Proper Operation of Vacuum Based Equipment

1. Use of Personal Protective Equipment

1. Safety glasses, lab coats, and face shields must be utilized when working with or near a vacuum apparatus.
2. A blast shield must be utilized to prevent flying glass or debris resulting from a sudden change in pressure.

2. Use of Proper Tubing and Equipment

1. Always use tubing, glassware, and other equipment that is rated for use with vacuum. Improper use can result in material failure and cause explosion/implosions.
2. Check the glass and tubing regularly for defects/cuts, as these can easily crack/break under vacuum.
3. The exhaust of the vacuum pump must be connected to a fume hood or a scrubbed building exhaust. This is particularly crucial if the vacuum is utilized on a system utilizing corrosive or toxic chemicals.
4. Depending on the experiment and extent of vacuum involved, a guard or protective barrier between the operator and vessel under vacuum should be employed. These can be the same type of barriers used to isolate operators from high-pressure equipment.

3. Traps

1. Always use a trap between the vacuum source (pump) and the apparatus that utilizes the vacuum. The trap protects the expensive vacuum source from damage in case of accidental leaks or material back flow into the vacuum line.
2. The traps also help to prevent vapors/odors from being emitted into the exhaust of the pump.
3. The traps are usually cryostatted using dry ice or liquid-nitrogen baths. Extreme care must be taken while utilizing such cryogenic temperatures, and proper PPE must be used to transfer the coolants in and out of the traps.
4. Since the use of cryogenic fluids (i.e., liquid nitrogen) for cooling purposes can lead to the liquefaction of oxygen, vacuum systems must be under vacuum before and during operation. After achieving the desired vacuum level, the dewar containing the oil trap can be subsequently filled with liquid nitrogen. After completion of the experiment requiring vacuum, while still under vacuum, remove the Dewar flask from the liquid nitrogen filled trap, let the trap warm to room temperature, and slowly open the system to atmospheric pressure.
5. The Dewar flasks themselves are under vacuum and must be handled with utmost precaution as they can instantaneously implode. Always use proper PPE when transporting or working with Dewar flasks.

4. Bleed lines

1. The vacuum lines must be slowly bled before disconnecting from the traps and vacuum source. A sudden change in the pressure stresses the materials and can cause premature fracture and explosions.

5. Glassware coating

1. Glassware larger than 250 mL that is utilized with vacuum equipment must be shrouded with either tape, netting, or a plastic coating to reduce the chance of flying debris, in case of an explosion. This includes traps, dewars, rotary evaporators, and any other glassware maintained under vacuum.