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Sealing boiler water level glass

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The_Paso_Kid

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I am currently repairing an old home-built model boiler. The sight glass was cracked and the rubber washers used for seals have long since dried out and deteriorated. I have ordered a new sight glass. I have some rubber gasket material from an auto parts store to make some new washers. I was inquiring if there might be other materials that can be used to seal around the water glass. I checked with the Flex Seal website and e-mailed an inquiry and was told that their products were not recommended for high temperature and pressures involved with steam boilers. I'm not sure about Fix-a-gasket or similar products. Anyone have any suggestions. Thanks.
 

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10K Pete

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Most any model live steam seller will have the exact item. Especially the UK.

That said, teflon tape rolled into a string or cord and then wound around the glass and pushed down into the packing gland works well.

Pete
 

rutzen

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LBSC used to recommend slices cut from rubber tubing and that works ok. As do O Rings. You don't need special O rings, the neoprene ones are fine. Silicone tubing slices work ok too.
 

Steamchick

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Most any model live steam seller will have the exact item. Especially the UK.

That said, teflon tape rolled into a string or cord and then wound around the glass and pushed down into the packing gland works well.

Pete
Agree with PTFE tape - thousands of different applications can work - if originally designed for graphited (cotton) packing. - I even ran an oscillating engine (worn) with ptfe tape wrapped around to replace the grahited string packing for piston rings. - Not a durable as the graphited string in dynamic applications, but showed me all the other problems with the old and worn engine.
Personally, I simply buy good quality silcon o-rings for all sight glasses - but ONLY TIGHTEN a tad more than the pressure required for sealing - Well over-tightening will cause the glass tube to crack or fracture under "seal pressure" which make not be detected until the boiler achieves a temperature and pressure to develop the crack to failure. (Differential expansion of the length of boiler versus length of tube between copper and glass when heated 150 degrees from cold! - You can't beat Physics!). I tighten gland nuts tight by fingers alone, then hydralic test the boiler to 1.6 times NWP and check glasses don't leak - or use the spanner a fraction of a turn until a leak is sealed. - That way I never have a problem running, and glasses have lasted decades in my boilers. - N.B. ALWAYS check and ensure fittings are truly aligned by using a drill or precision steel rod of the same OD as the glass tube to align fittings when tightening to the boiler. A mis-aligned fitting will cause stresses in the glass tube to be exacerbated and risk failure when in steam.
Do Not use liquid silcon seal as it often does not cure hard enough not to creep under pressure when in steam. - It depends on the manufactured grade of material, and few commercial grades form a hard enough silicon bead to resist boiler pressure.
By all means use it for the side of the bath though... I spent many years trying to cure leaking oil from motorcycles (1945~1970s variants) with "liquid gasket" silicon. But when I worked with a Japanese motor manufacturer and localised the Japanese liquid gaskets, the Europeans were amazed at the various formulations used by the Japanese, as they were beyond the applications and specifications required for most "general" European market products. To the extent, they declined to supply some materials and we had to import the Japanese products. But I learned "the West" had a lot of "low density" products, while Japan had a lot of "high density" applications and products. So maybe there are some liquid silicon products on the market suitable for gauge glasses, but not in my experience. - And O-rings cost "$1 for 5...".
K2
 

packrat

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Even with full size boilers we have trouble with sight glass and washers, the boiler water eats the glass at the bottom of the sight glass
and needs to be replaced from time to time, I have seen the high presser glass fail {blow} also. Return water {make up water] will also eat steam traps
and black steel pipe overtime, this of course is with 24 hour 7 days a week operation.
 
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Steamchick

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I am currently repairing an old home-built model boiler. The sight glass was cracked and the rubber washers used for seals have long since dried out and deteriorated. I have ordered a new sight glass. I have some rubber gasket material from an auto parts store to make some new washers. I was inquiring if there might be other materials that can be used to seal around the water glass. I checked with the Flex Seal website and e-mailed an inquiry and was told that their products were not recommended for high temperature and pressures involved with steam boilers. I'm not sure about Fix-a-gasket or similar products. Anyone have any suggestions. Thanks.
That's a geet big boiler for such a tiddley little engine, I guess it was made for something rather larger, that has taken a different journey in life, so now has a little Mamod oscillator - as shown. I suggest you lag the boiler and pipework to the engine, otherwise you'll be giving the engine lots of water, pushed by a bit of steam. - And it looks like the fibre washers on the fitting on the outside of the gauge glass holder need replacing? - cost pence from E&@y.
Ask on this thread if you need advice.

Cheers!
K2
 

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