What are the key factors to consider when sizing a hydraulic reservoir for your power unit?

1 Fluid volume

One of the main factors that determines the size of your reservoir is the fluid volume required by your HPU. This depends on the flow rate and pressure of your pump, the cylinder displacement and speed of your actuators, and the leakage and thermal expansion of your fluid. You need to ensure that your reservoir can hold enough fluid to prevent cavitation, which is the formation of bubbles that can damage your pump and reduce your system efficiency. A general rule of thumb is to have a reservoir volume that is at least three times the pump flow rate.

2 Fluid temperature

Another important factor that affects your reservoir size is the fluid temperature. The temperature of your fluid influences its viscosity, which affects the flow resistance and lubrication of your system. You want to maintain your fluid temperature within a certain range, usually between 50 and 60 degrees Celsius, to avoid overheating or freezing problems. To do this, you need to consider the heat generated and dissipated by your HPU, and design your reservoir accordingly. A larger reservoir can help dissipate more heat, but it also takes longer to warm up. You may also need to add a heat exchanger, a cooler, or a heater to your reservoir to control the temperature more precisely.

3 Fluid contamination

A third factor that impacts your reservoir size is the fluid contamination. The contamination of your fluid can come from various sources, such as dirt, dust, water, air, or metal particles. These contaminants can reduce the fluid quality and cause wear, corrosion, or blockage of your system components. To prevent this, you need to filter your fluid regularly and keep it clean. A smaller reservoir can help reduce the fluid contamination, as it reduces the exposure to air and water, and allows for more frequent fluid changes. However, you also need to ensure that your reservoir has enough space for a filter, a breather, and a drain plug, and that you can access them easily for maintenance.

4 Fluid level

A fourth factor that influences your reservoir size is the fluid level. The fluid level in your reservoir changes depending on the operation of your HPU, as some fluid may be stored or released by your actuators. You need to monitor your fluid level and keep it within a safe range, as too high or too low can cause problems. Too high can cause spillover, pressure build-up, or foaming of your fluid, while too low can cause cavitation, air entrainment, or fluid starvation of your pump. A larger reservoir can help accommodate the fluid level fluctuations, but you also need to install a sight glass, a level gauge, or a level switch to your reservoir to check the level easily.

5 Reservoir shape

A fifth factor that determines your reservoir size is the reservoir shape. The shape of your reservoir affects the fluid flow and distribution within your tank, and can have an impact on the heat dissipation, the contamination removal, and the air separation of your fluid. You want to avoid sharp corners, dead zones, or narrow passages in your reservoir, as they can create turbulence, stagnation, or restriction of your fluid. A rectangular or cylindrical reservoir is usually preferred, as it allows for a smooth and even flow of your fluid. You also want to position your inlet and outlet ports strategically, so that they create a baffle effect that separates the hot and cold fluid zones, and prevent short-circuiting or vortexing of your fluid.

6 Reservoir location

A sixth factor that affects your reservoir size is the reservoir location. The location of your reservoir influences the space availability, the noise level, and the safety of your HPU. You need to choose a location that is convenient, accessible, and secure for your reservoir. A smaller reservoir can help save space and reduce weight, but it may also increase the noise and vibration of your HPU. A larger reservoir can help reduce noise and vibration, but it may also pose a fire or spill hazard. You also need to consider the environmental conditions, such as temperature, humidity, or altitude, that may affect your reservoir performance and durability.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?