PNEUMATIC AND HYDRAULIC EQUIPMENT

APH-2-TMAv1.pdf

1. (a) Draw a pV diagram to illustrate the operation of a two-stage

compressor with intercooling.

(b) List the advantages to be gained by the use of a multi-stage design

compressor.

2. (a) With the aid of a sketch, describe briefly the operating principle of a

rotary vane compressor.

(b) State the reasons why oil must be injected into this machine for its

efficient operation.

3. (a) A mass of 400 kg is to be raised by the actuation of two identical

hydraulic cylinders with a piston diameter of 120 mm. Calculate the

required system pressure to just raise the load.

(b) If the load is to be raised 600 mm in 10 seconds, what will be the

required flowrate (Q) in � min–1?

4. Describe the operation of a variable displacement axial piston (swash

plate) pump, indicating the means by which its output is varied.

5. With reference to basic constructional features, contrast the methods of

compression employed by positive displacement and dynamic air

compressors.

6. An item of plant requires 2 m3 min–1 of pulsation-free and oil-free

compressed air supplied at a pressure of 7 bar. Select and size a suitable

type of machine with regard to output FAD (free air delivered) and

quality of air supply.

Teesside University Open Learning (Engineering)

7. Air is drawn into a compressor at normal temperature and pressure

(N.T.P.) and compressed to a pressure of 6 bar gauge. After compression

the air is delivered at 1.2 m3 min–1 and cooled to a temperature of 30°C,

at which point condensate is collected at the rate of 2 litres per hour.

Estimate the FAD (N.T.P.) of the compressor, and the relative humidity of

the air entering the compressor.

8. Describe the difference between regenerative absorption and chemical

absorption air drying.

Teesside University Open Learning (Engineering)