Single-curvature polyhedron bulging technology for manufacturing spher
ical vessels is to build spherical vessels by assembling and welding s
heet blanks of zero-curvature and single-curvature into a polyhedron,
then gradually bulging the polyhedron into a spherical vessel. With th
e technology, heavy presses and large dies are not needed, so spherica
l vessels can be built at low cost. In order to make a polyhedron afte
r being bulged satisfy given dimension requirements of the spherical v
essel, it is necessary to calculate wall thickness and diameter of the
polyhedron under bulging pressure. In this paper, wall thickness decr
ement and deflection of a point on a single-curvature polyhedron durin
g bulging are measured, it proves that the wall thickness decrement is
much smaller than the deflection. Under the assumption that wall thic
kness of a polyhedron keeps constant during bulging, the constant-area
spheritaxis principle is put forward. With this principle, methods of
calculating diameter, wall thickness of a polyhedron and pressure und
er which the polyhedron becomes a spherical vessel are got. Besides, o
ther applications of the principle are also given.