SOLVENT CABINETS

Hasenpusch, W., CLB Chem. Labor, Biotech., 1995, 46(5), 212, 214 Explosions in laboratory refrigerators are fairly common, often because volatile solvents such as ether are below their upper flammable limit in a refrigerator, but not in a solvent cabinet. The domestic refrigerators usually employed are far from flame-proofed. This review discusses causes and recommends precautions. 

AMMONIUM PEROXODISULFATE SODIUM SULFIDE EARTHQUAKE, SOLVENT CABINETS... 

Organics separated by class Solvents separated in solvent cabinets Oversized bottles on bottom shelf... 

Extrusion Processes. Polymer solutions are converted into fibers by extmsion. The dry-extmsion process, also called dry spinning, is primarily used for acetate and triacetate. In this operation, a solution of polymer in a volatile solvent is forced through a number of parallel orifices (spinneret) into a cabinet of warm air the fibers are formed by evaporation of the solvent. In wet extmsion, a polymer solution is forced through a spinneret into a Hquid that coagulates the filaments and removes the solvent. In melt extmsion, molten polymer is forced through a multihole die (pack) into air, which cools the strands into filaments. 

Before entering the spinneret, the extmsion solution, also caUed a dope, is heated to reduce the viscosity and provide some of the heat necessary to flash the solvent from the extmded filament, A thermostaticaUy controUed heat exchanger may be used to heat the dope, or the filter—spinneret assembly may be located inside the heated extmsion cabinet. 

The heated polymer solution emerges as filaments from the spinneret into a column of warm air. Instantaneous loss of solvent from the surface of the filament causes a soHd skin to form over the stiU-Hquid interior. As the filament is heated by the warm air, more solvent evaporates. More than 80% of the solvent can be removed during a brief residence time of less than 1 s in the hot air column. The air column or cabinet height is 2—8 m, depending on the extent of drying required and the extmsion speed. The air flow may be concurrent or countercurrent to the direction of fiber movement. The fiber properties are contingent on the solvent-removal rate, and precise air flow and temperature control are necessary. 

Provisions of the Clean Air Act have resulted in the regulation of certain wood finishing appHcations. Residential and Institutional Furniture and Kitchen Cabinet Industries are under regulations which specify the amount and types of solvent emissions allowed. The si2e and location of a finishing facihty determine the extent of the effect stemming from the regulations. 

The nitrogen supply used to purge the metal cabinet was also used to blow out the dryers. When the iiiirngcn supply pressure fell occasionally, solvent from the dryers entered ihrtmgh leaking valves into the nitrogen supply line,, ind into the metal cabinet. Low nitrogen pressure allowed air diffusion into the cabinet. 

Bee.iusa the nitrogen pressure was unreliable, it was difficult to maintain a pressure of 0.5 inch water gauge in the metal cabinet. Workers complained that the safety switch kept isolating the electricity supply, so an electrician reduced the setpoint first to 0.25-inch and then to zero, thus effeciocly bypassing the switch. The setpoint could not be seen unless the cover of the switch was removed and the electrician told no one what he had done. The workers though I lie wa,s a good electrician who had prevented spurious trips. Solvent and air leaked into the cabinet, as ilready described, and the next time the electricity supply was switched there was an explosion. 

Then I realized there was more going on. I went to work in my husband s office, which, unfortunately, was over a kitchen cabinet shop. They used a lot of solvents, and the fumes came into our office. I began to get really sick, and I phoned up an allergist for an appointment. I was told they wouldn t give me an appointment because it sounded like I was chemically sensitive and there was no cure for that. So I said to myself, I ll find a cure ... 

Small quantities [1 gal (4 I) or less] of flammable or combustible paints, solvents, or cleaning materials, including aerosol cans, should be stored in approved flammable liquid storage cabinets. Large quantities [more than 1 gal (4 I)] of these materials should be stored in separate, remote, or fire-rated... 

---