The interior of rail tank cars must be cleaned out on a regular basis.
Cleaning is required for a variety of reasons: switching out the content of the tank, maintenance that must be performed on the tank or periodic tank inspections. Standard methods used to clean tank cars include cold- or hot-water pressure washing, high-flow spray ball, high-flow rotating nozzles, robotic arms, low-pressure or high-pressure steam, chemical injection with steam and steam/rinse combinations, among others.
Cold-water pressure washing flushes the interior of the tank car, but does not provide a complete cleaning when used as the only method. High-pressure cold water alone will not remove all oily or sticky substances that adhere to the inside/liner of the tank car. It also produces excessive wastewater runoff that must be disposed of properly. Most importantly, using a high-pressure washer requires entry into the confined space of the tank car, which carries safety risks.
Heat is essential for properly cleaning most products out of rail tank cars. Using low-pressure steam is the preferred method for cleaning the interior of these cars. For some products, steam alone will clean and sanitize the tank, but a chemical injection using steam or a high-pressure rinse may still be needed for removing more difficult products.
There are many advantages to using steam as part of the cleaning process. Steam emulsifies temperature-sensitive products, allowing the remaining product to drain out of the bottom outlet valve with minimal added water. Steam opens the pores of the steel and heats the product, so residue and oily substances drain off of the surface.
Steam expansion also removes dangerous fumes from inside the tank car. When water turns to steam, it expands by 1,517 times its normal volume at 212 degrees Fahrenheit. This expansion displaces the oxygen and fumes inside the tank. After the steam displaces the fumes and the tank cools, it can be tested to ensure safe entry. Steam can also sanitize the inside of the car by heating the metal surfaces to 180 degrees Fahrenheit or more to meet specific product standards or Kosher requirements. After the tank is thoroughly steamed, the metal of the tank car liner is free of residue, the risk of asphyxiation and explosion are gone, and the car is safe to enter for final rinse, maintenance or inspection.
Mobile steam generators provide a safe, easy and efficient way to clean rail tank cars at remote locations. Low-pressure steam from a mobile steam generator is safe for the operator and tank car, and in most cases does not require a licensed boiler operator. Using low-pressure steam from a mobile unit brings the cleaning power of steam so that it does not take extra time to transport the cars to a dedicated cleaning facility. Mobile trailer units can be transported next to railcars, and depending on the size of the steam generator, multiple tank cars can be cleaned simultaneously. Once completely cleaned, the steam generator can be relocated to the next set of railcars. These turnkey steam generators are placed inside enclosed, insulated highway trailers for use year-round.
Some facilities utilize a high-pressure boiler for cleaning operations. A high-pressure system has some advantages, such as requiring smaller steam lines to move the steam from facility to railcar. However, a high-pressure boiler requires additional safety precautions. A facility using a high-pressure boiler is often required to have a certified boiler operator on-site. In addition to safety concerns for operators, the extreme temperatures produced by high-pressure boilers could also damage the interior of the cars.
In summary, cleaning rail tank cars with steam from a low-pressure steam generator removes the residue inside tank cars, including any residue in the pores of the steel. Mobile low-pressure steam generators use less water, can remove dangerous fumes and ignition sources, and can accomplish complete cleaning next to the cars rather than transporting the cars to a dedicated cleaning facility. Once cleaning is complete using a mobile steam unit, the cars are ready for the next load, maintenance or inspection.
For information about mobile low-pressure steam generators for tank car cleaning, visit www.sioux.com or call (605) 763-3333.
