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. It consists of 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). Model 530FP is for use in fire protection systems. Maximum Pressure: 300psi (20.67 bar). Adjustable Pressure Ranges: Sizes 1/2, 3/4 in. (15 to 20mm) - 50 to 175psi (3.45 to 12.06 bar), Size 3/4 in. (20mm) - 100 to 300psi (6.89 to 20.67 bar).