NATIONAL SENIOR CERTIFICATE GRADE 11 NOVEMBER 2015 MECHANICAL TECHNOLOGY MARKS: 200 TIME: 3 hours *IMCHTE* This question paper consists of 18 pages, including a formula sheet.
2 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) INSTRUCTIONS AND INFORMATION 1. Write your name and surname in the spaces provided on the answer book. 2. Answer ALL the questions. 3. Read all the questions thoroughly. 4. Number the questions carefully according to the numbering system used in this question paper. 5. Write neatly and legibly. 6. Show ALL calculations and units. Round off final answers to TWO decimal places. 7. Candidates are allowed to use non-programmable, scientific calculators and drawing/mathematical instruments. 8. Begin each question on a NEW page. 9. Use the criteria below to assist you in managing your time: QUESTION TOPIC MARKS 1 Multiple-choice questions 20 2 Safety 10 3 Tools and equipment 12 4 Materials 13 5 Terminology 30 6 Joining methods 25 7 Forces 30 8 Maintenance 15 9 Systems and control 25 10 Pumps 20 TOTAL: 200
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 3 QUESTION 1: MULTIPLE-CHOICE QUESTIONS 1.1 Which TWO items of safety equipment are used when working on the lathe? A Aprons and gloves B Helmets and goggles C Safety shoes and goggles D Gloves and goggles (1) 1.2 Which ONE of the following safety precautions applies to surface grinders? A Never clean or adjust the machine whilst it is in motion. B Protective clothes and eye protection are essential. C Do not operate the machine unless all guards and safety devices are in place and working correctly. D All of the above. (1) 1.3 Which of the following tools is used to determine the diameter of a cylinder block in a four-stroke engine? A Outside calliper B Telescopic gauge C Dial gauge D Outside micrometer (1) 1.4 Which of the following statements refers to a clearance size or tapping size, when using taps and dies? A The hole size of the bolt that is being used. B The size of the hole that must be drilled so that it will clear the outside diameter of a screw. C The size of the tap. D The size of the die. (1) 1.5 Identify the furnace in FIGURE 1.5 below. FIGURE 1.5 A Bessemer converter B Blast furnace C Open hearth furnace D Oxygen furnace (1)
4 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 1.6 Hardness refers to the material s ability to... A resist penetration. B be permanently shaped. C stretch. D absorb forces. (1) 1.7 Which taper-turning method is applicable on the centre lathe? A The tailstock can be offset for longer external tapers. B The taper-turning attachment can be used for external tapers and for short internal boring. C The compound slide rest can be rotated for turning short internal and external tapers. D All of the above. (1) 1.8 Calculate the indexing for a gear with 38 teeth. Choose the correct answer. A 2 turns and 2 holes in a 38 hole circle B 1 turn and 2 holes in a 38 hole circle C 1 turn and 13 holes in a 49 hole circle D 2 turns and 1 hole in a 49 hole circle (1) 1.9 Identify the component below that is supplementary to a milling machine. A Arbour B Saddle C Compound slide D Dividing head (1) 1.10 Which of the following statements defines the term purge during gas welding? A To release fumes from the equipment B To flush out gas before igniting the welding torch C To mix the oxygen and acetylene D To compress the fuel in the shank (1)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 5 1.11 Given a sketch of a welding flame as shown below, select the correct procedure to achieve a suitable welding or brazing flame. A B C D Adjust the oxygen until both first and second flame cones touch the third flame cone. Adjust the oxygen until the tip of the second flame cone touches the tip of the first flame. Adjust the oxygen until the tip of the first flame cone touches the third flame cone. Adjust the oxygen until the second flame cone touches the third flame cone. (1) 1.12 Which of the following constitutes the equilibrium of three forces? A Two forces acting on a body B The calculation of forces C The concept of triangle of forces D The reaction on the supports (1) 1.13 Calculate the moment as shown in the figure below. Choose the correct answer: A 8 Nm B 18 Nm C 15 Nm D 10 Nm (1) 1.14 Complete the following: The lack of lubrication or incorrect lubrication A speeds up the motion of a rolling object. B increases engine speed. C ensures that operating systems malfunction. D converts motion from one form to another. (1) 1.15 Which of the following should be checked, before balancing a wheel? A The wheel rim must be examined for damaged edges. B The suspension should be firm. C The kingpin should be tilted back. D The pivot angle radius should be 90. (1)
