Due to the high currents that are present in a control cabinet it is necessary to isolate any connections to the cabinet that can create a potential path to ground. Water is one of these. Therefore special attention to the connectors through the cabinet must be made to insure the fittings are electrically isolated.
These fittings insure that the water system will remain electrically neutral.
Reference: RWMA - Resistance Welding Manual 4th Edition
AWS Standard: J1.2 Guide to Installatio and Maintenance of Resistance Welding Machines