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Glossary

The vocabulary every P&ID-dependent workflow runs on.

Plain-English definitions of the terms that govern engineering, procurement, process safety, and turnaround work. Each entry explains the term in operational language and traces it back to the engineering drawings Armeta structures.

All terms

Ten terms. One drawing dependency.

EPC and FEED define how projects are contracted and engineered. HAZOP, PHA, MOC, and PSI define how process safety is governed. MTO, P&ID, LDAR, and turnaround define the operational record. Every one of them ultimately reads from, or writes to, a set of engineering drawings.

A.1
EPC

Engineering, Procurement, and Construction

The contract model under which a single contractor delivers a completed, operating facility to the owner — dominant across industrial capital projects.

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A.2
FEED

Front-End Engineering Design

The engineering phase between conceptual design and detailed engineering — where project cost, schedule, and scope are locked in for the EPC contract.

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A.3
HAZOP

Hazard and Operability Study

The structured PHA methodology that uses guide words to systematically identify hazards at every node of a process. The dominant PHA method for complex continuous processes.

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A.4
LDAR

Leak Detection and Repair

The EPA regulatory program under which facilities handling VOC and HAP streams systematically monitor equipment for fugitive emissions and repair detected leaks within specified timeframes.

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A.5
MOC

Management of Change

The OSHA PSM requirement under 29 CFR 1910.119(l) to formally manage every change to a covered process — and one of the most frequently cited PSM elements in enforcement.

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A.6
MTO

Material Take-Off

The structured inventory of equipment, piping, and components extracted from engineering drawings — and one of the most consequential numbers on any industrial project.

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A.7
P&ID

Piping and Instrumentation Diagram

The master engineering drawing for every process system — equipment, piping, valves, instruments, and every interconnection that defines how the facility is built, operated, and maintained.

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A.8
PHA

Process Hazard Analysis

The systematic evaluation of hazards OSHA PSM requires under 29 CFR 1910.119(e). Must be revalidated at least every five years; HAZOP is the most common methodology.

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A.9
PSI

Process Safety Information

The documentation package OSHA PSM requires on every covered process — the factual foundation on which PHA, MOC, Mechanical Integrity, and Pre-Startup Safety Review all depend.

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A.10
Turnaround

Turnaround

The planned, scheduled shutdown during which major equipment is opened, inspected, maintained, and replaced — the most consequential operational event outside of a major incident.

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These definitions are written for engineers, project managers, and operations teams who already work with industrial drawings — not as introductions, but as crisp references that connect each term to the workflows it governs and the regulatory frameworks it sits inside.

Your drawings, your data

Start with ten of your own drawings.

Vocabulary defines the conversation. The fastest way to see what each of these terms looks like when your P&IDs are structured, current, and drawing-traceable is to run Armeta on your actual drawings.