Pressure vessel (in conformance with the regulations of the Federal Republic of Germany). Vessels in which because of the method of operation there is or can be an operating pressure either greater than 0.1 bar or smaller than -0.2 bar (Pressure vessel regulation of 27 February 1980, Section 3.) Pressure vessels must be built and operated in conformance with section 4 of the pressure vessel regulation in accordance with the generally valid rules of engineering (and the AD Code). It is necessary to fulfill the requirements on construction, design, production, calculation and documentation as laid down in the pressure vessel regulation. Pressure vessels can also be designed in conformance with other regulations, e.g. ASME VIII. Further reading: Pressure vessel regulation, AD Code, ASME VIII.