scope:

ISO 19973-4 provides test procedures for assessing the reliability of pneumatic pressure regulators by testing and the methods of reporting the results of testing. General test conditions and the calculation method are provided in ISO 19973-1. The methods specified in ISO 19973-1 apply to the first failure, as obtained with the three-points moving average (3PMA) method, without repairs, but excluding outliers. The lifetime of pneumatic pressure regulators is usually given as a number of cycles. Therefore, whenever the term "time" is used in this part of ISO 19973, this variable shall be understood as either cycles or time. This part of ISO 19973 applies to manually adjustable and remote-piloted pressure regulators, both relieving and non-relieving. This part of ISO 19973 does not apply to pressure regulators that have a permanent bleed. This part of ISO 19973 also specifies test equipment and failure criteria (threshold levels) for tests to assess the reliability of pneumatic pressure regulators. The life determined by the method in this part of ISO 19973 and in ISO 19973-1 will be more closely related to applications that have a large variation in flow rate.