Types of Compressors: Rotary, Reciprocating, Centrifugal & Screw
Reciprocating Air Compressor
The electric motor provides a rotating motion to the crankshaft. The construction of a reciprocating air compressor is similar to that of an internal combustion engine. The connecting rod converts the rotating motion of the crankshaft into the reciprocating motion of the piston.
When the piston moves down, air at atmospheric pressure is drawn into the cylinder through the inlet valve. When the piston moves up, the air is compressed. The compressed air exits the cylinder through the outlet valve.
If high pressure is required, the number of stages or cylinders should be increased (multi-stage). The temperature of the air increases when it is compressed. After each stage (before entering the next stage), the air is cooled using an intercooler. After leaving the compressor outlet (before entering the air storage tank), the air is further cooled using an aftercooler.
Safety equipment fitted in an Air Compressor:
1. Relief Valve
2. Bursting Disc
3. Fusible Plug
4. Low-Pressure Lubricating Oil Alarm and Trip
5. Motor Overload Trip
Storage of Compressed Air
Compressed air is stored in air storage tanks.
Equipment/Safety equipment fitted in an Air Storage Tank:
1. Relief Valve: It is fitted on top of the air storage tank to prevent the air pressure inside the tank from exceeding the maximum working pressure.
2. Fusible Plug: If the relief valve can be isolated from the air storage tank, a fusible plug is fitted. It is also located on top of the air storage tank. In the event of a fire, the fusible plug will discharge the contents to the outside of the engine room.
3. Drain Cocks: They are used to drain the air storage tanks frequently to prevent the accumulation of oil or water. Drain cocks are fitted at the bottom of the air storage tanks.
4. Pressure Gauge: It is fitted at a visible height on the air storage tank to indicate the pressure of the air inside the tank.