Document O7OLxmjrKyDn4VDGdDL5eb9M

-Vv-3r*/1 ' y*t*< 1 < hi om ts. of to ier 1 loss *- as i ts is s r 166. i same. rags to tbe rttara ?,[.. h lid* lit* ,tro- tjlcl**1 ' uctof |M4..iina Uvuukm; Dlji wi application can give a definite basis fur llw nclotiMn >! * i*..n:iy (-ict'if,' iW.ern Urge pro duction volume# ore being conlunipUteri. there in -i to rtihKe * factor ut safety ind thereby cut initial cost#. Any red .ction f..m .**t.iA>nhetJ norm* should bu made only with a full understanding of ail the factor* imolv.M, A major flui:r*e*e in a previously ac cepted factor of safety can rarely be mad*:. However, uuerertsue of 10 to ls*,l arc often fea- t liblu and safe. For common designs, vKpvncneMi! designer* ds'vel-.p etaneard stress levels based on accepted safety factors, These fact or* may be euljh*t<J from a variety of sources. The selection of a safety factor is frequently governed by accepted standard des.yn stresses or by municipal or state codes. Uo*'Vvr, many tiinu*, pa rt i* . 1 r i y on mac Nine pa ris and devices* the selection of a safety factor is required in tin* curly tjcii.ii. stages, liy reference and use of the six factors listed* this choice ran ito u.dtin using comprehensive methodical analysis. True safety factors relating the damaging sires* <u the actual design stresses can be established, accurately representing the safety level intended by the designer. JOS Eye Injuries Due to Power Lawn Mowers. U. tiarsky. Arch. Ophthalmol, 6*4, Jb5 (Sept, iVoOj, , Five cases of missile eye injuries due to power lawn mowers are reported, covering a 4-year period beginning September 1955. In J coses* vision was totally lost, The need for safety features In the rotary type power lawn mower is stressed* Public awareness of the eye hatard should be aroused. - - J. Am. Med. Assn, Abets. L"MISCELLANEOUS 1Q& Research in Water Pollution, F, C, Livingstone. Water & Sewage Works 107* 126-123 (Mar. I960). This is a brief report of the research being conducted in o tpecial laboratory for water pollution research of the Department of Scientific and Industrial Research In Great Britain. Tests were mads on a new anionic surface-active material that had been developed by detergent menufaelurers seeking to find a biological soft substance. In trickling filter pilot plants, it was found that about 90% of the new type of detergent was removed as com pared with about 6B% of the material presently being marketed. Owing to the fact that the new laboratory is situated In a community where domestic sewage and industrial wastes can be kept completely separate* precise studies were made of the characteristics and rate of flow of domestic sewage. The laboratory has investigated possible methods of pru-treatment of tannery wastes to removu suspended matter, toxic metals, and sulfide, and also to neu* treble excessive alkalinity. Waele flue gates could be used to form calcium carbonate, to strip out the hydrogun sulfide, and to neutralise alkalinity. The waste gases containing hydro gen sulfide could then be passed through coke-packed filters irrigated with weak tannery wastes. Hydrogen sulfide is absorbed and oxidi/.ud biologically to sulfuric acid, Studies are also being mode of treatment of tannery wu*te hy trickling fillers. Simple v) snides and less stable com plex cyanides may be truated with ferrous sulfate and an alk.ili prior to discharge to a munici pal sewer, Where a higher degree of treatment is needed* chlorine and caustic are used. Al most complete removal of cyaniiliTw** affected from a solution uf NaCN equivalent to 90 mg./ liter HCN at a flow rate of 700 gal,/cn. yd./day, with tempe r.Murcs shove 10*C, - Cond, from Public Health Eng, Absis. j*h.unical Coagulation and Pressure Flotation for Aircraft Oil W.islvs, E. J, Mel hood, wastes Cog, 3^, 4J4-4J7 (Aug. !%0). * The waste flows In the United Alt' Lines MamN nsnvr JUsc *i S*?: i rancisco Inter national Alrpurt originate from numerous cleaning operation* of engines, engine parts, ac cessories and air frame parts a* well as paint stripping. The average workday wastes flow ,29