Is there any rule/book/standard to check displacement at Operating condition as per material/temp/pressure etc..

As I noticed in stress report the displacement at operating condition Dx is higher then Dy, Dz. for stream header line with temp 450C at 58 bar 20" alloy steel material, at nodes DX,DY,Dz Max displacement values are
MaxDx MaxDy MaxDz
245mm 34mm 190mm

I tied to reduce by adding line stop etc. finally I got this results....with code compliance stress 85%

My client comments says to maintain less then 200mm acceptable at Dx. (I checked at Site 200mm thermal displacement at Dx direction is free to expand without clashing to steel or other pipes)

My Question to all, Is there any thumb rule/standard/book reference/ to check Max displacement as per temp/press/material etc. as client comments says it should be less than 200mm acceptable. pipe is modeled in X direction with a loops/legs/straight run.