1. FIGURE 1 shows a pneumatic circuit diagram used for air supply and exhaust in an automatic controlsystem.
(a) Name all symbols (including pipelines) used in thesystem.
(b) Number the ports of eachDCV.
(c) Classify the sections of the components in thecircuit.
(d) State how the systemworks.
(e) State the functionsofvalves 1 and 2.
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 startvalve.
(b) Show, with the aid of a schematic diagram, how an electronic controller could be included in the circuit to control the sequence of cylinderoperations.
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.
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+).
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 retractedposition.
6. FIGURE 3 shows a hydrauliccircuit.
(a) State the name and purpose of the components shown in the circuit diagram.
(b) Explain the operation of thiscircuit.
(c) Explain the limitations of this circuit in terms of ‘speedcontrol'.
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.
