pop valve การใช้

• Pop valves derived from Adams's patent design of 1873, with an extended lip.
• A pop valve, like the later forms of steam locomotive safety valve, only flows once a certain pressure has been reached.
• This was mostly at the behest of stationmasters, but firemen also realised that any blowing off through a pop valve wasted several pounds of boiler pressure; estimated at 20 psi lost and 16 lbs or more of shovelled coal.
• :Firstly the pop valves were a type used in industry; secondly the dead-weight type could be held down ( so it would never work properly ); and thirdly a dead-weight valve tends to bounce and thus waste steam.