The thickness of the head calculated according to GB 150 is slightly thinner than that of the cylinder, but in the process of pressing the head, the nominal thickness of the head is thicker than that of the cylinder considering the process thinning (recommended process thinning rate in the appendix of the head standard).

In fact, the nominal thickness (feed thickness) of the head is the sum of calculated thickness, corrosion allowance, negative deviation of steel plate and process thinning, rounded to the standard thickness; The nominal thickness of the whole car body is the sum of the calculated thickness, corrosion allowance and negative deviation of the steel plate, and rounded to the standard thickness. It can be seen that the feed thickness of the pressure vessel head is generally thicker than that of the cylinder.