Cylinder Issues
Internal by-pass
Internal by-pass can reduce the cylinder’s ability to build and hold hydraulic force. It typically shows up as drift, slower response or repeated compensation from the hydraulic system. If left unresolved, it can affect pitch stability and contribute to periods of lost wind energy.
Understanding the Problem
What is internal by-pass?
Internal by-pass occurs when hydraulic fluid leaks past internal sealing surfaces inside the cylinder rather than staying separated across the piston.
The cylinder may still move, but it becomes less capable of maintaining force or holding position under load.
This can lead to continuous compensation in the hydraulic system and uneven pitch behaviour during changing wind conditions.
Typical symptoms
Pitch position drift
The blade angle slowly moves away from the commanded position when the system is supposed to hold.
Reduced holding capability under load
The cylinder struggles to maintain force during gusts or load changes, even if external leakage is not visible.
More frequent pressure compensation
The hydraulic system compensates more often to maintain pressure or position stability.
Slower pitch response
Pitch movements may become less sharp, especially during rapid adjustments.
Irregular pitch behaviour during stable conditions
Small corrections repeat even when wind and operational demand appear stable.
Increased operational cycling
Components may cycle more than expected as the system attempts to maintain performance.
Temperature trend deviations in the hydraulic system
Higher duty cycles can influence temperature behaviour during periods of high pitch activity.
Mismatch between expected and observed system stability
The turbine “works,” but behaves less consistently in regulation and holding phases.
Solution
Refurbished cylinders
Refurbished cylinders restore stable internal behaviour when wear patterns reduce holding capability. The refurbishment updates internal interfaces to current standards and supports pressure stability under load. This extends component lifetime while keeping the solution aligned with safety and lifecycle considerations.
