APPENDIX M — NONMANDATORY
FLANGE RIGIDITY
M-100 INTRODUCTION
Flanges which have been designed based on allowable
stress limits alone may not be sufficiently rigid to
control leakage. This Appendix provides a method of
checking flange flexibility.
The flexibility factors covered in M-300 have been
proven through extensive user experience for a wide
variety of joint designs and service conditions; however,
their use alone does not guarantee a leakage rate within
established limits, and accordingly their use must be
considered as only part of the system of joint design
and assembly requirements to ensure leak tightness.
M-200 NOMENCLATURE USED IN
FORMULAS
Epmodulus of elasticity for the material of the
flange at the design temperature (operating con-
dition) or atmospheric temperature (gasket seat-
ing), as may apply, psi
Jprigidity index ≤1.0. If the value of J, when
calculated by the appropriate formula in M-400,
is greater than 1.0, the thickness of the flange
tshould be increased and Jrecalculated until it
is within the above limit.
K
I
prigidity factor for integral-type flanges (see
M-300)
513
K
L
prigidity factor for loose-type flanges (see
M-300)
All other nomenclature used in this Appendix is defined
in 3-301.1.
M-300 RIGIDITY FACTORS
Experience has indicated that a K
L
value of 0.2 for
loose-type flanges and K
I
of 0.3 for integral flange
types are sufficient for most services. Other values may
be used with the User’s agreement.
M-400 FORMULAS
Integral-type flanges:
Jp52.14M
O
V
LEg
2
o
h
o
K
I
(1)
Loose-type flanges with hubs:
Jp52.14M
O
V
L
LEg
2
o
h
o
K
L
(2)
Loose-type flanges without hubs:
Jp109.4M
O
Et
3
ln(K)K
L
(3)
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