This document specifies a test method for the determination of the opening, closing and running torque of thermoplastics valves. This test is considered to be performed as part of the initial type testing. This document is applicable to all types of manually operable thermoplastics valves, with or without actuator, intended to be used for the transport of fluids.
NOTE 1 Examples of valve types tested with this method are in ISO 4437-4 , ISO 16135 , ISO 16136 , ISO 16138 , ISO 16139 , ISO 16486-4 , ISO 21787 , EN 1555-4 , EN 12201-4 .
It does not specify the relationship between the torque and its possible increase after prolonged use of the valve under a specific working condition or materials wear/chemical aggression.
NOTE 2 Concerning the chemical aggression of the materials, a collection of data is reported in ISO/TR 10358 ; concerning the endurance test necessary to confirm the ability of hand-operated plastics valves to withstand prolonged use with repeated opening and closing operations , further information is provided in ISO 8659 .