September 29 - October 3, 2014
How should surface preparation be conducted in non-sparking atmospheres?
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Aldrin Cordovez of Kuwait Oil Company on
October 9, 2014:
If the area where you are working requires no sparks allowed, the most suitable type of surface preparation is wet-abrasive blasting, preferably using garnet as abrasive. Alternatively, ultra high pressure water jetting may be considered.
M. Halliwell of Thurber Engineering Ltd. on
October 8, 2014:
Forgive my ignorance here....I do not usually work on the technical aspects of coatings (usually the environmental aspects of the same jobs)....but would dry ice blasting (get rid of the spark source) or atmospheric inerting (get rid of the non-spark atmosphere) be options?
gilbert urma of HHIC-phil on
October 7, 2014:
Water jetting, if appropriate to the area and the surface preparation grade, does not create sparks that can lead to an explosion.
Gavin Gooden of Blast-One on
October 3, 2014:
The sparks produced by blasting are called “cold sparks," meaning they are caused by friction and you are more likely to have a problem with static electricity.
We refer to the report done by Thornton Laboratories, Shell Research Ltd, UK, and other studies that have examined the occurrence of sparks produced during abrasive blasting.
All studies have shown that abrasive blasting using compressed air as the propellant produces "cold sparks," which are incapable of igniting hazardous combustible atmospheres. These studies have been done using different abrasives such as copper slag and steel grit (Thornton/Shell UK), as well as silica sand (Bradley, National Safety Council Congress, USA).
Chemically, Garnet and copper slag are both inert silicates, containing iron and aluminum in different proportions. Copper slag has a higher iron content while garnet has more aluminum. However, sparks are the result of friction and not material chemical composition. Smaller particles produce less friction than coarse particles, which explains why there are only smaller sparks when using garnet at 30/60 mesh, compared to a coarser copper slag of 12/40 Mesh. Obviously, because of the high iron content in steel grit, it will produce a higher intensity spark.
Two common abrasives used in explosive atmospheres are a natural garnet mineral abrasive or a bicarb soda abrasive.
OM PRAKASH JAT of self emplyed on
October 3, 2014:
Prior to starting surface preparation, especially in confined spaces, such as vessels, stacks, and tanks, we have to check and confirm there are no toxic gases through gladder test tube, air ventilation, and have a hole watcher, fireman, and in-out attendent to be 100% sure there are no life-threatening hazards. Scaffolding also must be checked prior to use. Using power tool cleaning or blasting with metallic abrasive increases the danger of working in confined spaces.After all precautions are taken, we can start surface preparation.
Francis Goss of Weserwind Offshore Construction on
October 2, 2014:
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Hello, I am assuming that the danger of explosion has to do with the mixture of chemical fumes and oxygen. In a confined space, for example, a large tank, there may be chemical remains on the surface you will be working on. These must be removed. Ventilation alone is not the answer. Be careful! Gather all necessary information possible about the chemical. Inform your local or state officials. Let them decide how the removal/cleaning should be done. After the cleaning, let them decide when it is safe to work. This process will probably cost you a lot more money. But please don’t put a price tag on the life that could be lost just to save a few dollars.
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