6 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 1.16 Which of the following statements is an advantage of the single helical gear as shown below? A The gears are expensive. B The contact between the meshing teeth takes place very gradually. C Friction due to the sliding motion between the meshing teeth is high. D It must run in an oil-bath. (1) 1.17 When will you be able to make use of a worm and worm gear drive? A When parts must be adjusted with reference to one another. B When the direction of the drive must change through 90 and the centre lines of the drive shafts are situated on the same plane. C When the drive is very rough. D When the rotary movement is changed to reciprocating motion. (1)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 7 1.18 Which of the following is an example of a third class lever? A B C D 1.19 Which of the following pumps is used mainly to pump sandy, muddy or sewerage water with ease? (1) A Rotor pump B Reciprocating pump C Centrifugal pump D Vane pump (1) 1.20 Which of the following is an advantage of a Vane pump in its operation? A The drive is always positive. B They are very efficient for slow-speed engines. C It has no valves or springs. D It has no moving valves. (1) [20] QUESTION 2: SAFETY 2.1 State whether the following statements are TRUE or FALSE. 2.1.1 Use a machine ONLY once the safety guards have been correctly fitted. (1) 2.1.2 Never clean or adjust a machine whilst it is in motion. (1) 2.1.3 Leave the chuck key in the chuck when you are NOT at the lathe. (1) 2.1.4 A drill should run at a high speed when drilling a 30 mm hole. (1)
8 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 2.2 Name any FOUR safety rules to be taken into account before working with a bench grinder. FIGURE 2.2 (4) 2.3 Mention TWO safety precautions to be taken when starting or stopping machinery. (2) [10] QUESTION 3: TOOLS AND EQUIPMENT 3.1 Name THREE important usages when operating the tap wrench. 3.2 Which lubricant would you use when cutting a thread on bronze, copper or steel? (1) 3.3 What is the function of a pitch gauge? (1) 3.4 Describe how you would care for a power saw. (2) 3.5 What is the function of the inverter (DC) welding machine? (1) 3.6 Give TWO reasons for using the torque wrench. (2) 3.7 What is the function of a power-driven shearing machine? (1) 3.8 How would you care for manual and electric guillotines? (1) [12] (3)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 9 QUESTION 4: MATERIALS 4.1 Identify the steel-making furnace in the FIGURE below. (1) 4.2 Define the properties of the following: 4.2.1 Elasticity (2) 4.2.2 Ductility (2) 4.2.3 Brittleness (2) 4.2.4 Malleability (2) 4.2.5 Plasticity (1) 4.3 Identify THREE of the several quenching media that are used to give different rates of cooling. (3) [13]
10 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 5: TERMINOLOGY 5.1 Use a milling machine to cut a hexagon on a 100 mm shaft. Calculate the depth of the cut. (6) 5.2 Explain the cutting procedure to cut a taper on the centre lathe, using the compound slide parallel with the lathe bed. 5.3 A taper 180 mm long, has to be turned on the end of a 90 mm diameter shaft. If the diameter of the small end of the taper is 80 mm, calculate the angle to which the compound slide must be set in order to cut this taper. (10) 5.4 A shaft with a diameter of 70 mm must be machined on a milling machine to a square. Calculate the distance across the flat side that must be cut away. (6) x Distance across the flat side 70 mm (6) 5.5 Calculate the index to cut a pentagon using simple indexing. (2) [30]
