Hydraulic and Pneumatic Motors in the Industrial Sectors

The motors in most industrial mechanisms are initiated by a source of energy that ignites the motors into movement. These motors are typically fueled by either hydraulic fluid pressure or pneumatic pressure, depending on the industrial application. Although there are many similarities between the two types of power, they frequently present different results. Selecting the best type of propulsion depends on a thorough understanding of each motor's strengths and weaknesses.

Defining Hydraulic Motors

Hydraulic motors rely on fluid pressure to drive mechanical loads and movements. In order for a hydraulic motor to work, the entire system must involve a pump, filters, valves, pressure hoses and a hydraulic fluid reservoir. The pump draws fluid from the hydraulic reservoir, forcing that fluid under pressure as it passes through the tubes until it is converted into mechanical power that moves the motor. Once the fluid has passed through the motor, it is returned to the reservoir to be filtered and used again to continue powering the motor.

There are many advantages that make hydraulic motors preferred over electric or pneumatic options. Hydraulic motors

• are small in size, especially compared to the heavy loads that these motors can handle.
• have high-pressure flexible hoses can be routed through small spaces, bends and other cramped quarters.
• offer the highest possible forces, able to move upwards of 100 tons.
• allow motors to achieve full velocity very quickly.
• are rugged, durable and suited for many dangerous or high-force applications.
• can have the motors, actuators and pumps located at a considerable distance from each other without losing much power or efficiency.
• can run several different motion axes at once.
• use their valves to adjust and save energy when the machines must move more slowly.
• can often be operated and repaired by unspecialized workers due to their simple construction and controls.

Because of the heavy loads that hydraulic motors can handle, they are most often used in construction and agricultural equipment. For example, excavators, forklifts, bulldozers and heavy trucks all rely on hydraulic motors to quickly and easily convert small amounts of power to move much larger loads. These are a few other applications for hydraulic motors:

• Car crushers
• Jumbo jet maintenance jacks
• Agitators in washing machines
• Poultry processing machinery
• Conveyer belts
• Milling and sawing applications
• Hydraulic mining, also called fracturing, to gain oil or gas
• Power steering and braking in vehicles
• Drilling rigs
• Plastic injection machines
• Drum drives for digesters

However, even with these many applications, there are some disadvantages to hydraulic motors:

• The motors will leak fluid at times which can reduce efficiency.
• Leaks can also cause issues with unclean motors and damage to components.
• There are many required parts to this type of motor, increasing the possibility for damage.
• They are very sensitive to temperature extremes and the formation of air pockets.
• Line ruptures can lead to hazards and serious injuries for workers using these motors.

Defining Pneumatic Motors

Whereas hydraulic motors rely on fluid pressure, pneumatic motors convert compressed air into energy and power for mechanical work. These motors have cavities throughout them in which this compressed gas can be held and controlled by a series of valves. The gas then expands, filling these cavities and pushing on the diaphragm, actuator or rotor to cause the motor to work. The inclusion of each of these parts, along with the possibility of hoses or other safety measures, depends on the type of pneumatic motor.

Pneumatic motors offer many advantages in industrial applications. Pneumatic motors

• are simple and easy to use.
• are easily controlled and adjusted in both speed and force.
• provide high speed and force at a low unit cost.
• run on air, an infinite source of energy.
• are not influenced by external issues, such as extreme temperatures, dirt, moisture or mechanical vibrations.
• can be lightweight.
• typically require little maintenance due to durable components.
• are one of the most intrinsically safe motor options because air is not flammable and does not explode.

Applications for pneumatic motors are varied since these systems require very little maintenance and last for extended periods. A few common uses include:

• Automotive assembly lines
• Paint and body shops
• Hand-held tools, such as wrenches, ratchets, drills and sanders
• Air brakes on buses and commercial trucks
• Exercise machines
• Mail and banking systems with pressurized air tubes
• Vacuums
• Air guns
• Jackhammers
• Raising foundry copes and drags
• Rotating turntables

Despite the advantages to pneumatic motors, there are some drawbacks:

• Operating and maintenance costs are often high.
• Electricity is often required for the compressor.
• There can be air leaks and nonessential uses of the motor.
• The pressure losses lead to decreased speed, force and effectiveness.
• The system can be very noisy when air escapes the exhaust.
• Motors must be sized for each specific job, leading to increased costs and complexities as motors are built to only have one use.
• Pressurized air can become condensed, so certain precautions and cleaning processes must occur prior to the air entering the motor.

Hydraulic motors allow a lot more force and power to be applied than pneumatic motors. Because hydraulics rely on pumps to pressurize fluids held in open spaces, there are many more parts involved in this process. The higher number of working parts, as well as the motor's sensitivity to adverse conditions, can deter many from using hydraulic motors. However, there is no other type of energy conversion that will produce as much power and pressure as hydraulic motors.

Pneumatic motors, on the other hand, are much more flexible in their applications because they are unaffected by external conditions and feature fewer working parts. Furthermore, air is an infinite, safe resource that makes pneumatic an attractive power option. Compressing air, however, can be noisy and expensive to produce, and leaks occur more often in pneumatic motors.

There are advantages and disadvantages to both types of motors, but the proof of their usefulness lies in their applications. Choosing the better type of motor depends entirely on the intended use and the conditions in which it will be applied.