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Fire and Explosion Hazards The Department of Transportation (DOT) has classified anhydrous methylamines as flammable gases and aqueous methylamines as flammable liquids. In addition to DOT requirements, federal, state, and local ordinances as well as insurance company requirements may apply to the shipping, handling, and storage of methylamines. The recommendations of the National Electrical Code for Class 1 Hazardous Locations7 should be followed. The aqueous methylamines are Class 1B flammable liquids, except 50% MMA, 60% DMA, and 40% TMA, which are Class 1A. OSHA regulations for "Flammable and Combustible Liquids" are contained in Title 29 of the Code of Federal Regulations (CFR) Section 1910.106 and must be followed when handling methylamine solutions. Even dilute methylamine-water solutions will burn and should be treated as flammable liquids. Consequently, water may not be effective on large fires (see Fire Fighting). Methylamine spills, even if not ignited, should be thoroughly diluted with a water spray to minimize the fire hazard by raising the boiling and flash points. All equipment such as moving machinery, vehicles, and methylamine storage tanks and containers must be properly grounded to prevent generation of sparks. Tank cars, tank trucks, and ISO tanks must be grounded prior to unloading. Storage and handling areas should be well ventilated to keep vapor concentrations below the lower explosive limit. (See Flammable limits in Table 1.) Air must be excluded from lines, tanks, and equipment used for the storage and handling of anhydrous methylamines to avoid a fire and explosion hazard. Before initial service and after shutdowns for inspection and maintenance, work systems should be purged with nitrogen. Before inspection or maintenance, lines, tanks, and equipment should always be evacuated and purged free of methylamines with water, steam, or nitrogen. Equipment to be worked on should be disconnected and tested for explosive atmosphere. The equipment and the entire work area should be well ventilated and tested before doing any welding. An evacuation plan should be prepared, because anhydrous methylamines are capable of generating hazardous vapor clouds if released.  TOP Fire Fighting In case of fire, immediately stop the flow of methylamine gas or liquid, provided this can be done with little risk of personal injury. In case of line or equipment ruptures without fire, immediately shut off the anhydrous amine flow to avoid accumulation of large volumes of flammable vapor and the risk of a vapor cloud explosion. Carbon dioxide or dry chemical extinguishers are effective on small fires. Water spray (to dilute and cool) and a polar-solvent, aqueous film forming foam (AFFF) should be used to extinguish large fires. Use water to protect personnel effecting the shutoff and to cool cylinders, tanks, and lines not yet involved in the fire. Depending on circumstances, it may be safer to permit the fire to burn until the flow of anhydrous amine can be stopped. TOPHazardous Chemical Reactions Direct contact of methylamines with mercury may produce an explosive reaction if ammonia also happens to be present in the methylamines. Avoid using instruments containing mercury for measurements and tests on methylamines. Both dimethylamine (DMA) and trimethylamine (TMA)8 will react with a nitrosating agent (e.g., nitrous acid, sodium nitrite, oxides of nitrogen) to form N,N-dimethyl-nitrosamine (DMN), (CH3)2NNO. DMN will form under acid or alkaline conditions, although acid media favor the reaction. DMN is not especially stable in the environment. It is rapidly metabolized by animals and is decomposed in sunlight with a half-life of about 30 min.9 While there is no direct evidence that DMN is carcinogenic in humans, it has been shown to be carcinogenic to several animal species. Thus, care should be taken that dimethylamine or trimethylamine are not inadvertently stored, contacted, or mixed with a nitrosating agent such as sodium nitrite. DMN is regulated as a cancer-suspect agent by the Occupational Safety and Health Administration (OSHA) under 29 CFR 1910.1016 (N-Nitrosodimethylamine).6 TOPCorrosion Hazards The methylamines are corrosive to copper, copper alloys, galvanized metal, magnesium, and zinc alloys. Iron and steel are satisfactory materials of construction for handling both the anhydrous methylamines and their aqueous solutions. TOPEngineering Control of Hazards Proper design of storage and handling systems from point of delivery to point of consumption and proper operating and maintenance procedures are essential to safeguard against serious accidents. Contact us for design, operating and maintenance recommendations. TOPTransportation Emergencies In the event of an accident or emergency involving DuPont methylamines in transit anywhere in the continental United States, make a toll-free telephone call (day or night) to the Chemical Manufacturers Association's Chemical Transportation Emergency Center ("CHEMTREC") in Washington, DC at: (800) 424-9300 In District of Columbia only, call: (800) 483-7616 The information specialist on duty will ask the name and location of the caller, the name of the shipper, the product, the shipping point and destination, what happened, nature of any injuries, weather conditions, proximity to populated areas, and such other questions as may be necessary to define the extent of the emergency. He/she will then give the caller recommendations for controlling the emergency