Document dnp6YX6m39b3XX3Lpy5pK01k6

FILE NAME: Trade Publications (TR) DATE: 1939 June DOC#: TR039 DOCUMENT DESCRIPTION: Trade Journal Article - Mechanical-Filter Type of Respirators Charter Member Associated Business Papers C o n c r e t e , with which has been com bined Cement Age, New York, and Concrete Engineering, Cleveland, is devoted to the Proper Use of Concrete and the Manufacture of Cement. Published. Monthly by Concrete Publishing Corporation 400 West Madison Street Chicago, Ulinois Telephone CENtral 8822 Volume 47 June, 1939 Number 6 Norman M. Stineman, Editor J. C. W(TT, Consulting Editor A. C. Bamberger, Assistant Editor Louis Brookraan, Jr., Business Manager L. Moeller, Circulation Manager Harold 0 . Hayes, Promotion Manager Representatives New York City E. Macdonald Bacon 17 West 45th--Room 909 Longacre 3-5260 Detroit Parker & Tarbell 9 Curtis Bldg.. 2842 W. Grand BUd. Madison 1540 San Francisco: Don fiarway Room 1009, 155 Montgomery St. Exbrook 6029 Los Angeles: Don Harvray .&Co. 318 West Ninth Street Tucker 9706 The Cement Mill Edition o f Concrete The Cement Mill Edition oC Concrete is edited exclusively for those interested in the manufacture of portland cement and related products. Its pages are devoted to discussions of plant design, management, operation, production effi ciency, chemical research and control, quarry op eration, progress and news of the industry. The Cement Mill Edition also contains all the material published in the corresponding Regular Edition and so provides news of the uses and merchandising of the materials whose manufacture is discussed in the Mill Edition. The Regular Section furnishes mill operating officials and mill executives valuable points of con tact with the users of the materials they produce. The subscription price is $4.00 a year in the United States and its possessions, and Mexico. One dollar additional for postage in all other countries. Current copies, 50 cents each. Charter M em ber CONTENTS Operation of Bowl Classifier in Conjunction with Slurry Thick ener .................. ....... _....................... - ................................................ 174 Cement Manufacturers Are Turning to Purchased Power .. ___ 176 Predict Further Reductions in Fuel Consumption .................177 P.CJ4. W ins Medallion (or Development of Soil-Cement Road . 173 Dust-Control Equipment Manufacturers Work With Other Groups 173 Find Biq Variation in Grinding Efficiency With Different Ball L oad s......... ............ 173 Mechanical-Filter Type of Respirators ......................................... 180 Determination of M an gan ese................................................................. 181 How Dust Is Controlled With Water Spray . ...... ................... 182 Editorial Discussion .......................................... ... Better Kiln Linings Cutting the Cost of Maintenance Waning Interest in Safety? Construction Keeps Up the Pace . . . . 183 Determination of Potassium and Sodium O x i d e s .........................184 Continued Study of System s Involving Alkalies ...........................185 May Build Cement Plant la Supply Shasta Dam ...................... 183 Mill Equipment ............................. - ............................................... ....... 187 Men and M ills ............................................................................................. 188 Advertisers' Index Page 40 CONCRETE is indexed in INDUSTRIAL ARTS [NDEX. which may be consulted in any Technical or Public Library. Audit Bureau of Circulations C O N C R E T E -- Cement Mill Section -- June. 1939 Copyright. 1939. by Concrete Publishing Corp Page 173  iraajiiM Mechanical -Filter Type of Respirators R e s p ir a t o r s of the mechanicaifilter type are discussed in the final report of the committee on the prevention of silicosis through engineering control, published by the United States Depart ment of Labor as Bulletin No. 21, Part 2. The sections dealing with respirators of the mechanical-filter type are a part of the portion of the report prepared by the subcommittee on personal respiratory protection, of which W. P. Yant is chair man. Other members of the subcommit tee are Philip Drinker and E. C. Meiter. Classification Mechanical-filter type respirators are sub-ciassified in accordance with the con ventional classification of atmospheric particulate matter, namely, dusts, fumes, and mists. This classification of matter embodies variations in physical state and particle size, and consequently the fac tors that have a direct relation to the arresting of the particles with filters, with in the scope of our present knowledge of dust-filtering phenomena and filter mate rials. The objective of the subdivision in accordance with the classification of mat ter is to provide more suitable filters for the particular kind of matter to be dealt with. Owing to similarity of design and op erating principles, the purpose of these three classes of respirators are presented briefly, with a summary discussion of the essential features, uses, and limitations. These respirators are for