This document discusses reasons why failure analysis is conducted. It provides examples of three failures: 1) A steam control valve stem failed due to fatigue cracking where the nitrided and threaded section was smaller and weaker than intended. 2) A combustor can on a power gas turbine failed when misaligned parts rubbed and cracked, removing weld material between two austenitic stainless steel components. 3) A reheat pendant tube splice failed when an incomplete weld penetration led to a notch that grew under pressure and vibration. The document advocates conducting failure analysis to determine root causes and prevent future failures.

1. What Makes Us Do FailureWhat Makes Us Do Failure
Analysis?Analysis?
ASM – AWS (NTX) Joint MeetingASM – AWS (NTX) Joint Meeting
Michael S. Beaton, PEMichael S. Beaton, PE
16 October, 200716 October, 2007

3. CategoriesCategories
• OUT of ORDEROUT of ORDER
• STRETCHING the NUMBERSSTRETCHING the NUMBERS
• ““WHAT WADDLES LIKE A DUCK…”WHAT WADDLES LIKE A DUCK…”
• COMEDY of ERRORSCOMEDY of ERRORS
• WORKMANSHIPWORKMANSHIP
• CHEAPNESSCHEAPNESS
• NATURENATURE

4. OUT OF ORDEROUT OF ORDER
• Steam control valve stemSteam control valve stem
• nitridednitrided
• then threadedthen threaded..
• Thread section was less strong / hardThread section was less strong / hard
AND smaller sectionAND smaller section
• Failure occurred in first full threadFailure occurred in first full thread viavia
FatigueFatigue

6. FATIGUEFATIGUE
• Repeated or fluctuating stressRepeated or fluctuating stress
• Stress below tensile strength of theStress below tensile strength of the
materialmaterial
• Progressive fracture from initiation point(s)Progressive fracture from initiation point(s)
– Often created by aggressive environment orOften created by aggressive environment or
sensitizing condition (corrosion, fretting, arcsensitizing condition (corrosion, fretting, arc
strikes & weld spatter)strikes & weld spatter)

7. ““WHAT WADDLES LIKE A DUCK…”WHAT WADDLES LIKE A DUCK…”
• Combustor can on Power Gas TurbineCombustor can on Power Gas Turbine
• Four detail parts joined by weldingFour detail parts joined by welding
• Two parts made ofTwo parts made of Austenitic StainlessAustenitic Stainless
SteelSteel
• Alignment off-center -> parts rubbed,Alignment off-center -> parts rubbed,
cracked, machined away weld metalcracked, machined away weld metal
• Weld repairs recrackedWeld repairs recracked

22. Off-Spec. conditionsOff-Spec. conditions
• Alloy selection was incorrect for twoAlloy selection was incorrect for two
componentscomponents
• Weld deposit was machined, REMOVEDWeld deposit was machined, REMOVED
100% for 30 degrees of circumference.100% for 30 degrees of circumference.
• Clearances were not symmetricalClearances were not symmetrical

23. WORKMANSHIPWORKMANSHIP
• Reheat Pendant Tube SpliceReheat Pendant Tube Splice
• Incomplete Penetration of Weld JointIncomplete Penetration of Weld Joint
• Deep Geometric Notch at Weld RootDeep Geometric Notch at Weld Root
• Tube Internal Pressure and Flow VibrationTube Internal Pressure and Flow Vibration
Caused Notch to Grow, Joint FailedCaused Notch to Grow, Joint Failed

28. What Makes Us Do FailureWhat Makes Us Do Failure
Analysis?Analysis?
• OUT of ORDEROUT of ORDER √
• STRETCHING the NUMBERSSTRETCHING the NUMBERS
• ““WHAT WADDLES LIKE A DUCK…”WHAT WADDLES LIKE A DUCK…” √
• COMEDY of ERRORSCOMEDY of ERRORS
• WORKMANSHIPWORKMANSHIP √
• CHEAPNESSCHEAPNESS
• NATURENATURE

29. Trinity Metals LaboratoryTrinity Metals Laboratory
QUALITY PHILOSOPHYQUALITY PHILOSOPHY
• QUALITY is a fundamental business strategy forQUALITY is a fundamental business strategy for
Trinity Metals Laboratory.Trinity Metals Laboratory.
• Our GOAL is to be the best provider of testingOur GOAL is to be the best provider of testing
services in our market in terms of accuracy,services in our market in terms of accuracy,
dependability, and value to our customers.dependability, and value to our customers.
• We are committed to providing our customersWe are committed to providing our customers
with consistently high quality testing services,with consistently high quality testing services,
– defect freedefect free
– on timeon time
– at competitive prices.at competitive prices.