Talk:Partial stroke testing

The Partial Stroke Test is used to check the function of the safe position of ESD (emergency shutdown) valves. The partial valve stroke prevents unexpected failure of the safety function by breaking down solid masses or the onset of corrosion, for example. Furthermore, a successfully executed partial stroke demonstrates that certain unresolved errors that would otherwise go undetected, such as spring fractures in the spring chamber of the pneumatic actuator, are not present. Consequently, the interval for testing for these undetected errors can be extended.

The test can be started both locally on the device in a time-controlled manner or from remote. The positioner evacuates output 1 until the position change defined in advance occurs. If this does not happen within the set time (timeout value), an alarm can be output.

Additionally, monitoring is performed to establish whether the valve has moved out of its end position within a defined period of time (dead time). If this has not happened, the test is cancelled as a "failed" test and an alarm is output. This behavior prevents a blocked valve from suddenly freeing itself from the end position and thereby disrupting the process.

At the end of the test, the positioner moves the valve to the last valid position and reverts to the most recently active control mode.

For documentation purposes, the test result is saved in the non-volatile memory.

Example for an electro-pneumatic positioner:

Manufacturer: ABB

Type: PositionMaster EDP300