Tank vehicles, cleaning

Tank vehicle cleaning and inspection operations frequently can be improved by better methods and supervision. Handling and warehousing of drummed and packaged goods have been upgraded by modern methods, but education, supervision and control of the human element is still a substantial challenge. 

The material used for the investigation was obtained from Volkswagen Golf and Passat vehicles, which have employed plastic fuel tanks for some 10 years. The time required for tank removal, cleaning, and elimination of tank components, made either of metal or a plastic other than HDPE, averaged some 5 min 30 sec. At a labour cost of DM 45/h this implies some DM 4.2 for recovery of a fuel tank 3nelding 3.8 kg of HDPE with, at a price of about DM 1.8/kg for secondary HDPE, a nominal value of DM 6.9. 

No premix is needed in the Kady mill. The vehicle is fed into the tank, the motor is started, and the pigments are added at a relatively fast rate. The mill is allowed to run for about 15-45 min until the required degree of dispersion is attained. The dispersion is rapid, the mill is easily cleaned, but pigment throughput is usually low. Since the mill depends on Impact for dispersion, the more easily dispersed pigments are reserved for this mill. 

The incident was a near-miss—the vapors did not light off, and no one was hurt. (There were, however, economic costs associated with cleaning out the tank safely.) However, the potential for a serious event was high—the vapors could have ignited at a vehicle engine or exhaust manifold. The flame front could then have entered the tank and caused a large explosion. 

The tank of the delivery vehicle should always be clean, before loading bituminous materials. Small proportions of foreign matter, usually petrol, diesel, oils and so on, directly influence bitumen s properties and, hence, the bituminous mixture and the quality of pavement. Furthermore, safety is affected since the presence of these substances may lower the flash point of the bitumen substantially. It has been found that 0.1% of diesel in bitumen can decrease the flash point up to 28°C and increase the bitumen penetration by 10 units (Asphalt Institute MS-4 2007). In case of transporting bitumen emulsions, the presence of foreign substances will certainly affect the breaking time of the emulsion. 

Concerns that have emerged from the last decades of the twentieth century relating to safety and environmental issues have led to further expansion of the applications of CF, including the production of natural gas tanks for vehicles due to their low carbon dioxide emissions and clean exhaust gas, and blades for wind-power generators (Ogawa, 2000). 

Pressurized air should never be used for unloading. Butadiene should be unloaded through a closed system using a vapor return line and compressor, or by use of pressurized inert gas (such as nitrogen). When all the liquid is removed from the transport vehicle, valves should be closed and no air permitted to enter the tank. Butadiene transport vehicles should not be used for any other product unless the tank has been cleaned, freed of gas, and purged of air. See the monograph on butadiene in Part III for additional information. 

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