The maximum allowable working pressure (MAWP) of a steam boiler is an absolute restriction of pressure within psig unit for a steam boiler is allowed to run. The ASME BPV Code (American Society of Mechanical Engineers Boiler and Pressure Vessel) says that absolutely no steam boiler should be run at a pressure above the MAWP with the exception of the safety valve is operated to discharge excessive pressure. Steam boiler has some technical terms that be generally used. One of them is MAWP (Maximum Allowable Working Pressure) which means that all of working pressure at the pressure part shall not exceed MAWP. MAWP on the header or drum can be calculated based on the equation below:
MAWP = (t x E x TS) / (R x SF)
Abbreviation of the equation above is:
MAWP = Maximum Allowable Working Pressure in the drum or header.
E = Joint efficiency of welding in the drum or header
t = Thickness of header or drum
TS = Tensile strength of the material, can be looked at ASME BPV Section II D
SF = Design safety factor, the value which is commonly used is five