situation until the shipper's specialist can relay help. "CHEMTREC" will immediately advise DuPont of the emergency, and one of our specialists will get in touch with the caller promptly. In Canada, call: DuPont Canada, Inc. Maitland, Ontario (613) 348-3616 TOPUnloading and Transfer of Anhydrous Methylamines DuPont ships anhydrous methylamines in tank cars, tank trucks, and ISO tanks. Anhydrous methylamines are flammable gases (see Personal Safety and First Aid). Tank cars and tank trucks of anhydrous methylamines may be unloaded by pump, compressor, or nitrogen pressure. DuPont tank truck shipments are unloaded by tractor mounted compressor. OSHA requirements (29 CFR 1910.101b, Compressed Gases) state that the in-plant handling, storage, and utilization of all compressed gases in cylinders, portable tanks, rail tank cars, or motor vehicle cargo tanks shall be in accordance with the Compressed Gas Association Pamphlet P-1-1965.10 Contact us for details for unloading tank cars and trucks by either pump, compressor, or nitrogen pressure. TOPStorage of Anhydrous Methylamines Anhydrous methylamines are stored in totally enclosed systems that exclude air. Tank Location New storage tanks should be located in accordance with NFPA requirements and in separate clearly defined areas that can be controlled in emergencies and be accessible to emergency personnel. The location should minimize the possibility of damage from external corrosion, mechanical activity, vehicles, fire, or explosion. The layout must include provisions for more than one escape route in the event of an emergency. Storage Tank Storage tank capacity of at least 1-1/2 times the normal shipment is recommended to provide adequate inventory protection. Tank car shipments usually range from 10,000-30,000 gallons. Tanks should never be filled shell-full, because of the high coefficient of expansion of methylamines. Leave at least 10% of the volume of the tank as vapor space for adequate protection. Tanks containing anhydrous methylamines should conform to the latest ASME Boiler and Pressure Vessel Code, Section VIII, as well as other local standards for pressure tank construction. A working pressure of 85 psig minimum is suggested. However, if the tank is heated, higher pressures may be encountered and must be specified in the design. Tanks should be hydrostatically tested at one and one-half times the design pressure before being placed in service. Tanks should be designed for full vacuum rating. Tanks are usually located out-of-doors. No insulation is required on anhydrous storage tanks, unless pressure buildup from an outside source of heat is a problem. Dikes, drains, and collection facilities for anhydrous methylamines must conform to federal, state, and local regulations. Consult NFPA Standard No. 30, "Flammable and Combustible Liquids Code." A closed dike sufficient to hold the tank contents may be built. A three-sided dike about 18-in high can be used to divert the tank contents into a safe drainage area or a waste pond. Because methylamines are highly flammable, the entire storage system must be electrically grounded. This includes grounding tank cars and tank trucks by means of portable ground connectors. Piping flanges should be electrically bonded. Grounding efficiency should be tested quarterly by qualified electricians. Overall resistance should not exceed 10 ohms. There should be no threaded fittings between the storage tank and the first isolation valve. Existing threaded fittings should be back-welded. Contact us concerning recommendations for storage tanks, pressure relief systems and associated equipment. TOPUnloading and Transfer of Aqueous Methylamines DuPont ships aqueous methylamines in tank cars and tank trucks. The U.S. Department of Transportation (DOT) classifies aqueous methylamines as flammable liquids. Contact us for recommendations on unloading and transfer of aqueous methylamines. TOPStorage of Methylamine Solutions Storage tanks for aqueous methylamines (except 50% MMA and 60% DMA) should be designed for an operating pressure of 15 psig. Minimum design pressure for tanks containing 50% MMA, 60% DMA, and 40% TMA solution is 35 psig. Steel storage tanks are recommended. Tanks and vessels must be properly vented, taking into account normal breathing requirements, anticipated maximum filling and emptying rates and an emergency relief system in case of external exposure to fire. All vents should be piped to a safe location outside the building, so that flammable vapors will not be trapped by eaves and other obstructions within the building. Tanks should be equipped with a nitrogen blanket. Individual storage tanks of 10,000 gallons or greater capacity should be diked. State or local regulations may require diking of smaller tanks. Consult 29 CFR 1910.106 for applicable OSHA construction requirements for flammable and combustible liquid storage. Detailed recommendations on drainage dikes and walls for aboveground storage tanks appear in NFPA Standard No. 30 "Flammable and Combustible Liquids Code." Bubble type manometers, differential pressure level gauges or armored sight gauges with ball check and shutoff valves (e.g., Penberthy X-500 reflux type glass) may be used to measure the storage tank level. Transfer from storage can be accomplished using a "canned" seal-less pump. A low level or low flow cutoff is required for seal-less pumps, because these pumps are easily damaged if run dry. Centrifugal pumps with a mechanical seal are satisfactory. Tanks, pumps, and lines for TMA solutions