ASME/PED TEST PRESSURE 1

[JACKSTAN]

How should be determinate pressure test value (PT) for carbon steel pressure vessel calculated acc. to ASME code + PED? It means expression f20/ft in equation PT=1.25.PS.f20/ft. Should this expression (f20/ft) be calculated acc. to ASME code or PED 97/23/EC annex 1 p.7 (min. [Re/1.5; Rm/3.5] or min [Re/1.5; Rm/2.4]).

 

[JohnGP]

Jackstan,

If you are designing to ASME Code then you should use the ASME allowable properties for the material (from ASME II Part D). For some of the materials I am familiar with, the ASME values are less than the limits specified in the PED anyway.

For hydrotest though you will likely find that the 2nd equation in the PED will govern, i.e 1.43 x [max allowable pressure], and material properties at temperature are not a factor.

Regards,
John

 

[JACKSTAN]

Many thank Johny for your answer, but I have still doubts.
Because some guys in case like above mentioned using allowable stresses from PED - f = min(Ret/1.5; Rm/2.4).
Regards

 

[JohnGP]

The PED is not a design code though, so if you are designing to ASME then you must use the allowables as derived by ASME. Those stresses should be used for the vessel design, and also for determining the hydrotest pressure. The PED does have a 2nd criteria for test pressure based on maximum allowable pressure only (x1.43), and this needs to be considered.

I'm not certain about the allowable stresses included in the PED, but I think they come from the Harmonised Standard EN13445. From previous postings on related subjects I don't think they can be directly compared to ASME as I think the application of safety factors is different.

Regards,
John