SOUR Service material - Pipe wall thickness

I have 2 - 900# CS Shell piping classes, one for SOUR the other non-SOUR is identical in pipe material and the corrosion allowance. Material is ASTM A 333 Gr 6. CA = 3 mm. The pressure temperture ratings are also the same. However the thickness differs for the same size, 12". For the non-SOUR class it is sch 120 and for the SOUR is sch 100. Which is about 4 mm less thick. What is that which makes the thickness lesser for the SOUR service material. Any guesses?

Sajit Received on Sat Jun 26 05:49:00 2004