XXVI. Safety Techniques for Research and Development of New High Energy Oxidizers* DENNIS G. NELSON, Product Design Engineer, Decorative Products Loborotory, 3 M Company, St. Poul, Minn.
Editor's Note: Limiting the quanbity of high energy oxidizers t,o be handled in glass apparat,us in the laboratory with protective clothing (leather gloves, leat,her mat, fare shield over safety glasses, and ear plugs) was b a d on extensive tests by the 3M Company. These tests demonstrated that protect,ive dothing would absorb tho momentnm imparted to glass fragments by explosion or detonat,ion of quantities of 0.25 g or less (based on Ihe molecular weight of the particular compo~mdsbhey were investigating). Safely e~igineersa t the 3hI Company cooperate closely with research personnel in the philosophy that any resoarch project ran be carried out without injury to personnel if adequale prersuf.ions are taken, and the design of protective shielding and equipment is based on tests rather than rough nssnmptions.
A considerable background in safety techniques for the characterization and development of new high energy oxidizers has been accumulated by the Contract Ihvelopmeut Laboratory of the 3M Company during the seven year3 the Laboratory has been in existence and working nndor n, series of contracts from the Advance Hesczuch Projects Agency. Uue to the variety and initial uncertainty of the hazards involved h handling energetic solids, liquids and gases, these techniques must necessarily be versatile and comprehensive. The majority of our Contract Devolopmcnt safety techniques are applications of the principles: Safety via Safety via Safety via Ssfoty via Safely via
minint,wizstion. dilution. remolo pruleetiun. simplicity of operation. testing and analysis.
*This paper was presented a t t,he Seventh Annual Explosives Safety Seminar on High Energy Solid Propellants sponsored by the Armed Services Explosives Snfel,y Board and hosted by Patrick Air Force Base at Cocoa Beech, Flnridn on A ~ g n s t26, 1965, and is reprinted with permiasinn.
Safety techniques have been developed for research, devekqment and smallscale produatiuu, as well as complete chemical analysis and testing of high energy oxidieers. hl addition, s eonti~mouscomprehensive safeby program is maintained throughout the area which reviews current projects and sets up safety standards for new projects.
Research Techniques The typical flow of a program ia from research through development and smallscale production. O w project safet,y program is organized in the same manner. The bulk of safety data is scenmulated a t a very smell scale to be later applied Lo larger scale operations. Figure 1 shows R
18/7 Ground Glass Joint
Venturi .Orifice
Dennis G. Nelson ~.w,.ivr.,l 1h.i Baclwlilr of Sr.in,cr, i d \ l i ~ d e r of S c i e ~ min Chernir:nl Gngiuerril~g degrees ft.om the IJnivemity uf Alinnemta, completing his education in 1962. After graduation, Mr. Nebon nmrked as Process Engineer in the Central Research Pilot Plant, of the 3M Company, St. Paul, Minnesota, and in the Contract Development Laboratory, where he was concerned wilh the design and development of processes for handling pilot plant quantities of high energy oxidizers. Since l9fi5, Mr. Nelson has been employed as Product Design Engineer in the Decorative Products Laboratory of the 3M Company.
Fieure 2 shows one of the NMR detection units at 3M. In particular, note the enclosed 1.2 cm thick Plexiglas glove box far the operator's pratectiar during sample injehon, analysis, and withdrawal. This unit is capable of detecting
Figure 1.
Nuclear rnognetic resononce tube.
schematic diagram of n nuclear-magnetic resonance tube, a hasic tool ior oxidizer research a t 311. These tubes are oft,en used for screening reactions by cumhining reactants in the tubes and analysing fur reaction prodncts. A quantity as s m d as 0.2 em3 of liu~lidin this t.nhe wit,h
Figure 2.
Nuclear magnetic rerononce detector.
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... RESERVOIR
-9' wVACUUM ASPIRITOR
7% Tr
314 INCH PLEXlGLASS SHIELDING
1 INCH DlA. PYREX PIPE CAP
'---- ---7 L---
I
I
MAGNETIC STIRRER
Figure 3. 20 ml. real-less reactor.
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iTFk SUP~LV
UP
V[
AIR SUPPLY
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'/? mmole (100-500 mg) of a fluorinecontaining oxidizer. This minute quantily of explosive material, along wit,h the relatively few manip~rlative analytical steps required, make this s, safe and versatile tool for the hasie researcher. Slightly farther along in our researchdevelopment sequence is the 20 ml "sealless" reactor shown in Figwe 3. These small units are useful in extending NhlR data int,o hasie processing information: optimum reaction conditions, conversion rate, 6s well as identification and resolution of sensitive processing steps. The gloss reactor body was made from a st,aodard 2.54 cm Pyrex douhle strength flanged pipe cap. The 2.22 cm Teflon coated magnet and magnetic stirring onit, are also standard commercial items. The Kel-F support rod prevenbs the magnet, from being t,hrown out of position. This unit develops 200-300 rpm and is suitahle far dispersing two-phase liquids, g a b liquid or dilute liquid-solid systems. It,s environmental capabilities are from frill vacuum to 1.4 atmospheres and from - 9 O T to greater than 200°C. The relative size and simplicity of these onit,s make them adaptable to oxidizer processing stndies where relatively little safety data is s v d a h l e . For rapid pr* eessing studies these reactors may be safely placed in series s w h that they are individually barricaded hut still sceefisihle to an operator wearing protective clothing, as shown in Figure 4. I n event of an eqlosion, normally only t,he glass component.. of the system m e destroyed. I n most instances operations may be
L Figure
4.
