Vacuum systems include those activities involving mechanical vacuum pumps, building vacuum systems, water aspirators, or steam aspirators. Work with vacuum systems poses a substantial danger of injury to the operator from flying glass shrapnel released during an implosion. Other hazards may include: The toxicity of the chemicals in the vacuum system Fire following breakage of a flask containing flammable solvents Toxicity from the mercury in manometers and gauges Over- or under-pressurization arising with thermal conductivity gauges Electric shock with hot cathode ionization systems. Operational Practices Vacuum Apparatus Vessels used in vacuum operations shall be protected with suitable relief valves (vacuum breaker). A protective shield shall be placed around evacuated systems. “Fish net” or electrical tape shall be wrapped around all glassware under reduced pressure. PPE for laboratorians shall include safety glasses or goggles AND face shields when working with evacuated systems or setting up such systems. The vacuum system shall be been arranged to allow the equipment to be moved without transmitting strain to the neck of the flask; flasks are to be supported from below as well as by their necks. The vacuum apparatus must be well out of the way of traffic to avoid being struck inadvertently. Belt-driven mechanical pumps shall be equipped with protective guards to enclose the moving belts (machine guarding). Capture of Contaminants Each vacuum system used for solvent distillation operations shall be protected by a suitable trapping device (cold trap, filter, liquid trap) with a backflow check valve. Water, solvents, and corrosive gases shall be trapped and not allowed to be drawn into the building vacuum (house) system. When mechanical vacuum pumps are used with volatile substances, the input line to the pump shall be fitted with a cold trap to minimize the amount of volatile materials entering the pump and dissolving in the oil. Use pump oil that is appropriate for the contaminant such as Fomblin® when working with corrosives or other materials that are not compatible with hydrocarbon based oils. If particulates could contaminate a vacuum line (e.g., from an inert atmosphere dry box or glove box), a HEPA filter shall be installed. If pump oil becomes contaminated, it shall be drained and changed to prevent the exhaust of chemicals into room air. Used pump oil shall be labeled Used Oil and disposed of through GT EHS. Records of pump use shall be maintained for general-purpose lab pumps in order to forestall cross-contamination or reactive chemical incompatibility problems. The exhaust from evacuation of volatile, toxic, or corrosive materials shall be vented to an air exhaust system such as a chemical fume hood or local exhaust duct. Vessels Glass vessels used in conjunction with the vacuum system should be checked with polarized light for cracks, scratches, or etching each time the vessel is used. At minimum, a visual inspection will be conducted. Dewar flasks shall be wrapped with tape or enclosed in wooden or metal containers. Reduced pressure must never applied to flat-bottomed flasks unless they have been designed for this purpose. Vacuum desiccators shall be made of borosilicate/Pyrex glass or plastic. Evacuated dessicators must never be carried or moved. Dessicators shall not be opened until atmospheric pressure has been restored. If rotary evaporators are used, increases in rotation speed and application of vacuum to the flask are gradual. ‹ Working with High Pressure Systems Up Distillations ›
