Boiler hydrostatic test

A boiler hydrostatic test proves the strength and tightness of a marine boiler pressure part by filling it with water and raising the pressure to 1.5 times the design or maximum allowable working pressure (MAWP), held while the surveyor checks for leakage, weeping at welds and tube ends, and permanent deformation. It is a shop and shipboard acceptance test under the classification society pressure-vessel rules, witnessed at new construction and repeated after major repair or retubing. Water is used, not air, so a rupture releases stored energy harmlessly. The boiler must be vented of air and the gauge calibrated; the hold time and acceptance follow the class rules and the boiler maker’s drawing.