Air 2.0

Question 1

Briefly describe the types of compressors used in service and give examples of the typical applications for each

Answer 1

Two major types : Dynamic displacement and Positive displacement

Dynamic displacement compressors are effectively fan type arrangements which can move large quantities of air and relatively low pressures are therefore unsuitable for compressed air systems.

Positive displacement machines can be broken down into two categories : Rotary and Reciprocating

Rotary compressors : screw type or rotary vane are ideally suited for low pressure systems , fridges and air conditioning plants.

Reciprocating compressors: used to produce high pressure air

Question 2

Describe the operation of a concentric plate valve

Answer 2

The compressor employs flat plate , spring loaded , non return type valves. These combine both inlet and outlet in one assembly and are retained in place by the valve cover. This permits easy access for servicing and creates smooth and efficient air flow through the cylinders.

Question 3

Describe the Pressure Maintaining Valve fitted to a typical typical HP air compressor

Answer 3

Designed to remain closed until the compressor reaches working pressure. It is either a dome loaded or spring loaded type. The valve is held shut by the dome or spring pressure until the compressor discharge pressure overcomes the setting (240-250 bar) when the valve will be forced off its seat allowing air to be discharged to the system.

Question 4

Describe the operation of a concentric plate valve operation

Answer 4

The compressor operates on a 2 stroke cycle involving 3 processes

Question 5

What are the 3 processes of concentric plate valve operation

Answer 5

1. Inlet
2. Compression
3. Exhaust

Question 6

Explain the inlet process of a concentric plate valve operation

Answer 6

As the piston travels down inside the cylinder the pressure drop inside the chamber causes the now higher pressure from atmosphere to exert force on the inlet valve plate forcing it open against the action of the spring allowing air to enter the cylinder. As the piston completes the inlet stroke the pressure inside and outside the cylinder will equalize and the spring will cause the inlet valve to close

Question 7

Describe the compression process of a Concentric Plate valve operation

Answer 7

As the piston rises in the cylinder the volume of the chamber will reduce and the pressure will rise.

Question 8

Describe the Exhaust process in the concentric plate valve operation

Answer 8

As the pressure in the cylinder rises it exerts force on the discharge valve which will open allowing the compressed air to leave the cylinder