VariStroke is Woodward’s line of linear electro-hydraulic valve actuators for operation of steam or hydro turbine control valves. They ensure the well functioning of the steam turbine , hydraulic turbine control or control valves in general. These linear actuators use a low pressure oil supply to generate an output force from the cylinder.
Thanks to its precision and high positioning resolution, it is ideal for direct control of steam turbine valves, including turbine speed and load. Its electronic module accepts one or two 4 – 20 mA position request signals (redundant) to position the valve control, as well as two redundant position feedbacks.
Features and benefits
- Dirt tolerant design
- Two moving parts
- 50 lbf chip shear force
- Self-cleaning valve design
- Integrated driver
- Two 4-20 mA demand inputs
- Included valve flow linearization table
- Side-load tolerant
- Shaft bearings
- Triple seal technology
- Precise position control
- Redundant MLDT position sensors
- Certified for hazardous locations
- High calibration capacity (from 50 to 100% of the nominal stroke)
- Speed response to significant load variations to avoid overspeed
- Hydraulic supply pressure from 5 to 35 bars
- Improve valve seal life thanks to controlled closing
- Increased reliability: power supply, control signal, position measurement redodants
- Self-tuning of the servo PID
- Fast slew rates/times
- Application dependant
- Slew rate up to 762 mm/s
Financial benefits:
- No special filtration required
- No need for dedicated oil center (use of the machine’s lubrification circuit)
- Cost reduction of a non-integrated servo distributor system
- Cost reduction of a non-integrated pilot system
- Reduction of engineering costs with a fully integrated system
- Reduction in storage costs for various square parts (filters, oil pumps, pilot valves, position feedback, servo-distributor, etc…).
- Reduction of installation costs
- Reduction of testing and commissioning costs
- Reduction of maintenance costs
- Reduction of turbine trips linked to polluted oils
- Reduction of turbine trips linked to significant load variations
- Energy saving on the supply of an auxiliary oil plant and its refrigeration
- 3 years warranty Wooward equipement
Modernization
Affected systems:
Any hydraulic control system of inlet valves can be replaced by our VariStroke systems, whether it is an ATEX zone or not.
Allows the elimination of a speed oil plant, the linkages between the various control and hydraulic power systems.
The investment is quickly paid for the system’s reliability (reduction of tripping) and the cost of maintenance.
Exemple de réalisation :
Associated equipment
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