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Welding, Cutting and Brazing

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Presentation on theme: "Welding, Cutting and Brazing"— Presentation transcript:

1 Welding, Cutting and Brazing
29 CFR & Subpart Q & J By: Chou Lor, Safety Coordinator UW-Eau Claire Facilities Planning & Management

2 Welding, Cutting and Brazing
Training Objectives Three Specific Types of Welding Modules Methods of Arc Welding Welding Hazards Safe Work Practices Fire Protection & Prevention Proper Ventilation for Welding Welding Operators Protection UW-Eau Claire Facilities Planning & Management

3 Three Specific Types of Welding Modules
In this Welding, Cutting, and Brazing module, three specific types of welding are covered. These are listed below: Oxygen-fuel gas welding and cutting Arc welding and cutting Resistance welding In this Welding, Cutting, and Brazing module, three specific types of welding are covered. These are listed below: Oxygen-fuel gas welding and cutting Arc welding and cutting Resistance welding. UW-Eau Claire Facilities Planning & Management

4 Oxygen-fuel gas welding & Cutting
The elements of Oxygen-fuel gas welding and cutting: General Requirements Cylinders Service Pipe Systems Pipe System Protection UW-Eau Claire Facilities Planning & Management

5 Oxygen-fuel gas welding and cutting
General Requirements Focuses on using Acetylene Safely Flammable Unstable Cannot be adjusted above 15 psi Safe Work Practices Blow out cylinder valve Turn on cylinder valve first and then adjust the regulator pressure screw. Never stand in front or behind a regulator when opening the cylinder valve Open cylinder valve slowly The pressure adjusting screw: Turning clockwise allows the gas allows to flow. Turning counterclockwise reduces or stop the gas flow. I. Speaker’s Notes: Acetylene is extremely dangerous because of its flammability range. Oxyacetylene torch cutting is very common throughout the industry as it has a wide flammable range. Acetylene is extremely unstable. Acetylene is generated in the cylinder from a reaction of acetone and calcium silicate. Relief valves for generating chamber shall be set to open at a pressure not in excess of 15 psi. Using acetylene at pressures in excess of 15 psig pressure (or about 30 psia pressure) is a hazardous practice. II. Speaker’s Notes: This slide lists basic rules to follow when welding with oxyacetylene. Before connecting to the regulator, always blow out the cylinder valve. Release the regulator by adjusting the screw before opening the cylinder valve. Always stand to the side of the regulator while opening the cylinder in case of accidental pressure release. Open the valve cautiously and slowly. Never use acetylene at pressures above 15 pounds per square inch. UW-Eau Claire Facilities Planning & Management

6 Oxygen-fuel gas welding and cutting
General Requirements Cont.: Safe Work Practices Purge oxygen and acetylene passages Light the acetylene Never use oil or grease Do not use oxygen as a substitute for air Keep your work area clean I. Speaker’s Notes: Before lighting the torch, remember to purge acetylene and oxygen passages. Before opening the oxygen on the torch, light the acetylene. Never use oil or grease on regulators, tips, or any part that may come into contact with oxygen. Do not use oxygen as a substitute for air. Always keep your work area free of items that could ignite. UW-Eau Claire Facilities Planning & Management

7 Oxygen-fuel gas welding and cutting
Cylinders Cylinder approval and marking marked for the purpose of identifying the gas content, with either the chemical or trade name of the gas Storage of cylinders Storage area must be well ventilated Cylinders must be at least 20 feet from combustibles Valves must be closed Valve protection must be in place Inside storage must be limited to 2,000 cubic feet. Cylinders must be stored in upright position Oxygen must be at least 20 feet from fuel gas or 5 feet with a 1/2 hour fire barrier Separate oxygen from fuel gas UW-Eau Claire Facilities Planning & Management

8 Oxygen-fuel gas welding and cutting
Cylinders Cont.: Operating Procedures Operation must emphasize the absence of oily or greasy substances. Follow these rules of operation: Cylinders, cylinder valves, couplings, regulators, hose, and apparatus shall be kept free from oily or greasy substances. Oxygen cylinders or apparatus shall not be handled with oily hands or gloves. A jet of oxygen must never be permitted to strike an oily surface, greasy clothes, or enter a fuel oil or other storage tank. UW-Eau Claire Facilities Planning & Management

