Red-Bag receives many questions about the PCC EN13480 Tee calculation versus the later issued EN10253 dimensions standard calculation in for example Annex A.

For example: if a Tee is calculated according EN13480 the maximum allowable design pressure at design temperature would be 1.2 N/mm2. If the same Tee is checked with the pressure factor in Annex B (calculated as per Annex A) the maximum allowable design pressure at design temperature would be 1.5 N/mm2.

The conclusion is that the EN10253 maximum allowable design pressure is higher than calculated as per EN13480.

The reasons is that the EN10253 definition of the reinforcement limits is different from the EN13480 or the EN13445.

The below images show the differences:

EN10253 Tee

This image of the EN10253 calculation base shows that the reinforcement limits follow the curve of the crotch

EN13445 Tee

This image of the EN13445 extruded branch (Tee) shows that the reinforcement limits are straight to the outside diameter of the header or the branch

EN13480 pipe-pipe branch

This image of the EN13480 shows the limits of a pipe to pipe branch. The limits are also straight to the outside of the pipes. ()Note: the EN13480 does not have an image as the EN13445 for the Tee)

EN13480 Y branch

This images shows the reinforcement limits for a Y branch. It illustrates that the EN13480 also uses straight lines as per the EN13445.

The difference in allowable design pressure for the EN10253 and the EN13480 is due to the different definition in reinforcement limits (which also has an effect on the pressure area). The EN10253 pressure factor calculation and the corresponding tables are 'INFORMATIVE'. However the PCC application will have in future the possibility to select between the EN13480 calculation or the use of the Annex A, B pressure factors.