Although two alerts have been issued on this equipment already, incidents are still occurring in the drilling industry. The serious potential consequences of mismatching 2″ hammer unions warrant issuing another one. Below are two recent incidents. One incident occurred when a 1502 wing nut male sub union holding a pressure sensor was attached to a 602 female union on the mud pump. The 1502 union and pressure sensor blew off the discharge of a mud pump. Another incident occurred when one service company’s 1502 wing nut for the male sub was made up to another service company’s 602 female half. While attempting to test the surface casing, the rams were closed and the standpipe pressure was slowly brought up. The intended test pressure was to be 1500 psi. When the pressure reached 1300 psi, the 1502 union stripped out and blew off and struck a third party service employee causing serious injury.