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Posts tagged: hydraulic power unit

The Power of a Hydraulic Power Unit

Lumberjacks. Miners. Search and rescue crews. What do they have in common? Well, they’re obviously some of the most hardcore people in America, but other than that, they also all work some with extreme machinery in their daily jobs. But where does a man find enough power to lift a massive tree, move huge volumes of earth, or drag a car out of a canyon? The answer is that the machinery they use are almost universally driven with a hydraulic power unit — a motor that converts the motion of liquid into mechanical force.

A hydraulic motor, at its essence, is fairly simple: a reservoir of hydraulic fluid, a power unit, and a machine that can be moved by any form of rotation. The power unit — usually a small electric device — pressurizes the fluid. Because fluid cannot be compressed, any amount of pressure from the pump causes the fluid to move, usually through a series of valves designed to make sure that the fluid can’t move backwards and harm the pump.

At the far end of the line, the fluid moves into a piston, which extends as it fills up, and voila! — a log is lifted easily off of the earth, swung about, and dropped onto a waiting truck. Or, perhaps, the fluid moves through a propeller, which generates a rotational force that is then fed into a series of gears that slows the rotations-per-minute but adds a huge amount of torque, and the winch on the far side of those gears pulls a truck out of a lake. The number of potential applications is huge.  After the fluid has done its job, it returns back to the reservoir along a different line, ready to be used again the next time the pump comes online.

Electric motors can only generate more power by being built bigger — so to get an electric motor to haul a ton of earth directly, you need one that is absolutely massive. But by using a hydraulic power unit — which is, ultimately, an electric motor, just used in conjunction with a hydrostatic system — the same job can be accomplished with a much smaller device.

What Does My Hydraulic Filter Do?

Hydraulic fluid has a number of purposes inside of a hydraulic system. In addition to it’s obvious purpose of transferring force from a hydraulic power unit to an actuator, it has a few less-obvious purposes as well:

  • It helps to seal the hydraulic system through the power of surface tension and adhesion,
  • It lubricates the system by preventing metal surfaces from contacting each other,
  • And it helps balance the temperature of the system by transferring heat from one area to another.

If any of these functions are compromised, the entire system can become compromised. The obvious question, then, is ‘what causes these functions to become compromised and how can we prevent that?’ As it turns out, the most common cause of compromised hydraulic fluid is particulate that builds up in the fluid.

Particulate build-up might not cause the force-transferring properties of the hydraulic fluid to dissipate, but all three of the other functions are vulnerable to particles. They breach the surface tension of the fluid, breaking the ‘seal’ that the fluid forms that prevent microscopic leaks from becoming problematic. They can get pinched between metal surfaces that would otherwise have been adequately lubricated and cause damage to those surfaces. And by causing excess friction, they can overcome the ability of the fluid to keep the system cool.

The way to prevent particulate build up, as you may have guessed, is to use and regularly change your hydraulic filter. A hydraulic filter eliminates particulate contamination, which in turn prevents a goodly number of the problems that can crop up within your hydraulic fluid.

What Won’t My Hydraulic Filter Do?
The hydraulic filter isn’t the be-all and end-all of hydraulic system maintenance, however. No filter can keep water entirely out of your hydraulic fluid, for example, and water has a variety of negative effects on the system. Furthermore, the particulate that gets into your fluid comes from the inside of the parts of your hydraulic system — microscopic chunks that break off. Given long enough, that wear can affect the performance of a part, which will need replacing.

That said, nothing is quite as cost-effective at increasing the functional lifespan of a hydraulic system like regular replacement of the hydraulic filter — so make sure you stay on top of it!

How to Buy an Industrial Hydraulic Power Unit

Hydraulic power units (HPUs) are everywhere — many jackhammers, most auto lifts that mechanics walk under, many fishing boats’ net-haulers, almost every big yellow machine you see at a construction site all use hydraulic power units. Obviously they come in quite a variety — how do you know you’re getting the right one for your needs?

At it’s simplest, when you need a single HPU to power a single tool, the answer is usually written right on (or in the instruction booklet of) the tool in question. You need an HPU that provides at least enough actual hydraulic fluid to power the tool (for handheld tools, a half-gallon is usually all you need, but for industrial applications, a 250 gallon tank isn’t unheard of.) It also needs to supply adequate pressure to get the job done — your typical hydraulic jackhammer, for example, won’t function at less than 1300 psi.

But the simplest is hardly adequate to most industrial applications. If you’re, say, a machine shop, and you need a single hydraulic power unit that can provide hydraulic power to a dozen different metal grinders, pipe benders, sheet stampers, and so forth, you’ve got a lot more to worry about than just matching one machine’s numbers to another’s.

Fortunately, it’s still not all that difficult — many providers have or can custom-build a hydraulic manifold that can ensure that, as long as your HPU is capable of producing adequate flow and pressure to handle all of the jobs you want to simultaneously accomplish, each tool gets the right amount of fluid at the right pressure. Such a manifold will have pressure-reducing valves and both automatic and controllable switches that will ensure no machine gets too much pressure or fluid for it’s own operation, but all machines get enough of each.

Those aren’t the only details — there are other considerations that range from the possible need to move your HPU to different areas at different times, or matching the power consumption of your HPU to the type of power provided by your shop’s outlets — but those should mostly be intuitive for your typical shop manager.

A Layman’s Guide to Hydraulic Power Units

Hydraulic Power Units are machines that create mechanical force using fluids. HPUs (Hydraulic Power Units) are used in any industry in which large things need to be moved smoothly — construction, theme parks, farming, commercial fishing, and dozens more.

If you’ve seen a backhoe, loader, crane, power shovel, forklift, or garbage truck, you’ve seen an HPU in action. There’s an HPU in every set of the Jaws of Life as well. And of course, every mechanic uses a powerful hydraulic lifter to pick your car up and get to its underbelly.

One of the most commonplace hydraulic power units is in your car: the braking system of every car in the world uses an HPU. When you push the brake pedal in your car, you’re pushing hydraulic fluid (in this case commonly called ‘brake fluid’ for obvious reasons) into a hydraulic cylinder, which in turn pushes a piston, generating mechanical force that moves the brake pads up against the rotor, slowing your car. That’s why keeping your brake fluid levels topped off (and your brake lines free of air bubbles) is so important to your safety.

Hydraulics is a very powerful force because of a simple law of physics: while liquid can take on the shape of any container it’s put in, it cannot be compressed. What that means in short is that liquid can transfer force perfectly through almost any number of twists, turns, and corners without needing to involve a lot of gears, levers, and other mechanical parts prone to breakdown. Instead, the hydraulic fluid moves through hoses and tubes, using hydraulic valves to ensure it takes the path you need it to take in order to perform the task at hand.

Hydraulic fluid is almost always some combination of petroleum oil, water, and antifreeze — dependent on the specific job the machine is intended to perform. A hydraulic filter keeps the fluid free of contaminants, and when unused, the fluid sits in a special container made to remove air bubbles from the fluid. Thus, the fluid remains in working order for as long as possible, and your HPU can continue functioning continuously for years with minimal maintenance.

These powerful machines are among the most versatile (and surprisingly common) of our mechanical aids. Everyone ought to know at least a little bit about the hydraulic power units that help them throughout their lives.