9 Oxygen-fuel gas welding and cutting
Service Pipe Systems There are special requirements for service pipe systems when using oxygen or acetylene. Oxygen Acetylene or Acetylene Compounds Speaker’s Notes: Oxygen: When oxygen is supplied to a service piping system from a low pressure oxygen manifold without an intervening pressure regulating device, the piping system shall have a minimum design pressure of 250 psig. A pressure regulating device shall be used at each station outlet when the connected equipment is for use at pressures less than 250 psig. Acetylene or Acetylene Compounds: Piping for acetylene or acetylenic compounds shall be steel or wrought iron. UW-Eau Claire Facilities Planning & Management

10 Oxygen-fuel gas welding and cutting
Pipe System Protection The entire service pipe system must be protected against build-up of excessive pressure and leaks. This protection is accomplished with: Protective equipment Regulators Proper hose and hose connections. UW-Eau Claire Facilities Planning & Management

11 Oxygen-fuel gas welding and cutting
Pipe System Protection Cont.: Protective equipment is divided into the two categories listed here: Pressure Relief Devices The pressure relief device should discharge upwards to a safe location. Pressure relief valves are required in fuel-gas piping systems to prevent excessive pressure build up within the system. Speaker’s Notes: Pressure Relief Devices: Relief valves will vent automatically at preset pressures or may be manually operated to relieve pressure in the system. UW-Eau Claire Facilities Planning & Management

12 Oxygen-fuel gas welding and cutting
Pipe System Protection Cont.: Approved protective equipment shall be installed in fuel-gas piping to prevent: Backflow of oxygen into the fuel-gas supply system Passage of a flash back into the fuel-gas supply system Excessive back pressure of oxygen in the fuel-gas supply system. Speaker’s Notes: The three function: The protective equipment in fuel-gas piping systems shall be located either at the main supply line, at the head of each branch line, or at each location where fuel-gas is withdrawn UW-Eau Claire Facilities Planning & Management

13 Arc Welding and Cutting
Definition: A fusion process wherein the coalescence of the metals is achieved from the heat of an electric arc formed between an electrode and the work. Application Installation Operation & Maintenance UW-Eau Claire Facilities Planning & Management

14 Facilities Planning & Management
Arc Welding & Cutting Application Applies to a large and varied group of processes that use an electric arc as the source of heat to melt and join metals. Installation Arc welding requires proper installation of equipment. A critical part of installation is ensuring that proper grounding is completed. UW-Eau Claire Facilities Planning & Management

15 Facilities Planning & Management
Arc Welding & Cutting Operation & Maintenance All connections to the machine shall be checked to make certain that they are properly made. The work lead shall be firmly attached to the work. Magnetic work clamps shall be free from adherent metal particles of spatter on contact surfaces. Coiled welding cable shall be spread out before use to avoid serious overheating and damage to insulation. UW-Eau Claire Facilities Planning & Management

16 Facilities Planning & Management
Arc Welding & Cutting Operation and Maintenance Cont.: During welding operations, cables with splices within 10 feet (3m) of the holder shall not be used. Welders should not coil or loop welding electrode cable around parts of their body. Cables with damaged insulation or exposed bare conductors shall be replaced. Joining lengths of work and electrode cables shall be done by the use of connecting means specifically intended for that purpose. The connecting means shall have insulation adequate for the service conditions. UW-Eau Claire Facilities Planning & Management

17 Facilities Planning & Management
Resistance Welding Definition: This is a group of fusion welding processes that use heat and pressure to make the coalescence. The heat comes from electrical resistance to current flow at the site of the weld. The processes include: Spot Welding Projection Welding Seam Welding Electric current and mechanical pressure Resistance to the flow of current heats the material. Pressure is simultaneously applied to the joint, forming a solidified nugget that attaches the pieces. Note: FP&M only does spot welding. UW-Eau Claire Facilities Planning & Management

18 Facilities Planning & Management
Resistance Welding Spot Welding A process typically used in high-volume, rapid welding applications. The pieces to be joined are clamped between two electrodes under force, and an electrical current is sent through them. The advantages of spot welding are many and include the fact that it is: An economical process Adaptable to a wide variety of materials including low carbon steel, coated steels, stainless steel, aluminum, nickel, titanium, and copper alloys Applicable to a variety of thicknesses A process with short cycle times A robust process Tolerant to fit-up variations UW-Eau Claire Facilities Planning & Management

19 Welding/Cutting Hazards
Potential Hazards Fires may start by hot materials igniting nearby combustibles. Burns to the operator may occur if unprotected skin comes into contact with the extremely hot work. Magnetic fields could easily destroy/disrupt electronic components, stored data if not careful. UW-Eau Claire Facilities Planning & Management

