Selecting Hazardous Area Standards: API RP 505 and IP15

After the specification assigns IP15 to hazard-radius development and API RP 505 to the electrical Zone framework, the classification basis, drawings, and equipment certificates can be checked without mixing two different functions. The quoted statement is usable only after that division of responsibility is made explicit and the certification requirement is tied to the applicable jurisdiction.

Governing Classification Basis

Before anything else, confirm which document performs each engineering task. IP15, the Model Code of Safe Practice Part 15 for installations handling flammable fluids, provides a methodology for classifying regions around equipment and determining hazard radii. API RP 505, titled Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class 1, Zone 0, Zone 1 & Zone 2, provides the Zone-based framework used for electrical installations at petroleum facilities.

The phrase “Area Classification shall be in accordance with IP15” establishes the classification method. The phrase “applicable Area Classification, as defined in API RP 505” should mean that the completed classification is expressed and applied through the API Zone framework. Record this interpretation in the project design basis. Do not move on until the specification owner accepts the role assigned to each document.

IP15 Classification Inputs

Build the classification from process conditions rather than assigning a radius from equipment type alone. The cited third edition of IP15 accounts for the released material, release conditions, release pressure, and mist or spray formation. It also applies dispersion modelling to hazard-radius calculation and provides a risk-based approach for secondary-grade release sources.

1. List every credible source from equipment that handles or stores flammable fluids.
2. Record the material composition and the process conditions governing each release.
3. Identify whether a release can form a gas, vapor, mist, or spray. A pressurized liquid release cannot be treated only as a pool when atomization changes dispersion.
4. Assign the release category required by the selected IP15 method. Document the justification rather than copying a category from adjacent equipment.
5. Apply the prescribed hazard-radius methodology and retain its inputs, calculation path, and assumptions.
6. Plot the resulting three-dimensional classified region on the hazardous-area drawings.

Outdoor location does not eliminate the need for classification, and placement inside a process shelter does not establish a Zone by itself. Release behavior and enclosure conditions drive the result. Check that every plotted boundary traces to a recorded release case and calculation before translating it into an electrical Zone.

API RP 505 Zone Translation

Apply API RP 505 after the release analysis has established where a flammable atmosphere can occur. The Zone designation communicates the classification to electrical designers and equipment selectors; it does not replace the analysis used to determine the boundary.

1. Take each classified volume developed under IP15 and assign the applicable Zone 0, Zone 1, or Zone 2 designation under the adopted API RP 505 basis.
2. Show vertical and horizontal limits. A plan-view radius alone can miss equipment mounted above or below the release point.
3. Identify overlaps between classified volumes. Apply the governing classification at every equipment location rather than selecting the nearest source only.
4. Mark walls, roofs, openings, and shelter boundaries that affect the classified volume.
5. Create a schedule connecting each area or equipment location to its Zone designation and drawing reference.

If the two documents use terminology that does not map directly, add a project mapping note approved by the responsible hazardous-area engineer. Do not silently substitute one document’s release terminology for the other document’s electrical Zone terminology. Check one representative source from calculation sheet through drawing, Zone schedule, and equipment location before releasing the full drawing set.

Equipment Certification Requirement

Classification and certification are separate controls. The classification establishes the environment; the certificate and equipment marking establish whether a particular device is suitable for that environment. “Certified by an internationally recognised body” is incomplete unless the project identifies who must recognize the body and what certificate information must be submitted.

1. Read the Zone and classified-volume boundary at the exact installed location.
2. Read the process material data needed for equipment selection from the approved classification dossier.
3. Compare the equipment certificate and marking with the complete location requirement, not merely the Zone number.
4. Confirm that the certification body and certification route are accepted by the authority governing the installation.
5. Check certificate conditions, installation drawings, cable-entry requirements, and any restrictions applicable to the selected device.
6. Record the device, location, certificate, drawing, and review status in the hazardous-area equipment register.

A certificate from a widely known organization can still be unacceptable to the governing authority. Conversely, an acceptable certificate does not make equipment suitable for every classified location. Do not move on until each installed item has a traceable match between location requirements, marking, certificate, and installation conditions.

Specification Correction and Interface Checks

Rewrite the requirement so that it cannot be read as ordering two independent classification studies or treating the documents as interchangeable. A technically controlled project clause can use the following structure:

Classify regions around equipment handling or storing flammable fluids using the project-adopted edition of IP15. Express and apply the resulting electrical hazardous-area classification using the Class 1, Zone 0, Zone 1, and Zone 2 framework adopted from API RP 505. Select and install electrical equipment and instrumentation for the classification at its installed location. Submit certification acceptable to the governing authority and comply with all certificate conditions.

Add the adopted editions to the project document register. The evidence identifies the first edition of API RP 505 from 1997 and the third edition of IP15, but the contract must state the editions actually adopted for the project. Also define which requirement governs if project, jurisdictional, and document requirements conflict.

Check the revised clause against the classification philosophy, equipment requisitions, drawing notes, and inspection forms. All four must use the same document roles and Zone terminology before procurement proceeds.

End-to-End Verification

1. Select a release source and trace its material data, pressure, release conditions, and mist or spray assessment into the IP15 calculation.
2. Confirm that the calculated classified volume appears correctly on plan and elevation drawings.
3. Trace the volume to its API RP 505 Zone designation and the hazardous-area schedule.
4. Choose equipment inside that volume and compare its marking, certificate, and certificate conditions with the location requirements.
5. Inspect the installed equipment, entries, and accessories against the approved installation documents.
6. Repeat the trace for outdoor equipment, equipment inside shelters, boundary equipment, and overlapping classified volumes.

Close the verification only when every sampled chain has an unbroken record from release source to classification calculation, Zone drawing, equipment certificate, and installed condition.

Frequently Asked Questions