Woodward VariStroke-I electro-hydraulic actuator: an innovative solution for steam turbine valve control

Danger: Failure to do so may result in death or serious injury (such as failure of overspeed protection).

Warning: Failure to avoid may result in death or serious injury (such as operating in explosive hazardous environments).

Attention: Failure to avoid may result in mild to moderate injuries.

Tip: May result in property damage.

Proper personal protective equipment must be worn during operation, and electrostatic discharge protection measures must be followed.

3.2 Global Compliance

The 'compliance code' in the VS-I model code indicates the hazardous area certification to which it applies:

0: Ordinary area (CE mark).

1: North American Div 1&2, ATEX/IECEx Zone 1&2.

2: North American Div 2, ATEX/IECEx Zone 2.

Other certifications include EAC (Russia), CCOE (India), TIIS (Japan), KCs (South Korea), and others.

Users must ensure that the actuator is installed in the licensed area according to the compliance code on the model name plate.

3.3 Installation Core Requirements

Mechanical installation:

Support vertical or arbitrary installation (it is not recommended to invert the servo valve).

The integrated actuator is supported by the bottom or top mating surface of the power cylinder.

The prescribed gap between the actuator and the installation surface must be maintained.

Use the provided lifting bracket for vertical lifting.

Hydraulic connection:

Oil supply port: 1.250 SAE Code 61 flange.

Return port: 1.500 SAE Code 61 flange.

Control port (remote kit): 1.000 SAE Code 61 flange (C1, C2).

All pipelines must be thoroughly flushed, and it is recommended to install a large capacity accumulator near the actuator on the oil supply pipeline to maintain pressure stability.

Electrical connection:

Power supply: It is recommended to use 1.5-2.5 mm ² wires and equip them with slow melting fuses or circuit breakers (rated 20% higher than steady-state current).

Signal line: All analog signals must use shielded twisted pair cables, with the shielding layer grounded at one end as shown in the diagram.

Grounding: It is necessary to connect the protective grounding (PE) and electromagnetic compatibility grounding (EMC) terminals.

Wiring: Pay attention to eliminating cable stress and avoid transmitting wiring stress to the terminal block.

4、 Configuration, Calibration, and Service Tools

4.1 VS-I Service Tool

The dedicated PC service tool software is the core for configuring, calibrating, and monitoring VS-I.

Function: Set system parameters, perform cylinder calibration, configure input/output, view diagnostic information, manual operation.

Connection: Connect to the actuator service port via RS-232 serial port (or USB to serial port adapter).

Safety Warning: Improper use may result in unsafe conditions, only for trained personnel.

4.2 Calibration Process

Before calibration, it is necessary to ensure that the system is in a safe shutdown state (demand signal below 2mA or operation enable disconnected).

Set fuel supply pressure: Enter the actual fuel supply pressure, and the actuator will automatically tune accordingly.

Select calibration mode:

Find the minimum stopping point: The actuator slowly moves to the mechanical minimum position.

Find the minimum and maximum stopping points: The actuator positions the mechanical minimum and maximum positions in sequence (note: it is necessary to confirm that the connecting mechanism can withstand the total deceleration force).

Set offset and maximum position: After calibration, the "minimum position offset" and "maximum stop position" can be fine tuned to accurately set the stroke.

Save Settings: After completing calibration, the configuration must be saved.

4.3 Key Configuration Options

Input configuration: It is possible to set the demand signal mode (single channel, dual channel average, high/low selection), run the enable logic, and provide feedback signal mode.

Output configuration: It can configure four discrete output behaviors (alarm indication, shutdown indication, cylinder position indication, etc.), as well as analog output functions (no output, demand signal, actual position).

Advanced configuration: Adjust bandwidth, Dither, Sill Buster cycle, etc.

Linearization: Provide an 11 point linearization table to compensate for the nonlinear characteristics of steam valve flow.

Alarm/shutdown management: Multiple diagnostic conditions can be set as "alarm", "shutdown", "disable", and whether to latch or not.

5、 Diagnosis, maintenance, and troubleshooting

5.1 Diagnostic Indication

System information page: Real time display of operating mode, demand value, feedback value, alarm/shutdown status.

Alarm/Shutdown Page: List all activated diagnostic conditions, including power failure, demand failure, feedback failure, temperature failure, performance failure, and internal failure.

5.2 Maintenance

Shaft seal replacement: Woodward provides shaft seal replacement kits for different cylinder diameters (such as 4-inch cylinder diameter: 8935-1216-10).

Servo valve/hydraulic cylinder replacement: Please refer to Woodward manual 26836 for specific steps.

Long term storage: Specific requirements must be followed to maintain equipment integrity.