Prudent Practices in the Laboratory Handling and Management of Chemical Hazards, Updated Version (2011) / Chapter Skim
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7 Working with Laboratory Equipment
7 Working with Laboratory Equipment
Pages 147-182
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From page 147... ...
7 Working with Laboratory Equipment 7.A INTRODUCTION 149 7.B WORKING WITH WATER-COOLED EQUIPMENT 149 7.C WORKING WITH ELECTRICALLY POWERED LABORATORY EQUIPMENT 149 7.C.1 General Principles 149 7.C.1.1 Outlet Receptacles 150 7.C.1.2 Wiring 150 7.C.1.3 General Precautions for Working with Electrical Equipment 151 7.C.1.4 Personal Safety Techniques for Use with Electrical Equipment 152 7.C.1.5 Additional Safety Techniques for Equipment Using High Current or High Voltage 152 7.C.2 Vacuum Pumps 153 7.C.3 Refrigerators and Freezers 153 7.C.4 Stirring and Mixing Devices 154 7.C.5 Heating Devices 154 7.C.5.1 Ovens 156 7.C.5.2 Hot Plates 157 7.C.5.3 Heating Mantles 157 7.C.5.4 Oil, Salt, or Sand Baths 158 7.C.5.5 Hot Air Baths and Tube Furnaces 158 7.C.5.6 Heat Guns 159 7.C.5.7 Microwave Ovens 159 7.C.6 Distillation 159 7.C.6.1 Solvent Stills 159 7.C.6.2 Column Purification Systems or "Push Stills" 160 7.C.7 Ultrasonicators, Centrifuges, and Other Electrical Equipment 161 7.C.7.1 Ultrasonicators 161 7.C.7.2 Centrifuges 161 7.C.7.3 Electrical Instruments 162 7.C.8 Electromagnetic Radiation Hazards 162 7.C.8.1 Visible, Ultraviolet, and Infrared Laser Light Sources 162 7.C.8.2 Radio-Frequency and Microwave Sources 162 7.C.8.3 X-Rays, Electron Beams, and Sealed Sources 162 7.C.8.4 Miscellaneous Physical Hazards Presented by Electrically Powered Equipment 164 7.D WORKING WITH COMPRESSED GASES 164 7.D.1 Compressed Gas Cylinders 164 7.D.1.1 Identification of Contents 165 7.D.2 Equipment Used with Compressed Gases 165 7.D.2.1 Records, Inspection, and Testing 165 7.D.2.2 Assembly and Operation 165 147
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From page 148... ...
148 PRUDENT PRACTICES IN THE LABORATORY 7.D.3 Handling and Use of Gas Cylinders 168 7.D.3.1 Preventing and Controlling Leaks 169 7.D.3.2 Pressure Regulators 169 7.D.3.3 Flammable Gases 170 7.E WORKING WITH HIGH OR LOW PRESSURES AND TEMPERATURES 170 7.E.1 Pressure Vessels 170 7.E.1.1 Records, Inspection, and Testing 170 7.E.1.2 Pressure Reactions in Glass Equipment 171 7.E.2 Liquefied Gases and Cryogenic Liquids 172 7.E.2.1 Cold Traps and Cold Baths 173 7.E.2.2 Selection of Low-Temperature Equipment 174 7.E.2.3 Cryogenic Lines and Supercritical Fluids 174 7.E.3 Vacuum Work and Apparatus 174 7.E.3.1 Glass Vessels 174 7.E.3.2 Dewar Flasks 174 7.E.3.3 Desiccators 175 7.E.3.4 Rotary Evaporators 175 7.E.3.5 Assembly of Vacuum Apparatus 175 7.F USING PERSONAL PROTECTIVE, SAFETY, AND EMERGENCY EQUIPMENT 175 7.F.1 Personal Protective Equipment and Apparel 175 7.F.1.1 Protective Clothing 175 7.F.1.2 Foot Protection 175 7.F.1.3 Eye and Face Protection 176 7.F.1.4 Hand Protection 176 7.F.2 Safety and Emergency Equipment 176 7.F.2.1 Spill Control Kits and Cleanup 177 7.F.2.2 Safety Shields 177 7.F.2.3 Fire Safety Equipment 177 7.F.2.4 Respiratory Protective Equipment 178 7.F.2.5 Safety Showers and Eyewash Units 180 7.F.2.6 Storage and Inspection of Emergency Equipment 180 7.G EMERGENCY PROCEDURES 181
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From page 149... ...
. Trained laboratory personnel should also strong flow pulse or sink drains are blocked by an ac consult state and local codes and regulations, which cumulation of extraneous material.
