Prudent Practices in the Laboratory Handling and Disposal of Chemicals (1995) / Chapter Skim
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Working with Laboratory Equipment
Working with Laboratory Equipment
Pages 107-138
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From page 107... ...
~ . : Working with Laboratory ~_11~1 1 41 1L 6.A INTRODUCTION 6.B WORKING WITH WATER-COOLED EQUIPMENT 6.C WORKING WITH ELECTRICALLY POWERED LABORATORY EQUIPMENT 6.C.1 General Principles 6.C.1.1 Outlet Receptacles 6.C.1.2 Wiring 6.C.1.3 General Precautions for Working with Electrical Equipment 6.C.1.4 Personal Safety Techniques for Use with Electrical Equipment 6.C.1.5 Additional Safety Techniques for Eauinment Using High Current car High Voltage 6.C.2 Vacuum Pumps 6.C.3 Refrigerators and Freezers 6.C.4 Stirring and Mixing Devices 6.C.5 Heating Devices 6.C.6.1 Ultrasonicators 6.C.6.2 Centrifuges 6.C.6.3 Electrical Instruments 6.C.7 Electromagnetic Radiation Hazards 6.C.7.1 Visible, Ultraviolet, and Infrared Laser Light Sources 6.C.7.2 Radio-frequency and Microwave Sources 6.C.7.3 X-rays, E-beams, and Sealed Sources 6.C.7.4 Miscellaneous Physical Hazards Presented by Electrically Powered Equipment 6.C.7.4.1 Magnetic Fields 6.C.7.4.2 Rotating Equipment and Moving Parts 6.C.7.4.3 Cutting and Puncturing Tools 6.C.7.4.4 Noise Extremes 6.C.7.4.5 Slips, Trips, and Falls 6.C.7.4.6 Ergonomics and Lifting 6.D WORKING WITH COMPRESSED GASES 6.D.1 Compressed Gas Cylinders 6.D.1.1 Identification of Contents 109 109 109 109 109 110 110 112 1 ~ Cal 112 112 113 114 114 6.C.5.1 Ovens 116 6.C.5.2 Hot Plates 116 6.C.5.3 Heating Mantles 116 6.C.5.4 Oil, Salt, and Sand Baths 117 6.C.5.5 Hot Air Baths and Tube Furnaces 117 6.C.5.6 Heat Guns 118 6.C.5.7 Microwave Ovens 118 6.C.6 Ultrasonicators, Centrifuges, and Other Electrical Equipment 118 118 119 119 119 119 119 119 c~ · C~ _ 107 120 120 120 120 120 120 121 121 121 121
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From page 108... ...
108 PRUDENT PRACTICES IN THE LABORATORY: HANDLING AND DISPOSAL OF CHEMICALS 6.D.1.2 Handling and Use 6.D.1.2.1 Preventing and Controlling Leaks 6.D.1.2.2 Pressure Regulators 6.D.1.2.3 Flammable Gases 6.D.1.2.4 Empty Cylinders 6.D.2 Other Equipment Used with Compressed Gases 6.D.2.1 Records, Inspection, and Testing 6.D.2.2 Assembly and Operation 6.D.2.2.1 Pressure-Relief Devices 6.D.2.2.2 Pressure Gauges 6.D.2.2.3 Glass Equipment 6.D.2.2.4 Plastic Equipment 6.D.2.2.5 Piping, Tubing, and Fittings 6.D.2.2.6 Teflon Tape Applications 6.E WORKING WITH ~GH/LOW PRESSURES AND TEMPERAIIJRES 6.E.1 Pressure Vessels 6.E.1.1 Records, Inspection, and Testing 6.E.1.2 Pressure Reactions in Glass Equipment 6.E.2 Liquefied Gases and Cryogenic Liquids 6.E.2.1 Cold Traps and Cold Baths 6.E.2.2 Selection of Low-Temperature Equipment 6.E.2.3 Cryogenic Lines and Supercritical Fluids Vacuum Work and Apparatus 6.E.3.1 Glass Vessels 6.E.3.2 Dewar Flasks 6.E.3.3 Desiccators 6.E.3.4 Rotary Evaporators 6.E.3.5 Assembly of Vacuum Apparatus 6.F USING PERSONAL PROTECTIVE, SAFETY, AND EMERGENCY EQUIPMENT 6.F.1 Personal Protective Equipment and Apparel 6.F.1.1 Personal Clothing 6.F.1.2 Foot Protection 6.F.1.3 Eye and Face Protection 6.F.1.4 Hand Protection 6.F.2 Safety and Emergency Equipment 6.F.2.1 Spill Control Kits and Cleanup 6.F.2.2 Safety Shields 6.F.2.3 Fire Safety Equipment 6.F.2.3.1 Fire Extinguishers 6.F.2.3.2 Heat and Smoke Detectors 6.F.2.3.3 Fire Hoses 6.F.2.3.4 Automatic Fire-Extinguishing Systems 6.F.2.4 Respiratory Protective Equipment 6.F.2.4.1 Types of Respirators 6.F.2.4.2 Procedures and Training 6.F.2.4.3 Inspections 6.F.2.5 Safety Showers and Eyewash Fountains 6.F.2.5.1 Safety Showers 6.F.2.5.2 Eyewash Fountains 6.F.2.6 Storage and Inspection of Emergency Equipment 6.G EMERGENCY PROCEDURES 122 122 123 123 124 124 124 124 125 125 126 126 126 126 126 126 127 127 128 129 129 130 130 130 130 131 131 131 131 131 131 132 132 132 133 133 133 134 134 134 134 135 135 135 136 136 136 136 136 137 137
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From page 109... ...
