a brief comparison between 3 power transmission systems:
Fluid Power Advantages
Hydraulic and pneumatic systems share many benefits for the machines in which they are installed. These include:
- high horsepower-to-weight ratio — You could probably hold a 5-hp hydraulic motor in the palm of your hand, but a 5-hp electric motor might weight 40 lb or more.
- safety in hazardous environments because they are inherently spark-free and can tolerate high temperatures.
- force or torque can be held constant — this is unique to fluid power transmission
- high torque at low speed — unlike electric motors, pneumatic and hydraulic motors can produce high torque while operating at low rotational speeds. Some fluid power motors can even maintain torque at zero speed without overheating
- pressurized fluids can be transmitted over long distances and through complex machine configurations with only a small loss in power
- multi-functional control — a single hydraulic pump or air compressor can provide power to many cylinders, motors, or other actuators
- elimination of complicated mechanical trains of gears, chains, belts, cams, and linkages
- motion can be almost instantly reversed
Hydraulic and pneumatic systems are both widely used in stationary (industrial) and off-highway (mobile) equipment. Hydraulic systems are widely used when heavy force or torque is involved, such as lifting loads weighing several tons, crushing or pressing strong materials like rock and solid metal, and digging, lifting, and moving large amounts of earth. And although pneumatics is capable of transmitting high force and torque, it is more widely used for fast-moving, repetitive applications, such as pick-and-place operations, gripping, and repetitive gripping or stamping. In both cases, electronic controls and sensors have been implemented into fluid power systems for the last few decades. These electronics make hydraulic and pneumatic systems faster, more precise and efficient, more reliable, and allow them to be tied into statistical process control and other factory and mobile equipment control networks.
Fluid Power Components
Fluid power systems consist of multiple components that work together or in sequence to perform some action or work. People well versed in fluid power circuit and system design may purchase individual components and assemble them into a fluid power systems themselves. However, many fluid power systems are designed by distributors, consultants, and other fluid power professionals who may provide the system in whole or in part.
The major components of any fluid power system include:
- a pumping device — a hydraulic pump or air compressor to provide fluid power to the system
- fluid conductors — tubing, hoses, fittings, manifolds and other components that distribute pressurized fluid throughout the system
- valves — devices that control fluid flow, pressure, starting, stopping and direction
- actuators — cylinders, motors, rotary actuators, grippers, vacuum cups and other components that perform the end function of the fluid power system.
- support components — filters, heat exchangers, manifolds, hydraulic reservoirs, pneumatic mufflers, and other components that enable the fluid power system to operate more effectively.
Electronic sensors and switches are also incorporated into many of today’s fluid power systems to provide a means for electronic controls to monitor operation of components. Diagnostic instruments are also used for measuring pressure, temperature and flow in assessing the condition of the system and for troubleshooting.
Off-highway equipment is probably the most common application of hydraulics. Whether it’s construction, mining, agriculture, waste reduction, or utility equipment, hydraulics provides the power and control to tackle the task at hand and often to provide motive power to move equipment from place to place — especially when track drives are involved. Hydraulics is also widely used in heavy industrial equipment in factories, in marine and offshore equipment for lifting, bending, pressing, cutting, forming, and moving heavy work pieces. Following are case histories housed on websites of industry publications describing the use of hydraulics in a variety of applications:
Traction is King on Grape Harvester
Accumulators Beat Boom Bounce
Slipform Paver has all the Smarts
Hydraulics Gives Multi-Articulated Excavator Wide Range of Motions
Electrohydraulics Runs Giant Elephant
Spider-Man Musical Relies on the Power of Hydraulics to Control and Lift Stages and Platforms
Thrills are tops, thanks to hydraulics
Marine & Offshore:
Crab Boat Catches Huge Fuel Savings
Wave Energy Presents New Challenges
Waste & Recycling:
Hydraulics Make Refuse Truck Quick, Quiet, and Efficient
Compact Motors Keep Sweepers Simple
Other industries where hydraulics is advantageous:
- Machine Tools
- Metal Forming
- Military & Aerospace
- Utility Equipment