| http://www.w3.org/ns/prov#value | - ??54.15-15 Relief devices for unfired steam boilers, evaporators, and heat exchangers (modifies UG-126).(a) An approved safety valve set to relieve at a pressure not exceeding the ???maximum allowable working pressure??? of the shell shall be fitted to all unfired steam boilers and evaporators except for evaporators of the atmospheric type designed for vapor discharge direct to a distiller with no
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