should be insulated and heated in areas where freezing of these solutions may occur. Heating may be provided by steam heating panels on the tank and steam tracing of the lines. Temperature controls must be provided to prevent excessive pressure caused by overheating. To minimize the obnoxious odor of methylamines from vents, all vents should pass through an absorber-scrubber or incinerator before discharging to the atmosphere. Minimum atmospheric pollution is achieved by the installation of a vent absorber or incinerator. Storage tanks should be grounded to avoid accumulation of a static charge. See Figure 7 for a satisfactory storage tank arrangement for methylaminewater solutions. Figure 7. Aqueous Methylamines Storage  TOPOn-Site Dilution of Anhydrous Methylamines Many users of aqueous methylamines have installed facilities permitting them to dilute anhydrous amines at their site. This avoids the freight on water shipped with solutions. Attractive savings are often possible through purchase of anhydrous amine rather than the aqueous solution. Diluting anhydrous methylamines produces substantial heat of solution. The necessary heat removal is usually accomplished by an external heat exchanger or by internal cooling coils in the storage tank. A simple, effective arrangement for preparing solutions is shown in Figure 8. This system includes a properly designed aqueous storage tank and a circulation loop through the heat exchanger. Anhydrous methylamine is fed into the circulating line directly upstream of the solution cooler. A temperature sensor after the heat exchanger sounds an alarm and/or shuts off feeds at high temperature. Other operating modes employing similar equipment have also been successfully used. Figure 8. Methylamine Dilution System  Sizing of the storage tank depends on the volume of anhydrous methylamine delivered and the required concentration of the methylamine-water solution. For example, 10,000 gallons of anhydrous dimethylamine (the smallest tank car) dilute to approximately 12,500 gallons of 60% aqueous solution or to approximately 17,500 gallons of 40% aqueous solution. DuPont will assist customers in their design of methylamines dilution facilities. This assistance includes a review of alternate operating modes tailored to the customer's site. For additional information, contact the DuPont Customer Service Center. TOPWaste Disposal Handling Leaks and Spills The potential for accidental leaks and spills of methylamines should be reviewed and plans made in advance for containment, drainage, collection, and disposal. Obey federal, state, and local regulations for reporting releases. Immediate steps should be taken to stop a methylamines leak, provided it can be done without risking personal injury. Water is particularly useful in handling methylamines leaks and spills. Properly applied, water will:
Air Pollution Control The control of air pollution in the manufacture and handling of methylamines is very important. To avoid odors and minor air pollution problems when disconnecting unloading hoses or when disconnecting piping for maintenance, care should be taken to prevent spills of liquid amines. Use nitrogen pressure to blow lines and hoses clear to the storage tank. Then, with the valves shut off, evacuate the lines by vacuum pump, steam jet, or water jet eductor. A running water hose should be available when hoses or pipes are disconnected. The water will promptly absorb vapors and flush away drops of liquid. Decontaminate hoses, piping and accessory equipment by thoroughly flushing with water until no odor remains (see Wastewater below). Four air pollution control methods are currently in use at various locations among the producers and users of methylamines. The most successful and economical method involves the collection of all methylamine vapors into a vent system equipped with an absorber-scrubber unit. When large volumes of amine vapors are absorbed, it is often practical to recover the amines by distillation. Amines can also be recovered by using the absorber effluent as an amine solution. A second method consists of feeding methylamine vapors to a small scrubber column packed with pall rings and using a 5% sulfuric acid solution as the scrubbing medium. The recirculating scrubbing medium is maintained at pH 4 by the periodic addition of acid. When the acid solution becomes saturated with amine sulfate, it is trickled into a waste treatment sewer. Care must be taken that the saturated solution does not run into a heavy concentration of sodium hydroxide or other neutralizing solution that will liberate the amine. Another method disposes of methylamine vapors by catalytic oxidation. A platinum catalyst is used in the presence of air as the oxidizing agent. A preheater must be used to bring the gases to the reaction temperature of approximately 310°C (590°F). The last method consists of flaring the gathered amines with fuel gas. Total destruction of the methylamine vapors is accomplished in a properly designed flare stack. Wastewater Wastewater containing small amounts of methylamines must be disposed of by procedures that comply with federal, state, and local water pollution regulations. Very dilute solutions have been successfully treated in biological oxidation waste treatment systems. It is sometimes economical to recycle or recover amines from scrubber effluents, evacuation systems, or from wastewater collected in washing down spills and leaks. TOPReferences and Notes
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