Hammer Unions for the Oil & Gas Industry are available in ten different styles to meet your applications needs. Unions Conform to NACE, ISO, DNV and API Standards. Materials Conform to ASTM Grade 65-45-12, ASTM A-105 ASTM A29. NPT Threads Conform to ASME B1.20.1. CWP (Cold Working Pressure) is the Maximum Pressure at Ambient Temperature (70°F).