Error Code 356 - Gasket width insufficient ( minimum=##.### mm ), the permissible gasket load is exceeded, use of a compression ring is recommended

This is an additional check is that is good practice to follow that came from the CODAP code paragraph C6.1.6(e) and (f):

Where:

Ab = Total cross-sectional area of bolts [n x ab (C6.1.3.1)]

Ab,min = Minimum required cross-sectional 

fb,A = Nominal design stress of the bolts or studs for gasket seating condition (fb,A is the nominal design stress for a normal operating condition at atmospheric temperature)

w = Contact width of the gasket on the facing (see C6.1.5)

G = Diameter of the circle on which gasket compression load acts (see C6.1.5)

y = Gasket seating pressure (see C6.1.5)

If you do not want to do this gasket check you can check the box on the gasket tab:

There may be an extra variable "(Hext)max" in the equation from CODAP.

“(Hext)max” means “maximum of all Hext values”. Depending on the load cases you are analyzing for there could be an operation case Hext, and a test case Hext, etc.

The gasket checking must be done with the maximum of the both values:

W + (H_ext)_max  >  2π N G y + r_l N_r y^'