20 Welding/Cutting Hazards
Potential Hazards Cont.: Metal fumes from vaporizing of the work with the extremely hot arcs may be inhaled into the worker’s lungs. Certain metals and metal oxide fumes, including zinc, cadmium and beryllium, produce serious illnesses when inhaled. Fluxes used with welding to create inert atmospheres at the point of the weld also present inhalation hazards. All welding and cutting must have adequate ventilation to protect the person doing the welding and those working around the welding area. UW-Eau Claire Facilities Planning & Management

21 Facilities Planning & Management
Methods of Arc Welding Three Types of Welding Methods: Tungsten Inert Gas Welding (TIG) Gas Metal Arc Welding (MIG) Shielded Metal Arc Welding (SMAW)/ Stick Welding UW-Eau Claire Facilities Planning & Management

22 Tungsten Inert Gas Welding (TIG)
Definition: TIG welding is an arc that is formed between a non-consumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool. Benefits: Welds with or without filler metal Precise control of welding variables (heat) Low distortion Shielding Gases: Argon 2 to 5% Hydrogen w/Helium In TIG welding an arc is formed between a nonconsumable tungsten electrode and the metal being welded. Gas is fed through the torch to shield the electrode and molten weld pool.  If filler wire is used, it is added to the weld pool separately.  (TIG welding has become a popular choice of welding processes when high quality, precision welding is required.  ) As with all processes there are advantages and disadvantages. Advantages Superior quality welds Welds can be made with or without filler metal Precise control of welding variables (heat) Low cost in comparison with processes such as electron beam and laser welding Disadvantages Requires greater welder dexterity than MIG or stick welding Lower deposition rates - The current is applied through a non-consumable tungsten electrode, as opposed to a consumable filler wire. UW-Eau Claire Facilities Planning & Management

23 Tungsten Inert Gas Welding (TIG)
Applications Most commonly used for aluminum and stainless steel For steel Slower and more costly than consumable welding Except for thin sections or where very high quality is needed UW-Eau Claire Facilities Planning & Management

24 Gas Metal Arc Welding (MIG)
Definition: The heat source is formed by creating an electric arc between the work piece and a wire, which is fed continuously into the weld pool. Benefits: Long welds can be made without starts and stops Minimal skill required Minimal cleaning of surface before weld Allows welding in all positions Gas Metal Arc Welding (GMAW) is frequently referred to as MIG welding.  MIG welding is a commonly used high deposition rate welding process.  Wire is continuously fed from a spool.  MIG welding is therefore referred to as a semiautomatic welding process.  UW-Eau Claire Facilities Planning & Management

25 Gas Metal Arc Welding (MIG) Cont.
Shielding Gases: Inert Argon, Helium Used for aluminum alloys and stainless steels. Active 1 to 5% Oxygen, 3 to 25% CO2 Used for low and medium carbon steels Applications Gas Metal Arc Welding (MIG) is used to weld all commercially important metals, including steel, aluminum, copper, and stainless steel. Inert – Ar (Argon), He (Helium) Used for aluminum alloys and stainless steels Active – CO2 Used for low and medium carbon steels UW-Eau Claire Facilities Planning & Management

26 Shielded Metal Arc Welding (SMAW)/Stick Welding
Definition: Consumable electrode coated with chemicals that provide flux and shielding The filler metal (here the consumable electrode) is usually very close in composition to the metal being welded. Stick welding is among the most widely used welding processes. The flux covering the electrode melts during welding.  This forms the gas and slag to shield the arc and molten weld pool.  The slag must be chipped off the weld bead after welding. The flux also provides a method of adding scavengers, deoxidizers, and alloying elements to the weld metal.   UW-Eau Claire Facilities Planning & Management

27 Shielded Metal Arc Welding (SMAW)/Stick Welding
Benefits Simple, portable,& inexpensive Self flux provided by electrode Provides all position flexibility Shielding Gases No shield gases added Lower sensitivity to Wind UW-Eau Claire Facilities Planning & Management

28 Shielded Metal Arc Welding (SMAW)/Stick Welding Cont.:
Applications Construction, pipelines, shipbuilding, fabrication job shops. Used for: Steels, stainless steels, cast irons. Not used for aluminum and its alloys, or copper and its alloys (energy density is too high). UW-Eau Claire Facilities Planning & Management

