Re: Drifting valve questions
| April 30, 2020 11:06AM |
|
flatcarwillie Wrote:
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> It’s not drifting valve—that’s something
> entirely different—but a cylinder relief or
> “snifter” valve. It’s purpose is to prevent
> unwanted accumulation of steam in the cylinders
> when the engine is standing (say from a leaky
> throttle) that could potentially cause undesired
> movement.
The main use of snifters is for drifting, so as the engine coasts without enough throttle, they drop and let air into the cylinders to break the vacuum that would otherwise cause cinders and other junk to get sucked into them as the valves open for exhaust. For preventing steam from building up when stopped, an ordinary globe or ball valve would do the trick. #90 had angle cocks in that service when she came here, and her cylinders were loaded with carbon from the pollution they sucked in, something that has never reoccurred once snifters were installed.
Sharrod Wrote:
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> As the others said - plus, on the Strasburg Rail
> Road we had (still have?) screws with valve
> handles mounted over the top of the snifter, and
> the snifter is screwed down, open, when the
> engines are banked at night. This is to prevent
> the engines running away due to a throttle leak.
Still do. It's nice to be able to bleed off a load of steam without having to balance a rock on the little stem while you are getting a face full of steam.
-------------------------------------------------------
> It’s not drifting valve—that’s something
> entirely different—but a cylinder relief or
> “snifter” valve. It’s purpose is to prevent
> unwanted accumulation of steam in the cylinders
> when the engine is standing (say from a leaky
> throttle) that could potentially cause undesired
> movement.
The main use of snifters is for drifting, so as the engine coasts without enough throttle, they drop and let air into the cylinders to break the vacuum that would otherwise cause cinders and other junk to get sucked into them as the valves open for exhaust. For preventing steam from building up when stopped, an ordinary globe or ball valve would do the trick. #90 had angle cocks in that service when she came here, and her cylinders were loaded with carbon from the pollution they sucked in, something that has never reoccurred once snifters were installed.
Sharrod Wrote:
-------------------------------------------------------
> As the others said - plus, on the Strasburg Rail
> Road we had (still have?) screws with valve
> handles mounted over the top of the snifter, and
> the snifter is screwed down, open, when the
> engines are banked at night. This is to prevent
> the engines running away due to a throttle leak.
Still do. It's nice to be able to bleed off a load of steam without having to balance a rock on the little stem while you are getting a face full of steam.
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488 stops for water at Los Pinos tank on closing day Oct. 1979. Photo courtesy Don Richter
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