Fluid Power Diagrams – Applications Of Pneumatics And Hydraulics, Tutor Marked Assignment 2, TU, UK

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) 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 litres per minute?

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

4. An item of plant 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.

5. Using the nomogram and charts (FIGURES 1 and 2) on pages 4 and 5, determine the diameter of a suitable air main for the distribution of 6 m3 min–1 FAD. System pressure is 6 bar, the length of the pipe run is 175 metres, and a maximum pressure drop of 0.3 bar is allowed.

The distribution main must also include the following:

•  4 bends (r = 2d)
• 2 elbow fittings
• 6 tee connectors
• 2 diaphragm valves.

6. A compressor delivers 300 litres per second of free air into a pipe at a
pressure of 6 bar gauge. Using the pressure drop formula:

𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝐷𝑟𝑜𝑝 =
800𝑙𝑄2 𝑅𝑑 5.3

calculate the minimum diameter of pipe if the pressure drop in a system is to be limited to 0.3 bar when is delivered through a pipe of equivalent length 160 m .

7. List four possible causes of overheating on a multi-stage reciprocating compressor.

8. State the precautions to be taken when changing the fluid in a hydraulic system from a mineral oil based hydraulic fluid to a fire resistant fluid.

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