2 Answer all questions 1. a. Air Service Unit (ASU) is used to distribute the air flow in pneumatic system. State the three (3) combinations parts of an air service unit. Question 1(b) is refer to Figure 1. Figure 1: Element of Pneumatic System b. Specify the equipment that is labeled A, B, C, D, and E in Figure 1 together with their functions c. Describe the operation of double acting cylinder circuit with a diagram. 2. . Sketch the symbol of components as below: i. Thermometer ii. Pressure Indicator iii. Flow meter
3 Question 2(b) is refer to Figure 2. Figure 2 b. Figure 2 showing a lifting system. Given that the area, A1 = 20cm2 , A2 = 60cm2 . Force, F2 = 5500N and Piston 2 move from origin for 1cm. Calculate: i. The Piston 1 distance (S1) has moved from its origin ii. The force F1 exerted on the A1 in kN c. List five (5) components of the power supply section of a hydraulic system. d. List four (4) applications of hydraulic system that mostly used in heavy industry. 3. a. List two (2) programming method for entering and interconnecting the individual logic elements in PLC b. Describe and sketch the operation of Counter as below with a suitable ladder diagram. i. Counter ON ii. Counter OFF F1 F2 A1 A2 S1 PISTON 2 PISTON 1 1cm
4 c. Design a PLC ladder diagram according to the process below “When push button ‘ON’ is pressed 3 times, the lamp at room 1 will be turned on. Then, when push button ‘OFF’ is pressed the lamp will turned off after delay of 2 seconds.”
5 4. a. List three (3) advantages of using PLC in control system Question 4(b) is refer to Figure 3. Figure 3 b. Transfer the ladder diagram in Figure 3 into a mnemonic code. c. Transfer the mnemonic code in Table 1 into a ladder diagram ADDRESS INSTRUCTION OPERAND 0000 LD 01 0001 OR 03 0002 AND 05 0003 LD 08 0004 OR 07 0005 AND LD 0006 OUT 1002 Table 1 d. Sketch the ‘OR’ and ‘NAND’ gate logic with their symbols and truth tables. 5. a. List five (5) characteristics of pneumatic gases that are used in pneumatic system.
6 Question 5(b) is refer to Figure 4 Figure 4 b. Figure 4 shows a pneumatic directional valve. Identify the component and state the name of the port. c. Sketch the symbol for 3/2-way valve and 5/2-way valve. d. Tubes are used as air distribution medium in pneumatics system. List the selection criteria for tubing diameter.
7 6. a. Briefly describe the definition of hydraulic system. b. List five (5) criteria’s when selecting and choosing the size of hydraulic pump c. List five (5) components in hydraulic system d. State four (4) disadvantages using a hydraulic system. Question 6(e) refer to Figure 5 Figure 5 e. Refer to Figure 5, the piston is in lock position where both side of oil flow was closed. If Pressure, P1 = 1MPa and A1 = 8cm2 Calculate: i. The pressure at P2, if given area A2 = 4.2cm2 . ii. The force at F2 in kN.