Preventing hydraulic motor failures requires a combination of proper design, maintenance, and operating practices. Although hydraulic motors are similar to hydraulic pumps, they are unique in that they convert hydraulic energy (in the form of pressure and flow) into rotational energy (in the form of operating torque). Hydraulic motors are used to drive winches, wheels, and pulleys, among other things, making them an irreplaceable and versatile actuator.
However, when the demands on a hydraulic motor are not met, failure is almost inevitable. More than many other components, hydraulic motors face the toughest conditions, harsh operating environments, and most extreme stresses. To prevent hydraulic motor failure, here are seven steps to help you ensure that both you and your machine are up and running.
1. Make sure the hydraulic oil is clean, dry and of the correct viscosity. As with other hydraulic equipment, contamination remains the leading cause of failure in hydraulic motors. Monitor the condition of the filter by observing the bypass indicator or replace the filter element regularly if there is no bypass indicator. The motor is the hydraulic component most likely to be completely submerged in water, such as the drive wheel motors used in various mobile machinery. Finally, take steps to keep the oil within the ideal viscosity range, which requires cooling in warm climates and heating in cold climates.
2. Do not overload the hydraulic motor. Avoid exceeding the torque and speed ratings of the motor, which can lead to excessive heating, cavitation due to excessive flow demands, and physical damage when the torque exceeds the mechanical and physical capabilities of the motor. Side loads should also be monitored, as damage to bearings, seals, and the shaft itself can lead to catastrophic failure.
3. Properly install and calibrate the hydraulic motor. Motors use shafts and usually drive other shafts, but they can also be inserted into gearboxes or other devices with female interfaces. In addition, the guides on the machine side should be accurate, axially true and parallel, which can prevent the above problems. Doing so can prevent wear on bearings, seals and the inside of the pump.
4. Keep the temperature moderate. It’s not enough to keep the hydraulic oil cool; you also need to take care to warm it up when the machine starts up in cold weather. Hydraulic oil and the machinery it drives prefer to operate within the viscosity operating window, so in cold climates, make sure you install a tank heater when needed. In addition, high temperatures not only reduce lubricity and increase oxidation, they soften and damage seals, accelerate oil wear, and increase metal-to-metal wear inside the motor. A hydraulic cooler is cheap insurance compared to a motor that costs thousands of dollars.
5. Clean and inspect the hydraulic motor. When you clean and inspect the entire machine, you can spot problems such as leaks, cracked hoses, and heat discoloration that would otherwise go unnoticed on a greasy and dirty machine.
6. Route the case drain correctly. You will know if this is correct within the first ten minutes of machine startup, as an incorrectly installed and routed drain can cause almost immediate failure. For example, some hydraulic piston motors have two case drain ports for installation flexibility. Using the bottom-most drain port allows the case to be completely drained, leaving the motor dry in terms of critical lubrication. Install the top-most drain port on the motor, then fill the case with oil before starting. Even with the correct orientation, the motor’s internal leakage will still fill the case, but the damage caused by running the motor dry at startup can reduce life expectancy by ninety percent in the first few minutes.
7. Choose the correct motor for your application. There is no point in selecting or replacing a motor if you choose a design that is not suitable for your application. When replacing a motor, always select the correct pressure and flow range that matches the factory installed design. For any given system pressure and flow rating, a larger motor will run at a lower speed and produce higher torque, while a smaller motor will run at a higher speed and have less torque.
By following these seven tips, you will ensure that you cover all the steps necessary to prevent hydraulic motor failure, whether it is a new application or repair and maintenance. By doing so, you will avoid wasted time and costs now and in the future.