Flange Leakage Check

START-PROF allows to use following methods of flange leakage check:

Equivalent pressure / Kellogg Method

Kellogg aka Equivalent pressure Method is conservative method, where the axial force and bending moment on the flange is converted into equivalent pressure using following equation

F - Axial force on flange

M - Moment on flange

G - Effective gasket diameter

Prating - allowable pressure for flange from rating table (ASME B16.5, EN 1092, GOST codes)

For ASME B16.5 code the allowable pressure for test state is taken greater by factor k, ASME B31.1: k=1.15, ASME B31.9: k=1.2, ASME B31.3: k=1.33, ASME B31.4: k=1.15, ASME B31.5: k=1.33, ASME B31.8: k=1.11, EN 13480: k=1.3.

Code Case 2901 / UG-44 ASME VIII-1 Method

The main advantage of this method is that it is less conservative than Kellogg method. This method is published in paper: "Improved Analysis of External Loads on Flanged Joints" PVP2013-97814 by Dr. Warren Brown, 2013.

And then included into Code Case 2901 at December 11, 2017.

This equation can be represented in the following form:

It is the same as Kellogg method, but allowable pressure is increased times (1+Fm), where Fm factor can be taken from the following table

DNV Method

The idea of DNV method is that flange allowable pressure in Kellogg method can be increased to hydrotest pressure that is 1.5 times the design pressure. But for safety reasons factor 1.3 is used instead of 1.5.

The equation can be represented in the following form:

NC 3658.3 Method

This method is used if flanges, bolts and Gaskets are designed based on as specified in ASME B 16.5a and bolting material have allowable stress value at 100°F(38°C) >=20000 psi (138 MPa) (High Strength Bolting)

Leakage check equation is as following:

C and Ab values should be specified by user in flange properties. Sy value is taken automatically from database according to design temperature.




Axial force

Calculated axial force N acting on the flange (+ for stretch, - for compression) without pressure thrust force.

Bending moment

Calculated bending moment M acting on the flange


Mx, My - bending moments acting in mutual perpendicular planes, going through the pipe axis


Design pressure in pipe for Peq methods

Bolt Area, Bolt circle diameter, and design pressure for NC 3658.3


Equivalent pressure on flange calculated using one of the Peq methods

For NC 3658.3:


Allowable pressure on flange calculated using one of the Peq methods

For NC 3658.3:


Menu Access

After analysis: Output > Flange Leakage