Part -1:

APPLICATIONS OF PNEUMATICS AND HYDRAULICS - FLUID POWER DIAGRAMS

Question 1. FIGURE 1 shows a pneumatic circuit diagram used for air supply and exhaust in an automatic control system.

(a) Name all symbols (including pipelines) used in the system.

(b) Number the ports of each DCV.

(c) Classify the sections of the components in the circuit.

(d) State how the system works.

(e) State the functions of valves (1) and (2).

Question 2. FIGURE 2 shows a pneumatic circuit in which four actuators are controlled.

(a) State the sequence in which the cylinders operate on the operation of the start valve.

(b) Show, with the aid of a schematic diagram, how an electronic controller could be included in the circuit to control the sequence of cylinder operations.

Question 3.

Design and draw a circuit using the cascade system to operate two cylinders (A and B) which, on the operation of a start valve, produces the sequence A - B + B - A+. The cylinders should park in the positions B - A + when the start switch is in the ‘off' position.

Question 4. Modify the circuit designed for question 3 to provide an emergency stop which will park both cylinders in the extended position (i.e. A + B +).

Question 5. Modify the circuit designed for question 3 to provide a fail safe. The fail safe should:

(a) act in the event of a reduced pressure at inlet to the group selecting valve

(b) park the cylinders in the retracted position.

Question 6. FIGURE 3 shows a hydraulic circuit.

(a) State the name and purpose of the components shown in the circuit diagram.

(b) Explain the operation of this circuit.

(c) Explain the limitations of this circuit in terms of ‘speed control'.

Question 7. Modify the design of the circuit shown in FIGURE 3 and draw a circuit diagram to provide rotary actuation in both directions using a single direction pump (to replace the bi-directional pump) and providing a means of preventing over-speeding in the case of an overhauling load in both directions.

Part -2: APPLICATIONS OF PNEUMATICS AND HYDRAULICS

Question 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.

Question 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.

Question 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 A min-1?

Question 4. Describe the operation of a variable displacement axial piston (swash plate) pump, indicating the means by which its output is varied.

Question 5. With reference to basic constructional features, contrast the methods of compression employed by positive displacement and dynamic air compressors.

Question 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.

Question 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.

Question 8. Describe the difference between regenerative absorption and chemical absorption air drying.

Attachment:- Assignment.rar