mechanically generated dusts resulting primarily from the mechanical disintegration of a solid, such as dust produced in the various processes of mining, construction, and manufacturing, and the various indus trial operations, such as drilling, blast ing, crushing, grinding, handling, and processing of rock strata and minerals; abrasive grinding; the handling, screen ing, and use of sand or other pulverized or dusty siliceous materials; stone and granite cutting and all similar operations and processes. Operation of Respirators Mechanical-filter type respirators re move by mechanical or physical filtration the dusts, fumes, or mists of hygienic sig- nificance from the air drawn by the indi vidual's normal inspiration from his surrounding contaminated atmosphere. The usual design of a filter-type respira tor is a half-mask facepiece covering over the nose and mouth, directly connected to a filter element in forms such as a disk, pad. bag, or cylinder; although it may also be a half-mask or full-mask facepiece connected by a breathing tube to a filter element on the chest, back, or even on the head in the form of a cap. The filter elements are usually con structed from specially selected or proc essed paper, cellulose fiber, cloth, or felt materials. The primary principle of dust removal by mechanical filters, appears to be sim ple physical trapping, filtration, or straining. Air laden with dust is passed through mats of fine fibers criss-crossed to form mesh-like entanglements with ex ceedingly small tortuous paths in which the particulate matter is trapped by en tanglement, impingement, and adhesion, by simple screening, or more possible, a combination of these processes. Electro static influences are undoubtedly present, but the extent of their importance has not been determined for filters in present-day Studies of Filtering Efficiencies Studies of comparative filtering effi ciencies of various filter fabrics have shown that both the filtering efficiency and the resistance to air flow increase with continued passage of particulate matter-laden air through the filter. This is the result of deposition of particles with attending reduction in size and plug ging of the paths through the filters. Obviously, a respirator which utilizes simple filtration provides its poorest pro tection and its lowest resistance to in halation (greatest breathing comfortI at the beginning of use; also that its life period is determined by the time required for the plugging to increase the resistance to breathing to a point where it is labori ous and uncomfortable. The basis which has been almost uni versally used in this country in the past for indicating the efficiency of a respira tor filter for removing particulate matter is the percentage of the total suspension in the air drawn through the filter that f| is trapped or retained by the filter, or as commonly expressed, the percentage effi ciency. An efficiency determined in this man ner is influenced by the dust concentra tion, size of dust particles, rate at which the dust-laden air is drawn into the filter, and the interval of the service life of the filter that is tested. For these reasons an efficiency value is meaningless as a meas- '| ure of portection afforded, unless the conditions of the determination represent conditions of usage with respect to the ;J aforementioned variables and influences. Further, the efficiency value determined under even representative conditions is no measure of adequate protection for a particular situation, without considera tion of whether or not the amount of dust represented by the percentage ineffi ciency (10 per cent minus the percentage efficiency) exceeds the amount that can be breathed without harm. It is further evident that a comparison of percentage efficiency values is not a dependable basis for judging the relative efficacy of pro tection of two different filters unless all the conditions of test are identical and the same method (and preferably the same investigator I is used for determin ing the dust. The fundamental basis for judging the suitability of a respirator is whether or not the amount of dust that is unretained or escapes through the filter under con ditions of practical use is below the amount that would be harmful to breathe. This is not related to any general state ment of percentage efficiency. Quarry Blasting Leads to Damage Suit Bl a st in g in a cement company quarry again forms the basis for damage claims in court, fhe defendant in this instance being the Lone Star Ce ment Corporation. The court action is directed against this company's quarry near Dallas. The plaintiff lives on a 25-acre tract adjoin ing the cement company's property. The assertion is made that frequent dynamit ing with heavy charges caused the forma tion of crevices in the earth about the plaintiffs premises, causing his three wells to dry up. In recent months, it is alleged, blasting operations have been carried on in an area from 300 to 500 yards from the home. Damages in the amount of $21,500 are claimed. 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