USE OF OXY-ACETYLENE UNITS

July 14 2015

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A number of recent incidents relating to the storage, transport and use of cylinders have occurred within WA, some with disastrous consequences to people and property.

Facts about fuel gases:

All fuel gases catch fire easily.  A naked flame is not necessary for ignition, a spark or heat source can set them off.  Read the MSDS that is provided with the gas cylinder and know the contents of cylinders before you use them.

  • Air containing between 4% and 74% hydrogen is explosive.
  • Air containing from 2.6% to 80% acetylene is explosive.
  • At 25 PSI, acetylene is unstable and can explode without an ignition source.

Porous acetone is added to an acetylene cylinder, which safely permits higher compression.

Acetylene is usually compressed to 250 PSI — well beyond its stability point of only 25 PSI.  Therefore the acetone is critical to safety.  Heat deprives acetone of its ability to hold acetylene.  Acetylene cylinders have fusible plugs that will melt at about the boiling point of water.

General Guidelines:

  • Because compressed fuel gases and acetylene are liquid while under pressure, keep the cylinders positioned so that the valve is facing up.  Gas cylinders should always be kept chained in an upright position, irrelevant as to whether they are full or empty.  Cylinders used for welding should be chained on an upright trolley for easy movement.
  • Fuel gases and acetylene are much heavier than air.  In the event of a leak, these gases will tend to sink, relative to the environment.  They will fill depressions in the floor, open toolboxes, and drains, replacing the safe air in lower work areas.
  • If you check for these gases with a gas meter, look in all the low places.  Remember, a concentrated pool of such gas in a low area may be hard to detect.  Meanwhile, you have a fire and explosion hazard .However, hydrogen is 14 times lighter than air, and will rise above normal air.  You could be breathing clean air under an explosive hydrogen blanket and not know it.
  • Handle compressed gas cylinders delicately.  Dropping one on the floor can break the valve, creating a rocket that can easily go through a brick wall while leaving a trail of explosive gas.  If you knock two cylinders together hard, both might explode.
  • If an acetylene valve ever freezes up, thaw it with lukewarm water.  Pour the water over the valve, not the cylinder.
  • Never use a flame to thaw a valve on an acetylene tank.  Doing so is dangerous when using any compressed gas, but it is especially dangerous when acetylene is present.
  • To reduce the likelihood of valve breakage, keep the cap screwed on any cylinder not in use.  Shut off the valve off if you are not using the cylinder, rather than leaving the regulator to act as a valve.
  • Shut off the valve and remove the regulator if you are transporting the cylinder.
  • Never lift a cylinder by the regulator or the valve.
  • Do not wrap hoses tightly.  Exceeding their bend radius will result in a weak hose that may burst in use.
  • Inspect hoses before use.  Replace any that appear cracked.  Replace hoses that have a “blister” or other deformity.
  • Always ensure flashback arrestors are fitted to both ends of hose (torch and regulator/tap end).

When using the equipment:

  • Ensure the area is clear of unnecessary objects and equipment.
  • Elevate leads and hoses.
  • Ensure flashback arrestors are fitted to both cylinder and torch end of hoses.
  • Remove any unnecessary equipment from work area.
  • Ensure all fittings and connections are secured prior to turning cylinder on.
  • Wear appropriate PPE.
  • Ensure other personnel are clear from area and that barricading and/or signage is present to prevent others from entering work space.
  • Conduct visual inspection of all hoses prior to commencement.
  • Ensure cylinders and stand/trolley is secured and on a flat, even surface.
  • Always ensure the cylinders are turned off prior to leaving the work area or the cylinder unattended.

For more information on this safety topic or to book an appointment to discuss any other OHS inquiry, please do not hesitate to contact Safety Solutions WA.