Operotion
of
multiple
red-less
reoctor.
quickly resumed after replacement oi standard components. The 300 ml stainless steel reactor shown in Figure 5 is the largest scale system still considered in the realm of research a t the Contract Development Lzbhorstmy. The picture shows the reactor housed in its separate barriw.de which can be isolated from the rest of the system. A glass overhead system is still accessible to a11 operator clothed in protective gear.
Figure 5.
300 milliliter reactor.
Analytical Tools for New High Energy Oxidizers Essential to the safe operation of an oxidizer research and development program is a complete set oi analytical tools. Both rapid in-process analyses and supplementary analytical terhniques are required. Probably the most widely used tool for both in-process and supplementary analyses i3 the gas-liquid chromatograph. As with previous devices, the microliter (Continued an page 4444)
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sample size and the few manipulative steps required far GLC analyses make this safe and versatile. A schematic diagram of a special GLC hookup is shown in Figure 6 . This system has been designed so that both identification and isalation/purification of two condensible components is possible. The euclosed 1.27 cm Plexiglas box, appropriate shielding for the quantity of oxidizer involved (normally less t.han 50 mg), protects the operator while allowiug full vision of the operation. The operator is able to monitor his product stream with the chromatograph and then switch the t,hree-way valves from vent to trap when a. desired product ~ e a kappears on the recorder chart. Following isolation in the liquid nitrogen cooled glass traps, a product may be expanded into a separate section of the box where it may he collected into bnlbs or vented. An I.R. gas sample is also possible a t this point. A Berkman AIegachrom Preparative Gas Chrmnittograph, operating on this same general principle, is also available for lamer " scale mtrifieation of samnles, lro to 50 g per day. For development and small-scale productmn facllities, a series of quantitative tools are reqr~ired that can be used remotely. Such a list of simple, versatile measurements that can be made without entering s, bay where a dangerous chemical operation is in progress includes:
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Pressure-volume relationships for gases. "In-line" graduates for liquids. Titrstion systems for chemical reactions. Remote micro-sampling systems for liquids and gases. Figure 7 shows the details of a liquid/gas oxidizer sampling system connected directly to the resctor inside the bay. This system was designed and constructed by 3M personnel far safe, reliable, remote
samples of extremely hazardous reactor charges. The system was designed so that a mezi7num of 1 g of liquid oxidizer could be present in the sample box a t any one time. The liquid sample line is cooled right up to the ssmple box to insure a sample representative of the resctor. Special washers around each of the orifices prevent any damaging shrapnel from escaping the box. Using this device, it is poss~bleto take "in-process" samples a t a. safe level from a reactor containing up to 250 gm of hazardous oxidizers.
FRONT VIEW
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that sro available within the reaction bay
Figure 9.
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Typical reoction boy.
include: hot and cold water, stmm, vacuum, pressure, inert gas, and flwrine. Although process explosions are not frequent at the Contrart Development
Safety
Figure 10.
.. .
Typical operator'> boy.
IdnhornLwy, wo treat "or material as t h w g h explosions occurred every day. Therefore, o w facilities plan for the worst to happen and direct the explosion where i t can do t,heleast damage. Figure 11 shows a twical blast door which ~ r o t e e t sall
any sudden over-pressure to relieve itself where i t can do no harm.
photograph of soch a system and cut before inst,sllation. Shndd at) nneral.inr~
Figure 1 1 .
Figure 12.
Reaction b o y blost door.
Since remote, twit) Imy i:u.ilil.ies of t.he t m e described above are 81, a preminm, they must, be eHiciently utilized. For this purpose the versatile &rt and cable teehnique ha8 been developed a t the Contract D u v e ~ o ~ m e l l tLaboratorv. Usine this system, process equipment for specific a p p l i e r t t i o ~is mounted on portable laboratory carts before transferring to reaction bays, thus expediting effective use of remote facilities. Figure 12 shows n
-
Cart and coble opparolur.
and the next system is wheeled in. I n most instances repairs and/or installations consume only a day or two of bay time. Another concept that is applied whereever possible for safe yet efficient operation is the use of readily available, ensily modified eqnipmenl. For emmple, conventional glassware is wed wherever possible for processing, thus: (Continued on page ,1452)
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Minimizing damaging shrapnel i n r.we of explosion. Allowing rapid replaeemenl of key eqttipment. Similarly, conventional valves, fittings, tubing, and other processing equipment. are used wherever feasible. I n addilion, pmeess equipment and techniques are evolved from simplified systems as the characteristic hazards of particular oridisers are determined. A fourth concept, applied to oxidizer handling is the use of flow proresses to replace batch processes, particdarly where scale-up data is desired. With t,his method, large quantities of oridiaer solutions are never allowed t
