gwr
Involved Member
Posts: 56
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Post by gwr on May 16, 2008 19:53:32 GMT
Anyone have any tips on sealing water gauge glass? I've already aligned the two fittings, lubricated the 'o' rings, but each time i tighten the last turn, the glass cracks about ten seconds later!
Help!
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Post by Tel on May 16, 2008 20:49:24 GMT
Lose the 'O' rings and twist some teflon tape into a string and use that instead.
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Post by Tel on May 16, 2008 20:52:04 GMT
..... and don't tighten it down to much - just a tweak past finger tight - like fitting an oil filter to your car.
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gwr
Involved Member
Posts: 56
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Post by gwr on May 16, 2008 20:58:09 GMT
When you teflon tape, do you mean p.t.f.e tape?
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Post by Tel on May 16, 2008 20:59:31 GMT
yep, ordinary plumbers tape
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gwr
Involved Member
Posts: 56
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Post by gwr on May 16, 2008 21:10:38 GMT
Many Thanks, I'll give it a try.
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Post by circlip on May 17, 2008 6:25:44 GMT
Just as an extra observation gwr, are you sure the bores of the fittings are truly in line with each other? Sliding a close fitting pin through them will ensure this. In the dim and distant days of yore, before the advent of "O" rings, slices of rubber tube were the order of the day. this meant that on FINGER tightening the sleeve nuts even a "slack" glass could be sealed due to the compression of the rubber. So you could try the rubber tube option. As Tel quite rightly points out, PTFE tape rolled into a "string" and wound round the glass is much more forgiving, but don't get spanner happy, don't nip up until you're actually steaming, all you're doing is stopping a leak. Whilst O - rings are a godsend in most applications, they are a bit too hard to use on gauge glasses and will harden further in this area. Regards Ian.
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Post by albert on May 17, 2008 8:58:41 GMT
Hello GWR,
I use "O" rings or rubber type seal,but I think your problem is clearance between the fittings + nuts and the glass.I make the clearance for the glass at least 30 thou,I aligne the fittings with a solid rod in place of the glass with no more than 2 thou.clearance. I have had no glass breakages in 40 years.I find PTF tape useless but PTF rings good but not as good as "O" rings.
My rings are from Peter Southworth,for use at our tempretures and pressures and do not work harden.Usual disclaimer.
Bye Albert.
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Post by Shawki Shlemon on May 17, 2008 9:16:07 GMT
I do what Albert do but i place a thin washer close fit ( not tight ) on the glass tube and loose in the nut .The washer press on the O ring . It works for me fine .The rest of the ideas has been mentioned above .
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Post by gilesengineer on May 17, 2008 9:34:45 GMT
Most of our loco's (10 1/4" gauge) use 10mm OD glass, and for years now we just use a bead of clear silicon (mastic) around the glass, and wind the nut down on to it (less than finger tight). this is good for service within 10 minutes or so, and seems to be completely reliable.
One distinct advantage with this is that the silicon 'distributes' itself in such a way as not to impose any stresses on the glass itself. I can't remember when a glass blew last.
Try it and see.
Giles
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