PED compliance for appliances designed according to ASME

For some appliances designed according to the ASME code, in particular ASME VIII Div. 1, it is necessary to verify that these appliances comply with the safety criteria of the PED, the European pressure equipment directive.

NextGen supports this process in two key points:

• Support in choosing the allowable in compatibility with the PED
• Calculation of hydraulic test pressure according to PED

Enabling PED compliance

The operation can be performed via a simple flag to be set in the Item properties, in the section relating to tests:

The demo item is composed of heads, main shell, nozzle and flange:

Choice of materials

For a 304L austenitic steel construction, not considering compatibility with PED, the choice would fall on the following:

The parts under pressure which in the event of deformation would not lead to the loss of fluid (sheets, pipes) would be sized considering the highest allowables according to note G5 of the material, while the flanges would use the reduced allowables.

However, NextGen will show the following warning on cylinders, heads and nozzle:

Selected material may have an allowable stress that does not respect minimum safety requirements according to PED. It is generally advisable to use low stress materials when an item shall be PED compliant.

This happens due to the fact that austenitic steels in their "low allowable stress" version have an allowable calculated by ASME which is lower, therefore compliant, than the allowable according to PED. This is not the case for "high allowable stress" variants. It is therefore sufficient, to comply with the safety criteria, to use the "low allowable stress" variants for all the materials used.

The other types of steel, such as carbon steel, have an ASME admissible grade that is always lower than the PED admissible grade and therefore no particular precautions are necessary in that case.

Calculation of hydraulic test pressure

In the calculation report, in the section relating to the calculation of the hydraulic test, two distinct summary tables will be shown: one for ASME and one for PED. The ASME table will also report the maximum value between the ASME and the PED as the calculated pressure.