Chapter 13: Hot Work – Welding and Cutting

A. General: Anytime cutting and weld activities, and associated ones like brazing and soldering are undertaken, potential health and safety hazards can exist. When one thinks about it, a welding arc is hot enough that it can melt steel, and the light it emits can literally blind. Hazard such as fire, burns, injuries to sight and respiratory consequences from fumes, gases, sparks, hot metal and radiant energy are the principle hazards, although some hot work equipment also produces high voltages or can utilize compressed gases, which can be hazards by themselves. Hazards associated with hot work can be appreciably reduced through implementation of effective control programs. These operations are generally found in facilities work, but can also be present in science research functions or Art Departments. OSHA requires that adequate controls and procedures are in place for hot work to be performed. (29 CFR 1910.252-255)

B. Specific Types of Welding Operation Hazards: There are 3 basic types of welding operations:

  1. Oxygen-Fuel Gas Welding: Oxygen-fuel gas welding is joining metal by generating extremely high heat during combustion.

  2. Resistance Welding: Resistance welding is joining or cutting metals by generating heat though resistance created by the flow of electrical current.
  3. Arc Welding: Arc welding is joining or cutting metals by generating heat from electric arc that extends between the welding electrode and the electrode placed on the equipment being welded.

C. Welding Safety Procedures:

Contact Safety Office for Hot Work approval and Fire Department System Deaction.

  1. Hot Work Areas: Hot Work areas should be properly designated and prepared. The area should not pose a hazard to others in nearby areas. If possible, such work should be confined to
    properly designed shop areas equipped with necessary controls and proper ventilation.

  2. Combustible and Flammable Materials: Combustible and flammable materials should be placed at least 3 feet from the work site, but if this is not possible, metal guards or flame-proof
    curtains or other appropriate covers should be used to create a barrier and protect them.
  3. Welding Machine Operators: Employees operating welding equipment should be restricted to authorized and properly trained employees.
  4. Floor Covers: Floor covers within 35 feet of the work area should be sufficient to prevent sparks from falling beneath the floor or to a lower level.
  5. PPE: Personal protective equipment such as tinted shields be used to protect operators from burns and ultra-violet light exposure. Other PPE may also be necessary, depending on the
    exact nature of the work. They might include an apron, leggings, safety shoes, protective helmet, ear protection, eye protection and respiratory protection. When working above ground, use a platform with toe boards and standard railings or a safety harness and life line.
  6. Stone and Cement Surfaces: Never aim a welding torch at a cement or stone surface, because moisture in the material could cause them to explode when they reach a certain temperature.
  7. Inspect Equipment Before Using: Equipment found to have bare conductors or damaged regulators, torches, electrode holders, or other defective components should not be used.
  8. Warnings: When finished welding or cutting, warn other workers of hot metal by marking or putting up a clearly visible sign.
  9. Electrode and Rod Stubs: These should not be left on the floor, but collected up.
  10. Tools: Tools should be stored safely when work is completed.

D. Fire Protection: A person other than the operator should perform fire watch duties and remain at the work site for at least 60 minutes after hot work operations have ended. A fire extinguisher rated at not less than 2-A:20-B:C must be present during ALL welding and cutting operations. If a building is equipped with a sprinkler system, the system must be operational at the time hot work is done.

E. Compressed Gases: Compressed gases come in 2 basic varieties – flammable and non-flammable.

  1. Flammable Compressed Gas: Flammable compressed gases have dangers besides high pressure. These gases can easily catch fire and burn rapidly. These include acetylene, hydrogen, natural gas and propane.

  2. Nonflammable Compressed Gas: These types of gases do not catch fire easily or burn quickly, but they will eventually burn and do possess other dangers. The cylinder label and MSDS will
    describe the toxic properties and physical hazards posed by specific nonflammable compressed gases. These include: ammonia, argon, carbon dioxide, nitrogen, oxygen, chlorine, and nitrous oxide. Generally speaking, they can cause dizziness, unconsciousness, or suffocation under certain circumstances. They can also be harmful if inhaled, and can cause irritation to eyes, nose, throat and lungs.

F. Compressed Gas Cylinder Handling and Storage: A primary danger of oxygen-fuel gas welding operations stems from welding with compressed gas cylinders (CGC’s) containing oxygen and acetylene. If CGC’s are damaged, gas can escape with tremendous force and the vessel itself can
explode, causing severe injuries. One particularly deadly condition is call “rocketing”. Rocketing occurs when a CGC ruptures and actually propelled with such force that it can penetrate a concrete wall.

  1. Handling and Storage Procedures:
    A. Handling:

    1. Securing: Cylinders should be secured in the upright position to prevent tipping.

    2. Regulator Compatibility: Regulators must be compatible with the cylinder and its content. Many regulators are similar in design and construction, so it is necessary to check the
    regulator’s model number and compare it with the cylinder’s requirements to ensure compatibility.

    3. Cylinder Carts: Cylinder carts equipped with cylinder restraints such as a chain or strap should be used for transporting CGC’s. Never drop cylinders or let things fall on them.

    4. Delivery: Do not accept delivery of acetylene CGC’s that arrive in the horizontal position. Transporting in this manner makes them much more susceptible to explosion.

    5. Inspection: CGC’s should be inspected before using to check for leaking, corrosion, cracking, burn marks, contaminated valves, worn hoses and faulty connectors, or broken gauges. If any defective condition is discovered, the CGC should not be used.

    6. Opening Valves: Never open valves until regulators are drained of gas and pressure adjusting devices are released. When opening CGC’s point outlets away from people and sources of ignition Open valves slowly. On valves without handle wheels, use only supplier recommended wrenches. On valves with handle wheels, never use wrenches. Never hammer a handle wheel open or closed.

    7. Empty Cylinders: When cylinders are empty, close and return them. Empty CGC’s must be marked “MT” or “Empty”.

    B. Storage:

    1. Protective Valve Caps: Protective calve caps should be in place on the CGC when it is placed into storage. This will reduce the likelihood that a blow to the valve will result in
    leakage.

    2. Barriers: When being stored, CGC’s should be stored at least 20 feet apart and they should also be separated by a noncombustible wall at least 5 feet high.

    3. Use Old Stock Before New: When stored, CGC’s should be arranged in such a way that old stock will be used before new stock.

G. Ventilation: Ventilation techniques for welding apparitions vary depending on size and type. For basic operations, wall fans will usually be all that is needed. Be aware, however, that ventilation should never be relied on as the only way to protect employees when air contaminants are toxic. Where ventilation is poor, respirator use should be evaluated before engaging in the activity.

H. Training Requirements: All persons performing hot work should be trained improper equipment operation, handling and storage of welding materials, compressed gas safety and chemical hazards. Additional training may be necessary improper selection and use of personal protective equipment, as well as training in confined space entry where appropriate. (Some instance require proof of certification, example, presure vessel repair)

I. Hot Work Permit Program: UMW has a Hot Work Permit requirement for all open flame work done on the university property. This includes all campus’s both inside and outside area. Hot Work permits are secured from the Safety Office located in Brent Hall. Safety will inspect the area for hazards and issue the permit. Permits are issued for daily operations only. All flammable materials must be removed or covered with non flammble protection. Fire watches must be provided for all hot work tasks and must be trained in applicable extinguisher usage. Fire Watch must remain in place for 60 mins. AFTER the work is completed. All Contractors are required to secure Hot Work permits as well as UMW staff.

 

 

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