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Earth MovErs A Primer in Skid-steer Hydraulics The auxiliary hydraulic capabilities of a skid-steer are one of the fea- tures that make it extremely versatile. Having a good understanding of the output you will need is important when you spec a machine. How much power is too much power, and how much power do your attachments need? AttAchments drive the decision A skid-steer's auxiliary hydraulic system provides the hydrau- lic flow that drives the machine's attachments. The key to remember is that not all attachments have the same hy- draulic flow requirement. The most common system is the standard-flow auxiliary hydraulics package. Although flow rates differ by manufacturer and skid-steer model, the flow rate of a standard-flow system ranges from 17.5 to 24.2 gallons per minute (gpm) 1 . Standard- flow auxiliary hydraulics are included on all skid-steers from the factory and operate on the same pressure on which the ma- chine's main hydraulics operate, which is approximately 3,000 pounds per square inch (psi). A standard-flow system powers many of the most common hydraulic attachments on the mar- ket, such as 4-in-1 buckets, hydraulic hammers, augers, tren- chers and grapples. A high-flow auxiliary hydraulics system further increases a skid-steer's versatility and productivity. As with standard-flow, it operates on the same pressures on which the main hydraulic circuits operate. The flow rate, however, ranges from 30.7 to 37.6 gpm. A high-flow system can be factory installed as an option or installed later in the field. It powers production-type attachments that require a high flow rate to perform as specified, like cold planers, rock saws, small mulchers and chipper/shredders. When even more hydraulic power is required, an enhanced high-flow auxiliary hydraulics package is available. This high- performance option has flow rates that are similar to a skid-steer with a high-flow package, but operates up to 4,000 psi. Examples of attachments that require an enhanced high-flow system in- clude larger cold planers, mulchers and rock saws. Also available is a secondary auxiliary hydraulics system for applications that require multiple hydraulic movements simul- taneously. This would include the side shift function on a cold planer or stump grinder, snow blower for direction change on the chute, or a tree spade with down riggers. UnderstAnding demAnds of AttAchments A common misconception is that a standard-flow system can adequately run high-flow attachments. Powering high-flow at- tachments with a standard-flow skid-steer will lead to inefficient operation or damage the attachment/skid-steer. When it comes to an enhanced high-flow auxiliary hydraulics package, it's important to know the system is designed for ex- treme situations where the operators are truly pushing the limits. The enhanced high-flow package is only available on larger skid- steers with the horsepower available to ensure proper operation of the attachment. Another common misconception and mistake in operation is that it's best to run the attachment "wide open" and use all of the flow and pressure available. This is incorrect, and many attach- ■ by WarrEn andErson Photos Provided by CAse ConstruCtion equiPment 18 April 2015 Landscape and irrigation www.landscapeirrigation.com