Norgren 237 series self venting safety couplings single shut off norgren 237231300 a self venting single shut off safety coupling socket to a hose barb the coupling will self vent during disconnection with no risk of pressurised hoses being freed when the sleeve of the coupling is pulled back the plug is released yet remains locked in the coupling valve closes and the air is vented from the air line at the same time then when the sleeve is once again operated uncoupling takes place s