Document mm4EpxdgXNE3KxVvygJVe63k0

-35- FUME OR DOST PRODUCED BT ARC WELDING (Continued) Material Being Electrode Size of Particles Welded Used Electrode Per cu. ft. Characteristics of Dust Particles. (Sizes and Per centages Estimated) Welding 2" Ring on 1" Mild ;Steel Boiler Plate Inside Booth. Fleetweld Coated 3/16" 27,662,976 All particles less than 2 microns. 70# round, opaque; 30# slightly angular, crystal line. Countless number of black particles, reddish brown' smudge. Mild Steel Scrap Plates Inside Booth. Stainweld A Coated 5/32" 2,605,440 All particles black opaque, 2 microns or less in size. Ka2S Steel Inside Booth. Stainweld A Coated 5/32" 12,460,800 About 80# angular opaque, 2 microns or less; 20# slight ly angular crystalline, 5 microns or less. Countless number black particles, brownish grey smudge. The U.S.Navy recently conducted some extensive tests with coated electrodes, and found that the quantity of dust or fumes developed while welding on galvanised steel plate was greater than when bare steel plates were used and the dust remain ed in suspension for far longer periods of time. It was also found that the average sire of the dust particles was 0.27 microns and that there were 130,000 par ticles under four microns diameter per cubio centimeter. Quoting the Wavy report: "It is apparent that considerable quantities of dust are found in any arc welding operation. The dust formed when operating on plain mild steel or corrosion resisting steel is largely derived from the flux coating on the eleotrodes, as is shown by the composition of these dusts". What Physiological Effect on Welders is Produced by The Use of Coated Electrodes. According to a study made by Doctors A. T. Doig and A. P. G. McLaughlin on lungs of Electrio Arc Welders (Lanoet - V. 20j 771 - 775 (April 4, 1936)), defi nite pulmonary lesions whio'h gave rise to striking X-ray changes in the appearance of the lungs were found in welders which had breathed the dust or fume from coated electrodes. Quoting Doctors Doig and McLaughlin: "The electrodes or welding rods which contain a core of metal and an outer covering are consumed gradually by the heat generated (about 1500C.) during the welding operation. The metal in the core of the rod becomes molten and, assisted by the flux contained in the covering, spreads over the surface of the metal which is being welded. The fume is therefore made up of the volatilised constituents of the coverings of the rods together with fine particles of oxidised metal, usually in the form of iron oxides. In addition the fumes probably contain gases suoh as nitrogen peroxide and osone which are formed by the action of an electrio spark on the air. The composition of the coverings of the electrodes or welding rods becomes, in the circumstances, a matter of some importance. Many substances, all of which we do not propose to enumerate, are used. The basis of the majority of the coverings is sodium silicate which acts as a flux. Again, the EK001525