The length of a shell plate to be cut for a cylindrical vessel is measured by the mean or bend-line circumference of the shell so that the plate will equal a required inside diameter after being rolled. The circumferences given in Table B.1 are for the inside diameter.

Areas are approximate but sufficiently accurate for estimating

Table B.1: Circumferences and Areas of Circles

When plates are to be cut to provide a given inside diameter, an amount equal to the plate thickness multiplied by 3.1416 must be added to the circumference shown in the table for that diameter. For example, suppose a vessel is to be 60 in in inside diameter and is to have a shell thickness of 1 in. The 60-in inside diameter generates a circumference of 188.496 in. To this figure must be added the plate thickness multiplied by 3.1416, or 3.1416 in. The length of plate to be cut to make a cylinder 60 in in inside diameter is therefore 188.496 plus 3.1416, or 191.6376 in.

A simpler method is to add the thickness of plate to the inside diameter and obtain the circumference directly from the table. For example, for a vessel requiring a 60-in inside diameter and a 1-in shell plate, add 1 in to 60 in for a total of 61 in. The circumference given in the table for a 61-in diameter equals 191.637 in.

The plate for cylinders with dished heads should never be cut until the heads have been taped...