scope:

PURPOSE

This standard establishes a minimum signal range capable of operating control valves equipped with spring-opposed diaphragm actuators.

It is necessary to establish such a signal range to provide sufficient pressure below and above the corresponding bench settings of pneumatic actuators.

This will enable control valves with common bench ranges of 3 to 15 psi (or less) to close; especially when an electronic controller or computer signal reaches 4 mA (when valve is at one of its limits of travel, depending on its configurations) or 20 mA (when valve is at the other limit of its travel). This applies to 2-way and 3-way control valves.

Electropneumatic tranducers having 4 to 20 mA input, for example, should be calibrated to provide such a minimum power signal when operating diaphragm-actuated control valves.