mbrown
Elder Statesman
Posts: 1,720
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Post by mbrown on Jan 26, 2015 22:43:47 GMT
Blimey! I never thought my query would spark off this string of exchanges.... All very interesting. One day, when I actually steam the beast, I will let you know how my smokebox O ring fares, assuming I fit one. And yes, I know it isn't necessary, but nor are miniature steam engines, come to that..... But I reckon it's often worth trying something just to see what happens.
Thanks to all who responded.
Malcolm
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Tony K
Elder Statesman
Posts: 1,573
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Post by Tony K on Jan 27, 2015 12:16:10 GMT
Guys, the 'Urban Myth' is associated with burning cars. The alleged threat being from viton seals buried deep in the engine getting cooked and posing a danger to firefighters. I expect we've all seen the boiling water in a paper cup demonstration so will understand that the engine seals shouldn't pose a risk. Similarly, modern cars are full of plastics so burning cars do provide a real risk to health but from a different vector. A decaying viton 'O' ring on a fire door exposed to hot gases or of unknown history can pose an unknown hazard. It's not quite in the realms of a radio active turd but simply treat the manky ones with caution. In fact, if the makers include details of a hazard, whether its arse covering or not, it could be real. Buttered bread will drop butter down. Very much agree. Temperatures in excess of 315 Deg C may be attained within the smokebox but the smokebox shell and door will remain relatively cool due to conduction of heat to the air. Touching a piece of metal at 315 C would remove skin instantly Yes, true. I have done measurements to smokeboxes various and the highest I have found is 180 C. Most are around 125 C. Viton O rings and balls give near enough zero risk in most environments used by us, provided they are not burnt irresponsibly afterwards. Using viton in a position where it is exposed to hot gases is getting towards inadvisable. If hydrofluoric acid is produced it is a very nasty substance. I have experienced viton at work in cooling systems and the precaution taken is to provide HF antidote gel and educate engineers as to the risk. HF antidote Gel has a shelf life of approx 1 year.
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