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From page 150... ...
Trained laboratory person- Locate receptacles that provide electric power for nel can significantly reduce hazards and dangerous operations in laboratory chemical hoods outside the behavior by following some basic principles and hood. This location prevents the production of electritechniques: checking and rechecking outlet recep- cal sparks inside the chemical hood when a device is tacles (section 7.C.1.1)
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From page 151... ...
The owners of does not protect the trained laboratory personnel from such facilities are responsible for ensuring that all electrocution but does reduce the risk of fire. electrical equipment and fixtures meet these codes and regulations.
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From page 152... ...
to handle equipment that is plugged in, be certain • If a person is in contact with a live electrical hands are dry and, if feasible, wear nonconductive conductor, disconnect the power source before gloves and shoes with insulated soles. removing the person from the contact and admin • Ensure that all laboratory personnel know the lo- istering first aid.
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From page 153... ...
Normally the vacuum source is a cold trap inside a refrigerator to search for a particular sample. cooled with dry ice or liquid nitrogen.
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From page 154... ...
tors for solvent removal. These devices are often used The use of steam-heated devices rather than electrically in laboratory chemical hoods, and they must be oper- heated devices is generally preferred whenever temated such that they do not provide an ignition source peratures of 100 °C or less are required.
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From page 155... ...
Because these or laboratory personnel from accidentally touching potential hazards exist, whenever laboratory personnel use a the wire carrying the electric current. This type of con- variable autotransformer with an unknown wiring scheme, struction minimizes the risk of electric shock and of prudent practice assumes that either of the output lines caraccidentally producing an electrical spark near a flam- ries a potential of 110 V and is capable of delivering a lethal mable liquid or vapor (see Chapter 6, section 6.G.1)
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From page 156... ...
Similar control devices are available that troller, responding to the false temperature drop will turn off the electric power if the flow of cooling reading, continued to supply power to the bath, water through a condenser is stopped owing to the loss resulting in overheating and fire. of water pressure or loosening of the water supply hose to a condenser.
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From page 157... ...
However, in practice, such modifications are After removal of all visible mercury, monitor the heated difficult to incorporate into many of the hot plates now oven in a laboratory chemical hood until the mercury in use. Warn laboratory personnel of the spark hazard vapor concentration drops below the threshold limit associated with these hot plates.
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From page 158... ...
This immediately and replaced with a cooling bath without practice protects the laboratory personnel against an having to readjust the clamps holding the equipment electric shock if the heating element inside the mantle setup. Never support a bath on an iron ring because of short-circuits against the metal case.
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From page 159... ...
Microwave ovens can heat material open containers of flammable liquids, in environments (e.g., solidified agar) so quickly that, even though the where appreciable concentrations of flammable vapors container lid is loosened to accommodate expansion, may be present, or in laboratory chemical hoods used the lid can seat upward against the threads and the to remove flammable vapors.
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From page 160... ...
, a second column of alumnia is Always set up stills in a chemical hood. Although used along with a dry nitrogen or argon purge to facilimany procedures suggest allowing the process to run tate oxygen removal.
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From page 161... ...
Ensure that they are hung properly. 7.C.7 Ultrasonicators, Centrifuges, and • Ensure that the lid is closed before starting the Other Electrical Equipment centrifuge.
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From page 162... ...
If trained laboratory personnel do undertake repairs, always unplug the cord before any disassembly begins. However, certain adjustments require connection to a 7.C.8.3 X-Rays, Electron Beams, and Sealed power source, and appropriate protective measures and Sources due diligence are required when working on energized X-rays and electron beams (E-beams)
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From page 163... ...
Trained Destruction or corruption of magnetic storage 20 laboratory personnel must know how to safely shut material down equipment in the event of an emergency; must Saturation of transformers and amplifiers 50 enclose or shield hazardous parts, such as belts, chains, SOURCE: Adapted from Site Planning Guide for Superconducting gears, and pulleys, with appropriate guards; and must NMR Systems (Bruker BioSpin GmbH, 2008b) and General Safety not wear loose-fitting clothing, jewelry, or unrestrained Considerations for the Installation and Operation of Superconducting long hair around machinery with moving parts.
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From page 164... ...
has established codes that ing step stools, ladders, and lifts to reach high areas, specify the materials to be used for the construction and walking along corridors and on stairways at a and the capacities, test procedures, and service presdeliberate pace. Floors that are likely to be wet, for sures of the cylinders in which compressed gases are example around ice, dry ice, or liquid nitrogen dispens transported.
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From page 165... ...
