FITTING AND TURNING NQF LEVEL 3 SEPTEMBER 2012

QUESTION 1            GRINDING TOOLS AND DRILL BITS

1.1

Safety is very important in any working environment. A mechanical fitter must grind a tool on a grinding machine. 1.1.1         What is it that is needed when grinding a tool with a grinder which                does not have a protective transparent shield? 1.1.2          What must the maximum distance be between a tool rest and the                 grinding wheel?

(1)   (1)

1.2

When machining a work piece you must always check that the tool is well grounded. With regard to wheel grinding, explain the following: 1.2.1          Wheel dressing 1.2.2          Truing

(1)   (1)

1.3

The markings on a grinding wheel are 32 A 54 – K 4V BE What does: A                The A stands for? B                The K stands for? C                BE stands for?

(1)   (1)   (1)

1.4

Name the grinding wheel below and list the purpose

(2)

FIGURE 1

1.5

What is the purpose of coolant during a grinding process?

(2)

[10]

QUESTION 2            MAINTAINING BEARINGS IN MACHINES AND EQUIPMENT

2.1

Name the TWO categories that bearings can be divided into.

(2)

2.2

Make a neat free hand labeled sketch of a ball bearing clearly showing at least THREE of the main parts of the bearing.

(5)

2.3

The job of a maintenance fitter is to ensure that all the machines in the workshop are in peak condition and in good running order. The job thus requires the fitter to inspect, remove, maintain and replace bearings. 2.3.1         During the daily inspection, how can the fitter check if the bearings                are functioning correctly? 2.3.2      List TWO items of equipment or tools that a fitter would need to        remove roller bearings from the shaft. 2.3.3         What is the preferred cleaning fluid for cleaning a roller bearing?                   2.3.4        On inspection of the ball bearings, it is found that there are                       indentations/grooves made into the bearing raceways. What could                 the likely cause be?

(1)   (2)   (1)   (1)

2.4

Summarise the problems that could arise if the correct procedure is not followed when replacing bearings in machines and equipment.

(3)

[15]

QUESTION 3            MAINTAINING BRAKES AND CLUTCHES

3.1

Explain the importance of being able to interpret a drawing when doing maintenance on brakes and clutches.

(2)

3.2

Choose the correct answer from within brackets. Write only the answer next to the question number. For example 3.2.1 Ball 3.2.1      In hydraulic brake system, the leakage that can be expected is:                        Air or Liquid              3.2.2     For the components to perform properly, the gap settings on brakes a              and clutches must be correct. This can only be possible if:                       The manufacturer’s manual is followed or                       The expertise of the artisan is followed 3.2.3      When doing maintenance on clutches, it is very important to note that               wear can be caused by:                          Grease or Dirt 3.2.4       When bleeding a hydraulic system with a bleeder valve, the bleeder                valve will then allow the air out of the system. The system is said to                be:                           Closed or Open 3.2.5       During stripping of parts on brakes and clutches, it might be                necessarry to mark the parts so that they are easy to re-assemble.                For marking the following can be used:                           Compass or Centre punch

(1)   (1)   (1)  (1)  (1)

3.3

Match the following brakes and clutches according to their categories. Write down only the letter (A – F) next to the question number in (3.3.1 -  3.3.5) in  the ANSWER BOOK. For example 4.8.6 G COLUMN A COLUMN B 3.3.1             Positive clutch 3.3.2             Friction clutch 3.3.3             Centrifugal clutch 3.3.4             Air-operated brake system 3.3.5             Electromagnetic brake system A   Exhaust      Compressor B   Spiral springs       Solenoid C   Square claw       Spiral claw D   Single disc       Multi disk E   Fixed-weight      Loose-weight F   Impeller      Rotor

(5)

3.4

Make a neat sketch of a metal brake system, clearly showing the following parts: a) The shaft b) The disc c) The brake pads showing how the pressure is applied onto the disc.

(3)

[15]

QUESTION 4            MAINTAINING DIRECT DRIVES

4.1

Name TWO advantages of the direct drive.

(1)

4.2

FIGURE 2 below shows the assembly of a metal disc coupling. 4.2.1         Explain the working principle of this type of coupling.                           4.2.2         Identify the parts numbered 4.2.1 – 4.2.4.

(2)   (4)

4.3

Name ALL the tasks that you need to carry out during the service of components of a direct drive.

(5)

4.4

State why waste material must be disposed of.

(2)  [15]

QUESTION 5            MAINTAINING DYNAMIC SEALS IN MACHINES AND/OR 

                                 EQUIPMENT

5.1

Name TWO types of dynamic seals that are used in the industry.

(2)

5.2

Depressurizing of the system takes place when doing maintenance. 5.2.1         What is the purpose of depressurizing? 5.2.2         What component must be used for the above? 5.2.3         Why should this depressurizing be done?

(1)   (1)   (1)

5.3

Irene must do maintenance on an engine. Before deciding on a specific seal she must first make sure that it is the correct seal that is to be used for replacement. 5.3.1          Where will Irene find the information about which seal to use? 5.3.2          Why must Irene clean the surface first before replacing the seal? 5.3.3          Why should Irene finish off by lubricating the job with a thin layer                   of lubricant?

