Translation of "Partial stroke test" in German

During the partial-stroke test the displacement movement is recorded and stored.

The actuating movement is recorded and stored, or passed on to the control system during the partial stroke test.

In a partial-stroke test initiated automatically by the instrumentation and control device 12 at regular time intervals, the control valve 4 is moved briefly from the respective current position over a part of its displacement path with the magnetic valve 7 activated and is then moved back again.

The partial stroke test is either initiated in active mode via HART communication or by using a second signal connection between the control system and valve.

After each partial-stroke test or every n-th partial-stroke test the operational capability of the magnetic valve 7 is tested by deactivating same.

After triggering, for example of the Partial Stroke Test, these positions can be reached by controlling the pneumatic output unit 20 by means of the processing unit 22 .

This embodiment requires only one two-wire current loop 28 for performing the Partial Stroke Test on an actuator 12 on the one hand, and for transmitting the actual travel path to the control system 14 which will then record and evaluate it using IEC 61508 certified software.

In the device described in WO 2008/135417 A1, a partial stroke test and a test of the solenoid valve are performed in a single test sequence by deactivating the solenoid valve, where the actuating movement of an actuating element is detected by a position controller and is monitored to determine when it reaches a prespecified path change and is re-activated when the solenoid valve reaches the prespecified path change.

In a partial stroke test that is automatically initiated at regular intervals by the control system 12, the open/close valve 4 is moved briefly out of the respective current position over part of its actuating path, and then moved back again, when the solenoid valve 6 is activated.

It is desirable to be able to initiate, monitor and evaluate both the partial-stroke test and the magnetic valve test automatically by means of an instrumentation and control device disposed outside of the final control device.

The partial-stroke test is rated as successful as a function of whether a predefined change in position is reached within a minimum time period or whether the change in position reaches a minimum value within a predefined time period.

Actuating the safety actuator 12, in particular for a Partial Stroke Test, is to be effected through communication via the two-wire current loop 28 .

These HART commands are for example output by the control system 14 and received by the positioner 10 in order to initiate a Partial Stroke Test.

Partial stroke test according to claim 7, wherein said algorithm for adapting said step width is changed such that said step width is reduced.

A partial stroke test can selectively be initiated manually by an operator control element on the position controller 8, by a signal which is transmitted to the position controller 8 over the communication line 11, or at regular intervals by a timer that is contained in the position controller 8 .

Preferably, the movability of the safety valve is ensured in a non-safety-critical operating situation in that a control pressure signal, particularly a low pressure control signal is applied to the pneumatic drive for actuating the safety valve and in the process, a partial stroke test, particularly between 100% of the open position and 80% of the open position of the safety valve is traveled.

In a Partial Stroke Test, PST, the armature is moved by a partial distance of its adjustable stroke.

In order to exclude a movement beyond the target value predefined for the partial stroke test, the pulse duration required for carrying out the PST, is evaluated by a method known per se in which, starting with short pulses, increasingly longer pulses are generated until the movement distance reached is within a movement range relevant for the PST, in particular within 5%-10% of the adjustable stroke.

Since the dead time of the actuator to be controlled may be longer than the required control time of the magnetic valve, the Partial Stroke Test is started with very short pulse duration.

Because the equality or balance of forces between the drive force and the break-away force can now be approximately determined, this information can be used in a particular advantageous way for carrying out the partial stroke test.

In order to be able to check the ability of the actuator device to function as part of a partial stroke test, the compressed air is supplied by an electropneumatic position controller.

During the partial stroke test, the open/close valve is moved from the operating position over part of its actuating path and then moved back again by the position controller.

In an exemplary embodiment, the at least two control pressure signals are provided with differently sized pressure amounts or air flow rates, wherein in particular only the high pressure control signal or the control signal with high air flow rate is switched on for opening or closing a safety valve and/or only the low pressure control signal or control signal with low air flow rate is switched on for carrying out a partial stroke test.