Arc Flash Explosion

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Safe and accident free completion of any welding operation should be the goal of all welders. Here are a few welding safety tips that will help you achieve that goal.

  1. Wear proper eye protection. Welders and their helpers should be sure to use the correct filter lens in their goggles or helmets to protect their eyes from infrared and ultraviolet light.
  2. Be cautious of fires in areas where welding is being done.  For example, isolate the welding and cutting area and remove fire hazards from the vicinity. If normal fire prevention precautions are not sufficient, a qualified person should be assigned to guard against fire during the operation and for a suitable time after completion of the work, to ensure that no possibility of fire exists.
  3. Be sure that fire extinguishing equipment is available and ready for immediate use. In areas where heavy dust concentrations exist, or where flammable paints or other flammable materials are present, welding, cutting or heating can create a significant fire hazard. Proceed with extreme caution!
  4. A non-combustible or flameproof screen should isolate the welding or cutting area to protect other workers in the vicinity from direct arc rays. Watch your slag; it could cause a serious injury to someone working below.
  5. If the electrode holder needs to be left unattended, the electrodes must be removed, and the holder must be placed so that electrical contact cannot be made with another employee or any conducting object.
  6. All arc welding and cutting cables must be completely insulated and capable of handling the maximum current requirements for the job. The insulation on any splice within 10-feet of the electrode holder must be equal to the insulation of the cable.

All welding and cutting operations, in a confined space, shall be ventilated to prevent the accumulation of toxic materials or possible oxygen deficiency.

Safe Operating Rules and Practices

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Safe operating rules and practices are to be established at the planning meeting, before a job is began. They are dictated by the hazards inherent in the nature of the work, federal and state Safety and Health Regulations, company policies, and owner and other regulatory agency requirements. Other safety rules may have to be added as work progresses due to changed conditions, new methods, new equipment, and as an outgrowth of accident experience.

General safe operating rules and practices apply to all employees, regardless of the nature of their duties. These rules are to be explained to each new hire during indoctrination and must be re-emphasized at toolbox meetings and in day-to-day contacts. These are minimum requirements, and are to be rigidly enforced. Examples of general rules follow:

  1. Wear personal protective equipment as required
  2. Wear suitable shoes and work clothes in good repair
  3. Lift correctly. Get help on heavy loads.
  4. Do not smoke in prohibited areas.
  5. Avoid off-balanced positions when pulling, pushing, or prying, especially at heights
  6. Report all injuries promptly, even though minor in nature,
  7. Keep alert around moving equipment
  8. Always inspect ladders prior to use and use ladders correctly.
  9. Always follow the approved lock and tag procedures.
  10. Operate equipment and vehicles only if authorized
  11. Correct unsafe conditions as noted, or if you can’t correct them, call them to the attention of your foreman immediately.
  12. Keep tools and materials away from the edge of scaffolds or floor openings where they can be knocked off on employees working below.
  13. Be considerate of the welfare of fellow employees. Do not distract their attention or engage in horseplay.
  14. Replace all guards removed for servicing or other reasons,
  15. Pressure cylinders should be used and stored in an upright position and secured against accidental tipping.
  16. Keep all stairways, ladders, ramps, scaffold platforms, walkways and work areas free from loose materials and trash.
  17. Riding on loads, hooks and hoists is prohibited.
  18. Always wear eye protection when grinding, drilling, burning, or performing any operation which may produce flying particles or objects.

Dealing with Gasoline

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Gasoline is the most common flammable liquid manufactured and used. Because virtually everyone uses gasoline it is often assumed that everyone is familiar with gasoline’s dangerous properties.  But with familiarity comes carelessness.  It may be a good idea to review this highly hazardous material. Here are some brief but important items to remember when dealing with gasoline.

