Disclosed is a mobile instrument assembly comprising: a housing for accommodating one or more components of an instrument; one or more wheels for mobility of the instrument assembly; and a mounting assembly comprising: a support plate that is moveable with respect to the housing between retracted position and one or more extracted positions and that comprises, in its distal end, a pair of protrusions projecting from a surface of the support plate, wherein in the retracted position the support plate is substantially unexposed from the housing, and in each of the one or more extracted positions the support plate extends from the housing to respective extent such that perimeter of the housing and the pair of protrusions define a circular area of respective predefined diameter to allow for mounting a pressure vessel of corresponding size on the support plate between the perimeter of the housing and the pair of protrusions.