Page review information
Edition covered
IEC 61511 · IEC 60079 · NEC Art. 500–505 · IEC 60204-1 — exact governing revisions not yet recorded — verify on the linked standards pages
Content status
Review pending
Coverage
Overlay routing for onshore oil and gas; SIS and hazardous-area routing at overview level. The Zone-vs-Division decision was corrected in August 2026 against public OSHA sources (29 CFR 1910.307, 1910.399, NRTL programme FAQ) — classification system and US equipment approval are now stated separately. That correction is not author-reviewed, and the earlier review did not catch the defect.
Last content update
August 2026
Technical validation
Not yet completed
Primary reference
The official published standard — required for final decisions

Confirm the governing edition, jurisdiction, and project-specific requirements before applying anything on this page.

Industry Overlay — Petroleum / Oil and Gas

Petroleum and Oil and Gas Standards

Industry Profile

Field Value
Industry Petroleum, oil and gas — onshore upstream / midstream / downstream
Typical systems ESD, F&G, HIPPS, wellhead control, pipeline control, compressor control
Markets US, international
Special concerns Hazardous areas (Ex), Safety Instrumented Systems (SIS), process safety management

Standards Applicability by Project Phase

Phase Standards Purpose
Concept / HAZOP IEC 61511 §5–6, ISO 12100 Hazard identification, consequence assessment
SIL Determination IEC 61511 §9 (LOPA), IEC 61508 Determine required SIL for each SIF
SIS Design IEC 61511 §10–11, IEC 61508 Part 2/3 Logic solver selection, SIF architecture, PFDavg calculation
Ex Equipment Selection IEC 60079-0, IEC 60079-10-1, IEC 60079-11 Zone classification, EPL/T-code selection, IS barrier sizing
Electrical Design IEC 60204-1, NEC Art. 500/504/505 Machine electrical, US hazardous location wiring
Installation IEC 60079-14, NEC Art. 300/250 Cable selection, IS segregation, equipotential bonding
Commissioning IEC 61511 §12, IEC 60079-14 §6 SIS FAT/SAT, Ex installation initial verification
Maintenance IEC 61511 §16 (proof testing), IEC 60079-17 Periodic SIF proof tests, Ex inspection regime

Standards Selection Flow

Is the installation in a hazardous area (flammable gas/vapor)?
  YES → Classify zones per IEC 60079-10-1
       → Select Ex equipment by EPL, gas group, T-code (IEC 60079-0)
       → US installation: NEC Art. 505 (Zone) or Art. 500 (Division)
       → IS field devices: IEC 60079-11 + entity parameter check

Does the process have a credible loss-of-containment hazard?
  YES → Perform HAZOP (IEC 61511 §5)
       → Determine if a Safety Instrumented Function (SIF) is required
       → Run LOPA to establish SIL target
       → Design SIF per IEC 61511 §10

Is the SIL target ≥ SIL 3, or is the logic solver a custom design?
  YES → Apply IEC 61508 directly for logic solver development
  NO  → IEC 61511 reference to IEC 61508 is sufficient

Standards Path Summary

Category Standards Corpus Status
US electrical installation NEC Art. 240, 250, 300, 500, 504, 505 Needs revalidation — the hazardous-location articles (500, 505) had their certification-boundary content corrected in August 2026 from public OSHA sources; both notes are drafts with a licensed NEC 2023 clause-level check outstanding
Machine electrical design IEC 60204-1 Reviewed
Process safety (SIS) IEC 61511 Reviewed
SIS foundation IEC 61508 Reviewed
Hazardous area equipment IEC 60079 (6 parts) Needs revalidation — the 60079-0 certification-scheme section was corrected in August 2026; see the IEC 60079 page
API standards API 14C, API 670 Not in corpus

Key Engineering Decisions for O&G

Zone vs. Division classification — a classification choice, separate from equipment approval: Both systems may be used for a Class I location; OSHA’s 29 CFR 1910.307 permits either. Zone (Art. 505) keeps the area classification, protection concepts, and EPLs in IEC vocabulary, which suits a project whose classification drawings and equipment population are already IEC-based. Division (Art. 500) is the traditional US vocabulary and is what most legacy US installations and US inspectors use.

Neither choice settles whether a given product may be installed. An ATEX or IECEx certificate is evidence about the product’s protection concept, not a US approval: 29 CFR 1910.399 defines “approved” as acceptable to the authority enforcing OSHA Subpart S, resting normally on certification, listing, or labelling by an OSHA-recognised NRTL, and OSHA’s NRTL programme guidance states that equipment intended for potentially explosive atmospheres in the US must bear the mark of an NRTL recognised for that equipment type. Confirm the NRTL mark and its scope on the actual product at specification time, then confirm the installation with the AHJ. See the approval boundary.

Zener barrier vs. galvanic isolator: Use zener barriers where a dedicated IS earth ≤1 Ω is available and galvanic isolation is not needed. Use galvanic isolators where multiple ground loops cause measurement errors or where the field device is floating. See IEC 60079-11.

SIL 2 vs. SIL 3 architecture: SIL 2 SIFs can typically be achieved with 1oo2 or 2oo3 voted architectures using proven-in-use devices. SIL 3 generally requires 1oo2D or 2oo3 with hardware fault tolerance ≥2 and full IEC 61508 application for the logic solver.

Pre-Commissioning Compliance Checklist

See Oil & Gas Process Skid scenario →

← Industry matrix

Trust Boundary — Engineering Judgment Required

This site is an independent educational reference for industrial automation standards. It paraphrases and organizes guidance in original language; it is not a substitute for the official published standards, professional engineering judgment, or legal review, and content has not been independently verified against current published editions.

Items marked Review pending await technical review against the identified edition. Items marked Planned have no reviewed source material behind them. Do not rely on this site for compliance determinations, safety-critical design decisions, or legal interpretation.