Pneumatic Systems: Components and Function
Compressor
Compressors are machines that suck air from the atmosphere and compress it to a high pressure. This compressed air is then used to power various pneumatic tools and equipment. The movement of the compressor is achieved through belts and pulleys.
Types of Compressors
A) Piston Compressors
Piston compressors work by drawing in air through a suction valve as the piston moves downward, driven by the crankshaft. The air is then compressed and deposited in a high-pressure zone thanks to the exhaust valve. Piston compressors can have one or more cylinders.
- Diaphragm Compressors: These compressors use a flexible synthetic rubber membrane to produce the pumping action. Advantages include the inability of lubricating oil to become airborne, making them suitable for use in the food and pharmaceutical industries.
B) Rotary Compressors
- Vane Compressors: These compressors have a cylindrical carter with a rotor that rotates inside. The rotor has a certain number of vanes that slide within slots. Advantages include their small size, quiet operation, and uniform flow.
- Screw Compressors: Screw compressors utilize two helical screws that are geared to one another. As the screws turn, they axially move the air. These compressors are often used in domestic air conditioning systems.
- Roots Compressors: Roots compressors transport air from right to left. They were first used in supercharged or turbocharged engines.
C) Turbochargers
- Radial Turbochargers: These turbochargers suck air in the center and then throw it radially outward using centrifugal force.
- Axial Turbochargers: In axial turbochargers, the air runs parallel to the axis of the turbocharger.
Components of an Air Reservoir
- Thermometer and Pressure Gauge: These instruments are used to monitor the temperature and air pressure within the reservoir.
- Compressor Shut-off Valve: This valve is used to turn the compressor on or off.
- Water Discharge Valve: As the air in the reservoir cools, it produces water condensation. This water must be eliminated to prevent it from entering the distribution network. The water discharge valve, often referred to as a “drain valve,” accomplishes this task.
- Pressure Limiting Valve: This valve acts as a control mechanism, opening to release excess air and prevent potential explosions.
Air Distribution Network
The air distribution network consists of the following components:
- Pipes: Pipes are used to transport fluids and are typically made of copper, plastic, or steel, depending on the type of fluid being transported.
- Hoses: Hoses are flexible tubes used to connect tools to the distribution network. They are typically made of a rubber-coated conduit reinforced with twisted steel.
- Connection Elements: These elements join pipes and hoses together. Common connection methods include welding and threading.
Types of Connections
- Joining Tubes: In pneumatic systems, tubes are typically joined using threaded connections and secured with nuts.
- Joining Pipes and Valves to Actuators: Pipes and valves are connected to actuators using fittings. There are many types of fittings available, including detachable fittings for hoses, conical metal fittings, seamed fittings, tapered plastic fittings, and quick-connect fittings.
Maintenance Unit
Before entering a machine, compressed air should pass through a maintenance unit. This unit typically consists of a filter, lubricator, and regulator, which are connected in series. Often, the filter and regulator are combined into a single unit.
Components of a Maintenance Unit
- Water Separator Filter: This filter removes impurities from the compressed air. It should be cleaned frequently to ensure optimal performance.
- Pressure Regulator: The pressure regulator reduces the air pressure to a constant value.
- Lubricator: The lubricator adds a controlled amount of oil to the compressed air to lubricate moving parts. It’s important to avoid over-lubrication, as this can clog small ducts.
Valves
Valves control the flow and direction of compressed air within a pneumatic system.
Types of Valves
- Distributors: These valves direct the path of the fluid and can be actuated manually, mechanically, pneumatically, or electrically. Examples include push buttons, pedals, levers, cams, rollers, and solenoids.
- Flow Control Valves: These valves regulate or restrict the flow of fluid. They can be two-way or one-way and include shut-off valves, throttling valves, quick exhaust valves, and selector valves.
- Pressure Regulators: These valves control the pressure of the compressed air and include pressure relief valves, pressure reducing valves, and sequence valves.
Work Items
A) Cylinders
Cylinders are divided into two main groups:
- Single-acting cylinders: These cylinders perform work in one direction only. The return stroke is typically achieved using a spring that returns the piston to its initial position.
- Double-acting cylinders: These cylinders perform work in both directions.
There are also special types of cylinders, including diaphragm cylinders, tandem cylinders, impact cylinders, rotating shaft cylinders, cable cylinders, and multi-position cylinders.
* Motors
Pneumatic motors convert the pressure energy of compressed air into rotary motion. Vane motors are the most commonly used type of pneumatic motor.
Symbology
- P: Compressed air supply
- A, B, C: Cylinder ports
- Z, Y, X: Pilot lines
- R, S: Exhaust ports
Double Check Valve
A double check valve is used to charge an air duct that receives air from two different sources.
Compressor (Vehicle Applications)
In vehicles, the compressor is responsible for supplying compressed air to the system, particularly for the brakes and tires.
Antifreeze Device
Antifreeze devices are used to prevent the risk of freezing in circuits and devices that utilize compressed air.
Check Valve
A check valve allows compressed air to flow in one direction only and automatically prevents air from flowing in the opposite direction.
Brake Chambers
Brake chambers are pneumatic devices that receive compressed air and convert it into mechanical force, which is then transmitted to the brakes through a linkage system.