29 Facilities Planning & Management
Cutting Definition: A stream of oxygen is directed against a piece of heated metal, causing the metal to oxidize or burn away. Making a Cut Mark a line as a guide. Turn on acetylene as for welding and light. Turn on oxygen adjusting flame to neutral. Make sure the oxygen lever flame remains neutral. Place metal on the cutting table so metal will fall clear. Flame Types: Oxidizing Carborizing Neutral UW-Eau Claire Facilities Planning & Management

30 Facilities Planning & Management
Brazing Definition: A process which a filler metal is placed at or between the faying surfaces, the temperature is raised high enough to melt the filler metal but not the base metal. The molten metal fills the spaces by capillary attraction. Torch Brazing Oxy-fuel torch with a carburizing flame First heat the joint then add the filler metal UW-Eau Claire Facilities Planning & Management

31 Facilities Planning & Management
Safe Work Practices Electric & Gas Welding Safety Check: Ensure electrical cord, electrode holder and cables are free from defects No cable splices within 10 feet of electrode holder. Ensure welding unit is properly grounded. This helps to avoid over heating. All defective equipment shall be repaired or replaced before using. UW-Eau Claire Facilities Planning & Management

32 Facilities Planning & Management
Safe Work Practices Electric & Gas Welding Cont.: Safety Check: Remove all jewelry – rings, watches, bracelets, etc… Ensure PPE e.g.. welding hood, gloves, rubber boots or safety shoes, apron are available and in good condition. Ensure fire extinguisher is charged and available. Ensure adequate ventilation and lighting is in place. Set Voltage Regulator to Manufacture’s specifications. Avoid electrical shock DON’T wrap cables around any body part. Ensure fittings are tight. UW-Eau Claire Facilities Planning & Management

33 Facilities Planning & Management
Safe Work Practices Electric & Gas Welding Cont.: Safety Check: Inspect hoses for cuts and frayed areas. Set gauges to desired PSI. Ensure that sufficient PPE is made available. Locate welding screens to protect employee’s – DON’T block your exit. Ensure that adequate ventilation and lighting are in place. UW-Eau Claire Facilities Planning & Management

34 Fire Protection & Prevention
Fire hazards must be removed, or Guards installed, or Welding/cutting must NOT take place Hot work permit should be used outside designated areas to ensure that all fire hazards are controlled Use of fire watch 1/2 hour after operation ceases UW-Eau Claire Facilities Planning & Management

35 Fire Protection & Prevention Cont.:
Welding areas should meet the following requirements: Floors swept & cleared of combustibles 35 ft. radius of work area. Flammable and combustible liquids kept 35 ft. radius of work area. At least one fire extinguisher – on site Protective dividers to contain sparks and slag Welding curtains Non-combustible walls Fire resistant tarps & blankets UW-Eau Claire Facilities Planning & Management

36 Proper Ventilation for Welding
Proper ventilation can be obtained either naturally or mechanically. Natural Ventilation is considered sufficient for welding and brazing operations if the present work area meets these requirements: Space of more than 10,000 square feet is provided per welder A ceiling height of more than 16 feet. Mechanical ventilation options generally fall into two basic categories. Low vacuum system which takes large volumes of air at low velocities. High vacuum system that are captured and extracted fumes as near to the work as possible. Speaker’s Notes: Local exhaust Ventilation have enough velocity to draw away the contaminants. Natural Ventilation: Welding is not done in a confined space, and Welding space does not contain partitions, balconies or structured barriers that obstruct cross ventilation Mechanical Ventilation: These systems consist of hoods positioned at a distance from the work area. UW-Eau Claire Facilities Planning & Management

37 Proper Ventilation for Welding
Ensure protection from fumes and gases by one or a combination of the following: Good general ventilation. Use of a booth. Local exhaust ventilation on the hand piece. Air supply to the helmet. UW-Eau Claire Facilities Planning & Management

38 Welding Operators Protection
Welding involves specialized personal protection that must be worn every time you perform welding operations. The following is a list of basic PPE: Fire-resistant gloves Aprons Safety shoes Helmet Ultraviolet radiation filter plate (arc welding) Goggles with filter lenses UW-Eau Claire Facilities Planning & Management

39 Welding, Cutting and Brazing
Summary Major hazards include: Fire Burns Shock Toxic Exposure Follow proper procedures to prevent fires Use appropriate engineering controls Wear appropriate PPE UW-Eau Claire Facilities Planning & Management

40 ?? Any Questions Please visit FP&M Website
(www.uwec.edu/facmgt./index.htm) for additional information. UW-Eau Claire Facilities Planning & Management


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