Q. Sustained Bending Moment?
When sustained bending moments or axial thrust loadings are applied to the flanged joint during operation in sufficient magnitude to warrant consideration in the flange design, the design pressure ‘P' used in the calculation of H (total hydrostatic end load) in the flange design calculations, should be replaced by the following design pressure:
PFLG = P + PEQ
Where M = Sustained bending moment applied across full section at flange during the design condition, in-lb
F = Axial tensile force applied at flange, lb
G = Diameter, in, at location of gasket load reaction.
Note: Experience has shown that axial tensile forces, resulting from a properly designed piping system, have no significant effect on the flange design, and hence, are typically not included in the PEQ determination.
Therefore, the hydrostatic end load H used in the flange calculations is determined as follows:
H = 0.785 G2 PFLG