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in the Chemical iaboratory
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Edited by NORMAN V . STEERE, 140 Melbourne Ave., S.E. Minneapolis, Minn. 554 14
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XCI. An Investigation of High Impact Body Shields* G. N. QUAM, Professor of Chemistry Emeritus, Research and Development Division ond JAMES SHEA, Mechanic, De~artmentof Chemistry. .. ~illonov&~ " i v e r s i t ~ Villanova, , Pa.
Many kinds of bench and suspended shields are available or known. The windows may he: (a) I/cin. laminated glass; ( b ) combination of '/&-in. laminated glass ilnd '/s-in. polycarbonate; ( c ) combination of 'Icin. acrylic and l/rin. polycarbonate; and ( 4 ) combination of '/r and 'Irin. polycarhonate. Plastics other than palyearbonate and acrylic are or have been used in similar srrangements. Simulated laboratory explosions (I) have shown laminated glass to be 8. "one blast" window while (b), (c), and (d) above may withytand several moderate lahoratofy explosion impacts. In our present i~~vestigatian a controlled blast of glass missiles from a glass missile "cannon" (B) showed similar results under better control. In regolar course laboratory experimeniations we may keep the explosion i m ~ a c ta t a low level bv workine with s m d l quantit,ies, hut removal of Gckage lots, for example, of dangerous chemicds
from a storeroom or a laboratory may involve very high impacts ( 3 ) . Frequently in research procedures a compound may establish a reputation of considerable stability over a long period of experimentation-then suddenly without warning a "runaway" violent reaction may occur. Some compounds may develop secondary compounds which combine to form a. very sensit,ive mixture. The following casehistories illustrate these observations. Case I. Daily Mail (Britain) June 1966 An a m p o ~ ~ lofe boron trichloride exploded causing the death of a chemical engmeer and serious injury to a physicist. The compound had been considered stable under the experimental conditions.
Case II. M.C.A. Case History #I164 Recovery of an overage supply of potassium resulted in two deaths. The formation of KO1 in the defective contziner was considered the cause of the violent explosion. To meet the requirements of high impact shields is the purpose of our current study. To evaluate shield windows we chose to use 22-caliber high-speed short hullets for fixed impacts (approximately 80 ft,/lh). We believe this gives s, reasonably wide margin of safety. Our aim is to reduce laboratory injnries to zero.
Figure 2. lmpoct tert of combined lmminoted ond polycorbonate window.
and caused t,he l/,in. acrylic to splinter and flake a t the point of impact (Figure 3). A custom-built suspended shield (4) was provided with a double polycarbonate window, I/&. in front and '/&-in. on the apparatus side. The "22 short" fired from the apparatus side penetrated the '/gin. window ilnd caused a slight dent in the '/,-in. window (Figure 4).
EXPERIMENTAL Failures described above eliminated Iaminated glass and acrylic sheets fromfurther
EVALUATIONS OF SOME CURRENTLY MANUFACTURED AND CUSTOM-BUILT BODY SHIELDS
Figwe I .
Lominoted gloss impact test.
*This investigation was supporbed by PHS Research Grant E C 00007-iNational Institute for Ocmpatiunal Safety and Health).
In an early invesligation (1) the '/,-in. laminated glass window was found to withstand but one simulated laboratory explosion impact. A 2 2 - c d sbort bullet penetrated the window as shown in Figore 1. A modified '/,-in. lsminated g l m shield has been reinforced with s. '/gin. polycarbonate liner on the apparatus side. The 22-csl. short bullet penetrated the polycsrbonate and then shabtered the laminated glass, as shown in Figure 2. Another shield of ~irnilarconstmetinn had a '/
