You are currently reviewing an older revision of this page.
Fatigue analysis with AutoPIPE Harmonic analysis command :
AutoPIPE does not have cyclic type of stress, therefore need to add a new code combination with H1 by itself for the RPM of the harmonic from a rotation compressor:
Combination Name = H1
Description = Harmonic Load case #1 for RPM = xxx .
Combination method = 1 Sum
Category = Occasional,
Case = H1.
We can now set an allowable stress from Automatic because typical 1.33 *Sa but in this case because it is high cycle fatigue, the API618 mentions using a value of 26000 psi peak to peak so you can use half of that which is 13000 psi peak to peak or if you want to consider some SIF values typically would suggest using 13000/2 = 6500 psi for the Stress allowable.
Therefore, 26000/2 for peak to peak /2 assuming a weld stress factor = 2 because the piping codes are typically based on SIF while fatigue values are typically based on stress concentration factors and there is a factor of 2 between SIF and stress concentration factors
AutoPIPE Compressor Vibration Method
How can I include pulsation forces from piston type pump to piping?
Answer: (from Karim Rinawi)
The best way is to simulate the acoustic model using Bentley PULS. It will calculate the shaking forces and can export these using harmonic HMF file.
Otherwise you would need to assume some pipe harmonic forces at elbows. Sometimes you need to change the load frequency to match pipe resonance for worst scenario.
Bentley AutoPIPE
Bentley Technical Support KnowledgeBase
Bentley LEARN Server
Bentley's Technical Support Group requests that you please submit any comments you have on this Wiki article tothe "Comments" area below. THANK YOU!