welding, cutting and brazing -...
TRANSCRIPT
29 CFR 1910.251 & 1926.350Subpart Q & J
Prepared by County of Henrico Risk ManagementLoss Prevention
October 2nd 2013
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
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
The elements of Oxygen-fuel gas welding and cutting: General Requirements Cylinders Service Pipe Systems Pipe System Protection
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
to flow.– Turning counterclockwise
reduces or stop the gas flow.
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
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.
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
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.
Service Pipe Systems There are special requirements for service pipe
systems when using oxygen or acetylene. Oxygen Acetylene or Acetylene Compounds
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 acetyleniccompounds shall be steel or wrought iron.
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.
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.
Pressure Relief Devices: Relief valves will vent automatically at preset pressures or may be manually operated to relieve pressure in the system.
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
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
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.
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.
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.
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
.
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
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.
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.
Three Types of Welding Methods: Tungsten Inert Gas Welding (TIG) Gas Metal Arc Welding (MIG) Shielded Metal Arc Welding (SMAW)/ Stick Welding
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
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
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
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.
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.
Benefits Simple, portable,& inexpensive Self flux provided by electrode Provides all position flexibility
Shielding Gases No shield gases added Lower sensitivity to Wind
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).
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.
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
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.
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.
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.
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
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 andslag Welding curtains Non-combustible walls Fire resistant tarps & blankets
• Ventilation 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.
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.
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
Summary Major hazards include: Fire Burns Shock Toxic Exposure
Follow proper procedures to prevent fires Use appropriate engineering controls Wear appropriate PPE
Any Questions
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