Piping Classification

After we talk about Pipe Size, Pipe Wall Thickness and Piping, now we entering The Piping Classification, which mean that we will explain about the Classification of Piping according ASME Standards and this is Piping & Fabrication will start.

Piping Classification

PIPING CLASSIFICATION
It is usual industry practice to classify the pipe in accordance with the pressuretemperature rating system used for classifying flanges. However, it is not essential that piping be classified as Class 150, 300, 400, 600, 900, 1500, and 2500. The piping rating must be governed by the pressure-temperature rating of the weakest pressurecontaining item in the piping. The weakest item in a piping system may be a fitting made of weaker material or rated lower due to design and other considerations. Table A1.2 lists the standard pipe class ratings based on ASME B16.5 along with corresponding pression nominal (PN) rating designators. Pression nominal is the French equivalent of pressure nominal.

In addition, the piping may be classified by class ratings covered by other ASME standards, such as ASME B16.1, B16.3, B16.24, and B16.42. A piping system may be rated for a unique set of pressures and temperatures not covered by any standard. Pression nominal (PN) is the rating designator followed by a designation number, which indicates the approximate pressure rating in bars. The bar is the unit of
pressure, and 1 bar is equal to 14.5 psi or 100 kilopascals (kPa). Table A1.2 provides a cross-reference of the ASME class ratings to PN rating designators. It is evident that the PN ratings do not provide a proportional relationship between different PN numbers, whereas the class numbers do. Therefore, it is recommended that class numbers be used to designate the ratings. Refer to Chap. B2 for a more
detailed discussion of class rating of piping systems.