Dear Shabeer,

You should not combine Acceleration and blast case together. Acceleration is a accasional case whereas blast case is an accidental case. You shall make two files. One for design and another is blast case. As allowable stress for blast is much higher compared to accasional case. Blast should be treated as wind loads except it has vertical loads and also Dynamic load factor. Before doing blast calculation, please go through Design of accidental loads (DAL) prepared by techical safety department. It would say direction of blast pressure. In my opinon 0.3 bar of drag pressure is significant.

As one of the participant send, please read DNV-RP-D101 code for pipe stress analysis. this code available on internet for free.

best regards

Rao