Liquid cargoes, which must be kept under constant pressure in accordance with their technological requirements, are carried in pressure cisterns. During their shipping in tankers, such loads remain under continuous pressure control. Pressure tank cupolas, which are used for the placement of transportable liquid freights, have special wall thickness. These pressure autocisterns are also equipped with special filters, valves, breathers, pipes and couplings, which allow compressed air or gas supply to pressure tank  semi trailers after the freight loading and pressure control during the hauling process. Manufactured pressure cistern undergo overpressure testing and have appropriate certificates regarding pressure test verification. Pressure tank trucks weigh more than non-pressure ones.