Electrically powered equipment found in the laboratory includes fluid and vacuum pumps, lasers, power supplies, both electrophoresis and electrochemical apparatus, x-ray equipment, stirrers, hot plates, heating mantles, and, more recently, microwave ovens and ultrasonicators. Attention must be paid to both the mechanical and the electrical hazards inherent in these devices.
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From page 110... ...
This location prevents the production of electrical sparks inside the hood when a device is plugged in or disconnected, and it also allows a laboratory worker to disconnect electrical devices from outside the hood in case of an accident. Cords should not dangle outside the hood in such a way that they can accidentally be pulled out of their receptacles or tripped over.
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From page 111... ...
DOC, 1993) or air motors instead of series-wound motors that use carbon brushes, such as those generally used in vacuum pumps, mechanical shakers, stirring motors, magnetic stirrers, and rotary evaporators.
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From page 112... ...
However, the distillation of less-volatile substances, removal of final traces of solvents, and some other operations that require pressures lower than those obtainable with a water aspirator are normally performed with a mechanical vacuum pump. The suction line from the system to the vacuum pump should be fitted with a cold trap to collect volatile substances from the system and to minimize the amount of material that enters the vacuum pump and dissolves in the pump oil.
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From page 113... ...
Such guards are particularly important for pumps installed on portable carts or tops of benches where laboratory workers might accidentally entangle clothing or fingers in the moving belt, but they are not necessary for enclosed pumps. 6.C.3 Refrigerators and Freezers The potential hazards posed by laboratory refrigerators involve vapors from the contents, the possible presence of incompatible chemicals, and spillage.
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From page 114... ...
These include ovens, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, hot-air guns, and microwave ovens. The use of steam-heated devices rather than electrically heated devices is generally preferred whenever temperatures of 100 °C or less are required.
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From page 115... ...
Resistance devices used to heat oil baths should not contain bare wires. Laboratory heating devices should be used with a variable autotransformer to control the input voltage by supplying some fraction of the total line voltage, typically 110 V, to the heating element of the device.
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From page 116... ...
As previously noted, only hot plates that have completely enclosed heating elements should be used in laboratories. Although almost all laboratory hot plates now sold meet this criterion, many older ones pose an electrical spark hazard arising from either the on-off switch located on the hot plate, the bimetallic thermostat used to regulate the temperature, or both.
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From page 117... ...
For the same reason, oil baths left unattended should be fitted with thermal sensing devices that will turn off the electric power if the bath overheats. These baths should be heated by an enclosed heating element, such as a knife heater, a tubular immersion heater such as a Calrod@, or its equivalent.
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From page 118... ...
These baths should be constructed so that the heating element is completely enclosed and the connection to the air bath from the variable autotransformer is both mechanically and electrically secure. These baths can be constructed from metal, ceramic, or, less desirably, glass vessels.
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From page 119... ...
If laboratory workers do undertake repairs, the cord should always be unplugged before any disassembly begins. However, certain adjustments can be made only when the instrument is connected to a power source.
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From page 120... ...
Laboratory workers must know how to shut down equipment TABLE 6.1 Summary of Magnetic Field Effects in the event of an emergency; must enclose or shield hazardous parts, such as belts, chains, gears, and pulleys, with appropriate guards; and must not wear loose clothing, jewelry, or unrestrained long hair around machinery.
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From page 121... ...