  • Gasoline as a liquid does not burn. It is the vapors that the liquid gives off that burns.
  • Vapors usually cannot be seen but frequently travel long distances to a source of ignition. Thus the gasoline can be located a great distance from an actual ignition source.
  • Gasoline gives off enough vapor to flash, when exposed to an external ignition source at temperatures as low as -450 F! In other words, hazardous vapors are almost always being released….. unless you work in temperatures colder than -450 F.
  • Gasoline vapors are heavier than air. Vapors will settle to the ground and flow similar to a liquid. This is why gasoline vapors tend to find their way into drains, sewer lines, basements and other low spots.
  • Gasoline must be mixed with air before it can burn. It does not take much gasoline to make an ignitable mixture. If the gas-to-air mixture contains as little as 1.4% gasoline by volume, it can be ignited with explosive force.
  • It has been said that the potential energy in a one gallon can of gasoline is equal to numerous sticks of dynamite.
  • A gasoline/air mixture can be ignited by a hot surface, a smoldering object such as a cigarette, an open flame, or even a static spark.
  • Practice good hygiene after handling gasoline. Wash hands and other areas that may have come in contact with gasoline. Avoid prolonged inhalation of vapors as gasoline contains benzene, a known carcinogen.

What can you do to avoid a gasoline disaster?

  1. Never use gasoline for anything other than its intended purpose, as a fuel.  Never use it as a cleaning solvent!
  2. Store gasoline in UL approved safety containers.
  3. Never smoke when anywhere near gasoline.
  4. Shut off all equipment before refueling and allow it to cool off first. Inspect all fuel hoses, pipes and pumps frequently. Fix leaks now!

Gasoline was chosen as a fuel for the same reasons that make it so dangerous. It is easily vaporized, easy to ignite and explodes powerfully when ignited. Never let yourself become complacent around this volatile liquid that we use everyday.

Electrical Sources in Hazardous Locations

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An explosion or fire can cause all sorts of havoc in any company’s operations. Rebuilding, after a fire, can take a company years. One of the major causes of explosions and fire in industry is from electrical sources. Potential losses from these fires can be reduced by having proper electrical installations and equipment.

Hazardous locations require specially designed electrical equipment to protect people and property against increased fire potential. Certain electrical components and instruments are engineered specifically for locations designated as hazardous due to the possible presence of ignitable quantities of flammable liquids, gases, vapors, combustible dusts, or ignitable fibers.

Hazardous locations are classified as Class I, Class II, or Class III. The class is dependent on the physical properties of the combustible materials which may be expected to be present.
Class I: locations where flammable vapors or gases may be present.
Class II: locations where combustible dusts may be found.
Class III: locations where there may be ignitable fibers and filings.

Each of these three classes are divided into two hazard categories, Division 1 and Division 2. The divisions identify the degree of potential for an ignitable atmosphere to exist. Class and Division explanations are detailed in Articles 500 – 503 of the National Electric Code (NEC), and in OSHA 29CFR 1910.39.

Before selecting electrical equipment and the associated wiring for any hazardous location, the exact nature and concentrations of the flammable materials must be determined. An electrical fitting or device which is safe for installation in an atmosphere of combustible dust may not be safe for operation in an atmosphere containing flammable vapors or gases. There are electrical fittings specifically designed for each hazard.

Class I electrical wiring applications are commonly referred to as “Explosion Proof.” Properly installed and maintained Class I equipment will not ignite the dangerous atmosphere surrounding it, and is approved for use in specific hazardous areas. Explosion proof fittings are designed to contain any arcing, intense heat, and explosions. These fixtures are distinctive in appearance. Class II locations may require “Dust-ignition proof” fixtures. These fixtures are designed in such a manner that their construction prohibits ignitable amounts of dust from entering the devices.

Hazardous areas that must have approved electrical installations include, but are not limited to: locations where volatile flammable liquids are transferred from one container to another; interiors of spray booths; in the vicinity of spray painting operations where volatile flammable solvents are used; locations where dangerous concentrations of suspended dust are likely, such as in grain elevators; and gasoline fueling stations.
Remember!  Think electrical safety when proposing any electrical systems that will be located in a hazardous location.

Arc Welding Safety Tips

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Safe and accident free completion of any welding operation should be the goal of all welders. Here are a few welding safety tips that will help you achieve that goal.

