This part of ISO 19973 provides test procedures for assessing the reliability of pneumatic directional control valves 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 and electro-pneumatic directional control valves is usually given as a number of cycles. Therefore, whenever the term “time” is used in this part of ISO 19973, this variable is to be understood as cycles.

This part of ISO 19973 also specifies test equipment and threshold levels for tests to assess the reliability of pneumatic directional control valves.