[Steam-engine] Safety Valves - Part 2

[Bruce & Marlene Babcock]

    The significance of the difference between had-fired and automatically-fired boilers is that the pressure in automatically-fired boilers can be easily controlled so as not to get within 10% of the set point.   Because of this, valve manufacturers have been able to manufacture more economical valves that do not need to seal tightly within this 10% range.   We are using valves that are designed for a different application.  We have no other choice.  If we wish to use a new valve this is all that is available today .    

    The modern safety valve's role as a back-up device and its inability to withstand severe use was clearly supported by the Kunkle Valve Company in its Catalog 85 in 1985:  "Avoid excessive 'popping' of the safety/relief valve as even one opening can provide a means for leakage.   Safety/relief valves should be operated only often enough to assure that they are in good working order."   Kunkle does not suggest a schedule for verifying the operation of their valves.   In contrast, in 1909, Lunkenheimer suggested that their valves should be operated at least once a day.   

    At one  time, Jayco was considering producing old-style valves for use on hand-fired boilers.  I do not know if they are proceeding with their plans. 

    Until old-style valves are available, I suggest that we do whatever we can to make the new style valves more satisfactory.   Specifying the setpoint at 4%, as I mentioned in my previous message, may be one approach.  Some owners are experimenting with nonmetallic seats.  

Bruce E. Babcock