  1. Wear proper eye protection. Welders and their helpers should be sure to use the correct filter lens in their goggles or helmets to protect their eyes from infrared and ultraviolet light.
  2. Be cautious of fires in areas where welding is being done.  For example, isolate the welding and cutting area and remove fire hazards from the vicinity. If normal fire prevention precautions are not sufficient, a qualified person should be assigned to guard against fire during the operation and for a suitable time after completion of the work, to ensure that no possibility of fire exists.
  3. Be sure that fire extinguishing equipment is available and ready for immediate use. In areas where heavy dust concentrations exist, or where flammable paints or other flammable materials are present, welding, cutting or heating can create a significant fire hazard. Proceed with extreme caution!
  4. A non-combustible or flameproof screen should isolate the welding or cutting area to protect other workers in the vicinity from direct arc rays. Watch your slag; it could cause a serious injury to someone working below.
  5. If the electrode holder needs to be left unattended, the electrodes must be removed, and the holder must be placed so that electrical contact cannot be made with another employee or any conducting object.
  6. All arc welding and cutting cables must be completely insulated and capable of handling the maximum current requirements for the job. The insulation on any splice within 10-feet of the electrode holder must be equal to the insulation of the cable.
  7. All welding and cutting operations, in a confined space, shall be ventilated to prevent the accumulation of toxic materials or possible oxygen deficiency.

Static Electricity Safety

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We have all walked across the rug and reached for the door knob, only to have a spark jump from our hand to the knob. We have also seen the effects of “static cling,” your white tube sock, stuck to the back our your black t-shirt!

Static electricity, as a source of ignition for flammable vapors, gases, and dusts, is a hazard common to a wide variety of industries.  A static spark can occur when an electrical charge accumulates on the surfaces of two materials that have been brought together, and then separated (between two solids, between a solid and a liquid, or between two immiscible liquids, i.e., incapable of mixing). One surface becomes charged positively and the other surface becomes charged negatively. If the materials are not bonded or grounded, they eventually will accumulate a sufficient electrical charge capable of producing a static spark that could ignite flammable vapors, gases, and dusts.

Some common processes capable of producing a static ignition are as follows:

  1. The flow of liquids (petroleum or mixtures of petroleum and water) through pipes or fine filters.
  2. The settling of a solid or an immiscible liquid through a liquid
    (e.g., rust or water through petroleum).
  3. The ejection of particles or droplets from a nozzle
    (e.g. water washing operations or the initial stages of filling a tank with oil).
  4. The vigorous rubbing together and subsequent separation of certain synthetic polymers
    (e.g. the sliding of a polypropylene rope through PVC gloved hands).

Preventing static electricity as an ignition source can be accomplished through bonding, grounding, or possibly substitution.

  1. Bonding is the process of connecting two or more conductive objects together by means of a conductor.
  2. Grounding (earthing) is the process of connecting one or more conductive objects to the ground.
  3. If grounding or bonding is not possible, substituting may be an alternative. For example: some absorbent pads used in shops can produce a static spark when separated. If the conditions are right a static spark could be a source of ignition for flammable vapors. By substituting a non-conductive pad (3M – HP556) as an alternative, the risk of static spark can be eliminated.

Remember, taking the time to bond or ground when working around flammable

vapors, gases, and dusts will help prevent a serious accident.

Preventing Welding Flashback

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Knowledge and precautions can prevent fires and violent explosions.

For many years oxy-acetylene torches have been used for cutting, welding, brazing, and heating of metals. The equipment used today is safe, but every year, hundreds of employees are injured or die as a result of improper use.

Burn Back: If your oxygen cylinder is low or empty, reverse flow of gas may occur. The fuel gas, being at a higher pressure, can travel up the oxygen line and mix with gas in the hose, regulator and cylinder. If you light your torch without purging the lines, a burn back may occur with explosions in the hose, regulator, or cylinder.

