See the point in the middle, at the origin, is a saddle point. If you look at the tangent plane to this graph, you will see that it is actually horizontal at the origin.

Analysis and discussion was made on the influence of saddle position change on the axial stress, shearing stress and circumferential stress of the cylinder of double-saddle horizontal vessel.

The number of saddle supports will be determined by the length of the horizontal storage tanks; in general the distance between the saddles is equal or less than 1.5times of the tanks 'diameters.