Adjustable from 50 PSI to 175 PSI - Maximum 300 PSI - Series 530C Calibrated Pressure Relief Valves are used in commercial, residential and industrial applications to protect against excessive pressure in systems containing water, oil, or air. They have a bronze body construction with NPT threaded male inlet and NPT threaded female (drain) outlet connections, stainless steel spring, brass bonnet, Buna-N disc, and Buna-N O-ring. Series 530C has a calibrated adjustment feature for setting the valve to the required relief pressure, and is ideal for by-pass thermal expansion pressure relief (not ASME approved).