Integrity Field Guide Damage mechanisms, fitness-for-service, and the inspection methods that find them
Pipeline pigging calc & planner All articles Open the guide
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.

37 articles

Pipeline pigging

Pipeline piggingPipeline pigging calculatorFree calculator for pig speed, back pressure, volumes, nitrogen and spread sizing.Pipeline piggingHow to calculate pig speedFlow rate, bore and the speed windows for cleaning and ILI runs.Pipeline piggingHow much back pressure does a pig run need?Static head, gas expansion and the differential the pig itself needs.Pipeline piggingHow much nitrogen does it take to pig a pipeline?Line volume, standard volume at run pressure, and what you actually consume.Pipeline piggingWhere is the pig? Position from volume pumpedTurning the flow meter into a position and an arrival time.Pipeline piggingPig bypass: what it does and how much to useThe flow split, the speed penalty, and typical port percentages.Pipeline piggingIs the line piggable? The checks before you launchBends, valves, unbarred tees, bore changes and trap geometry.

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.Choosing a methodWhich method for exchanger tubes — eddy current, remote field, MFL or IRIS?The material picks the method before you do.

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 mechanismAmine cracking: what it is, where it hides, and how to look for itA weld problem, a residual stress problem, and an entirely preventable one.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 mechanismDead legs and injection points: the two places CML grids missTwo locations that break every assumption behind a thickness grid.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 mechanismHow to find sulfidation before it finds youUniform thinning that varies wildly from one component to the next.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 579After a fire: deciding what can return to serviceThe plant tells you how hot it got, if you read it properly.API 579Brittle fracture: the one damage mechanism you cannot inspect forNo precursor, no warning, no thickness reading that helps.API 579Calculating corrosion rate: short term, long term, and which one governsTwo rates from the same data, and they rarely agree.API 579How API 579 decides whether a crack can stay in serviceTwo failure modes, one chart, and one dominant uncertainty.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.

Inspection planning

Inspection planningRisk-based inspection, without the consultancy languageHow inspection buys interval — and when it does not.

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 · Pipeline pigging calc & planner