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 11 QUESTION 6: JOINING METHODS 6.1 What do you understand by permanent joining applications? (1) 6.2 Explain step-by-step the application of soft solder. (4) 6.3 What joining application is being performed in the illustrations below? FIGURE 6.3 (1) 6.4 How does the number of welds on a welding joint influence the parent metal? 6.5 How does the size of the weld influence the welding joint? (2) 6.6 Identify the welding joints as shown in the illustrations below. (2) A B C G D E H F (8) 6.7 Identify the remaining FOUR primary factors that influence a welding joint, excluding the number of welds and size of welds. (4) 6.8 Identify the following welding symbols in the illustrations below. 6.8.1 6.8.2 6.8.3 (3) [25]
12 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 7: FORCES 7.1 Define the following basic concepts of systems of forces: 7.1.1 Equilibrant (2) 7.1.2 Bow s notation/triangle of forces (2) 7.1.3 Components of a force (2) 7.2 The following system of forces contains three forces. Use Bow s notation to construct a triangle of forces and show how they are in equilibrium. 7.2.1 Draw the space diagrams using the scale 4 cm = 10 N. (3) 7.2.2 Draw the vector diagram using the scale 4 cm = 10 N. (3) 7.2.3 Why do you think the triangle of forces is in equilibrium? (1) 7.3 A beam is subjected to two point loads and one UDL, and is supported at each end by RL and RR. 7.3.1 Calculate the magnitude of RR and RL. (4) 7.3.2 Calculate the bending moments at points A and B. (4) 7.3.3 Test the beam for equilibrium. (1)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 13 7.4 Calculate the compressive stress in a 32 x 32 x 3 mm square tube if it is subjected to a load of 70 kn. 7.5 A 220 N force is inclined at 30 to the horizontal. 7.5.1 Draw the diagram and indicate the two components (X and Y) of the force that need to be calculated. (1) 7.5.2 Determine (by calculation) the horizontal and vertical components of the force. (2) [30] QUESTION 8: MAINTENANCE 8.1 Inadequate maintenance affects operating systems. Explain how inadequate maintenance will affect the following: 8.1.1 Balancing of wheels (4) 8.1.2 Overloading of machines (2) 8.2 Define positive camber with regard to wheel alignment. (2) 8.3 Briefly explain kingpin inclination. (5) 8.4 Make a sketch showing the Ackerman principle (toe-out on turns), indicating the different steering angles and relevant components on the drawing. (5) [15] (2)
14 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 9: SYSTEMS AND CONTROL 9.1 With the aid of the illustrations below, explain the operating principle of the handbrake on a motor vehicle. 9.2 Explain the basic operating principles of the hydraulic clutch in a motor vehicle. (3) 9.3 Calculate the rotational frequency (speed) of the driven shaft in FIGURE 9.3. (6) Drive shaft 12 r/s T A 20 teeth Driven shaft? T C 63 teeth T B 80 teeth Intermediate shaft T D 42 teeth FIGURE 9.3 (5)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 15 9.4 A driving pulley with an effective diameter of 300 mm rotates at 950 rpm. The tension at the tight side of the belt is 600 N and the ratio of tensions is 2:1. Calculate the power transmitted. 300 mm 9.5 A piston acts on liquid with a force of 7 500 N and the area of the piston is 3 m 2. Find the pressure in the liquid. (6) Piston Liquid 9.6 Describe the use of a piston in hydraulics/pneumatics systems. (2) [25] (3)
16 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 10: PUMPS 10.1 FIGURE 10.1 below shows a gear-type pump. Label the parts A E. A C E B FIGURE 10.1 D (5) 10.2 Describe the operating principle of a vane pump. (6) 10.3 Identify TWO specific uses of the mono pump. (2) 10.4 Identify TWO typical areas where you will use a mono pump. (2) 10.5 Explain the operating principles of a centrifugal pump. (5) [20] TOTAL: 200
