TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: A gap is not formed between the horizontally adjacent rail elements or only a very small gap having a dimension of 0-5 mm, is formed between the horizontally adjacent rail elements. The pivoting angle depending on average diameter (5) of the tubular cylindrical container wall and axial effective length of the rail element, is 1-25 degrees , where the actual pivoting angle depending on thickness of the container wall (34) exhibits a deviation of calculated pivoting angle of plus minus 1-10%. The rail elements of the upper- and the lower rail chains with their curvatures are oriented in opposite directions on the upper side of the container wall. The curvatures of the rail elements of the upper- and the lower rail chains are respectively present vertically above each other. The convex curvatures of the rail elements of the upper rail chain are present vertically above the concave curvatures of the rail elements of the lower rail chain and vice versa. The horizontally adjacent upper rail elements of the upper rail chain are connected with each other by horizontal connecting strips and vertical connecting elements. The connecting elements of the connecting strips are simultaneously holding elements for connecting to the upper side of the container wall in a form-fit manner. The center points of the mutually associated convex- and concave curvatures of adjacent upper rail elements, are superimposed. The vertically adjacent rail elements of the upper- and the lower rail chains are connected with each other by vertical holding elements. The vertically adjacent rail elements of the upper- and the lower rail chains, at its two ends, are connected with each other by the vertical holding elements in the form of bolts or screws, which extend in the rail elements through openings or holes, where the bolts or screws are driven in the container wall. The rail elements of the lower rail chain are sealed gastight for the upper side of the container wall, through an annularly applied sealant (19) which is plastically mounted and cured after mounting. The rail elements of the lower rail chain exhibit holes or openings spaced from each other, through which the plastic sealant passes, during the mounting on the upper side of container wall and produces a form-fit connection after curing. The edges of the concave- and/or convex curvatures of the lower rail elements comprise notches through which the sealant passes, during mounting on the upper side of container wall and produces a form-fit- and/or gas-tight connection after curing. All the rail elements of the lower- and the upper rail chains are identically formed. The axial distance between lowest point of the convex curvature and highest point of the concave curvature of the rail elements, exhibit an effective length of pi /4 m, preferably 78.54 plus minus 1 cm. EXAMPLE - No suitable example given.