This flange rating calculator contains p/T ratings of frequently used non-austenitic steels (carbon steel and low alloyed carbon steels) materials. It is based on Annex G of the harmonised standard EN 1092-1. The temperature-dependent strength values of the forged materials according to EN 10222-5 were taken as a basis (different product thickness ranges of the forged products were also taken into account).

Other flange materials can be calculated on the basis of Annex F of this standard, taking into account temperature-dependent strength values of the material standards.

The p/T ratings are calculated by using the strength values of steel forgings and are verified for flat steel products of the same group.

Using standard flanges for pressure vessels and industrial piping without calculation

EN 13445-3 clause 11.4.2 and EN 13480-3 annex D clause D.4.2 stated: Flanges (but without main pressure bearing flanges) that conform to an European Standard for pipework flanges may be used as pressure vessel components and industrial piping without any calculation,

provided all the following conditions are fulfilled:

a) Under normal operating conditions, the calculation pressure does not exceed the rating pressure given in the tables of the relevant European Standard, for the flange and material under consideration for the calculation temperature.
b) Under testing conditions or exceptional conditions, the calculation pressure does not exceed 1,5 times the rating pressure given in the same tables, at appropriate temperature.
c) The gasket is one of those permitted for the relevant PN or Class series.
d) The bolts are of a strength category at least equal to the minimum required by Table 11.4-1 as a function of the gasket type used in the connection.
e) The vessel is subjected to loadings of predominantly non-cyclic nature, see 5.4.2.
f) The difference between mean temperatures of bolts and flange does not exceed 50 °C in any condition.
g) The bolt and flange materials have coefficients of thermal expansion at 20 ° C that differ by more than 10 % (e.g. austenitic steel flanges with ferritic steel bolts) but the calculation temperature is < 120 °C, or the bolt and flange materials have coefficients of thermal expansion at 20 °C which do not differ by more than 10%.

PN-Flange
p/T-Rating Calculator

Determination of the max. allowable pressure PS
at higher temperatures
EN 1092-1

Input

Flange material

TS [°C]

max. PN

(1) TS [°C]

Material reference thickness v_R [mm]

Material reference thickness v_R of unmachined parts (see below)

(2) TS [°C]

(3) v_R max. [mm]

Remarks

Limits of the selected material

Output

(1) Max. allowable temperature TS;

(2) Max. allowable temperature TS taking into account the creep strength of 100,000 h;

(3) Max. material reference thickness v_R;

max. PS [bar]

Calculated max. allowable pressure taking into account higher operating temperatures as entered above;

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Material reference thickness v_R

Mechanical properties are dependent from thickness value of unmachined parts („v_R” for forgings, „t“ for flat products). As the result of the machining this dimensions will be reduced. EN 1092-1 stated for machined flanges and collars the flange dimensions C1 to C4 or F shall not be less than 80 % of „v_R” for forgings, and the flange dimensions C1 to C4 or F shall not be less than 80 % of t for flat products.

This means that if approx. 20% is added to the flange thickness dimensions (C1 …C4, and F) of EN 1092-1 (or actual measured values) for machining, the approximate thickness of the unmachined forged or plate material used is obtained and thus a value for „v_R”.

The maximal reference thickness v_R for all materials is 150 mm (except for material 1.4903 where v_R ≤ 130 mm. Thickness-related strength values (if available) are taken into account in the calculation.

PN-Flange p/T rating calculator for austenitic and ferritic-austenitic steels

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