about 500deg F. Graphites will go up to ~900deg F.

What is most likely to drive your choise is cost and availability, and do you have to buy a pound when less than a foot will out last you? A pound of 1/8" is ~100Ft & 1/4" ~50Ft.

Good Luck

Dave

[barts]

For non-superheat applications, teflon faucet packing from the hardware store works really really well; I used this for 20 years on Otter's converted refrigeration compressor engine; I replaced it a couple of times when I had the engine head apart to resurface the slide valve, but didn't need to.... For superheated steam, woven graphite packing is often used, but so far I've not had enough superheat to worry about that. Mcmaster.com has a complete selection.

- Bart

[JonRiley56]

Thanks all !

Anything I should know about installing it ?
Is it like a stuffing box where you put in two
Pieces with the joints staggered ?

Jon

[barts]

The teflon stuff is soft and packs/flows very nicely. Wrap it as evenly as you can; I've never had it not work - at worst, you'll need to tighten it an extra time or two. It does go solid more quickly than graphited string (which also works), so don't just reef on it because you'll get a lot of friction.

- Bart

[DetroiTug]

Hi Jon,

That is 1/4" square woven graphite in the piston rod gland. And it's two wraps if I remember correctly. There are slots in the perimeter of the gland nut, just put a screw driver in the slots and tap it around tight. I never ran that engine on steam. Typically, when the packing is new, it needs to be checked frequently at first and then periodically and make sure the gland nut is tight, because as the packing forms to cavity with heat and motion, the nut can loosen.

That gland was machined already when I bought that engine. I noticed the threads were free-fitting. On the twin when I machined those, I left some friction in the threads.

-Ron

[marinesteam]

Jon,

Packings of all kinds are available from McMaster-Carr at http://www.mcmaster.com/#gore-tex-packing/=kzu28g

I will be using graphite impregnated expanded teflon which is listed as ultra corrosion resistant in the catalog. (It's Palmetto Packings 1389)

Ken

[fredrosse]

If you have a Harbor Freight store near you, buy a set of "Packing Picks" This is a set of four steel shanks with screwdriver handles, the ends are various pointed shapes to help in pulling out old packings, and installing new. The set of four tools is $3 USD, but I have bought them on sale at $1 USD for the set. Very handy to have on the boat.

A little steam cylinder oil on the rod of the initial installation will keep the rod from sticking to the packing. The main piston rod packing on the Margaret S. has been in place for 3 years now, and (5/8 dia rod, 1/8 inch square graphite packing) does not leak any noticable steam. This is with a ground and chrome plated rod, a good finish on the rod surface is important. I have snugged it up a little, once or twice in the three years. Tightening the packing too tight adds alot of friction, and will destroy the packing in a hurry. Best to just slightly tighten the packing, then when first steaming, run the engine some, then gradually tighten the packing until little or no steam leaks out with pressure on the gland. Best to do this with the engine running, but tightening of the gland in small steps with a stopped engine is generally safer if you or your tools might get pinched by the moving parts. Remember to burn yourself at least once during this process!