Hello Everyone

If I use a de-rated method (With design pressure/Temperature) to calculate the wall thickness of a large bore pipe (48"), do I need to consider wall thickness calc due to Hydrotest pressure separately(design pressure is almost ATM and Hydrotest increases the wall thickness)? If yes, do I have to consider C.A for that calculation and is it correct to consider 0.9 of the allowable as Hydrotest allowable?

Thanks