Pneumatic and hydraulic systems have a lot in common. Both pneumatics and hydraulics are applications of fluid technology. They each use a pump as an actuator, are controlled by valves, and use fluids to transfer mechanical energy.
The biggest difference between the two types of systems is the media used and the applications. Pneumatics use an easily compressible gas such as air or other sorts of suitable pure gas—while hydraulics uses relatively incompressible liquid media such as hydraulic or mineral oil, ethylene glycol, water, or high-temperature fire-resistant fluids.
Neither type of system type is more popular than the other as its applications are specialized. This article will help you make a better choice for your application by describing the two types of systems, their applications, advantages, and disadvantages. The load or force you need to apply, the output speed, and the cost of energy determine the type of system you need for your application.
What is Pneumatics?
Pneumatics is a branch of engineering that uses pressurized gas or air to affect mechanical motion based on the working principles of fluid dynamics and pressure. The field of pneumatics has changed from small hand-held devices to large machines that perform different functions.
Pneumatic systems are usually operated with compressed air or inert gases. The system consists of interconnected components including a gas compressor, transition lines, air tanks, hoses, standard cylinders, and gas (atmosphere).
The compressed air is supplied by the compressor and transmitted through a series of hoses. The air flow is regulated by manual or automatic solenoid valves and the pneumatic cylinder converts the energy provided by the compressed gas into mechanical energy.
A centrally located and electrically operated compressor drives cylinders, air motors and other pneumatic devices. Pneumatic systems are controlled by a simple ON/OFF switch or valve.
Most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch (550 to 690 kPa). The compressed air is stored in collection tanks before it is sent on for use. The compressors’ ability to compress the gas is limited by the compression ratios.
What does a pneumatic system do?
Pneumatic machinery and equipment use pressurized gasses, such as air, for moving and cooling applications. Pneumatic fluid power systems compress air, so movement is not instantaneous, as it is with hydraulics.
Advantages of pneumatic System
- More cost-effective than hydraulics – air is free
- Pneumatic safety – the system can be used in inflammable environments and does not
- More power in a smaller and lighter unit compared to most other technology systems
- Cleaner technology
- Fluid used absorbs excessive force, which means fewer threats of damage to equipment
Applications of Pneumatic System
Pneumatic systems are typically used in construction, robotics, food production and distribution, material handling, medical applications (dentistry), pharmaceutical and biotechnology, mining, mills, buildings, and tools in factories.
Pneumatic systems are primarily used for shock absorption applications because gas is compressible and equipment is less prone to shock damage.
Applications of pneumatic systems include:
- Air compressors
- Vacuum pumps
- Compressed-air engines and vehicles
- HVAC control systems
- Conveyor systems in the pharmaceutical and food industries
- Pressure sensor, switch, and pump
- Precision drills used by dentists
- Air brakes used by buses, trucks, and trains
- Tampers used to pack down dirt and gravel
- Nail guns
- High-pressure bank’s drive-teller tubes
- Manufacturing and assembly lines
- Pneumatic motor, tire, and tools
What is Hydraulics?
Hydraulics is used to generate, control and transmit power using pressurized fluids. It is a technology and applied science that deals with mechanical properties and the use of fluids.
Hydraulic systems require a pump and, like pneumatic systems, use valves to control the force and speed of the actuators.
Industrial hydraulic applications use 1,000 to 5,000 psi or more than 10,000 psi for special applications. The word hydraulic comes from the Greek words hydor – water and aulos – pipe.
A hydraulic system requires the following equipment: hydraulic fluid, cylinders, pistons, pumps, and valves that control the direction of flow, which is always one-way.
In contrast to pneumatic systems, hydraulic systems are often large and complex. The system requires more space because a reservoir is required to contain fluid flowing through the system. Because the system is larger, it requires more pressure; making it more expensive than pneumatic systems.
Due to their overall larger size and the incompressibility of oil, hydraulic systems can lift and move larger materials. Hydraulic systems are slower because oil is viscous and takes more energy to move through pipes.
