Download 7 Fatigue PDF

Title7 Fatigue
TagsPipe (Fluid Conveyance) Pump Fluid Dynamics Fatigue (Material) Valve
File Size251.3 KB
Total Pages13
Table of Contents
                            Acoustic Fatigue – Turbulence Induced Fatigue Failure of Relief System Piping
In Salah Gas Flare Header Rupture
ISO 23251/API RP521
NORSOK
Harris Shock and Vibration Handbook, Chapter 29VIBRATION OF STRUCTURES INDUCED BY FLUID FLOW by R. D. Blevins
MTD 99/100
MTD 99/100 (Example Flowchart)
CONCAWE 85/52
In Salah Gas Incident
Turbulence Induced Vibration Failure
Path Forward
                        
Document Text Contents
Page 1

Acoustic Fatigue – Turbulence
Induced Fatigue Failure of Relief

System Piping

Ed Zamejc
BP

Spring 2006 API Refining Meeting
May 3, 2005

Page 2

In Salah Gas Flare Header Rupture

Page 6

Harris Shock and Vibration Handbook, Chapter 29
VIBRATION OF STRUCTURES INDUCED BY FLUID

FLOW by R. D. Blevins

• Oscillatory flow (reciprocating pumps, flow through
valves and obstructions) in pipes can cause vibration

• If pressure and velocity in the pipe oscillate, then fluid
force on the bend will oscillate, causing pipe vibration

• Problem most prevalent in unsupported pipe bends
adjacent to pumps and valves.

• Two solutions:
– (1) support pipe bends and changes in area so that fluid forces

are reacted to ground and
– (2) reduce fluid oscillations in pipe by avoiding large pressure

drops through valves and installation of oscillation-absorbing
devices on pump inlet and discharge.

Page 7

MTD 99/100
• “Guidelines for Avoidance of Vibration Induced Fatigue

in Process Pipework” ISBN 1 870553 37 3, 1999.
• Use of thinner wall pipe (flexible) causes higher stress

concentrations at small bore connections
• Higher velocities causing greater turbulence
• Guidelines are for “steady state” plant operation
• Piping excitation mechanisms:

– High frequency acoustic excitation
– Flow induced turbulence @ low frequency (< 100 Hz)
– Mechanical (reciprocating compressors loads)
– Pulsation (fluid flow from recip. compressors)

• Guidance to determine “Likelihood Of Failure” (LOF) and
design solutions

Page 12

Turbulence Induced Vibration Failure
• In Salah Gas Incident
• Longer time to occur than acoustic vibration

failure (minutes or hours)
• Visible motion of piping often observed
• Consider when velocities >0.5 to 0.8 Mach
• Potential failure with low frequency vibration

(1-15 Hz) where high stress (e.g. > 3000 lbf)
• No weldolets
• Mitigate by bracing, wrapping pipe, thicker

wall pipe,…

Page 13

Path Forward

• Propose to add guidance on acoustic and
turbulence induced fatigue potential of
relief system and blowdown piping
systems

• Guidance based on references provided,
any others?

• What do other companies do?

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