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 17 GRADE 11 FORMULA SHEET 1. GAUGE BLOCKS Set nr. M.50 2. FRICTION: Range increment in mm number of blocks 1,0025 to 1,0075 0,0025 3 1,01 to 1,09 0,01 9 1,1 to 1,9 0,1 9 1 to 25 1,0 25 50; 75; 100 3 0,5 1 F = force of friction µ = co-efficient of friction N = Normal force F = μ N 3. TORQUE: T T = Force x Distance T = N.m. were 4. BELT DRIVES 4.1 Belt speed = πdn 60 4.2 Belt speed = π(d+t)n (t = belt thickness) 60 4.3 Belt mass/kilogram = Area length density (A = thickness width) 4.4 Dia.of driven pulley Speed ratio = 4.5 Output speed = 4.6 4.7 Dia.of driver pulley drive pulley driven pulley Open-belt length = π(d+d) 2 Crossed-belt length = π(d+d) 2 drive pulley driven pulley + (D d)2 4c + 2c + (D+d)2 4c 4.8 Power (P) = 2πNT 60 4.9 Ratio of tight side to slack side = T 1 T 2 4.10 Power (P) = (T 1 T 2) πdn 4.11 T Width = 1 Permissible tensile force 4.12 DiaA x NA = DiaB x NB 60 + 2c input speed
18 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 5. GEAR DRIVES: SPUR GEAR 5.1 Power (P) = 2πNT 5.2 Gear ratio = 60 product of driven gears teeth product of drive gears teeth 5.3 N in product of driven gears teeth = N out product of drive gears teeth 5.4 Torque = force raduis 5.5 Torque transmitted = gear ratio input torque 5.6 TA x NA = TB x NB 6. HYDRAULICS 6.1 Force (F) Pressure = Area (A) 6.2 Volume = cross-sectional area x stroke length (l or s) 6.3 Work done = force x distance 7. Forces 7.1 Stress = Force 7.2 Strain = 8. Indexing 8.1 Crank T = 40 9. Taper Turning Area Change in Length Original Length N 9.1 Tan Ө = D d 2 x L 10. Depth of hexagon cut = Diameter of shaft distance across flat side 2
NATIONAL SENIOR CERTIFICATE GRADE 11 NOVEMBER 2015 MECHANICAL TECHNOLOGY MEMORANDUM MARKS: 200 This memorandum consists of 10 pages.
2 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 1: MULTIPLE-CHOICE QUESTIONS 1.1 C 1.2 D 1.3 B 1.4 B 1.5 B 1.6 A 1.7 D 1.8 B 1.9 D 1.10 B 1.11 B 1.12 C 1.13 C 1.14 C 1.15 A 1.16 B 1.17 B 1.18 A 1.19 C 1.20 B (20 x 1) [20] QUESTION 2: SAFETY 2.1 2.1.1 True (1) 2.1.2 True (1) 2.1.3 False (1) 2.1.4 False (1) 2.2 Ensure that there is no oil or grease on the floor. Check that the tool rest is not more than 3 mm away from the grinding wheel surface. If the wheel is running unevenly dress it with an emery-wheel dresser. Grind only on the face of a straight grinding wheel and never on the side of the wheel. Use the various wheels only for their intended purpose. Never force grind so that you cause the motor to slow or stop. (Any 4 x 1) (4) 2.3 All machinery must be fitted with an efficient stopping and starting device. Never start a machine while another person is repairing, cleaning, oiling or adjusting or even dangerously close to it. Machines with foot-operated pedals should have an automatic locking device to stop. (Any 2 x 1) (2) [10]
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 3 QUESTION 3: TOOLS AND EQUIPMENT 3.1 Should be used in the correct order (taper tap first). A tap must be entered squarely in the tap wrench. The correct size tapping drill must be used. A tap is at a right angle to the stock once cutting has started. The tap is turned forwards a part-turn and then turned backward about half a turn to break off the chippings. (Any 3 x 1) (3) 3.2 Cutting fluid or cutting paste (1) 3.3 To compare the threads on a bolt to the teeth cut on the gauge or To assess the pitch of the bolt. (1) 3.4 Always select correct blade. Always clean cuttings out of slots and guides to prevent blades from becoming clogged. Always adjust down pressure in order not to overload. Check that the filler tank is in a serviceable state. (Any 2 x 1) (2) 3.5 Changes the welding current from AC to DC. (1) 3.6 It prevents bolts and nuts from loosening. It prevents bolts or studs from breaking. It prevents castings from warping. (Any 2 x 1) (2) 3.7 To cut material by means of an electrical method. (1) 3.8 Always keep blades sharp and in good condition. Ensure guards are in place and operational. (Any 1 x 1) (1) [12] QUESTION 4: MATERIALS 4.1 Open-hearth furnace (1) 4.2 4.2.1 Refers to the material s ability to absorb forces and flex in different directions and return to its original shape when the load is removed. (2) 4.2.2 Refers to the material s ability to change shape by stretching it along its length, or to be drawn into wire form. (2) 4.2.3 Refers to the material s behaviour when fractures occur with little or no deformation e.g. glass. (2) 4.2.4 Refers to the materials ability to be reshaped in all directions without cracking e.g. lead. (2) 4.2.5 Refers to the material s ability to change shape permanently. (1)
