IFG

Integrity Field Guide Damage mechanisms, fitness-for-service, and the inspection methods that find them

Guide › Articles

Articles

Written answers to the questions that come up when you are deciding how to inspect something — which method finds what, what each one misses, and what the standard actually asks for.

22 articles

Choosing a method

Choosing a methodGuided wave or pulsed eddy current for corrosion under insulation?Two screening methods, two different blind spots.Choosing a methodMagnetic particle or dye penetrant?The material decides it, not the inspector — and grinding can hide the crack.Choosing a methodPAUT, TOFD or radiography for weld inspection?Three ways to look inside a weld, and one of them misses cracks.Choosing a methodUT spot readings versus corrosion mappingThe most common inspection, and the most common way damage is missed.

Detection method

Detection methodFired heater tube inspection: what actually gets measuredThree measurements decide whether a tube runs another cycle.Detection methodIn-line inspection tools: MFL, ultrasonic, EMAT and caliperFour tool families, four different threats. Choosing the wrong one finds nothing.Detection methodTank floor inspection: MFL scanning and what it missesThe damage nobody sees until the tank leaks.

Finding a mechanism

Finding a mechanismCorrosion under insulation: every method that finds it, and what each missesSix methods, and the survey that comes back clean on a corroded line.Finding a mechanismDents and gouges: which ones matter and how to tellA plain dent and a dent with a gouge look identical to a caliper tool.Finding a mechanismDetecting high-temperature hydrogen attackThe mechanism where a negative result proves nothing, and everyone says so.Finding a mechanismFlow-accelerated corrosion: where it happens and how to find itThins from the inside, leaves the surface smooth, and has killed people.Finding a mechanismHow to detect creep damageDamage that accumulates for years, then accelerates.Finding a mechanismHow to detect microbiologically influenced corrosionBacteria drilling holes through the wall in stagnant water.Finding a mechanismHow to detect pitting corrosionSmall, deep, and invisible to nearly every screening method in use.Finding a mechanismHow to detect stress corrosion crackingWhy every thickness reading in the world will report a cracked vessel as sound.Finding a mechanismWet H₂S damage: blistering, HIC, SOHIC and SSCFour mechanisms, one cause, and four different inspections.

API 579

API 579API 579 Level 1, Level 2 and Level 3: what actually changesThree levels, and the one thing that changes between them.API 579API 579 Part 4 or Part 5: general or local metal loss?The decision that comes before the calculation.API 579Calculating corrosion rate: short term, long term, and which one governsTwo rates from the same data, and they rarely agree.API 579MAWP, MAP and design pressure: what each one meansThree numbers, routinely confused, and only one of them changes with corrosion.API 579What the Folias bulging factor actually doesWhy flaw length punishes you twice.API 579What the remaining strength factor actually isOne number, and why the threshold is 0.90.

Who writes this. A mechanical engineer with twelve years in oil and gas — in-line inspection, fired heater and furnace inspection, and pipeline integrity. What is here comes from the published standards and from what those years in the field actually looked like. It is not written by an API-certified inspector.

This is not an assessment. Nothing on this site may be used to justify a decision about real equipment. Assessing plant requires the current editions of the applicable codes, data from a licensed source, and a competent engineer who signs for the answer. · Integrity Field Guide