Scenario
Art and Ray were sent to the Tank Farm to replace bearings on an isopropanol pump located on the alcohol pad. They found the bearings "frozen" in place. When Art told his supervisor they would have to pull the pump, he said, "Let's see if we can't pull those bearings in place; we've got too much downtime in that area already." First they tried to loosen the bearings with a bearing heater, a powerful electric heat gun, without success. Ray then called a welder who heated the casing with her torch until the bearings came free. While the welder was there, the supervisor had her weld brackets on an I-beam so he could install a "Warning-Flammable Area" sign.
A piece of slag from the welding rolled into a nearby pile of damp wooden shims. After the mechanics and the welder left the area, the wood began to smolder and then burst into flames. At the same time an operator began to charge ethanol to his unit by remote computer control. The ethanol transfer pump started to leak around its mechanical seal creating a pool of alcohol on the pad. The vapors from the pool traveled towards the fire, which then ignited them.
The fire spread instantly to the pump and grew in intensity as the heat increased the size of the leak. The tank farm operator saw the fire, sounded the alarm and attacked the fire with an extinguisher. She was overcome by vapors and fell unconscious. Quick response by the in-plant emergency response team saved her life and stopped a potentially disastrous fire.
Task
Think about the incident and, based on your experience, answer the following questions.
What could have been done to prevent this fire?
Importance of Welding Location
Weld or cut only in locations specifically designated for this purpose unless you have obtained approval of the job and have taken the necessary precautions to eliminate fire and explosion hazards.
Do not weld in any location outside the shop unless you take the necessary precautions and get authorization. Before you weld in any compartment, room, tank, or adjacent space which contains or which has contained flammable or explosive materials, liquids, or vapors, make sure they are:
- made safe,
- tested, and
- proclaimed safe.
Restrictions
Allow welding or cutting only in areas that are or have been made "fire safe."
- When you cannot move work practically, as in most construction work, the area must be made safe by removing combustibles or protecting combustibles from ignition sources.
- If you cannot remove fire hazards, install suitable guards, or take special precautions as discussed below, then welding and cutting should not be performed.
- If you cannot move the object to be welded or cut and if not all the fire hazards can be removed, use guards to confine the heat, sparks, and slag, and to protect the immovable fire hazards.
Prohibited Areas
Do not permit welding or cutting in the following situations:
- in areas not authorized by management
- in sprinklered buildings while such protection is impaired
- in the presence of explosive atmospheres (mixtures of flammable gases, vapors, liquids, or dust with air)
- inside uncleaned or improperly prepared tanks or equipment which have previously contained such explosive atmospheres or have the potential for explosive atmospheres
- in areas with an accumulation of combustible dust
- in areas near the storage of large quantities of exposed, readily ignitable materials such as bulk sulfur, baled paper, or cotton
Special Precautions for Fire Prevention
Relocation of combustibles: If possible, relocate all combustibles at least 35 feet (10.7 m) from the work site. When relocation is not possible:
- protect combustibles with flame-proofed covers, or
- shield combustibles with metal or asbestos guards or curtains.
Floors: Where combustible materials such as paper clippings, wood shavings, or textile fibers are on the floor, sweep the floor clean within a radius of 35 feet (10.7 m). In addition:
- If floors are combustible, keep them wet, covered with damp sand, or protected by fire-resistant shields.
- Protect workers operating arc welding or cutting equipment from shock where floors have been wet down.
Hot Work
Hot work is any work that involves burning, welding, using fire- or spark-producing tools or that produces a source of ignition. Follow these general best practices below for hot work.
- Do not perform hot work where flammable vapors or combustible materials exist.
- Relocate work and equipment outside of the hazardous areas, when possible.
- Make suitable fire-extinguishing equipment immediately available in a state or readiness. The equipment may consist of pails of water, buckets of sand, hose, or portable extinguishers dependent upon the nature and quantity of the combustible material exposed.
- When performing hot work, assign a fire watch to guard.
Fire Watch: A worker designated as the "Fire Watch" is required whenever welding or cutting is performed in locations where other than a minor fire might develop, or any of the following conditions exist:
- Appreciable combustible material, in building construction or contents, closer than 35 feet (10.7 m) to the point of operation.
- Appreciable combustibles are more than 35 feet (10.7 m) away but are easily ignited by sparks.
- Wall or floor openings within a 35-foot (10.7 m) radius expose combustible material in adjacent areas including concealed spaces in walls or floors.
- Combustible materials are adjacent to the opposite side of metal partitions, walls, ceilings, or roofs and are likely to be ignited by conduction or radiation.
Fire Watch Duties: The duties of a qualified fire watch include:
- They must have fire-extinguishing equipment readily available.
- Train them in how to use fire-extinguishing equipment.
- They must be familiar with facilities for sounding an alarm in the event of fire.
- They must watch for fires in all exposed areas, try to extinguish them only when obviously within the capacity of the equipment available, or otherwise sound the alarm.
- They must maintain a fire watch for at least a half hour after completion of welding or cutting operations to detect and extinguish possible smoldering fires.
Welding or Cutting Containers
Used containers: Do not weld, cut, or perform other hot work on used drums, barrels, tanks or other containers until you clean them.
- Clean them so thoroughly to make absolutely certain there are no flammable materials present or any substances such as greases, tars, acids, or other materials which when subjected to heat, might produce flammable or toxic vapors.
- Disconnect or blanket any pipelines or connections to the drum or vessel.
Venting and purging: Vent all hollow spaces, cavities or containers to permit air or gases to escape before preheating, cutting or welding. You should purge with inert gas.