Trade of Plumbing Phase 2 Module 3

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Module 3 Domestic Heating/MMA Welding Unit 5 – Manual Arc Welding Duration – 36 Hours

Trade of Plumbing – Phase 2 Module 3 – Unit 5 In this module we learn how to: _ Describe the manual arc welding process and equipment. _ Describe welding defects and their causes. _ Set up manual arc welding equipment. _ Weld butt, lap and fillet joints on mild steel plate.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 • Key Learning Points _ Rk _ _ _ _ Rk Sc Sk Sk Rk Sk H P P Manual arc welding process. Manual arc welding equipment – AC and DC plant, leads, holder, electrodes etc. Weld defects, causes and prevention. Setting up manual arc welding equipment. Selecting correct current and electrodes. Care of electrodes. Welding techniques for butt, lap and fillet joints. Hot metal, arc eye, electric shock etc. Working independently. Good working practice.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Manual Metal Arcing _ Manual metal arc welding was first invented in Russia in 1888. _ Development of coated electrodes early 1900 s - Kjellberg process was invented in Sweden. _ When an arc is struck between the metal rod (electrode) and the workpiece, both the rod and workpiece surface melt to form a weld pool.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Protection for Operator: _ _ _ _ _ No open-neck shirts. Regulation inflammable overalls only. No trainers/runners to be worn. Overalls not around waist. Always wear protective clothing. Ensure adequate ventilation. Check your surroundings. Examine all welding cables. Never weld enclosed tanks. Do not wells over Paint/Oils/Grease/Solvents.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Protection for Others: _ Screen rays from others. _ Safe removal of a victim.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 General Protection: _ Carbon tetrachloride. (C. T. C. ). _ Carbon Dioxide (CO 2). _ Foam.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Access and Exits: _ Ensure adequate clear access. _ Exits must be kept be free of obstacles. _ When welding inside large vessels a safety harness must be worn.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Symbols on Drawings

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Symbols on Drawings. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 B. S. Symbols

Trade of Plumbing – Phase 2 Module 3 – Unit 5 B. S. Symbols. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Intermittent welds

Trade of Plumbing – Phase 2 Module 3 – Unit 5 The Manual Metal Arc Process

Trade of Plumbing – Phase 2 Module 3 – Unit 5 The Manual Metal Arc Process. . . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Manual metal arc welding equipment

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Manual metal arc welding equipment. . . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Welding Techniques Current too low

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Welding Techniques. . continued Current too high

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Welding Techniques. . continued Correct Current

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Arc Length

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Speed of Travel Too Fast

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Speed of Travel. . continued Too Slow

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes Lack of Penetration

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Lack of Fusion

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Porosity

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Slag Inclusion

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Undercut

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Overlays

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Crackling

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Blowholes

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Burn Through

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Weld Defects and Their Causes. . continued Excessive Penetration

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Control of Distortion Presetting - Backstepping or Stepwelding - Jigging - Preheating.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Electrodes

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Functions of the Electrode Coating _ _ _To act as a flux and remove the impurities from the surfaces being welded. _To form a slag over the weld protects the molten metal from contact with the air slows down the cooling rate of the weld helping to prevent brittleness of the weld provides a smoother surface by preventing ripples It forms a neutral gas atmosphere. It helps to stabilise the arc, allowing a. c. to be used. It can add certain constituents to the weld by replacing any lost during the welding process. It can speed up the welding process by increasing the speed of melting of the metal and the electrode.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Functions of the Electrode Coating. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 American Welding Society (AWS) Classification System for Electrodes Mild steel electrodes: The method of classifying of electrodes is based on the use of a four-digit number, preceded by the letter ‘E’ for ‘Electrode’. The classification of E 6012 electrodes is derived as follows: _E 601 2 = Metal arc welding electrode. _E 601 2 = Weld metal UTS 60, 000 psi mm. _E 601 2 = Usable in all positions. _E 601 2 = Rutile type coating: AC or DC negative.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 American Welding Society (AWS) Classification System for Electrodes. . . continued First and second digits: _E 6 Oxx - As-welded deposit. UTS 60. 000 psi mm. for E 6010, E 6011, E 6012, E 6013, E 6020, E 6027 UTS. _E 7 Oxx - As-welded deposit, UTS 70. 000 psi mm. for E 7014, 7015, 7016, 7018, E 7024 and E 7028. Third and fourth digits: The third and fourth digits indicate positional usability and flux coating types e. g. _Exxl 0 - High cellulose coating. bonded with sodium silicate. Deeply penetrating. forceful, spray-type arc. Thin, friable slag. All-positional. DC. electrode positive only. _Exx 11 - Very similar to Exxl 0, but bonded with potassium silicate to permit use on AC or DC positive. _Exxl 2 - High rutile coating, bonded with sodium silicate. Quiet arc, medium penetration. all-positionat. AC or DC negative.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Hazards and Safety

