OISD-118 summary
OISD-STD-118 and QRA should be used together for different purposes. The standard addresses layouts for oil and gas installations; QRA tests how credible fire, explosion and toxic-release scenarios could affect people, equipment and boundaries. A study should first check the current OISD-STD-118 layout requirements, then use QRA to examine scenario-specific consequences, risk drivers and additional mitigation. QRA does not waive a prescriptive layout requirement.
For refineries, terminals, depots, pipeline installations and other applicable oil and gas facilities, layout is a primary risk-control layer. Separation, access, orientation, drainage, occupied buildings and future expansion can influence both the likelihood of escalation and the exposure of people. OISD-STD-118 provides the layout framework, while a quantitative risk assessment provides scenario-based evidence about the proposed or existing arrangement.
What is OISD-STD-118?
The Oil Industry Safety Directorate lists OISD-STD-118 as “Layouts for Oil and Gas Installations.” The official OISD Standards List identifies June 2025 as the current edition in vogue. OISD also identifies STD-118 among standards included in the Petroleum Rules, 2002; applicability must still be established for the specific facility, licence and activity.
Two facts to verify before starting
- Edition: OISD’s current list shows OISD-STD-118, June 2025.
- Regulatory link: OISD lists STD-118 as one of six OISD standards included in the Petroleum Rules, 2002.
Use the official standard and current regulatory documents. A blog summary is not a substitute for the controlled publication.
OISD layout review versus QRA
| Layout compliance review | Quantitative risk assessment |
|---|---|
| Checks applicable layout provisions and prescribed separation | Models credible release, fire, explosion and toxic scenarios |
| Reviews facility arrangement, access and segregation | Estimates consequence distances and, where required, risk |
| Identifies departures from the applicable standard | Identifies dominant scenarios, receptors and escalation paths |
| Produces a compliance or gap register | Produces scenario records, contours, risk results and mitigation options |
A facility may perform well in one review and still need action from the other. A compliant separation distance does not prove that every scenario has acceptable risk, and a favourable model result does not cancel an applicable statutory or licence requirement.
Inputs needed for an OISD-STD-118-aligned QRA
1. Controlled facility layout
Use the latest plot plan with a drawing number and revision. Identify the battery limit, property boundary, roads, gates, tank farms, process areas, loading or unloading points, utilities, flare or vent locations, control rooms, substations, workshops, warehouses and emergency facilities. The geometry used for modelling should be traceable to this drawing.
2. Equipment and hazardous inventory
Record equipment tags, materials, normal and maximum quantities, composition, pressure, temperature and operating mode. Confirm tank dimensions, fill levels, vessel data, line sizes and transfer rates. The inventory must agree with process documents and any licence or approval drawing.
3. Occupancy and receptor data
Map permanently and intermittently occupied buildings, work areas, contractor zones, security posts, muster points and relevant offsite receptors. Use realistic day/night or shift occupancy when societal-risk calculations are in scope.
4. Safeguards and emergency response features
Document detection, isolation, shutdown, depressurisation, drainage, containment, fire protection, access routes and emergency resources. Treat a safeguard as credited only when its function, reliability and response time are defensible.
Eight-step layout and QRA workflow
- Confirm applicability: identify the facility type, regulatory route, licence condition and current OISD edition.
- Create a clause register: record applicable layout requirements and the evidence used to check them.
- Perform the drawing review: identify clear compliance, gaps, uncertainties and items requiring authority interpretation.
- Develop QRA scenarios: link credible releases to tagged equipment and activities on the same layout.
- Model consequences: assess relevant thermal radiation, overpressure and toxic effects using stated endpoints.
- Evaluate escalation and exposure: review nearby equipment, occupied areas, boundaries, access and emergency functions.
- Optimise mitigation: prioritise inherently safer layout changes before relying only on procedural controls.
- Close and revalidate: update the drawing, action register and model when changes materially affect the study.
Layout questions the QRA should help answer
- Which scenarios determine the largest onsite or offsite consequence distances?
- Could an initial event escalate to adjacent tanks, vessels, pipe racks or buildings?
- Are occupied buildings or control functions exposed to material thermal or overpressure effects?
- Can emergency access, isolation and firefighting functions remain available during a credible event?
- Does drainage or containment reduce spread, or could it direct a release toward vulnerable areas?
- Would a layout change reduce risk more reliably than adding complex protective systems?
Common review failures
- Using an earlier OISD edition without checking the official current list
- Quoting separation distances without confirming facility type, service and exceptions
- Running QRA on a superseded plot plan
- Omitting loading points, temporary occupancy or planned expansion
- Calling consequence contours “risk contours” without including frequency
- Using QRA results to justify a departure without documenting the applicable regulatory process
- Closing actions in a spreadsheet while the approved drawing remains unchanged
What should the final deliverable contain?
A useful package contains the scope and applicability basis; controlled drawing list; layout compliance matrix; data register; scenario register; modelling assumptions; consequence and risk results; readable contour drawings; occupied-building and escalation observations; recommendations; action owners; and a record of final layout changes. Assumptions and limitations should be explicit.
For a new project, link this work to the design-stage QRA gates. For calculation review, use our QRA frequency and consequence guide.
Does an OISD-STD-118 QRA guarantee approval?
No. Compliance and approval depend on the current standard, applicable legislation, licence category, submitted drawings, other safety standards and the responsible authority’s review. QRA is evidence for risk-informed decisions, not an approval certificate. Project teams should also identify other applicable OISD standards for fire protection, storage, pipelines, LPG, electrical systems and operating practices.
How Elion supports layout-focused QRA
Elion Technologies and Consulting can combine a controlled layout review with quantitative consequence and risk analysis. The work is structured to keep the clause register, model geometry, scenario inputs and mitigation actions aligned. Learn more about our quantitative risk assessment services or our PESO-facing QRA submission checklist.
Planning or modifying an oil and gas installation?
Share the facility type, licence context, latest plot plan, equipment inventory and project stage. Elion can define a layout-review and QRA scope using the current controlled references. Final applicability and approval decisions remain with the relevant authority.