Similarly, the relief courage trained laboratory personnel to lease the pressure -- the pressure at which the safety system (e.g., cylinders and, in essence, only purchase the contents. rupture disk or safety vent)
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From page 166... ...
Inspect all tubing frequently and re- the spring-loaded safety valves used with vessels for place when necessary. transferring liquefied gases.
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From page 167... ...
The reaction solids, etc., avoiding spray into the work- resulting limited factor of safety makes careful gauge space in the event of a release and minimizing the selection and use mandatory and often dictates the use potential of a fire and aiding clean up. The relief of accessory protective equipment.
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From page 168... ...
blies for use with specific compressed gases is available from the supplier. To minimize undesirable connec 7.D.2.2.8 eflon Tape Applications T tions that may result in a hazard, use only CGA stan Use teflon tape on tapered pipe thread where the dard combinations of valves and fittings in compressed seal is formed in the thread area.
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From page 169... ...
. If toxic gas is leaking from a cylinder, washers or gaskets, check the materials of construction donning of protective equipment and evacuation of before the regulator is fitted.
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From page 170... ...
For many experiments, of freeze-up and corrosion problems, regulators used extremes of both pressure and temperature, such as with carbon dioxide gas must have special internal reactions at elevated temperatures and pressures and design features and be made of special materials. work with cryogenic liquids and high vacuum, must be Regulators used with oxidizing agents must be cleaned managed simultaneously.
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From page 171... ...
Trained laboratory personnel are ized. On applying a wrench to the fitting, the flexstrongly advised to consult an expert on high-pressure ible hose disconnected completely and whipped work as they design, build, and operate a high-pres- off the regulator, striking the individual on the sure process.
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From page 172... ...
The sealed glass tubes can be placed either inside it can be condensed out of the atmosphere during the pieces of brass or iron pipe capped at one end with use of these lower boiling-point cryogenic liquids. a pipe cap or in an autoclave containing some of the With the use of liquid hydrogen particularly, explosive reaction solvent (to equalize the pressure inside and conditions may develop.
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From page 173... ...
Trained laboratory personnel are gloves when handling dry ice. Do not lower the head also encouraged to wear long sleeves when handling into a dry ice chest because carbon dioxide is heavier cryogenic fluids.
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From page 174... ...
The same explosion hazard Use an explosion shield and a full-face shield to protect can be created if liquid nitrogen is used to cool a flam- laboratory personnel, and carry the procedure out in mable mixture that is exposed to air. Caution must a laboratory chemical hood.
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From page 175... ...
made of Pyrex or similar glass, completely enclosed in a shield or wrapped with friction tape in a grid pat 7.F.1 Personal Protective Equipment and tern that leaves the contents visible and at the same Apparel time guards against flying glass if the vessel implodes. Plastic (e.g., polycarbonate)
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From page 176... ...
7.F.2 Safety and Emergency Equipment Safety equipment, including spill control kits, safety 7.F.1.4 Hand Protection shields, fire safety equipment, respirators, safety show Use gloves that are appropriate to the degree and ers and eyewash units, and emergency equipment type of hazard. At all times pay special attention to the should be available in well-marked highly visible hands and any skin that is likely to be exposed to haz- locations in all chemical laboratories.
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From page 177... ...
Specific procedures for cleaning up spills vary de 7.F.2.3 Fire Safety Equipment pending on the location of the accident, the amount and physical properties of the spilled material, the de- 7.F.2.3.1 ire Extinguishers F gree and type of toxicity, and the training of the person- All chemical laboratories should have carbon dioxnel involved. A typical cleanup kit may be a container ide and dry chemical fire extinguishers.
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From page 178... ...
A number of other more automatic fire-extinguishing system is in place, inform specialized types of extinguishers are available for laboratory personnel of its presence and advise them of unusual fire hazard situations. All trained laboratory any safety precautions required in connection with its personnel are responsible for knowing the location, op- use (e.g., evacuation before a carbon dioxide total-flood eration, and limitations of the fire extinguishers in the system is activated, to avoid asphyxiation)
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From page 179... ...
the provisions of OSHA's Respi is important. Replacing the cartridge after each ratory Protection Standard (which indicates the use ensures the maximum available exposure need for a safety harness and an escape system time for each new use.
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From page 180... ...
, and Use them for immediate first-aid treatment of chemi- • chemical spill cleanup kits and spill control equipcal splashes and for extinguishing clothing fires. All ment (e.g., spill pillows, booms, shoe covers, and trained laboratory personnel should know where the a 55-gal drum in which to collect sorbed material)
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From page 181... ...
promptly. Be aware that many organizations limit • Examine safety showers and eyewash units vi- fire extinguisher use to designated trained person sually and test their mechanical function.
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