4820-00-683-8922 (959BC475)
NSN 4820-00-683-8922 (NIIN 00-683-8922) is a safety relief valve in Federal Supply Class 4820, Valves, Nonpowered — a valve designed to automatically release excessive pressures. Manufacturer part number 959BC475 (Superior Valve Co, CAGE 58553); also referenced as 959B (Superior Valve Co).
Key specs: valve stem lock shield; 500 psi maximum single response operating pressure; full characteristics table below. NIIN assigned January 1963; DEMIL A (none required); export Schedule B 8481.40.0000.