M&M diaphragm operated cast iron and diaphragm-assist operated bronze ASME Safety Relief Valves are designed to protect fired and unfired hot water pressure vessels against over pressure conditions. The diaphragm's "oversized" effective area generates a greater operating force which helps to overcome the effects of fouling. These valves feature a unique fail-safe disc with sufficient area to permit the valves to maintain their safety relief function in the event of a diaphragm rupture. These valves are designed, manufactured, tested and labeled in accordance with the requirements of Section IV of the ASME Boiler and Pressure Vessel Code. They are offered in a wide range of capacities to permit a close match with the boiler output rating