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Hazardous Area Classification (HAC) Service in Oman

What is Hazardous Area Classification (HAC)?

Hazardous Area Classification (HAC) is a process used to assess and categorize parts of a facility based on the presence of flammable materials. The primary goal of HAC layout is to identify areas at risk for dangerous events like fires or explosions and distinguish them from safer areas by selecting suitable equipment and installation methods.

Hazardous Area Classification Systems

This classification is done using either the Class/Division system or the Zone system. The classification also considers the ignition characteristics of the gas or vapor, such as ignition energy and ignition temperature.

HAC is especially important in places like gas wells, oil rigs, refineries, chemical plants, storage areas for flammable liquids, fuel stations, and factories that produce paint or paper.

Objectives of Area Classification

  • Determination of hazardous zone type
  • Establishment of zone extent

What Defines a Hazardous Location?

A hazardous location contains enough flammable gases, dust, or vapors to create a potential risk of fire or explosion.

Classes of Hazardous Locations

  • Class I: Areas where flammable gases or vapors might be present.
  • Class II: Areas where combustible dust could exist.
  • Class III: Areas with easily ignitable fibers or particles in the air.

Hazardous Area vs. Non-Hazardous Area

  • Hazardous Area: High risk of explosive atmosphere; requires extra safety measures.
  • Non-Hazardous Area: No risk of explosive atmosphere; standard safety practices are sufficient.

Zone Classification

A structured text representation of hazardous area zone classification. It categorizes three zones: Zone 0 (gray) – rarely found but possible within Zone 1; Zone 1 (red) – may occur locally within Zone 2; and Zone 2 (green) – generally found inside plant boundaries. The classification is displayed in a numbered format with distinct colors.
Hazardous Area Classification: Zone 0 (Rare), Zone 1 (Local), Zone 2 (Common).
  • Zone 0: Rarely found, but possible within Zone 1 areas.
  • Zone 1: May occur locally within Zone 2 areas.
  • Zone 2: Generally found inside plant boundaries.

Hazardous Area Classification Layouts

HAC layouts provide a clear understanding of zone boundaries, reducing the risk of coincident flammable atmosphere and ignition sources by:

  • Minimizing the existence of flammable/explosive atmosphere.
  • Correctly selecting electrical equipment.
  • Ensuring segregation of ignition sources from flammable gases.

Industries Requiring HAC

  • Oil and gas industries
  • Offshore and onshore platforms
  • FPSO
  • Oil/gas processing units
  • Refineries
  • Pipelines and distribution points
  • Petrochemical industries
  • Mining and storage areas
  • Sewage treatment plants
  • Sugar mills
  • Grain handling and processing units

Standards for Hazardous Area Classification

  • API RP 500: Classification for Class I, Division 1 and Division 2.
  • API RP 505: Classification for Zone 0, Zone 1, and Zone 2.
  • EI 15 IP 15: Safe practice for installations handling flammable fluids.
  • SP-2311: HAC and ignition control standards.

HAC Methodology

Flowchart showing the Hazardous Area Classification (HAC) process with three main sections: Input, Activity, and Output. Inputs include P&IDs Plot Plans, Heat & Material Balance, Physical Properties, Ventilation, and Air Dispersion. Activities cover steps like identifying release, determining grade of release, fluid category, establishing zone classification, calculating hazardous radius, creating HAC drawings, reviewing, and finalizing the agreed hazardous area classification. The output aims to amend design by removing continuous or primary sources of hazards.
HAC process flow from input data to final classification.

The HAC process flowchart starts with inputs like P&IDs, heat and material balance, ventilation, and air dispersion. Key steps include:

  • Identifying the release
  • Determining grade and fluid category
  • Establishing zone classification
  • Calculating hazardous radius
  • Reviewing and agreeing on the classification

Techniques for Area Classification

Point Source Approach

  • Used when the release hole size is known.
  • Considers temperature, pressure, equipment, and ventilation variability.
  • Hazard radius determined using EI-15 standard tables.

Risk-Based Approach

  • Applied when release rate, hole size, or pressure is unknown.
  • Adjusts release frequency and hazard radii based on process scenarios.
  • Used for failures like pump seal leaks or operational errors.

Direct Example Approach

  • Uses generic industrial equipment examples from EI-15 Annex D.
  • Includes drilling sites, wellhead installations, and tank storage facilities.
HAC Layout image is an engineering blueprint showing a large, central structure, likely a tank or vessel, surrounded by detailed annotations for measurements, elevations, and slopes. It also includes labeled elements such as transformers, service roads, and ramps, providing a comprehensive layout of an industrial site.
Engineering Blueprint – Detailed layout with measurements.

HAC Layout image is a technical drawing showing the layout of a wellhead installation. It includes labeled components such as the wellhead, cellar valve pit, telecom cabinet, and AC/DC panels, with detailed measurements and references to specifications like API 10000. The drawing uses a 1:500 scale and provides spatial information for equipment placement with annotated details like "Detail-B" and "Detail-C
Wellhead Installation – Labeled technical drawing.

The image shows a cross-section of a containment bund around a liquid storage tank. It includes the bund wall, the liquid level, and a pit or depression near the base. Key measurements include a 3-meter space above the bund, a 2-meter height from the liquid to the bund top, and the horizontal distance to the bund, marked "L.
Containment Bund – Cross-section with key dimensions.

HAC Layout Illustrations

  • Engineering Blueprint: Shows a central structure with annotations for measurements and layout.
  • Technical Drawing: Details a wellhead installation layout with labeled components.
  • Containment Bund Cross-Section: Displays key measurements like liquid levels and bund dimensions.

Importance of HAC Studies in Process Plants

  • Prevent fatalities and reduce fire/explosion risks.
  • Control or eliminate ignition sources.
  • Accurately classify hazardous areas.
  • Minimize design and installation phase risks.
  • Ensure safe plant operations and protect personnel.

Explore Our Case Study!

Explore Elixir Engineering's detailed study on Fire, Gas Dispersion, and Explosion Analysis (FGDEA) combined with Hazardous Area Classification (HAC) for the Kauther Gas Lift Project. This analysis ensures optimal safety through precise vent dispersion and leak modeling, safeguarding both personnel and equipment. Discover how Elixir's expertise in physical effects modeling, zone classification, and risk assessment can enhance the safety and efficiency of your operations. Click Here

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