4 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 4.3 Water and salt. Tap water. Fused or liquid salts. Molten lead. Soluble oil. Oil or air. (Any 3 x 1) (3) [13] QUESTION 5: TERMINOLOGY 5.1 Set the indexing for 6(six) divisions(six flat sides) Calculate the distance x across the flat sides. Sin Ө = x 100 X = Sin 60 x 100 X = 0,866 x 100 X = 86,6 mm Depth of cut = Dia.of shaft distance across flat side = 100 86,6 2 2 Depth of cut = 6,7 mm (6) 5.2 Release the lock nuts of the compound slide. Swing the compound slide to half the included angle. Tighten the lock nuts (take care not to over tighten). Mount the cutting tool in the tool holder in the tool post. Set the cutting tool to the centre of the tailstock. Use the compound slide feed handle and feed the cutting tool slowly into the work piece. Proceed to the end of the cutting length. Return to the starting position and feed the cutting tool in for the next cut. Repeat the procedure until the taper is completed. On completion, test the taper with the taper ring gauge for size and correct angle. (10) 5.3 Taper angle = D d 2 x L = 90 80 2 X 180 = 10 360 = 0,O27 Ө = 1 59 Ө = 1 35 The angle is 1 degree and 35 minutes. (6)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 5 5.4 Sin Ө = X 70 X = 70 Sin Ө = 70 Sin 45 x = 49,5 mm Depth of cut = 70 x 2 = 70 49,5 2 = 10,25 mm (6) 5.5 Indexing: Number of turns = 40 N Number of turns = 40 5 Number of turns = 8 full turns of the shank (2) [30] QUESTION 6: JOINING METHODS 6.1 It is permanent joints that do not have to be dismantled or serviced. (1) 6.2 Flux is used together with soldering to dissolve metal oxides and impurities on the metal This allows the solder to flow into the joint. The soldered joints are usually heated by an electric soldering iron or LP gas blowtorch. The solder is applied when the surfaces are heated to melting point. (4) 6.3 Hard soldering. /Brazing (1) 6.4 The more welding runs that are required in a welding joint, the greater the heat in the parent metal. It can lead to stress and distortion if not managed correctly. (2) 6.5 Sizes of weld depends on the type of weld. The size of the weld will affect how many weld runs will be needed to complete the joint. (2) 6.6 A Square butt B Single bevel butt C Double bevel butt D Single V-butt E Double V- butt F Edge G Single-U-Butt H Stud (8) 6.7 Type of material. Type of welding rod. Presence of oxygen/hydrogen Preparation (4)
6 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) 6.8 6.8.1 Fillet 6.8.2 Plug or slot 6.8.3 Stud (3) [25] QUESTION 7: FORCES 7.1 7.1.1 If a system of forces acts on a body but a single force keeps the body at rest, the single force is known as the equilibrant of the system of forces. (2) 7.1.2 If three forces, whose lines of action meet at a point, can be represented in magnitude and direction by the sides of a triangle, they are in equilibrium. (2) 7.1.3 If two or more forces have the same effect as a single force, these forces are called the components of the single force. (2) 7.2 7.2.1 8 cm C 8 cm 30 30 B 8 cm A Scale: 4 cm = 10 N (3) 7.2.2 a Draw to scale 8 cm c 8 cm 8 cm 30 b (3) 7.2.3 Because the force diagram s end point is the same as its starting point. (1)
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 7 7.3 7.3.1 RR x 10 = (6 x 3) + (5 x 8) = 18 + 40 RR = 58/10 RR = 5,8 N RL X 10 = (5 x 2 ) + (6 x 7) = 10 + 42 L = 52/10 RL = 5,2 N (4) 7.3.2 BM A = (5,2 x 3) = 15,6 N/m BM B = (5,2 x 8) (6 x 3) = 23,6 N/m (4) 7.3.3 RL + RR = DOWN FORCES 5,2N + 5,8N = 6N + 5N 11N = 11N (1) 7.4 Cross sectional area = (32 x 32) (26 x 26) Load: 70 kn = 70 x 10 3 = 1024-676 = 348 mm² Stress = Force Area 7.5 7.5.1 = 70 x 103 348 10 6 Stress = 2011494253 Pa OR = 2011,49 x 10 6 Pa Stress = 2011,49 MPa (5) Y 30 O X (1) 7.5.2 X = F Cos 30 = 220 x 0,866 Horizontal component = 190, 52 N Y = F Sin 30 = 220 x 0,5 Vertical component = 110 N (2) [30]
