Auxiliary high-flow hydraulic systems can dramatically increase skid-steer loader productivity in the right applications. The higher the horsepower, the more work you can accomplish in a given period of time.
To calculate hydraulic horsepower, you multiply the flow rate in gal./minute (gpm) times the pressure in pounds/sq. in. (psi), then divide by 1,714. So let's assume a skid-steer loader has an operating pressure of 3,100 psi and comes in a 22-gpm standard-flow or a 34-gpm high-flow configuration. Using the above equation, the standard-flow model would provide: (22 gpm x 3,100 psi)/1,714 = 39.8 hp. The high-flow model would offer: (34 gpm x 3,100 psi)/1,714 = 61.5 hp. As you can see, the high-flow unit has quite a bit more capacity to get more work done in a specified time frame.
"With higher hydraulic flow, the loader can provide more performance to power high-flow, high-performance attachments," says Kelly Moore, product manager, skid loaders, Gehl Co. "The increase in productivity is the greatest benefit - being able to perform more work more efficiently and more quickly. For instance, a high-flow trencher or auger attachment coupled to a high flow-equipped loader will run at a faster speed with plenty of torque to avoid stalling in highly compacted materials."
Chris Giorgianni, general manager for product marketing, JCB, states, "The major advantage of a high-flow skid steer is that you have the option to run attachments that require the high hydraulic horsepower and flow, allowing them to run in their optimum performance range. Generally, attachments that require high flow are ones that have a component that needs to be run at a high rate of motion. Examples would be certain varieties of stump grinders, cold planers and slot cutters. A high-flow machine would be of greatest benefit for these, because without the high flow, these types of attachments lose their effectiveness."
"Relatively speaking, the larger a hydraulic attachment, the more flow it will require to engage the ground or spin a drum faster," adds Gregg Zupancic, product marketing manager for skid steers and compact track loaders, John Deere Construction.
A compatible option
Standard-flow auxiliary hydraulics do have limitations. "The limitations are the types of attachments that you can run," says Jim Hughes, product manager, Case Construction. "If your attachment requires 30 gpm and you only have standard auxiliary hydraulics, you will not be able to run the attachment at peak efficiency, which runs the risk of damaging the attachment and/or the machine."
"A standard-flow machine will only be able to run attachments designed for standard flow," agrees Giorgianni. "The high-flow machine, however, can run both standard- and high-flow attachments. With a standard-flow machine you limit the machine's versatility, as it reduces the range of attachments you can run."
Because skid-steer loaders equipped with auxiliary high-flow hydraulic systems are compatible with standard-flow attachments, purchasing a high-flow model doesn't necessarily mean you have to upgrade to high-flow attachments.
Giorgianni explains, "On a high-flow machine, you have both a high-flow connection and a separate standard-flow connection. In other words, the high-flow system is standalone and can be used only when needed. The machine can be operated as a standard-flow machine the rest of the time."
Couplers for both are usually included. "A separate set of standard-flow couplers are provided distinct from the high-flow couplers," notes Moore, "which allows proper operation with the standard-flow attachments."
So you essentially get two systems for the price of one. "It's not simply a matter of having a machine that has either standard-flow or high-flow hydraulics," says Hughes. "When you order the high-flow option, you get additional high-flow connectors to hook the hoses from the attachment to the machine. Therefore, if you are using an attachment that requires standard flow, you attach it to the standard-flow connectors. If you are using a high-flow attachment, you attach it to the high-flow connectors.