Organic Acid

Organic acid is a hydrocarbon derivative family. They can be flammable and toxic and all are corrosive. In chemistry, there are two general types of acids: organic and inorganic. Inorganic acids do not burn, but they can be oxidizers and support combustion. Some organic acids burn, whereas others do not. If a flammable placard is found on an acid container or the MC 312/DOT 412 acid tanker, it is an organic acid. Organic acids are polar; in fact, of all the hydrocarbon derivatives, they are the most polar. They have both the carbonyl structure CO like the ketones, aldehydes and esters and the OH structure like the alcohol. The formula for a generic organic acid is COOH. One radical is attached and the name comes from the radical with an "ic" added and with the ending word "acid." Acetic acid is formed when a methyl radical is attached to the generic COOH of the organic acid. This does not follow the naming conventions of other derivatives, however, the reasons why are not important in terms of Applied Chemistry. It can be found in varying concentrations from strong, as in glacial acetic acid which is the pure compound (99.8%), to weak solutions known as vinegar. Acetic acid is a clear, colorless liquid with a pungent odor. It is one of the organic acids that are flammable, and are toxic by inhalation and ingestion in higher concentrations, with a TLV of 10 ppm in air. Other types of common organic acids include formic acid, acrylic acid, butric acid and propionic acid.

Organic acids are used in plastics production, in water purification, as solvents and in decalcification. Hydrocarbon and hydrocarbon derivative families all have particular hazards associated with each other. If responders become familiar with the hazards of the family, they will have an idea of the hazards facing them during an incident, because all compounds in a particular family will have similar hazards (Hazardous Materials Chemistry for Emergency Responders).

Flammable Liquid Containers

MC/DOT 306-406 tanker is primarily an atmospheric pressure, non- insulated, flammable liquid container, which is hydrostatically tested to 3 psi (Figure 3.103). Its capacities vary from 2,000 to 9,000 gallons. It generally has an elliptical shape, although some manufacturers do make a round version, and is used to haul gasoline, diesel, ethanol, aviation fuel and other flammable liquids. Materials used to construct these tanks include aluminum, steel or stainless steel. Baffles installed within the container limit product movement during transportation. These tanks may have multiple compartments and may be carrying several different flammable materials.

Specification plates are usually located on the right frame rail of the trailer. Specification plates are small and difficult to read. They may be

MC/DOT 306-406 tanker is primarily an atmospheric pressure, non-insulated, flammable liquid container

Figure 3.103 MC/DOT 306-406 tanker is primarily an atmospheric pressure, non-insulated, flammable liquid container.

of more use during training and preplanning than during an incident. The plate contains information about the type of tank, manufacturer, construction material, date built, design and test pressures and number of compartments and capacities. Specification plates for other bulk tanks contain similar information and are located in the same general area.

Relief valves on 306/406 tanks are spring loaded and remain closed during transportation. Valve operation can be mechanical, pneumatic or hydraulic. All valves are equipped with an automatic heat-activated closure system. This system is usually a fusible link, but could operate by some other means which operates at temperatures up to 250°F. There is also a secondary closure system which is separated from the fill and discharge valves and mounted inside the tank. Manual controls for the secondary system are usually on the left front of the container. This type of tank is unloaded on the bottom. Bottom valves are designed to shear off in the event of a collision of such force that the valve would be damaged.

There may be up to 10 gallons of fuel in the valve and piping system under the tank. Fill openings on top of the tank are protected by manhole covers that are securely closed. Tanks are provided with rollover protection and a safety device that prevents the covers from releasing when excessive internal tank pressure exists. Vacuum and relief vents are located on top of the barrel of the tank or internally. The vacuum vent is set to open at 6 oz of vacuum, and the relief vents open with as little as 1 psi. Both vents are designed to prevent the release of product during a rollover. If mounted on the outside of the tank, valves must be protected from rollover damage.

Some 306/406 tanks have vapor recovery systems in place to prevent vapors from reaching the atmosphere. Bumpers extend 6 in. from any vehicle part, serve to protect the vehicle and provide a method of gauging the impact of an accident on the vehicle. Response personnel can use the information during damage assessment. If the bumper is significantly damaged, the tank's baffles are also likely to have been damaged and their integrity compromised.

MC/DOT 307/407 is a low-pressure tank that is used for the transport of flammable liquids, Class 6.1 poisons (poison liquids) and light corrosives (Figure 3.104). Working pressure in the tank is 25 psi and not greater than 40 psi. Tank capacities range from 2,000 to 8,000 gallons, and they are constructed of aluminum or stainless steel. This tank may be insulated or uninsulated. Insulated tanks have a horseshoe shape when viewed from the rear. Uninsulated tanks are generally round, and some have reinforcing rings similar to the 312/412, but the tank diameter is much larger. Insulated tanks that no longer meet low-pressure specifications are sometimes used to transport molten solids such as asphalt. These materials have temperatures in excess of 300°F and can be a thermal hazard.

Vehicles carrying molten materials are placarded with a FIOT and, in addition, sometimes a miscellaneous hazardous materials designation.

MC/DOT 307/407 is a low-pressure tank that is used for the transport of flammable liquids, Class 6.1 poisons (poison liquids) and light corrosives

Figure 3.104 MC/DOT 307/407 is a low-pressure tank that is used for the transport of flammable liquids, Class 6.1 poisons (poison liquids) and light corrosives.

Valve location and information are the same as for the 306/406. Pressure lines may be present on the 307/407 which contains inert gases that may be injected into the tank to absorb moisture or used to assist in off-loading the product. Pressure vents are installed in the 307/407 tanks to limit the internal pressure to 130% of the maximum allowable working pressure. Vents are pressure activated by a spring-loaded mechanism. Fusible and/ or frangible (breakable) venting may be provided with fusible vents activating at 250°F. Frangible disks are designed to burst at not less than 130% or more than 150% of the maximum allowable working pressure.

Hazmatology Point: DOT/MC 412 acid containers may also be found with flammable corrosive materials carried in highway transportation. Organic acids do burn. So, don't be confused by a red flammable liquid placard on a corrosive tanker. Remember what the container tells you as well as the placard.

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