Hammer Union According to API-7K Size:1''--12'' FMC WECO Interchangeable NPT Thread; Butt-Weld; Socket-Weld Hammer Union According to API-7K Size:1''--12'' FMC WECO Interchangeable NPT Thread; Butt-Weld; Socket-WeldHammer UnionHammer Unions are suitable for standard and sour environment, ranging in size from 1’’to 12’’with cold working pressures from 1,000 psi to 20,000 psi. All unions have their ...