Gas Pressure: One cause of fires and explosions is high acetylene pressure. When more than 15 pounds of pressure is used, acetylene becomes unstable and decomposes explosively. This is the major reason for using other fuel gases such as MAPP, propylene, propane, and natural gas which may be safely used at higher operating pressures.

Backfire: The same thing can happen with high oxygen pressure and low fuel gas pressure if a backfire occurs, which is usually caused by holding the cutting torch too close to your work. This causes gas starvation of the cutting flame and results in the flame being sucked into the torch head. Usually you will hear a popping sound that turns to a whistle when this happens.

Flashback: When a backfire takes place in a mixing chamber, unless you shut off the oxygen valve, the flame burning in the torch head may ignite gases in the hoses and result in a flashback. A flashback is an explosion that progresses through the torch, hoses, regulators, and into the cylinders. Consequence can range from a burst hose to a violent explosion of the regulator and cylinders.

Follow these guidelines to help prevent flashbacks, fires and explosions:

  1. If using acetylene, keep the pressure below 15 pounds.
  2. Purge your hoses before lighting the torch.
  3. Never light your torch with a mixture of fuel and oxygen. After purging the lines, light the torch with only the fuel gas valve open.
  4. Check valves should be installed on both torch inlets and operating properly. Check valves can stop the reverse flow of gases, but will not prevent flashbacks.
  5. To prevent flashbacks, flashback arrestors must be installed on the outlets of both regulators, and/or torch inlets. 6) Check The Torch: How can you tell if the torch you are using has flashback arrestors and check valves? If you look at the torch you will notice a small cylindrical valve on each inlet with the hoses screwed onto this valve instead of hooked directly to the torch. Most of these valves are combination flashback/check valves and will say so on the valve body. Often, combination valves are also installed on regulator outlets.

Before welding, take time to inspect the equipment you will be using.  Be sure check valves and flashback arrestors have been installed. This precaution can prevent a deadly cylinder explosion.

Flammable & Combustible Liquids

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Here are a few safety guidelines that you should remember when handling flammable or combustible liquids.

  1. Store and handle them in APPROVED containers.
  2. NEVER smoke around these liquids. Post ‘NO SMOKING’ signs on liquid petroleum tanks.
  3. While in storage, fuel gas cylinders and oxygen cylinders must be separated by a minimum distance of 20 feet, or with fire resistant barriers.
  4. Fuel storage tanks must be guarded to prevent damage from vehicular traffic.
  5. Fire extinguishers need to be properly distributed around the worksite and kept free from obstructions.
  • Are you trained in the use of each type of extinguisher?
  • Do you use safety cans when dispensing flammable and combustible liquids?
  • Do you have a plan to clean up spills properly and promptly?
  • Plastic milk cartons and glass bottles are not approved containers for these liquids.
  • Are all flammable or combustible liquids you use in approved, closed containers when not in use?

A ‘Flammable Liquid’ is defined as any liquid having a flash point below 140’F and having a vapor pressure not exceeding 40 psi at 1000F. A liquid with a flash point at or above 1400F (600c) and below 2000F (93.40C) is a ‘Combustible Liquid’. You will find both of these liquids on most construction sites. Two of the most common liquids we use are gasoline and diesel fuel. Each has a flash point of less than 1400F and therefore is classified as a flammable liquid. For easy reference — the flash point of a liquid is the temperature at which it gives off sufficient vapor to form an ignitable mixture with air, near the surface of the liquid or within a vessel.

ONLY FOOLS SMOKE AROUND FLAMMABLES OR COMBUSTIBLES.

PRIOR TO LIGHTING UP, CHECK YOUR AREA CAREFULLY.

Tool Box Chat: Burns

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Steam pipes, electrical arc flashes, hot machine components and chemicals are just a few areas where you have exposure to burn injuries.

Most often, a burn happens when someone does not realize a component is hot, or they are not aware of their body’s position to an object.  Take extra time to note these hazards and make a conscious effort to keep away from these hot components.

Your best protection for these exposures is Awareness!
The second line of defense for these injuries is to wear PPE (personal protective equipment).