Resources
Plain answers to the terms the work runs on: the inspection codes, the NDE methods, and the math behind run, repair, or replace. One definition each, written the way a practitioner would say it.
Built in, not bolted on
The vocabulary, area by area. Plain, to the clause.
Programs, methods, and the math behind run, repair, or replace: each term defined the way a practitioner says it.
23 terms · 4 areas
Four groups, from the programs that decide what to inspect to the math behind the verdict. Pick a starting point, or read straight through.
The decision frameworks that turn inspection data into a plan: what to inspect, when, and whether the equipment can keep running.
ReadThe published rules an inspection program is measured against. The numbers an auditor expects to see cited.
ReadNondestructive examination: how condition gets measured in the field without cutting the asset open.
ReadThe engineering math behind the verdict: corrosion rate, remaining life, criticality, and the methods that rank risk.
Read01 · 5 terms
The decision frameworks that turn inspection data into a plan: what to inspect, when, and whether the equipment can keep running.
Risk-Based Inspection (RBI) is a method for planning equipment inspection by ranking each item on its risk, the likelihood of failure multiplied by the consequence. High-risk equipment earns more frequent, more thorough inspection, and low-risk equipment earns less, so inspection effort follows the risk instead of a fixed calendar. The methodology is set out in API RP 580 (the practice) and API RP 581 (the quantitative model).
Fitness-for-Service (FFS) is a quantitative engineering assessment of whether in-service equipment with a known flaw, such as wall loss, cracking, or a dent, is safe to keep operating. It answers run, repair, or replace using the actual measured condition rather than the original design assumptions. The standard reference is API 579-1 / ASME FFS-1, which provides leveled assessment procedures for each damage type.
A Condition Monitoring Location (CML), sometimes called a thickness monitoring location (TML), is a designated spot on a piece of equipment where the same measurement, usually wall thickness, is taken on every inspection. Measuring the identical location over time is what makes a corrosion rate trustworthy: it tracks real metal loss instead of comparing two different points. CMLs are the data backbone of a mechanical integrity program.
A turnaround is a planned, scheduled shutdown of a process unit so equipment can be opened, inspected, repaired, and re-certified. None of that work can be done while the unit is running. It is the most expensive and highest-risk event in a plant's calendar, often running tens of millions of dollars over a few weeks, so scope, schedule, and cost are managed tightly from readiness through close-out. Inspection findings drive a large share of turnaround scope.
A digital twin is a living digital model of a physical asset, its hierarchy, geometry, and condition, kept in sync with the real equipment as inspections and readings land. For asset integrity it is the single record every discipline reads from, so a corrosion reading, a 3D model, and a fitness-for-service verdict all point at the same circuit. It turns scattered files into one source of truth for the equipment.
02 · 6 terms
The published rules an inspection program is measured against. The numbers an auditor expects to see cited.
API 510 is the inspection code for pressure vessels in service. It covers in-service inspection, rating, repair, and alteration of vessels after they have been placed in operation, including inspection intervals, thickness measurement, and the qualifications an inspector must hold. It is published by the American Petroleum Institute and is widely adopted across refining and chemicals.
API 570 is the inspection code for in-service piping systems. It governs inspection, repair, alteration, and rerating of metallic piping that has been in operation, and it sets inspection intervals based on piping classification and corrosion rate. Like its sister codes, it defines the certification an authorized piping inspector must carry.
API 653 is the standard for inspection, repair, alteration, and reconstruction of aboveground storage tanks. It applies after a tank is in service, covering the shell, bottom, and roof, and it sets inspection intervals and out-of-service inspection requirements. It is the tank counterpart to API 510 for vessels and API 570 for piping.
API 579-1 / ASME FFS-1 is the joint standard for Fitness-for-Service assessment of in-service equipment. It provides tiered procedures, organized by damage mechanism such as general metal loss, local thin areas, pitting, and crack-like flaws, for deciding whether flawed equipment is safe to keep running. The leveled structure lets engineers start with a conservative screening assessment and escalate to detailed analysis only when needed.
API RP 580 and API RP 581 are the paired recommended practices for Risk-Based Inspection. API 580 describes the principles and the program: how to set up RBI, what data it needs, and how to manage it. API 581 supplies the quantitative methodology, the equations and tables that turn that program into a calculated probability and consequence of failure.
The ASME Boiler and Pressure Vessel Code (BPVC) is the body of construction rules for boilers, pressure vessels, and related components, published by the American Society of Mechanical Engineers. Its sections cover design, materials, fabrication, and examination, and it sets the original requirements equipment is built to before the in-service inspection codes take over. ASME also co-publishes the Fitness-for-Service standard as FFS-1.
03 · 7 terms
Nondestructive examination: how condition gets measured in the field without cutting the asset open.
Nondestructive Examination (NDE), also called Nondestructive Testing (NDT), is the set of methods for inspecting a material or weld without damaging it or taking it out of service. The methods reveal surface and internal flaws, thickness, and material condition so equipment can be evaluated and put back to work. Common methods include ultrasonic, radiographic, magnetic particle, liquid penetrant, eddy current, and phased array.
Ultrasonic Testing (UT) uses high-frequency sound pulses sent into a material to measure thickness or detect internal flaws. The time it takes the echo to return reveals how much metal is left or where a discontinuity sits below the surface. It is the workhorse method for tracking wall loss at condition monitoring locations.
