Pressure stress act in the axial, circumferential and radial directions:

See AutoPIPE Help Code Compliance Calculations for actual equations, example: ASME B31.1 2016:

Hoop (Circumferential) pressure = 

Axial (Long) pressure = 

Note: equation could be different depending on "Long Pressure [P/A/M/N]" setting

"Include Axial P case in sustain" setting = 

Comments, Questions, and Answers

Item #1: How to find the pressure thrust on an anchor in AutoPIPE?

Item #2: When should I perform a Pressure Analysis in AutoPIPE?

Item #3: From FAQ #67: "Note: P1 force does not include the capped internal pressure force. However this pressure force PiAi can be manually subtracted from the Local - X P1 force to give a true P1 axial force i.e Total P1= P1- PiAi" 

Answer:

It is true that P1 case does not directly apply cap force. It does that indirectly by apply pressure strain that accounts for it and for poisson ratio. In the case of a flexible joint, AutoPIPE does apply the cap force P x Pressure Area to properly get the extension at the joint. 

Item #4: How to perform a Pressure analysis in AutoPIPE?

Item #5: Is External Pressure used for Hoop Stress Calculation in AutoPIPE?

Item #6: Reorder the Pressure / temperature load case pairs

See Also

Loads and Load Sets - AutoPIPE

Bentley AutoPIPE