Be aware of atmospheric hazards in confined spaces, cautions Afrox
Many fatalities occur each year while working in confined spaces, with the majority of deaths caused by atmospheric related hazards. “This is one area in the industry that really gets neglected as far as safety is concerned with using oxygen, fuel gases and equipment in confined spaces,” says Afrox Hennie van Rhyn – Application Development Manager - Cutting, Heating and Safety.
A confined space can be defined as an area that has limited or restricted access, or an open vessel or structure that requires ladders, stairs or other means of entrance or exit. Examples of confined spaces are boilers, pipelines, columns (boxes), silos, process vessels, ducts, furnaces, rail tankers, cold boxes, pits, drains, manholes, vaults, chutes and hoppers. Confined spaces are generally opened when inspection, cleaning or maintenance needs to be performed, such as pre-heating for a specific welding application, inspecting of welds, repairing trays in a distillation column, replacing linings in a storage tank, or repairing leaks in a heat exchanger, boiler or chiller coils in a rail car.
Extreme caution must be taken before any oxy/fuel or welding application is used in any confined space, advises van Rhyn. “Oxygen deficiency occurs at less than 19.5 percent. This will cause difficulty in breathing that could lead to loss of consciousness and even death. Oxygen enrichment greater than 23 percent will accelerate combustion in the presence of an open flame or other source of ignitions. Any fuel gas leak could create an explosive mixture with air in the confined space, and any ignition or open flame will cause serious explosions.
“Afrox strongly recommends that only fuel gases with a density less than air should be used for any pre-heating, cutting, brazing or soldering applications in confined spaces, such as acetylene. Acetylene features a particular property of high value with a density of 1.095 kg/m3 (at 15 degrees C/1 bar). This means acetylene is about 10% lighter than air. If it should escape inadvertently, it will rise and disappear in the atmosphere. Any fuel gas mixed with air could form an explosive mixture, while fuel gases that are heavier than air will sink to the lowest level and increase the risk of asphyxiation,” explains van Rhyn.
Using acetylene for hot work processes means higher cutting speeds, faster start-up and pre-heating, concentrated heat input and therefore significant time saving. New technology enables the use of acetylene with air (no oxygen) for pre-heating processes which is totally safe, and eliminating the risk pf any flashbacks occurring. Acetylene and air burners are particularly suitable for pre-heating in welding or for the drying of the region near the weld or heat affected zone. These flame gases are very dry in comparison with other fuel gases like LPG. As acetylene has approximately 30% less moisture content, the possibility of hydrogen induced cracking in the weld or heat affected zone is reduced.
Customers performing any hot work processes in a confined space must ensure that all the relevant permit requirements are in place and conduct risk assessments. Afrox’s safety specialists are able to assist customers with conducting detailed risk assessments and issue risk assessment reports with immediate recommendations. For further information, contact Afrox on cell: +27 (0) 79 883 5716.
Issued by: Serendipity Events, Promotions & Exhibitions
On behalf of: AFROX
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Client contact: Hennie van Rhyn – Application Development Manager - Cutting, Heating and Safety.
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