By Ed Wade, The IFH Group

Mobile reservoirs for off-road vehicles are more than storage tanks for hydraulic fluid. Though their prime function is to act as storage containers for hydraulic fluid, they should also function as fluid conditioning devices. They can not only provide fluid to meet varying demands as actuators extend and retract, but can also prepare the fluid for its next working cycle.

Mobile hydraulic reservoirs are expected to perform as well as industrial reservoirs, but since they operate under adverse conditions, they require special design considerations. Machine motion and extreme ambient temperatures are but two examples of the special problems designers and manufacturers of hydraulic systems in mobile equipment face.

When comparing industrial and mobile designs, size is perhaps the most striking difference. Industrial standards, developed by NFPOA and accepted by ANSI, specify that reservoir capacity should equal 3 to 12 times maximum pump output: today this may exceed 2000 gallons. However, size and weight limitations may require the equipment to operate with reservoirs as small as one time pump output.

Because of the special limitations of mobile hydraulic reservoirs, their design and build must be fully developed. Cost, size, and weight must be minimized while maintaining performance and efficiency.

Custom versus Off-the-Shelf

Custom made hydraulic reservoirs have an advantage over off-the-shelf reservoirs because they can be designed to fit the exact space and technical requirements necessary for optimal performance. Reservoir manufacturers should maintain a complete engineering department to assist in developing the most economical and practical hydraulic reservoir design.

Aluminized steel (sheet steel hot dip coated on both sides with an aluminum-silicon alloy) can be used to solve the contamination problems inherent in uncoated steels. It combines the corrosion resistance of aluminum with the structural strength (and lower weight and cost) of steel. Aluminized fuel tanks are resistant to virtually all petroleum-based and synthetic fluids while providing excellent protection from atmospheric corrosion. These tanks can be readily welded using resistance, MIG, TIG or robotic welding processes and can be formed using normal methods, with no peeling or flaking of the coating.

The Weld

With any hydraulic reservoir, the quality of the weld is all-important. Any competent manufacturer should combine MIG, TIG, robotic and electrical resistance welding to provide hydraulic reservoirs of the highest quality. Manufacturing equipment should be state-of-the-art, including CNC turret punches, CNC controlled forming equipment and CNC controlled welding equipment.

The Finish

Powder coating is the future. Increasingly stringent environmental regulations, rising costs in all areas, and demands for better quality and more durable products make it the smart choice for a better looking, more durable finish. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a “skin.” It creates a hard finish that is tougher than conventional paint.

Cleaning and maintenance

Reservoir servicing must also be taken into account. There must be provisions to drain both return and suction areas of the tank, especially if a baffle is used to separate them. Pipe couplings are often used, but SAE O-ring ports provide better sealing. Valves should also be provided for closing off inlet lines when replacing pumps or other components that are below fluid level.

Access should be provided for cleaning and maintaining the interior of the tank. Clean out covers should be large enough for service personnel and cleaning tools. There should also be means for lighting each portion of the tank for inspection. Clean out covers should be attached to the tank so leaks can be detected and repaired from the outside.

Questions? For more information, contact Ed Wade, IFH Group, emwade@ifhgroup.com

By Ryan McCarty, The IFH Group

Hydraulic reservoirs in mobile equipment can be prone to corrosion when humid air is drawn in when the oil level drops. Once moist air gets into the reservoir, water can condense on the interior walls when the ambient temperature drops. Desiccant breathers can be specified to filter and dry ambient air drawn into the reservoir. However, the desiccant has a finite service life, so if the breather is not changed at recommended intervals, moisture will be drawn in unimpeded. The condensate, ultimately, will enter the hydraulic system and pose several problems.

The condensate will also adhere to the interior surfaces of the reservoir, which could lead to rust deposits that can also enter the hydraulic system. These deposits can cause problems of their own, including premature wear to components, clogging of filters and orifices, and valve malfunctions.

Reservoirs made of aluminized steel can help prevent corrosion if moisture does get into the reservoir. Aluminized steel is sheet carbon steel that is hot-dip-coated on both sides with an aluminum-silicon alloy to avoid the contamination problems inherent to uncoated steels. Essentially, aluminized steel combines the corrosion resistance of aluminum with the higher mechanical strength — and lower cost — of steel. Aluminized steel reservoirs are compatible with virtually all petroleum-based and synthetic fluids while also providing protection from atmospheric corrosion.

For more information, contact rmccarty@ifhgroup.com