Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

For those of you that have windowed sight glass on a Jensen boiler such as on a Jensen 50, or a 75, or 55, etc; I have experimented with probably 20 different ways to get the “perfect” seal;  while others have worked to 95-99% seal with only “slight to minor” leakage, this is a complete seal that I found works so well there isn’t even a slight steam leak.


While I find all Jensen products made well, the windowed sight glass wing nuts just don’t prove enough even with their flimsy paper gaskets… and I know we’ve all tried the dollar bill gaskets which prove very effective but not 100%.


If you follow these steps in the exact order you will achieve a perfect seal that lasts months or years.

From inside to out:

Dollar bill gasket
Paper Jensen gasket
Glass (wrapped in PFE tape around edges, 3 wraps.)
Dollar bill gasket
Paper Jensen gasket
Wing nut (wrapped clockwise with PFE tape, 3 wraps)

Tightened down until no longer able to tighten.  What’s also best, is the PFE tape prevents rusting and corrosion.  Can change out the PFE tape 2-3x a year for maintenance.
 

After doing this you’ll have alot of stringy material in the window. Just clean it up, then use a blow torch (small) to touch up the excess strings, but only for brief seconds to not crack your sight window.

Steam it up, you’ll see how amazing the seal is.

PS-  put a drop of oil in the threads before placement! [ Guests cannot view attachments ]

A single teflon gasket from Teflon sheet also makes a perfect seal. Doesn’t burning Teflon give off a deadly fume? Oliv on the Mamod forum has posted warnings about that…

This is the Teflon gasket material I use.  It's soft and seals easily.  It's thicker than the paper gaskets or the hard Teflon gaskets so two of them with the sight glass will put the boiler nut flush with the edge of the threads but that's never been an issue.

[ Guests cannot view attachments ]

Only downside with this stuff is that it's difficult to cut with a knife so you really should punch it out. I had to make a larger punch for this set for the boiler glass.

I also thought the same thing about frying pans as I have a gas stove, but when he seen us using these gaskets for SV’s/whistles, he put out all kinds of warnings. Some of us use the teflon for whistles/sv’s on flame fired Jensens where the flame can come up around the boiler and touch the gasket. He made posts about machinists who after machining teflon had a little dust on their fingers and when lighting their cigarettes ended up dying from the powder burning, don’t know if that would happen with the teflon tape, but Oliv was sure worried about us all using it.

Good thing I don’t do a lot of cooking 😂

The dollar bill was for tighter fitting areas like between the boiler and engine base of the 35 or under the steam domes.

Quote from: Nick on November 30, 2024, 07:16:58 pm

The dollar bill was for tighter fitting areas like between the boiler and engine base of the 35 or under the steam domes.

Well I got that memory wrong Nick, I used to really like Rog's site and all the helpful hints he had (which was many!).

I believe Rog got the dollar bill gasket tip from me. It is .004" thick and very strong. They are perfect for replacing gaskets on a #20 or 4 screw cylinder #10/25 cylinder. Great for all other flanges and any place a thin sturdy gasket is needed.