The D-Stop is modular – it can be used and applied many different ways!

The figure at left shows the D-Stop in it’s most economical and manual format.  The device is manually operated by a key—simple and safe

The D-Stop may also come equipped with it's own data point device (such as limit switches, as shown in this middle illustration) for positive annunciation to the control room indicating whether the device is engaged for testing the Safety Instrumented System.

Some users may want to use such devices to gather information for their data acquisition system such that auditable reports, testifying to time and date of the test, can be generated (Reference ISA-S84.01, para 9.8.1).

For remote and/or automated applications the Key and Safety Release are not required. By adding a pilot actuator (as shown in the illustration at the left) the D-Stop can be remotely controlled.  The top actuator controls the valve, while the pilot actuator on left engages and disengages the D-Stop. 

Using control system logic, the user can program the device to be configured to automatically disengage the D-Stop in the unlikely event of an ESD occurring during the partial stroke test.