Going global – hydropower hydraulics from Knoll headed towards China.

Wasserkraft Hydraulik für ein asiatisches Stauklappenprojekt

82 new hydraulic units with hydraulic cylinders for an Asian control flap project.

At the beginning of 2018, a renowned small-scale hydropower plant and steel hydraulics construction provider tasked us with producing 82 hydraulic units for its Chinese client. This was a follow-up order resulting from the positive collaborative relationship maintained in recent years, during which we provided our client with advice and support while they were equipping their hydropower hydraulics solution. What made this project so special was the extremely short time frame in which the hydraulic systems had to be planned, assembled and flown out to Beijing as turnkey solutions.

The requirements included quick delivery, corrosion-free V2A components and reliable monitoring functions.

The client’s key requirement was that a control flap with two cylinders and a hydraulic unit be fitted – as part of a scalable solution and within a clearly defined time frame. Provision of the components was to be guaranteed within ten weeks from receipt of the order.

Because the components can be flooded outside of the unit, the relevant system parts including the hydraulic cylinders or oil sump have to be made of V2A standard stainless steel, and all of the safety-related requirements have to be met. This also includes monitoring the final cylinder positions and reliably checking the opening and closing pressures. Due to the water’s counter pressure, the control flap has to open very quickly during a power failure.

There were to be no compromises with regard to quality – hydraulics had to be provided as a full service package.

Extreme operating conditions require reliable, tried-and-tested hydraulic solutions.  We therefore only installed high-quality components which we had continuously good experience with, with most of them coming from Bosch-Rexroth.

We opted to use a robust external gear pump with a capacity of 11 ccm/rev and valves from Bosch Rexroth. Corrosion protection is guaranteed due to V2A hydraulic cylinders with final position querying and stainless steel oil sumps. All of the electrical components outside the unit also meet the IP69 standard as a bare minimum. A 2/2-way seat valve which opens when de-energized ensures that the control flap is opened reliably in the event of a power failure. To remain as flexible as possible, we defined a standard unit for all flap sizes.

Intense communication with both the client and suppliers, and close collaboration between the Project Management team and the Procurement, Production and Logistics departments enabled us to successfully implement the project on schedule – without jeopardizing the progress of the construction project as a whole. Even in future, we will be able to respond quickly and fly the units out to the Middle Kingdom at the drop of a hat, all the while maintaining a consistent level of quality.  

The most important information about the project:

  • Implementation time: May 2018 to September 2018. 
  • Client requirements: Fitting a control flap with two cylinders and one hydraulic unit. Possible component flooding in the outside area. One unit for all cylinder sizes. 
  • Our solution: Corrosion-resistant V2A components. A robust external gear pump with a capacity of 11 ccm/rev and 2/2-way seat valves from Bosch Rexroth. Standard unit defined for all flap sizes. Pressure sensors in the A and B channels.
  • Special features: 82 units produced in the space of just 16 weeks.


Anton Brehm

Hydraulics project manager
+49 9208 657439-36

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