When the factory or plant has several hydraulic machines, it is ideal when configuring and planning to have a central power pack to reduce the noise level.
What does a hydraulic system do?
Instead of air, machines that use hydraulics rely on mostly incompressible liquid material under pressure to lift, hold and move goods. Examples include hydraulic or mineral oil, or water, just to name a few.
Advantages of a Hydraulic System
- Moves heavier loads with greater force than mechanical, electrical, or pneumatic fluid power systems
- Ease and accuracy of controlling the system by levers and push buttons
- Generates large amounts of power
- Uses fewer moving parts than some mechanical and electrical systems, which makes it more durable and less prone to break down
Applications of Hydraulic System
Due to the risk of potential hydraulic oil leakage from faulty valves, seals, or hoses, hydraulic applications do not apply to anything that would be ingested, such as food and medical applications. They are used in a variety of everyday machine applications:
- Machine tools: hydraulic presses, hoppers, cylinders, and rams
- Amusement parks
- Dump truck lift
- Wheelchair lift
- Excavating arms for diggers
- Hydraulic presses for forging metal parts
- Wing flaps on aircraft
- A hydraulic braking system in cars
- Lift cars using a hydraulic lift
- Jaws of life
Pros And Cons of Hydraulics and Pneumatics
In hydraulic wrenching terms of sustainability, air-pressure powered tools are typically used when performing maintenance of valves and flanges because the pressure they use is more controllable.
Pneumatics display rapid movement of gears and have the advantage of availability in very small sizes. This is mainly due to air compressor flow rates. Air is very agile and can flow through hoses very quickly and easily with little resistance, while hydraulic oil is a viscous substance and requires more energy to move.
Pneumatics offers a very clean system, suitable for food manufacturing and other processes that require no risk of contamination. Due to the risk of hydraulic oil leaks from faulty valves, seals, or burst hoses, hydraulics are generally not used in these environments.
Pneumatic tools and valves can dump their compressed air straight to the atmosphere when they need to change direction or alter their state quickly, compared with hydraulic pumps where the oil must be routed back to the reservoir.
However, pneumatics does not have the potential force that hydraulics has to offer. Typical pneumatic systems operate at around 80 to 100 pounds per square inch of pressure, with pressures greater than this restricted by the materials used within the system.
Hydraulic jacks can smoothly lift and move large loads because the hydraulic oil is not compressible. In general, a much larger pneumatic cylinder is needed to obtain the same force that a hydraulic ram can produce.
What is the Difference between pneumatics and hydraulics?
The biggest difference between the two systems is what substance you use to operate them. Pneumatics uses gases, and hydraulics uses liquids. Both have many practical applications, and it is up to the design team and engineers to make the machines as to which system is will be best.
Because of this primary difference, some other aspects of these two power circuits also follow suit. Industrial applications of pneumatics utilize pressures ranging from 80–100 pounds per square inch, while hydraulics use 1,000–5,000 psi or more than 10,000 psi for specialized applications.
Moreover, a tank would be needed in order to store the oil by which the hydraulic system can draw in cases of a deficit. In a pneumatic system, however, air can simply be drawn from the atmosphere and then purified via a filter.
Best Uses for Hydraulics and Pneumatics
Pneumatics are typically used in factories, construction, mills, buildings, and technology by using a central source of compressed air for power supply. Medical applications of pneumatics are also widespread, including a dentist’s heavy-duty drill.
Practically everything could run pneumatically, including all means of transport. The small tube in a bank’s bank teller operates pneumatically from a source of high-pressure compressed air.
Hydraulics has many uses in everyday life and most of them are applicable to machines. Hydraulics are used, for example, in the braking system of a car. They only require a small amount of force when the driver applies the brakes, but a greater force is already generated to stop or slow a car because it acts equally on all 4 brake pads.
Hydraulic applications are also found in hoists such as wheelchair lifts, excavator arms on machines such as excavators, hydraulic presses for forging metal parts, and wing flaps on airplanes. Obvious applications of hydraulics are with heavy equipment.