Fluid Power Devices
Hydraulic and pneumatic technology belongs to the category of fluid power. Fluid power is a method of power transmission. Since there is no single method that is optimal for all automation activities, fluid power is often used in combination with electrical and mechanical power transmission.
Advantages of fluid power over electrical and mechanical power transmission:
- Produces linear motion without the mechanical assistance of a rotating device
- Provides high torque in a smaller space requirement
- Control valves are an economical control option
- Can be configured to be safer in flammable environments
As subsets of fluid power, hydraulics and pneumatics are similar but have significant differences. They both convey fluids for power transmission and share terminology and component categories, but that's about it for similarities. The difference between pneumatics and hydraulics is the type of fluid. For power transmission, pneumatics deliver gases while hydraulics deliver fluids. The difference in media creates a significant difference in results and applications.
Pneumatic Components
Pneumatic technology can provide the gentler cushioning pressure needed for many automated tasks. Pneumatic technology utilizes compressed air or other inert gases to transmit power in drives. Pneumatics are a simple solution for machine operations that require fast response times and close power transmission.
When comparing pneumatic systems to other power transmission models, advantages include the use of affordable components, ease of installation, and unrestricted use of atmospheric gases (air). While air is free, there are some added costs associated with this technology. The air in the system needs to be compressed and cleaned.
Compressing the gas requires a significant amount of energy, so long-term operating costs may be higher than other power transmission models. Compressed air also needs to be prepared to prevent water and contaminants from entering the system. You will need to use filters and air dryers to keep the system clean and dry.
Air Valves
Valves help to stop and start the flow of air in a pneumatic system. These can be manual like a foot valve or motorized like a solenoid valve.
Air Preparation
The air preparation assembly ensures optimum performance and health of the pneumatic system by providing clean, dry air at adjustable pressure. Air filters protect machine function by cleaning incoming air. Air regulators ensure consistent pressure for optimum performance of pneumatic equipment. Air lubricators reduce leakage, slow wear and increase the speed of pneumatic components.The FRL (Filter/Regulator/Lubricator) combination unit combines these functions into one unit.
Cylinders
Cylinders use a piston rod to move a load in a straight line. Compressed air pushes or pulls the piston rod into or out of the cylinder barrel. Two key parameters of a cylinder include stroke and bore. Stroke is the distance a cylinder piston or rod extends when actuated. The bore is the diameter of the cylinder. The larger the bore, the more pressure or force the cylinder can exert.
Hydraulic Components
Hydraulic systems provide constant force and torque in applications that require more force than is generated by pneumatic or electromechanical systems. Hydraulic systems use a compressed fluid, usually oil (hydraulic fluid), for power transmission. This fluid power is a force multiplier that can be easily manipulated with simple push-button and lever controls.
With few moving parts and easy controls, hydraulic systems can be safe, simple and economical. Do not use oil; liquid power has its drawbacks. Before selecting a hydraulic system, it is important to understand the dangers and overall mess of hydraulic oil in a manufacturing environment. Hydraulic lines leak and can burst, which can cause injury to workers. There is also the potential for combustion in hazardous environments.
Hydraulic Fluids
In addition to being a power transmission medium, hydraulic fluid serves four functions. These functions are transferring heat for cooling, removing contaminants, sealing and lubricating.
Hydraulic Valves
Hydraulic valves direct the flow of fluid through a system and are activated either electronically or mechanically. These valves control the flow of fluid from the pump to other hydraulic components and are often used to control the direction of a hydraulic cylinder or motor.
Hydraulic Cylinders
Hydraulic cylinders are mechanical actuators that provide one-way force through a one-way stroke. The two main types of cylinders are welded and tie rod.
Hydraulic Pumps
Hydraulic pumps cause fluid movement and flow and convert mechanical energy into hydrodynamic energy.