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Servovalves and hydraulic pumps

Servovalves and hydraulic pumps are critical, high-precision components in turbine power generation (gas, steam, and hydro), primarily used in Electro-Hydraulic Control (EHC) systems to manage turbine speed, load, and safety through fast-acting valve actuation. These components, often supplied by industry leaders like Moog, Bosch Rexroth, and Oilgear, convert electrical signals from controllers into high-force hydraulic movements to control fuel flow or steam admission.

Servovalves in Turbine Power Generation

Servovalves are the core of the hydraulic actuator systems, providing high-frequency, precise positioning of turbine valves to prevent overspeed and manage power output.

Function: They control hydraulic flow to cylinders that adjust turbine admission valves, stop valves, and inlet guide vanes.
Key Applications:
- Steam Turbines: Governing valve control and emergency stop systems.
- Gas Turbines: Controlling fuel metering valves, bleed valves, and guide vanes.
- Hydro Turbines: Regulating water flow via guide vane actuation.
- Wind Turbines: Blade pitch control.
Types: Single-stage (direct drive), two-stage, or three-stage valves are used, with two-stage being common in high-performance applications.
Performance Metrics: High reliability is essential, with some valves capable of operating over 1 billion cycles.

Hydraulic Pumps and Power Units

Hydraulic pumps provide the pressurized fluid required to operate the servo mechanism, acting as the power source for the entire control system.

Servo Pumps: These combine a servo motor with a fixed displacement pump, allowing for precise control of flow and pressure, reducing energy consumption when not in use.
Types: High-pressure piston pumps are frequently used for their durability and efficiency in harsh power generation environments.
Key Features: Modern units often include integrated filtration, cooling, and safety components, making them “plug & play” solutions.
Power Recovery: Hydraulic Power Recovery Turbines (HPRT) are used to convert residual pressure in systems (like amine regeneration in gas plants) into usable power.

Key Manufacturers and Solutions

Moog Inc.: Specializes in high-performance servo valves and actuators for gas/steam turbines, including PGO (Power Generation Optimized) valves.
Bosch Rexroth: Offers servo-directional valves, hydraulic power units, and control blocks.
Oilgear: Provides hydraulic piston pumps and systems specifically for hydroelectric power generation.
REXA: Produces electromechanical actuators that can replace traditional hydraulic systems in steam turbines.
Hawe Hydraulik: Manufactures compact servo hydraulic power packs (Type HS).

Maintenance and Efficiency

Fluid Cleanliness: Due to high-precision tolerances, servovalves require highly filtered, clean hydraulic fluid.
Conditioning Monitoring: Proper maintenance and repairing to original specifications are crucial for long-term reliability.
Efficiency Upgrades: Replacing old analog controls with digital valve upgrades can enhance diagnostics and performance.

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