Standard API | ASTM | BS | DIN | DNV | GB | ISO | JIS | KS | LR | NF | Others ASTM Standard Number A 688 (Welded Austenitic Stainless Steel Feedwater Heater Tube ) Grade TP304 TP304L TP304LN TP316 TP316L TP316LN TPXM-29 TP304N TP316N [ All grade ]