(a) After a boiler has been completed, it shall be subjected to a hydrostatic test of one and one-half times the maximum allowable working pressure. The pressure shall be under proper control so that in no case shall the required test pressure be exceeded by more than six percent. When a completed boiler is ready for hydrostatic test, it shall be tested with water of a temperature not less than the temperature of the surrounding atmosphere and in no case less than 70° Fahrenheit.

(b) During a hydrostatic test, the safety valve or valves shall be removed or each valve disk shall be held by its seat by means of a testing clamp and not by screwing down the compression screw upon the spring.