Installation, Operation, and Maintenance Manual
VCIOM-15596-EN Rev. 0
November 2021

Bettis RTS – Partial Valve Stroke Test (PVST)
Electric Actuator

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Section 1: General

For a PVST (Partial Valve Stroke Test) the actuator performs in regular intervals a defined movement. This also moves the connected valve.
With the PVST, only a part of the full valve stroke is passed through. If the full valve stroke is passed through, this is called FVST (Full Valve Stroke Test) or FST (Full Stroke Test).
Typically, a PVST is applied to valves that are in the OPEN limit position for a long time (e.g., emergency shutdown valves). These valves are only used in the event of system malfunctions, maintenance, or functional tests. Between these events, the plant operator has no information if the valve can still be closed if required.
Normally a short, small movement of the valve in the closing direction is not disturbing
the system process. The PVST performs this movement regularly. As a result, on the one hand, a fixation of mechanical components is reduced and, on the other hand, errors are detected prematurely before any emergency shutdown is required.
This procedure increases the security system metrics.
The PVST can either be triggered by the control unit on the actuator itself (internally) or by the control system (externally).
Internal trigger:
Manual trigger of the PVST via the menu of the control unit: see parameter P16.11.
Time-based trigger of the PVST: see parameters P16.7, P16.9, and P16.10.
External trigger:
The PVST can be triggered via binary inputs or an optional Fieldbus system.

The procedure of the PVST:

1. The actuator must be in the start position which is set in parameter P16.2. The set hysteresis in parameter P1.8 is taken into account.
2. The actuator must be in the REMOTE mode and READY state.
3. Release of the PVST (internal or external).
4. The status of PVST is set as PVST-Active.
5. The actuator moves from the start position to the test range which is defined in parameter P16.3.
6. After reaching the final test position the actuator remains in this position for a specific time, defined in parameter P16.4.
7. Then the actuator moves back to the start position.
8. If the PVST was successful the status will be set to PVST-OK otherwise to PVST-Error.
9. The status of the PVST can be monitored continuously via the binary outputs or via the optional Fieldbus.

Result of the PVST:
For a successful PVST the following terms must be fulfilled:

1. The actuator must be in the start position.
2. The actuator must be in the REMOTE mode and READY state during the whole PVST (no error).
3. The PVST must not be interrupted by another command (binary inputs, commands from optional Fieldbus).
4. The switch-off torque must not be exceeded during the PVST.
5. The total time of the PVST must be lower than the maximum time, set in parameter P16.8. If one or more of the above terms are violated the PVST is not successful.

Section 2: Parameter Menu

2.1 Parameter Group: PVST

Table 1.

| Menu Item| Subitem| Options| Explanations/Comments
---|---|---|---|---
P16.1| Stroke test| Stroke test| | This parameter activates the PVST. For standard actuators (without fail-safe function) the PVST is only viable electrically by the motor. For fail-safe actuators, the PVST can additionally be executed as a fail-safe operation in a fail-safe direction by spring.
0| No stroke test is executed.
1| The stroke test is executed electrically.
2| The stroke test is executed in fail-safe operation by spring.
3| Two-stroke tests.
1. Test: electrically
2. Test: in fail-safe operation
4| Two-stroke tests.
1. Test: in fail-safe operation
2. Test: electrically
P16.2| Stroke test| Start position| 0-100%| Start position for the PVST. This value must be 0% or 100%. If the actuator is not in one of these positions in case of a PVST start the test is not executed and not successfully concluded.
P16.3| Stroke test| Test range| 0-100%| In this range, the actuator is moved during the PVST.
e.g. Start position: 100%, test range: 30% The PVST starts at 100% and moves the actuator to 70% (100%-30%). After that, the actuator moves back to 100%.
P16.4| Stroke test| Resting time| 0-10s| Amount of seconds how long the actuator remains in the end position of the PVST before moving back to the start position.
P16.5| Stroke test| Speed open| 0-100%| With this parameter, it is possible to set the speed in the OPEN direction for the PVST as far as the actuator has this capability.
P16.6| Stroke test| Speed close| 0-100%| With this parameter, it is possible to set the speed in the CLOSE direction for the PVST as far as the actuator has this capability.
| Menu Item| Subitem| Options| Explanations/Comments
---|---|---|---|---
P16.7| Stroke test| Time Trigger| | If this value is set greater than 0 the PVST will be repeated cyclic according to the specific set value. The start command for the PVST is set for one minute and is reset after the test till the next cyclic start.
0| Off
1| Every hour
2| Every 2 hours
3| Every 3 hours
4| Every 4 hours
5| Every 6 hours
6| Every 8 hours
7| Every 12 hours
8| Every day
9| Every week
10| Every 2 weeks
11| Every month
12| Every 2 months
13| Every 3 months
14| Every 4 months
15| Every 6 months
16| Every year
P16.8| Stroke test| Max. time| 0-120s| The maximum timespan for the duration of the PVST. If the test takes longer than the adjusted time it is not successful. The function is deactivated by setting the value to 0.
P16.9| Stroke test| Start date| yyyy-mm-dd| With this parameter, the date for the first PVST is set. The parameter is only relevant if the P16.7 Time trigger is greater than 0.
P16.10| Stroke test| Start time| hh:mm: ss| With this parameter, the time for the first PVST is set.
The value for the seconds is not relevant.
The start command is active for the whole minute independent of the adjusted seconds. The parameter is only relevant if the P16.7 Time trigger is greater than 0.
P16.11| Stroke test| Start test| 0-1| With this parameter, the PVST function can be started from the control menu to test the adjusted values. When the parameter is set to 1, the PVST starts once the actuator is in REMOTE mode.

2.2 Parameter Group: Binary Inputs (Extension)
Table 2.

| Menu Item| Subitem| Options| Explanations/Comments
---|---|---|---|---
P9.x| Bin. Input| Input x| 53: PVST Start| If the signal is active the PVST is started.
54: PVST Start inv.| If the signal is not active the PVST is started (active low).

2.3 Parameter Group: Binary Outputs (Extension)
Table 3.

| Menu Item| Subitem| Options| Explanations/Comments
---|---|---|---|---
P10.x| Bin. Output| Output x| 65: PVST OK| The last PVST was successful.
66: PVST Error| The last PVST was not successful.
67: PVST Active| A PVST is currently running.

Section 3: Troubleshooting

3.1 Error List (Extension)
Table 4.

54: PVST Error

55: PVST OK| The last PVST was not successful. The last PVST was successful.

61: PVST> Start| The Partial Valve Stroke Test was started.

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