Radiographic Testing (RT) passes X-rays or gamma rays through a part to produce an image of its interior, much like a medical X-ray. Internal flaws such as porosity, slag, or incomplete fusion in a weld show up as density changes on the radiograph. It gives a permanent image of internal condition that can be archived and reviewed.
Magnetic Particle Testing (MT) finds surface and near-surface flaws in ferromagnetic materials by magnetizing the part and applying fine iron particles. A crack distorts the magnetic field and the particles gather at the flaw, making it visible. It is fast and sensitive for detecting cracks in steel welds and components.
Liquid Penetrant Testing (PT) reveals surface-breaking flaws by coating a part with a dye that seeps into any opening, then drawing the dye back out with a developer. The flaw shows as a bright or colored indication against the developer. It works on most nonporous materials, including the nonmagnetic ones that magnetic particle cannot inspect.
Phased Array Ultrasonic Testing (PAUT) is an advanced form of UT that uses a probe with many small elements fired in timed sequence to steer and focus the sound beam electronically. That produces a detailed cross-sectional image of a weld or component and inspects a volume from a single position. It is widely used for weld inspection and corrosion mapping where standard UT would be slower or less complete.
Eddy Current Testing (ECT) induces small circulating electrical currents in a conductive part with a coil, then reads how flaws disturb those currents. It is well suited to finding surface cracks and to inspecting heat-exchanger and condenser tubing at speed. Because it needs no couplant and no contact, it works quickly over large numbers of tubes.
04 · 5 terms
The engineering math behind the verdict: corrosion rate, remaining life, criticality, and the methods that rank risk.
Corrosion rate is the speed at which a material is losing thickness, usually stated in mils (thousandths of an inch) or millimeters per year. It is calculated from the change in measured wall thickness at a location divided by the time between the two readings, which is why repeatable condition monitoring locations matter so much. The rate feeds directly into remaining-life and next-inspection-date calculations.
Remaining life is the estimated time a piece of equipment can stay in service before its wall thickness reaches the minimum required for safe operation. It is computed by taking the metal available above that minimum and dividing by the corrosion rate. It sets the maximum inspection interval and signals when to plan repair or replacement, often during the next turnaround.
Reliability-Centered Maintenance (RCM) is a structured method for deciding the right maintenance strategy for each asset based on how it can fail and what those failures would cost. It asks what functions the equipment performs, how it fails to deliver them, and which maintenance task, if any, best manages each failure mode. The aim is to spend maintenance effort where it actually reduces risk, rather than servicing everything on the same schedule.
Failure Modes and Effects Analysis (FMEA) is a step-by-step technique for listing the ways a component or system can fail, the effect of each failure, and how serious and likely it is. Each failure mode is scored so the highest-priority risks can be addressed first, often with a risk priority number. It is a building block of reliability programs and feeds the strategy choices made in RCM.
Criticality is a ranking of how important a piece of equipment is, based on the consequence if it fails, covering safety, environmental, and production impact. It lets a plant sort thousands of assets so inspection, maintenance, and spares attention goes to the equipment that matters most. Criticality is a core input to both Risk-Based Inspection and Reliability-Centered Maintenance.
One record, one source
Every term here traces to the clause that governs it, so a reviewer checks the basis instead of trusting it.
Why the grouping matters
Each area hands its output to the next: the codes set the scope, the methods take the measurement, the math sets the verdict, and the ranking decides what gets attention first.
API 510, 570, and 653 set how vessels, piping, and tanks are inspected, rated, and repaired in service.
UT, RT, PAUT, and the rest measure wall loss and find flaws without cutting the asset open.
API 579 weighs the measured flaw against the design minimum to answer run, repair, or replace.
Corrosion rate, remaining life, and criticality rank assets so attention follows risk, not the calendar.
“A fitness-for-service assessment determines whether equipment containing a flaw is safe to keep running, at what pressure, and for how long.”
Answers
These are the words that decide work in the field: the inspection codes, the NDE methods, and the math behind run, repair, or replace. We define the terms operators ask about during a turnaround or an audit, not every entry in a textbook. If a term sets a verdict on a vessel, a tank, or a line, it belongs here.
The programs and methods that govern fixed equipment: API 510 for pressure vessels, API 570 for piping, API 653 for storage tanks, API 579 for fitness-for-service, and API 580/581 for risk-based inspection. Where a term comes from materials or process safety, we tie it to ASME, NACE/AMPP, or OSHA PSM.
They are plain-language explanations, written to match how each term is used under its governing code. They are not a substitute for the published standard. When a number or a method drives a decision, read the clause itself: the code is the authority, and we point you to it.
Because a definition without a source is an opinion. Every term here traces to the standard that governs it, so a reviewer can check the basis instead of taking it on trust. That is the same rule the platform runs on: a verdict you can read back to the clause that set it.
Most terms link to the module that puts them to work on a real asset. RBI, fitness-for-service, CMLs, and corrosion rate live on one record, each calculation cited to the standard behind it. The glossary explains the term; the platform runs it on your own equipment.
RBI, Fitness-for-Service, CMLs and corrosion rate, on one record, cited to the standard. See it on your asset class in twenty minutes.
