This graduate thesis is based on the analysis of the quality management systems in the welding of pressure equipment. The theoretical part of this thesis gives an analysis of the quality assurance system of pressure equipment through all steps in production. As pressure equipment presents a potential source of danger, critical places in the system that can affect product integrity and quality are identified. This takes into consideration influence of the stresses that occur, the materials that are being used and all factors that need to consider during construction and production. Since welding is the most common method of production, a quality control needs to be carried out before, during and after welding, and a comparison of nondestructive test requirements for unfired pressure vessels and water-tube boilers are presented. In the experimental part, thanks to the company Monter- Strojarske montaže d.d., the analysis of the quality assurance system on the real product, the pressure vessel ED-241, was carried out. In order for the manufacturer to establish the fulfillment of the requirements in accordant with the relevant standard on which the pressure vessel was designed and with the requirements of the pressure equipment directive, a safety analysis was carried out. Finally, the instructions for welding, anticorrosion protection and hydrostatic test are presented. The experimental work contains a number of data relating to the technical documentation which must enable the conformity assessment of the pressure equipment with relevant requirements for commissioning.