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Hazards and Safety. . continued Arch Flash

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Hazards and Safety. . continued Arch Flash. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Hazards and Safety. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 AC and DC Welding Plants Types of Welding Plant - Direct Current

Trade of Plumbing – Phase 2 Module 3 – Unit 5 AC and DC Welding Plants. . . continued Types of Welding Plant

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Alternating Current (A. C. )

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Alternating Current (A. C. ). . . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Effect of Short Circuiting

Trade of Plumbing – Phase 2 Module 3 – Unit 5 The Advantage and Disadvantages of A. C. and D. C. Welding The Advantage of A. C. Welding Plants _They are cheaper to buy than D. C. Sets. The initial cost is approx. V of that required for a D. C. set of equivalent rating. _Little or no maintenance cost, this is because there are no moving parts in an A. C. Transformer. _There is no “Arc Blow” as with D. C. The Disadvantages of A. C. Welding Plants _Non ferrous electrodes are not so well deposited. _The electric shock hazard is more pronounced with A. C. than with D. C.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 The Advantage and Disadvantages of A. C. and D. C. Welding. . continued The Advantages of D. C. Welding _They can be used to deposit both ferrous and non-ferrous electrodes. _Smoother welding giving an advantage when welding thin sheet metal. _Safer to use in damp conditions where risk of electric shock is greater i. e. boiler work etc. _Petrol or diesel sets can be used in remote areas where there is no mains supply. Site work etc. Disadvantages with D. C. Welding _More expensive to purchase than A. C. Sets. _Perodic maintenance of the plant is necessary because of the moving parts. _Troubles from “Arc Blow”.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Arc Blow _Weld away from the earth connection. _Change the position of the earth wire on the work. _Wrap the welding cable a few turns around the work, if possible on girders etc. _Change the position of the work on the table if working at a bench.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Arc Blow. . continued

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Power Supply _Alternating Current (A. C. ) _Direct Current (D. C. )

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Advantages of A. C. Welding Sets _Cheaper than D. C. sets. _Low maintenance – no moving parts. _No arc-blow Disadvantages of A. C. Welding Sets _Unsuitable for non-ferrous electrodes. _Greater danger of electric shock.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Advantages of D. C. Welding Sets _Ideal for ferrous or non-ferrous electrodes. _Deposits a smoother weld. _Safer to use in damp conditions. _Petrol or Diesel sets. Disadvantages of D. C. Welding Sets _More expensive than A. C. sets. _Need more maintenance. _Prone to arc-blow.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Electrodes Coating: _Stabilize the arc. _Protects the molten metal from contamination during welding. _Protects the weld while cooling. Sizes: _2 mm. _2. 5 mm. _3. 2 mm. _4 mm. _5 mm. _6 mm.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Care of Electrodes _Electrodes for welding mild steel should be kept dry. _They should be kept in the packet. _They should not be bent.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Types of Flux _Cellulosic _Rutile _Basic

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Faults & Imperfections in Arc-Welding _Porosity. _Slag Inclusion. _Lack of Fusion. _Lack of penetration. _Undercutting. _Excess spatter. _Unequal leg length.

Trade of Plumbing – Phase 2 Module 3 – Unit 5 Types of Joints _Fillet. _Square Butt. _Corner Joint. _Lap Joint. _Single Vee. _Double Vee. F = Flat / Downhand. H = Horizontal / Vertical. V = Vertical (upwards). D = Vertical (down). O = Overhead.