This International Standard specifies the endurance test necessary to confirm the ability of hand-operated plastics valves to withstand prolonged use, with repeated opening and closure. It does not specify the ability of valves to withstand adverse conditions, in particular those of chemically agressive fluid media and /or environments, or excessive fluid velocities and cavitation. This International Standard includes values of the parameters necessary for the proper performance of the endurance test, with the reservation that parameters may be different in par­ ticular product standards (see 5.1).