Flange Leakage & Kellogg Equivalent Pressure Calculator

Check ASME B16.5 / B16.47 bolted flange leakage integrity under combined external bending moments and axial tensile forces using the M.W. Kellogg method.

Flange Class & Operating Pressure

Nominal Pipe Size (NPS):

ASME B16.5 Pressure Rating:

Internal Design Pressure P (psi):

Operating Temperature Allowable (psi): B16.5 Table 2 rating at design temp

Piping External Mechanical Loads

External Bending Moment M (ft-lb): Resultant M = √(Mb² + Mt²)

External Axial Tensile Force Fax (lbf): Thermal expansion tensile pull

Leakage Check & Stress Margin

Kellogg Equivalent Pressure (Peq)

-- psi

Status: --

Bending Moment Pressure

-- psi

-- bar

Axial Force Pressure

-- psi

-- bar

Allowable Flange Rating Pressure (Pallow): -- psi

Flange Joint Utilization Ratio (Peq / Pallow): -- %

Residual Safety Margin: -- psi

Gasket Reaction Diameter G: -- in

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Frequently Asked Questions

What is the M.W. Kellogg equivalent pressure method?

The Kellogg method is an industry-standard structural piping check that converts external pipe bending moments (from thermal growth and weight) and axial tensile loads into a fictitious internal hydraulic pressure: Peq = P + 16*M / (pi*G^3) + 4*Fax / (pi*G^2). If Peq is less than the ASME B16.5 flange pressure rating at design temperature, the flange is deemed safe against leakage.

Why do bending moments unload flange gaskets?

When an external bending moment acts across a bolted flange, it creates tension on one side of the flange and compression on the opposite side. The tensile bending stress directly counteracts the initial bolt clamping force, decompressing the gasket below its minimum maintenance stress (m * P) and opening a leak path.

How does ASME Section III NC-3658 compare with Kellogg?

Both evaluate external moments against flange rating, but ASME Section III NC-3658 uses a codified moment limit formula M_limit = C * S_b * A_b based on actual bolt tensile capacity. Kellogg remains the universal standard in refinery and chemical plant piping engineering (B31.3) because it directly maps to ASME B16.5 pressure ratings.