Harold, poor choice of words on my part. Iam happy to accept boiler pressure is generally isothermic, throughout the stream space.
However, in a hobby boiler, this pressure is far from static. Boiler pressure changes rapidly and repeatedly due to repewted introduction of feed water, cut off and throttle settings, firing, the presence of froth and airborne droplets in the steam space, etc.
So Probably more accurate to say, one is likely to pick up the highest quality (dry and hot) steam pressure at the highest point above the water surface - that being a steam dome, if there is one...
This sort of mirrors my observations with the Ottaway. The whistle and safeties always seem to blow with considerable water mixed with the steam. This I think, due to the valves being threaded directly into the top of the boiler, as there is no steam dome, or “dry pipe” space to pick up better steam flow.
Glenn
Safety valve location
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Re: Safety valve location
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge
Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge
Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....