Welding, Brazing, Cutting = - PowerPoint Presentation

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Welding, Brazing, Cutting =Hot Work

Bureau of Workers’ CompPA Training for Health & Safety(PATHS)

OSHA 29CFR1910.251-255

Subpart Q

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Fire Prevention & ProtectionNFPA 51 B – “Standard for Fire Prevention in Use of Cutting and Welding Processes.”

Move all fire hazards away from work area.Use guards (fire blankets, etc.) if fire hazards cannot be moved.

General Requirements

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Working on floors with openings/cracks/grating: fire blankets to protect lower level from sparks and slag.Have suitable fire extinguishing agents (extinguisher, water, sand, etc.) ready near cutting and welding operations.

General Requirements (cont.)

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A “fire watch” must be available where there is a fire potential or where;Combustible materials are closer than 35 feet to the point of operation.Walls opening within the 35 foot radius, exposing combustible material.

Material opposite metal walls and roofs could catch fire from conduction or radiation.

Fire Watch Requirements4

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Fire Watch Requirements (cont.)

A person acting as a “fire watch” must have fire extinguishing agents readily available and be trained in their use.

A fire watch must be maintained for at least 30 minutes after work ceases.

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Obtain a “burn permit” (hot work permit) authorized by the designated responsible person.Sweep away all paper clippings, wood shavings or textile fibers within a radius of 35 feet of cutting/welding operations.

Before Welding

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Hot Work Permit7

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Is a hot work permit required under related OSHA standards? NO!Is a hot work permit a “best practice?”

YES!

Hot Work

Permit (cont.)

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Welding/cutting is prohibited in

Areas not authorized by company management.Areas near large quantities of readily-ignitable materials, such as baled paper or cotton.

Sprinkler-equipped buildings while sprinklers are impaired or out of order.

The presence of explosive atmospheres such as unclean or improperly-prepared tanks.

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Recognize safe usage of welding/cutting/burning equipment on its property.Establish areas for cutting and welding operations.Protect welding leads from damage by vehicles, slag, etc.

Management Responsibilities

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Designate a responsible individual to authorize hot work permits.Insist that cutters/welders are trained in safe work habits for their specific tasks.Advise all contractors about flammable or hazardous materials.

Management Responsibilities (cont.)

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Ensure that used containers (drums, barrels, tanks) have been thoroughly cleaned of flammable materials including grease, tars and acids.All spaces must be vented and purged before welding.Purging with inert gas is recommended.

Welding or Cutting Containers

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Keep all cylinders outside of confined spaces. Turn off gases at cylinders and purge lines when away from the confined-space work area.

Remove electrodes (rods) from electrode holders (stingers) and disconnect machine power source.

Confined Spaces

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Workers on platforms, scaffolds or open sided floors must be protected from falls with:A guardrail system or lifeline.Safety harnesses with lanyards.

Welding cable and hoses must be kept clear of passageways, ladders and stairways.

Working at Heights

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Welders and welders’ helpers must wear appropriate eye protection.Lens of welding hoods, cutting goggles, and hand shields must: Be arranged to protect face, neck and ears from radiant energy.

Be made of tempered glass and free of bubbles.Have lens shade readily identified on glass.

Eye Protection Requirements

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Results of excessive exposure to ultraviolet radiation:Causes eyes to feel like they are full of sand.Can lead to premature cataracts of the eyes.

Protect against ultraviolet radiation, sparks, fumes and slag. Wear protective clothing and respirators.

Provide warning signs to warn of hot metal.

Use ventilation or suitable respiratory protection.

Radiation Hazards

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General - mechanical, 2000fpm 10,000 ft3 per welder

ceiling less than 16 feetaround structural barriers

Local - mechanical, 100 linear fpm in weld zone

When ventilation cannot meet the needs supplied, air respirators shall be used.

Ventilation

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Mostly require local exhaust ventilation or airline respirators (reference OSHA standard):Fluorine compoundsZinc

LeadBerylliumCadmiumMercuryStainless steel

Chlorinated hydrocarbons

Ventilation (cont.)

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Liquefied petroleum gasFormed when calcium carbide is submerged in water or in petrochemical processes.

Very unstable at pressures over 15 psi.

Never operate above 15 psi.

LEL = 2%, UEL=100%

Acetylene

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Acetylene (cont.)

Does not require high storage pressure (the case with most LP gases).

Is usually pressurized around 250 psi.

Turns to liquid over 300 psi.

Acetone liquid in cylinder lying horizontally takes at least 1 hour to settle to bottom when

cylinder is set

up

vertically.

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Gases in a typical acetylene cylinder:Acetylene gas 36%

Acetone 42%Porous filler 8-10%

Reserve volume 10-12%

Cylinders are filled with a porous material with millions

of voids to help keep pressure from building up.

Acetylene Gas Cylinders

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Oxygen CylindersOxygen will not burn but will support combustion.

Oxygen is pressurized around 2,200 psi and the cylinder is hollow.

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Keep oil and grease off oxygen cylinder valves and fittings (oil and grease will burn violently).Protect valves of oxygen cylinders

(if valves are knocked off, the cylinder becomes a “bomb”).Separate oxygen cylinders from fuel gas cylinders or combustible materials by a distance of

at least 20 feet.

Oxygen

Cylinders (cont.)

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“Crack” cylinders to blow out dirt or dust.Open acetylene cylinders no more than 1 ½ turns (3/4 turn recommended).Do not stand in front of regulator when turning it

on, the diaphragm in the regulator could blow outward.

To

Begin Welding or

Cutting

Oxygen

=

Acetylene

=

threads-right-handed

threads-left handed

hoses-green

hoses-red

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Light acetylene first. Open acetylene valve.Adjust to no more than

15psi (5 to 7psi is common, depending on size of metal to be cut).Then turn on oxygen.

Adjust valve at torch head to “fine tune” flame to where blue flame is about 1/4 inch.

NOTE: Each fuel-gas cylinder lead should

have a back-flow check valve and flash-back arrestor.

To

Begin Welding

or

Cutting

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Shut oxygen valve off first, then acetylene.Oxygen cylinder valves should be opened entirely

.Turn main valve off and bleed lines.

Mark empty cylinders “MT” or “Empty” with railroad chalk

.When moving cylinders, roll them on their bottom

edges.

To Stop Welding or

Cutting

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Welding fumes from zinc, cadmium, beryllium, lead, mercury and stainless steel are addressed in OSHA standards.Argon gas used in MIG welding operations must be handled as an inert gas and stored accordingly.

Special Precautions

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When transporting cylinders, secure vertically and with gauges unattached.Do not pry frozen cylinders - use warm water because of the fuse plug on the cylinder bottom.Do not use valve caps to lift cylinders.

Safe Handling of Gas Cylinders

Improper

and

unsafe storage

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Clean torch tips with tip cleaners, wires, etc.Do not re-light torch tip with hot metal.

Safe Torch Handling

Tip Cleaner in Use

Welding Tip Orifice Cleaner

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Only do “hot work” in designated/authorized areas.Ensure permit is in place and all parties are aware.Ensure fire protection equipment is readily available.Ensure “fire watch” is posted for at least 30 minutes after work is done.

Review

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If welding above openings/gratings ensure “guarding” is in place.Ensure welding gases and equipment are stored properly and safely.Ensure compressed gas cylinders are handled correctly.

Review (cont.)

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Any Questions?

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