This Bachelor’s thesis was made for Air Liquide Finland’s Raahe production unit. The aim of the thesis was to plan a pressure vessel test for an ASU5- air gas plant. The first periodic inspection to this plant will be done in the coming summer. Another aim was to plan a pressure test that will be done four years later. The pressure test design was done in writing. After that the plan was drawn to flow charts, which describe the closed and opened valves and equipment. The pressure test was performed simultaneously. Safety valves which are related to the process had to be lo-cated and based on this, do the table which ease the survey.

This thesis is based on pressure equipment law which specifies the date and type of inspection for pressure equipment. The work also studied the limits of the registration for pressure equip-ment. After this pressure equipment law was adapted to the ASU5- air gas plant. All inspections cannot be done to every equipment. The reasons for it have been presented with a possible al-ternative inspection, too.

The result of the thesis was a clear instruction for inspections. For pressure equipment, it was also found an applicable type of inspection, which can be done to these types of pressure equip-ments. Further research for this work could be to adapt a method that is approved. This system allows to do a pressure test of safety valves while the plant is running. This would prevent the defrosting of the plant, which could decrease the production so low that it isn't enough for the needs of Ruukki Oyj. This method could also be adapted to other plants to be avoided the de-frosting stoppage.