Skid steers and compact track loaders (CTLs) are two of the most useful pieces of mobile equipment, tackling jobs ranging from construction and landscaping to brush cutting and snow removal. Adding attachments to the machines makes them all that much more versatile. In a recent CASE LIVE presentation, “Understanding Auxiliary Hydraulics and Attachment Settings,” product managers George Macintyre and Ted Polzer of CASE Construction Equipment discussed the basics and nuances of these important hydraulic systems.
What are the different levels of auxiliary hydraulics on skid steers and CTLs?
George: CASE offers three core systems: standard, high-flow, and enhanced high-flow. The most-common system is the standard-flow auxiliary hydraulics package. Although flow rates differ by model, standard-flow systems typically range from 17 to 24 gpm. They are included in all machines from the factory and operate on the same pressure as the machine’s main hydraulics, approximately 3,000 to 3,500 psi. A standard-flow system powers many of the most common hydraulic attachments on the market, such as 4-in-1 buckets, hydraulic hammers, augers, trenchers and grapples.
Beyond that standard functionality is the high-flow auxiliary hydraulic system, which further increases a machine’s versatility and productivity. As with standard-flow, it operates on the same pressure as the main hydraulic circuit. The flow rate, however, ranges from 30 to 42 gpm. A high-flow system can be a factory-installed option or added later in the field. It powers production-type attachments that require a higher flow rate. Examples include cold planers, many snow blowers, rock saws, small mulchers and chipper-shredders.
Enhanced high-flow auxiliary hydraulics have flow rates similar to that of a high-flow package, but it operates at a higher pressure. For example, the new CASE TV620B CTL with an enhanced high-flow system offers 42 gpm flow and a higher pressure rating of 4,100 psi. Attachments that use enhanced high-flow systems include large cold planers, rock saws and large mulchers.
How do pressure and flow relate to matching attachments with machines?
Ted: People often don’t understand the difference between pressure and flow, but these parameters are critical to determining the type of system needed to run a specific attachment. Let’s start with the fundamentals. Flow equates to the speed of an attachment under no restriction. So when an attachment’s specs say it is rated for maximum 30 gpm, that’s usually at no pressure or resistance to flow. But as soon as we start to resist flow, pressure starts to build.
Pressure gives an idea of how much work you can do. High-flow and enhanced high-flow attachments might use the same flow, but the added pressure in the latter case is important for demanding attachments like a mulching head. Running at 4,000 psi versus 3,000 psi means overcoming more resistance to the drum turning the mulcher, letting users clear brush and small trees much more efficiently.
So it’s important to understand the maximum constraints on flow and pressure for your attachment. And it’s also important to know that the two cross at some point to basically create the most productive point where you want to use that attachment. Take cold planers, as an example. Running it hard at the maximum 3,000 psi may generate excess heat that hurts the productivity of the machine. By actually backing off a little bit and reducing some of that resistance to the flow can improve performance because your attachment will run at a more-consistent speed. So it’s extremely important to understand exactly what your machine can do and exactly what your attachments are capable of accepting.
One of the training aids we’ve used for years is to simply mount a pressure gauge in an area that’s visible to the operator and shows how you’re more productive at a certain pressure and lower. A growing number of attachments come with pressure gauges installed.
Why is hydraulic horsepower important, and what does that mean in terms of overall effectiveness and productivity in the attachment?
Ted: Hydraulic horsepower (hhp) is important because it essentially tells you hydraulically what your machine is capable of doing, and what kind of productivity to expect. Many OEMs and attachment manufacturers publish the rated hydraulic horsepower of their products, and users can quickly calculate it themselves. Numerous website calculators are also available. (Editor’s note: Hydraulic HP = P × Q/1714, where P is pressure in psi and Q is flow in gpm.)
What advice would you give about properly matching attachments to the machine?
Ted: Many attachments are rated by their hydraulic horsepower. We typically use this as a way to gauge and judge the match between the attachment and the machine. It doesn’t make a lot of sense to put on attachment that can only accept 40 hhp on a 90 hhp machine, or vice versa. And it’s always important to have those matched when you’re looking at new attachments.
Or you could lay out the maximum pressure and flow that your attachment will take. Attachment manufacturers do publish the range of acceptable flow rates for their products. Compare those to the max outputs of your machine. That’s probably the easiest way to know quickly if they match.
And then, of course, you still have to make sure that the coupler itself fits your machine and that your quick disconnects for your hydraulic hoses also match.
A common misconception is that if I buy a larger-than-necessary attachment, I can grow into it, I’ll have it longer, and it will work on more machines. Well, it will function. However, you have to remember that when we build an attachment for high pressure such as enhanced high-flow, we’re typically looking at a different type of drive motor inside of that attachment. Maybe it’s an axial-piston motor versus a gerotor motor on a low flow, low pressure type of attachment. So it’s really important to understand that while an attachment may be capable of coupling up to other machines, it may not be as productive. Always drill down and make sure exactly what the attachment can do on your specific machine.
That said, lot of newer machines let operators adjust flow from inside the cab. And with that option, there can be some confusion when setting the flow best suited for a specific attachment. One customer made a laminated card that basically told all of their operators, “If you’re going to run this attachment, set the flow to this.” That ensured better productivity out of their attachments, and it also reduced the risk of having the wrong attachment. For instance, a low flow attachment coupled to a large high-pressure, high hydraulic horsepower machine could lead to a failure. That’s what they’re trying to avoid.
Another great feature on some newer skid steers is the creep-control function. Creep control is especially important when using attachments like a mulcher or cold planer that demands a consistent long hydraulic horsepower pull out of that attachment. The operator can set the precise speed needed to get the highest productivity from the attachment, versus back in the day when you sneeze and jerk the controls and stall the attachment.
In “11 tips for best use of hydraulic attachments,” the CASE experts offer some additional advice for selecting and using hydraulic attachments.
CASE Construction Equipment