ASTM A815 Wrought Ferritic, Ferritic/Austenitic, and Martensitic Stainless Steel Piping Fittings
Class WP fittings are subdivided into four subclasses:
Class WP-S fittings are those manufactured form seamless product by a seamless method of manufacture;
Class WP-W fittings are those which contain welds where the fitting fabrication or construction welds have been radiographed;
Calss WP-WX fittings are those which contain welds where all welds have been radiographed;
Class WP-WU fittings are those which contain welds where all welds have been ultrasonically tested.