Multiple material choices for rotomoulded hydraulic oil tanks

There are several material options for making plastic hydraulic oil tanks, depending on the maximum oil temperature. If the operating temperature is a maximum of 75 degrees for a long time, polyethylene can be used. At higher operating temperatures, alternatives are available such as cross-linked polyethylene (up to 85 °C), polypropylene (up to 90 °C) and nylon (up to 100 °C). The short-term peak temperature, assuming 0.5 hours per day, can be about 10 °C higher than the long-term operating temperature. In general, hydraulic systems work with an operating oil temperature of 60°C and a maximum temperature of 80°C. This makes it very well possible to use a rotomolded tank.

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Complex design possibilities

In the nacelle of a wind turbine a place must be found for many components. In addition, there are structural components such as steel beams and profiles, cable ducts, floors and shutters. This makes it difficult to find enough space for a hydraulic oil tank with sufficient volume capacity. A simple rectangular steel tank is not possible. To use all available space, a tank with a complex design needs to be created. In rotational moulding, a complex design is often beneficial and gives an advantage because this design makes the tank stiffer. The design criterion is not so much complexity, but whether the tank can be removed from the mould. However, a mould for rotational moulding does not necessarily have to be two-part, but can consist of several parts, so that complicated shapes can also be manufactured.

Up to 50% lower costs than a steel tank

A steel tank is assembled from several metal plates, especially if the design deviates from a simple rectangular shape. These plates are cut and set and then have to be liquid tight welded along all seams. In addition, durable stainless steel must be used. If a standard type of steel is used, the tank must be coated inside and outside against corrosion. With rotational moulding, a production mould is made once, which determines the complete design, and the series production costs are relatively low. The plastic material does not corrode, so no secondary treatment is necessary. Threaded inserts can also be cast in the process. There are many examples where the mould pays for itself very quickly, often with a few hundred tanks. Rotational moulding is a very interesting option for small to medium-sized series (from approximately 300 to 10,000 units per year).

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Mariusz Bidol


Business Development Director

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