8 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 8: MAINTENANCE 8.1 8.1.1 Unbalanced wheels will cause: Unnecessary tyre wear. Poor driving condition. Excessive wear on the steering and suspension. Shaking of the wheel assembly from side to side (wheel shimmy). (4) 8.1.2 Overloading of machines: When a machine is overloaded it will cause the lubricating barrier of oil to be squeezed out of the machine bearings. This results in metal to metal contact that causes more friction due to heat. Metal surfaces become scratched and scored, which will finally seize the operating system. (Any 2 x 1) (2) 8.2 It is the outward tilt of the wheel at the top away from the vehicle when viewed from the front. (2) 8.3 It is the setting of an angle relative to the true vertical line, as viewed from the front or back of the vehicle. OR Kingpin inclination is the inward tilt from the vertical in degrees. (2) 8.4 23 20 Centre of turning wheels Steering control arms marms Rear axle (5) [15]
(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 9 QUESTION 9: SYSTEMS AND CONTROL 9.1 The handbrake lever pulls on a single cable, which is coupled to a pivoted T-piece to transmit the pull identically or evenly to both rear brakes, or there may be two cables from the handbrake lever, one to each of the rear brakes. (3) 9.2 When the driver pushes down on the clutch pedal, a push rod is forced into the master cylinder. As the push rod moves down into the master cylinder, the rod forces a piston down the cylinder. This action puts pressure on the hydraulic fluid in the cylinder, and some of the fluid is forced out. The fluid flows through a tube or pipe into a servo cylinder at the clutch. The fluid flowing into the servo cylinder from the master cylinder, forces the piston in the servo cylinder to move. This movement is carried through a push rod to the release lever, thus releasing the clutch. (6) 9.3 Revs of final driven Revs of first driver Product of Number of teeth on all the drivers = Product of Number of teeth on all the driven N D = T A x T C N A T B T D N D = T A x T C X N T B T A D = 20 X 63 X 12 80 42 N D = 4,5 Rotational frequency of driven shaft = 4,5 r/s. (5) 9.4 Determine the effective tension: Given: T A T B = 2 : 1 = 2 AND T A = 600 T B = 600 2 Effective tension in belt Distance moved S = 300 N = T A - T B = 600 300 = 300 N = X D X N 300 = X X 950 1000 60 = 14,92 m/s 300 X 14,92 Power transmitted = 1000 = 4,48 kw (6) 9.5 Pressure = Force Area = 7500 3 = 2 500 Nm² = 2 500 Pa (3) 9.6 It draws in fluid as it is pulled back (or retracted) and expels it on the forward stroke. (2) [25]
10 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015) QUESTION 10: PUMPS 10.1 A Inlet port B Driven gear C Driver gear D Casing E Outlet port (5) 10.2 When one of the vanes moves past the inlet port, the space between this vane, the rotor and the housing increases gradually. This causes a vacuum in the space, which causes oil to be drawn from the sump. When the next vane moves past the inlet port, the oil is trapped and is carried along by the rotating rotor. Due to the eccentric rotor, the space now decreases and the oil is pressurised. The first vane now moves past the outlet port while the space is still decreasing. The decreasing space and the next vane force the oil through the outlet port to the oil channels. (6) 10.3 Pumping grout/cement Pumping lubrication oil Pumping marine diesel fuel Pumping mining slurry Pumping oilfield mud (Any 2) (2) 10.4 Grout/cement pump Lubrication oil pump Marine diesel fuel pump Mining slurry pump Oilfield mud motors Winery use (Any 2) (2) 10.5 The centrifugal pump consists of a casing which contains a rotating wheel with blade or vanes. This rotating wheel is known as an impeller of the pump. If the pump casing is filled with fluid and the impeller is in operation, the impeller will sling the fluid outwards by centrifugal force, and force it out at the outlet. This creates a vacuum at the centre, or eye, of the impeller. As a result of atmospheric pressure, fluid is again drawn through this eye into the pump casing. (5) [20] TOTAL: 200