Dear All,

For the above subject,

CODE : ASME 31.8
Service : Nirogen gas
Pipe Material : API 5L GR. B
Mu : .3
Temp 184 degree F
Pressure 267 psi

Forces are in lbs & distance in inch

Please see the attached model CAESAR .ZIP file contains (Caesar II ver 5.0 underground & Above ground ) & Thrust force.pdf

Pipeline modeled such a way that 16” above ground off plant main header pipeline tapped with 12” tie in branch connection , the branch is running at A/G and dropped into underground ( about 600 ft ) due to road crossing ,other pipeline corridor and brought to above ground @ plant inside area , the pipe size is reduced to 6” to plant metering station.


The above model is passed in substation & Operation case.

Initially operation case failed due to the overstress in elbow at buried portion of pipeline. Subsequently z restraint placed either side of the below ground elbow raiser to resist the thrust force. Later operation stress is within the limit

My question is it correct procedure to place the z restraint for the under ground portion.
Or do I replace with anchor at meddle of buried portion of pipeline. .( tried with anchor at middle of underground portion but failed.

Please find attached pdf for manual thrust force calculation, caesar II value differ from manual cal.