875—93.4 (89) Safety valves. Boilers covered by this chapter shall be equipped with a sealed spring-loaded pop safety valve of not less than ½-inch pipe size. The minimum relieving capacity of the safety valve shall be determined in accordance with rule 875—92.7(89). In addition to these requirements, the safety valve shall have sufficient capacity to discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than 6 percent above maximum allowable working pressure.