4.3　Pipes

4.3.1　It is preferred that seamless steel pipes should be used for nozzles and tracing pipes for the tanks.Service limitations of seamless steel pipes shall meet the requirements in Table 4.3.1-1 and Table 4.3.1-2.

Table 4.3.1-1　Service limitations of seamless steel pipes

Table 4.3.1-2　Allowable stress values of seamless steel pipes

Note:The allowable stress of all high alloy steel pipes only applies to those parts，of which a slight permanent deformation is permitted.

4.3.2　For structural pipes used in stairways，ladders and platforms，welded pipes may be used.