Types and models
Tank trucks can have a number of configurations according to cargo types. The simplest models are used to transport neutral liquids (e.g. water). These tanks have a single-layer coating made of aluminum and stainless steel. Besides, there is a metal frame installed inside the tank to make it lighter and to increase its firmness. The top manhole is used to fill a tank with liquid and the bottom couplings with locking gates are used to empty a vessel (though some models have special pumps to remove the transported liquid).
Tankers for liquid fuels transportation
This type is the most widespread. As in case of water tank trucks, the container is installed with an inner frame. But since the density of engine fuel is lower than that of water, the capacity of fuel tanks is larger. Fuel belongs to hazardous materials. It’s flammable and highly explosive. Also, it can be exposed to significant thermal expansion and evaporation during its transportation. The containers are equipped with special valves (to stabilize internal pressure) and grounding systems (to eliminate static electricity) and often have mirror surface from the outside to reduce fuel heating. Some containers are designed with several isolated sections to optimize the process of transportation. Thus, different liquids (e.g. petrol, diesel and engine oil) can be carried in one tank at the same time.
Tankers for foodstuff transportation
The containers of such tankers are made of aluminum and noncorrosive steel. Nevertheless used tank semi-trailers for foodstuff should be regularly checked for corrosion inside the tank. If the cargo requires temperature stability, as in case of milk, the container has double shell with thermal insulation in between.
Dry bulk tanks
A dry bulk tank has a cone-shaped end with bottom manholes for unloading. There are models that can bear from 7 to 12 atm of pressure inside a container. To unload such a tank the pneumatic system is used. It empties a container via a pump and forced air with the possibility to shift the cargo immediately to the heights.
This type of tankers is distinguished from others by self-supporting containers that can operate under high pressure. The equipment includes such safety measures as emergency valves, grounding systems and fire precautions. Gas tankers should be inspected by qualified specialists on a regular basis.
Due to the high level of specialization and the variety of operational conditions there are a great number of tank semi-trailers manufacturers in each segment. The common structure of all the models consist of chassis and units of standard semi-trailers – Schmitz, Kögel, Krone, Fruehauf, Lamberet, Grünwald.
Before making a choice of a used tank for sale it’s necessary to check out the most vulnerable points. Firstly, the inner frame of a tank and its coating should be inspected for corrosion. Secondly, pay attention to the leakproofness of the emptying fittings and compare your standards with those, which your clients apply. Thirdly, you need to make sure that the chassis frame is preserved from coiled deformation typical for tank semi-trailers as they are always filled to capacity. And finally, examine the life time of a used tank that constantly operates under pressure and thus has service life limit.