One of the great advantages of Krah pipes is that it is easily adaptable to all different kinds of project requirements.
According to different norms and standards, the pipes shall be designed according to nominal ring stiffness classes (SN) like SN2 (only for pipes DN > 500), SN4, SN8 or SN16 (according to ISO9969), or other standard stiffness classes (DIN16961, ASTM F894, NBR 7373 etc) not depending on the testing method (constant speed or constant load).
In addition, according to EN13476-3 9.1, the manu facturer is also allowed to produce pipes DN/ID > 500mm in between the SN classes, in case he is able to prove and underline this decision with the help of a static calculation.

The real pipe quality consists of the right waterway wall thickness, a good raw material and a secure jointing technology; but not the stiffness.