AD2000 German pressure vessel code

[techwarrior08]

Good morning to all,
I would like to share my views regarding AD 2000 Merkblatt with respect to ASME codes as I have used and compared it for designing of high pressure Vessels.
First and foremost, the AD code does not compromise with safety factors and nor it is limited in terms of design temperature. Let me be a bit more specific.

Safety Factors :
AD code uses allowable design stress based on yield stress of the material only and the safety factor depends on the ductile/brittle nature of the material. In fact the safety factor for ductile materials is 1.5 on yield stress i.e. same as ASME code. However the ASME code allowable values come out lower because in ASME code a minimum value of yield stress/safety factor and tensile stress/safety factor is used. So any material which has yield strength and tensile strength close to each other will always result in lower allowable stress for ASME code. But the allowable stress will be higher in AD code as it depends only on yield strength.
So the thickness of pressure parts in AD code comes out to be lesser than ASME code.
Infact ASME Sec VIII Div 2 was released in order to compete with the German code to provide for lower cost of equipments as ASME VIII Div 1 always gave higher thickness due to high safety factor and lesser inspection requirements.

Also having a low safety factor in no way undermines the strength of equipment if the NDT performed is more stringent.
That is why both ASME Sec VIII Div 2 and AD 2000 code provides for a more stringent NDT inspection in order to make up for low safety factor.

Also regarding materials properties, AD2000 refers to the more established EN codes which can be used for higher design temperatures also.

Hope this helps.
Thanks

[techwarrior08]

Just to add to my above post,
Kindly note that the AD merkblatt also requires additional testing at the product manufacturing stage.
I.e it mandates hot tensile test to be performed for all materials at the maximum design temperature or 300 deg C (if design temperature is not mentioned) so that the actual yield strength at design temperature is verified.

Thus the allowable stress based on yield strength which is considered during design can be safely used.