Understanding your tractor's hydraulic system

Under Pressure...Understanding your tractor's hydraulic system.

Take a U-shaped tube, fill it with water, and put a plunger in either end. Push down on one plunger, and the other goes up..that's elementary hydraulics. It's a simple concept, but without it, your tractor wouldn't be much more than four wheels and an engine. So take a minute and learn more about the system that makes your tractor a workhorse.

Every hydraulic system owes its effectiveness to a basic rule of physics. Liquid can't be compressed. It can, however, transfer power from one place to the other; that's why one plunger moves up when you push the other down, the water is transferring power.

The mechanics of a tractor's hydraulic system are, of course, a bit more complicated. The tractor's system uses oil, not water. A pump pressurizes the oil and sends it to a value; the valve then sends pressurized oil wherever it's needed. And every component is built to withstand the pressure required to lift a loaded bucket, bale fork, or other implement. Remember, the hydraulic system has to lift not only the bale or the load of dirt, but also the bale fork or the loader bucket. Even a small tractor's hydraulic system is under enormous pressure, so it's important to make sure you've got the right system for the job.

Choose wisely when you're choosing your tractor and the hydraulic system. The hydraulic system is one of the most important considerations depending on the range of duties you'll need it to perform. Lifting and stacking hay bales will require more hydraulic capacity than occasional mowing or tilling.

There are three primary considerations:

  1. The flow rate in gallons per minute (GPM)
  2. The maximum pressure in pounds per square inch (PSI)
  3. The number of selective control values (SCVs) or attachment points for hydraulic implements.

The flow rate affects how fast the implement responds to operator input; the higher the flow, the faster the response. Pressure determines the system's lifting capacity; more pressure means more capacity. And the number of SCV's will determine how many hydraulic implements can be attached to the tractor at any one time.

Once you have the right tractor and the right system, there's not much maintenance to be done on the hydraulics. Dirt and water are the biggest enemies of a hydraulic system. Regular replacement of the air filter on the fluid reservoir will help keep dirt out; most of the water that gets in naturally through condensation will evaporate out, as long as the hydraulic system is used regularly. So keep these contaminants out, change the hydraulic fluid at the recommended interval, and the system should last the life of the tractor.

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