Hydraulic Tank (Reservoir) Design for Rotational Molding

Taking the step from traditionally constructed steel hydraulic tanks to a plastic molded tank can be a daunting prospect for designers and engineers who aren’t familiar with rotational molding process. This brief guide gives an introduction to the possibilities, advantages and constraints of the process.

A rotationally molded hydraulic tank can free the designer from many constraints, reduce manufacturing costs and increase performance. A specialist manufacturer in rotational moulded tanks will help the designer or engineer to produce a fantastic product but it’ll be your creativity that can make the real difference.

In its simplest form a rotational molded hydraulic tank can just replace a conventional steel tank. However this approach misses out many additional benefits that can be moulded in. You should understand that a hydraulic tank will perform many more functions than just being a vessel to contain a fluid so first we need to consider what these functions are and how these can be integrated with rotational molding.

Functional and Performance Considerations for Rotational Molded, Plastic, Hydraulic Tank Designs

1. To contain oil safely over long periods and prevent contamination in all extremes of operating conditions. Rotomolded hydraulic tanks don’t have joints to crack due to thermal stresses and vibration. The materials used are inherently resistant to chemical deterioration and corrosion free internally and externally. Tanks constructed from steel can rust internally from condensed moisture in the oil and externally when coatings are breached.

2. To deliver and receive oil and flow rates required and ensure oil is circulated or cycled evenly, preventing a particular volume of oil being overused. Flow and return fittings should be positioned so oil flows through the tank. A rotationally molded hydraulic tank can be designed to take in to account the required pipe and hose runs even in the tightest engine or machinery compartments.

3. A hydraulic tank can be a crucial component of the thermal design of a hydraulic circuit. Although steel will transfer more heat per square inch or square millimetre of tank wall area, a rotationally moulded tank can incorporate many surface design features that increase the overall surface area. These can be ribs or fins that can also increase the structural strength allowing thinner wall designs. rotational molding companies near me

With careful consideration of air flows around the tank or within a compartment the overall heat loss from the hydraulic tank can lead to a reduction in the size of any necessary radiator type oil cooler.

If radical designs are possible the tank surfaces can also be used as external components, adding to external aesthetics of a design and providing more opportunities for passive cooling.

4. Hydraulic tanks can perform a major function to maintain the condition of the oil, reducing the service intervals, maintaining hydraulic performance, reducing system and pump wear and even contributing to a reduction in failures.

Hydraulic oil can be contaminated by solid particles, water and air. If the flow through the tank is slow enough and long enough, water and solids can drop to the bottom and air will rise out. Conventional tanks may incorporate added baffles to increase the distance the oil has to travel. A rotational molding can include integrated baffle features. In addition a “lowest point sump” can be molded in and fitted with a tap-off drain to extract water. Solids can be extracted via a molded in, threaded, access point fitted with a large diameter cap allowing a service engineer to reach in to the tank. The same access could be used to reach a suction strainer/filter or any other internal components.

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