(1)  (1)  (1)

5.4

List FIVE steps in the procedure when removing a seal from a machine.

(5)

5.5

Before the operator can conclude that a seal must be replaced on a machine, a visual inspection must be made. What should be checked?

(2) [15]

QUESTION 6            MAINTAINING HEAT EXCHANGERS AND PRESSURE VESSELS

6.1

Can you tell the difference between a heat exchanger and a pressure vessel by looking at it? If not, explain the difference between the two.

(2)

6.2

What instrument is used to blank off a pressure vessel?

(1)

6.3

What liquid is used inside a pressure vessel?

(1)

6.4

What instrument is used to calibrate a pressure vessel?

(1)

6.5 6.6 6.7 6.8

Before a pressure vessel can be used in industry, what must be done? Also indicate what proof is needed to prove the equipment is safe? Name THREE components that must be inspected when doing visual inspection on a pressure vessel or heat exchanger. Give TWO working conditions that must be in place when working in the area where there is a heat exchanger or pressure vessel. Briefly explain the evidence needed and the person responsible for such evidence once the pressure has been tested.

(2)  (3)  (2)  (3) [15]

QUESTION 7            LUBRICATION SYSTEMS

7.1

Name any TWO of the main parts of a lubrication system.

(1)

7.2

There are different types and methods of lubrication used. Give ONE example of a lubricating device that you would use for each of the following methods of lubrication: 7.2.1         Manual oil lubrication 7.2.2         Pressure lubrication

(1)   (1)

7.3

FIGURE 3 below, shows the main components of a lubricating device:

(1)  (3)

        FIGURE 3

               7.3.1          Name the lubricating device shown in FIGURE 3.                                

               7.3.2          Name the labeled components (A – D) in FIGURE 3.                              

7.4

FIGURE 4 below shows a drawing of a Splash Feed lubrication system. Explain step by step how the bearing is lubricated.

(4)

