[Steam-engine] lap seam boiler pressure

[Lawrence Swanz]

Robert,

I'm in agreement with you that the ultra-sonic tool is the best way to determine boiler condition.  Myself, since I own one, I won't operate or purchase an engine till I do a preliminary check.  That is unless a state official or other qualified person has looked the boiler over and given its approval to operate.  But, I don't agree with "You did a hydro at 200 psi, with an assumed operating pressure of 100 psi; that could ruin the boiler right there."  If the boiler plate was .375" original thickness, then the boiler can be assumed that the design pressure was 150 lbs., a standard design pressure of the time, not to be confused with operating pressure.  That would be a pressure either an official or an individual owner determined to operate the unit at.  I know of engines here in Minnesota that have safety valves set at lower pressures than the boiler equates to.  Some do it because it was the safety valve on the engine when they bought it or that was the size they had ready available to put on the unit.  Either way, don't always assume that the pressure releif valve coincides with design pressure.

As for lap seams.  Yes, many inspection agencies pay more attention to a lap seam boiler.  But if the numbers work, then there won't be a problem obtaining the desired pressure rating.

Lawrence