For example, liquefied gases such as propane and ammonia will exert their own vapor pressure as long as any liquid remains in the cylinder and the critical temperature is not exceeded. Prudent procedures for the use of compressed gas cylinders in the laboratory include attention to appropriate purchase, especially selecting the smallest cylinder compatible with the need, as well as proper transportation and storage, identification of contents, handling and use, and marking and return of the empty cylinder.
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From page 122... ...
Compressed gas cylinders should be secured firmly at all times. A clamp and belt or chain, securing the cylinder between "waist" and "shoulder" to a wall, are generally suitable for this purpose.
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From page 123... ...
If a leak at the cylinder valve handle cannot be remedied by tightening a valve gland or a packing nut, emergency action should be taken and the supplier should be notified. Laboratory workers should never attempt to repair a leak at the junction of the cylinder valve and the cylinder or at the safety device; rather, they should consult with the supplier for instructions.
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From page 124... ...
Testing the entire assembled apparatus with soap solution and air or nitrogen pressure to the maximum allowable working pressure of the weakest section of the assembled apparatus can usually detect leaks at threaded joints, packings, and valves. Before any pressure equipment is altered, repaired, stored, or shipped, it should be vented, and all toxic, flammable, or other hazardous material removed completely so it can be handled safely.
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From page 125... ...
Experiments involving highly reactive materials that might explode may also require the use of special pressure-relief devices and may need to be operated at a fraction of the permissible working pressure of the system. Examples of pressure-relief devices include the rupture-disk type used with closed-system vessels and the spring-loaded safety valves used with vessels for transferring liquefied gases.
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From page 126... ...
Laboratory workers should ensure that equipment for operalions using pressure vessels is appropriately selected, properly labeled and installed, and protected by pressure-relief and necessary control devices. Vessels must be strong enough to withstand the stresses encountered at the intended operating pressures and temperatures.
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From page 127... ...
Laboratory workers are strongly advised to consult an expert on high-pressure work as they design, build, and operate a high-pressure process. Finally, extreme care should be exercised when disassembling pressure equipment for repair, modification, or decommissioning.
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From page 128... ...
. Liquid nitrogen, helium, and argon, and slush mixtures of dry ice with isopropanol are the materials most commonly used in cold traps to condense volatile vapors from a system.
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From page 129... ...
Dry ice and liquefied gases used in refrigerant baths should always be open to the atmosphere. They should never be used in closed systems, where they may develop uncontrolled and dangerously high pressures.
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From page 130... ...
When the potential for such a problem exists, a water aspirator with a solvent collection device and a trap with a check valve installed between the water aspirator and the apparatus, to prevent water from being drawn back into the apparatus, should be used as the vacuum source. Mechanical vacuum pumps should be protected by cold traps, and their exhausts should be vented to an exhaust hood or to the outside of the building.
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From page 131... ...
This attitude begins with wearing appropriate apparel and using proper eye, face, hand, and foot protection when working with hazardous chemicals. It is the responsibility of the institution to provide appropriate safety and emergency equipment for laboratory workers and for emergency personnel.
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From page 132... ...
Full-face shields with throat protection and safety glasses with side shields should be used when handling explosive or highly hazardous chemicals. If work in the laboratory could involve exposure to lasers, ultraviolet light, infrared light, or intense visible light, specialized eye protection should be worn.
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From page 133... ...
These creams should be used only to supplement the protection offered by personal equipment. 6.F.2 Safety and Emergency Equipment Safety equipment, including spill control kits, safety shields, fire safety equipment, respirators, safety showers and eyewash fountains, and emergency equipment should be available in well-marked, highly visible locations in all chemical laboratories.
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From page 134... ...
Because of the potential risks involved in using water around chemicals, laboratory workers should refrain from using fire hoses except in extreme emergencies. Otherwise, such use should be reserved for trained firefighters.
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From page 135... ...
When effective engineering controls are not possible, suitable respiratory protection should be used after proper training. Respiratory protection may be needed in carrying out an experimental procedure, in dispensing or handling hazardous chemicals, in responding to a chemical spill or release in cleanup decontamination, or in hazardous waste handling.
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From page 136... ...
Every laboratory worker should know where the safety showers are located in the work area and should learn how to use them. Safety showers should be tested routinely to ensure that the valve is operable and to remove any debris in the system.
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From page 137... ...
The examiner should look for signs of deterioration or wear of rubber parts, harness, and hardware and make certain that the apparatus is clean and free of visible contamination. · Safety showers and eyewash fountains should be examined visually and their mechanical function should be tested.
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