         FIGURE 4

7.5	During the inspection of the lubrication system you may find problems given below. Give ONE reason why the following problems occur: 7.5.1             The oil is dark and dirty. 7.5.2             The oil becomes foamy. 7.5.3             The oil feels thin.		(1)  (1)  (1)
	TOTAL MEMORANDUM QUESTION 1            TOOL GRINDING 1.1       1.1.1               Use goggles/safety glasses/ face shield√                                                 (1)             1.1.2               3mm√ 1.2       1.2.1               align or dress a wheel to make it even. Sharpen dull cutting edges.                                     Alter cutting edges. Expose sharp grains. Sharpen the wheel. √          (1)             1.2.2               Material is removed from the cutting surface of the wheel to make                                     it flat or even again. Correct out of round conditions/by truing the                                     wheel runs concentric. Make the wheel straight.√                                (1) 1.3       A                     The abrasive Aluminium oxide √                                                                (1)             K                     The grade. Medium √                                                                                    (1)             BE                   Manufacturer’s symbol√                                                                               (1) 1.4       Straight grinding wheel√                                                                                             (1)             Purpose: -      For internal and external, universal or tool and cutter grinding and                                     surface grinding.√                                                                                  (1)             1.5       Coolant controls the heat and keeps the grinding wheel and reduces formation             of rust on the cutter by automatically lubricates it.√√                                                  (2)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               (10) QUESTION 2            MAINTAINING BEARINGS IN MACHINES AND EQUIPMENT 2.1       Friction/Plain bearings√                                                                                                     (1) Anti – friction/ roller bearings√                                                                                          (1) 2.2       MARK ALLOCATION FOR SKETCH Neat Sketch 2  Part A (Inner Race) 1 Part B (Cage) 1 Part C (Outer Race) 1 Total 5                                                                                                                                                             (5) 2.3.1   ANY ONE Listen to the sound of the bearings: noisy bearings Measure the temperature: hot bearing Check the lubricant : Oil and grease                                                                                (1) 2.3.2   ANY TWO                                         Bearing puller Impact puller Hydraulic puller Screw puller Hammer and bearing removal collar Bearing heater                                                                                                                     (2) 2.3.3   Preferred cleaning fluid: DEIESEL√                                                                                (1)             WHY: oil – based and provides lubrication back onto the bearing.√                          (1) 2.4       ANY THREE Bearing and associated components could be damaged It could delay production time It will shorten the shelf – life of the bearing May lead to the job not being completed on time√√√                                                    (3) (15) QUESTION 3            MAINTAINING BRAKES AND CLUTCHES 3.1       ANY TWO Easy to identify parts to work on Helps the technician to assemble or dismantle parts Details parts for more information Saves time Able to plan dismantling procedure                                                                                 (2) 3.2             3.2.1   Liquid√                                                                                                                       (1)             3.2.2   The manufacturer’s manual√                                                                                (1)             3.2.3   Dirt√                                                                                                                            (1)             3.2.4   Closed√                                                                                                                     (1)             3.2.5   Centre punch√                                                                                                         (1) 3.3             3.3.1   C√                                                                                                                               (1)             3.3.2   D√                                                                                                                               (1)             3.3.3   E√                                                                                                                               (1)             3.3.4   A√                                                                                                                               (1)             3.3.5   B√                                                                                                                               (1) 3.4       Show the disc 1 Show the shaft 1 Brake pads and direction of pressure 1                                                                                                                                                             (3)                                                                                                                                                             (15) QUESTION 4            MAINTAINING DIRECT DRIVES 4.1       ANY TWO It reduces the force on the bearing, which makes them last longer. It reduces the wear on different parts of the coupling. It reduces the chance of the seals breaking or becoming damaged. It reduces the amount of vibration in the machine casing and bearing housings. (2) 4.2                   4.2.1   Ehen the shaft are misaligned but still need to be connected by a                         coupling this particular coupling consists of several layers of thin steel                         plates to accommodate misalignment between shafts. √√                                (2)             4.2.2.  Driven shaft√                                                                                                                        (1)             4.2.3   Clutch√                                                                                                                      (1)             4.2.4   Driving shaft √                                                                                                          (1)             4.2.5   Laminated plates√                                                                                                   (1) 4.3       Check all the bolts on the drive system and tighten them again if necessary.√ Take the safety guard off the coupling and check the parts of the coupling for unusual wear.√ Check the shaft extensions for excessive axial or radial run – out.√ Inspect the drive for lubricant leaks.√ Check the operating temperature of the drive.√                                                             (5) 4.4       ·         In order to reduce the risk of fire, save space,√ and ·         Create a safe and efficient working environment√  or                                                 (2) ANY OTHER APPROPRIATE ANSWER                                                                                                                                              (15) QUESTION 5            MAINTAINING DYNAMIC SEALS IN MACHINES AND/OR                                   EQUIPMENT 5.1       ANY TWO Reciprocating seals Rotary seals Compression seals                                                                                                              (2) 5.2             5.2.1   The liquid in the system must escape before maintenance is done                         to eliminate pressure.√                                                                                           (1)             5.2.2   Pressure release valve√                                                                                        (1)             5.2.3   Safety, liquid spillage, tidiness√                                                                          (1) 5.3                   5.3.1   ANY ONE ·         Engineering drawing ·         Manufacturer’s guide ·         Supervisor                                                                                                               (1)             5.3.2   To avoid escape of pressure/liquid and therefore also tidiness.√                  (1)             5.3.3   To allow the seal to slide into the correct position.√                                       (1) 5.4       ANY FIVE Drain the oil or grease from the system. Isolate the machine Get a clean working area Have the correct tools ready Clean the components and check for damage. Replace the seal accordingly. Assemble the components and fill in oil again. Test the component for any leakage, before taking it back to the machine.             (5) 5.5       ANY TWO Check for any leakage of oil/liquid for the seal. Check whether flexible parts of the seal are rigid. Check for cracks on some of the parts. Check whether discolouration is evident.                                                                                   (2) (15) QUESTION 6            MAINTAINING HEAT EXCHANGERS AND PRESSURE VESSELS 6.1       Pressure vessels are used where the pressure is higher than in a heat exchanger. It becomes a pressure vessel when it exceeds a specific  pressure.√√                                                                                                                          (2) 6.2       A tube plug√                                                                                                                         (1) 6.3       Water√                                                                                                                                   (1) 6.4       A testing gun√                                                                                                                      (1) 6.5       A certificate of compliance, issued by an officer of a statutory authority must             be produced when required to.√ Also the pressure vessel must undergo a full operational test run before it can             be used.√                                                                                                                              (2) 6.6       ANY THREE Valves Cracks in the pressure vessel or heat exchanger shell Gauges Control – instruments                                                                                                         (3) 6.7       ANY TWO Good planning Personal protection Safe constructions Clean layout Walkways free from objects/equipment                                                                           (2) 6.8       The certificate must be provided as evidence.√ Only qualified officials can issue a certificate.√ A certificate has a number for the official to show he/she is competent to carry – out the test.√                                                                                                            (3)                                                                                                                                                 (15)                                                                                                                                                 QUESTION 7            LUBRICATION SYSTEMS 7.1       ANY TWO Pump Filter Container/reservoir                                                                                                              (2) 7.2.1   ANY ONE Oil can Grease gun/pump                                                                                                                (1) 7.2.2   Pressure lubrication is normally supplied to the parts by a pump.√                           (1) 7.3.1   Needle lubricator√                                                                                                               (1) 7.3.2             A – Needle√             B – Bearing√             C – Stopper√                                                                                                                         (3) 7.4       The shaft rotates√ The splash ring rolls on the rotating shaft√ The ring picks up the oil from the oil reservoir/tank√ The oil is led to the bearing and lubricated via the oil ring.√                                       (4) 7.5.1   ANY ONE The oil is old The oil picked up dirt in the system. The oil filter needs to be replaced.                                                                                    (1) 7.5.2   Water comes in contact with the oil.√                                                                               (1) 7.5.3   The oil may have lost its viscosity√                                                                                   (1)                                                                                                                                                           (15)                                                                                                                                     TOTAL 100		[15] 100