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 Hazardous Area Classification layout is to identify which areas are at risk for dangerous events like Fires or Explosions and by selecting suitable equipment and installation methods distinguish them from safer areas.

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 vapour 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.

Area classification has two main objectives, the determination of the type of any hazardous zone, and the extent of the zone.

What defines a hazardous location?

A hazardous location is an area where the atmosphere contains enough flammable gases, dust, or vapors to create a potential risk of fire or explosion.

What are the 3 classes of hazardous locations?

The three classes of hazardous locations are:

1. Class I: Areas where flammable gases or vapors might be present.
2. Class II: Areas where there could be combustible dust.
3. Class III: Areas that are hazardous due to the presence of easily ignitable fibers or particles in the air.

What defines a hazardous area versus a non-hazardous area?

• A hazardous area is where there's a high risk of an explosive atmosphere, so extra safety measures are needed for installing and using equipment.
• A non-hazardous area is where there's no risk of an explosive atmosphere, so standard safety practices are enough for equipment.

Hazardous Area Classification HAC:

• Determination: Uses calculated hazard radii along with physical geometry or shape factors.
• Risk-Based Approach: Adjusts release frequency and hazard radii to match specific process scenarios.

Typical Zone Distribution:

• Zone 2: Generally found inside plant boundaries.
• Zone 1: May occur locally within Zone 2 areas.
• Zone 0: Rarely found, but possible within Zone 1 areas.

Hazardous Area Classification Layouts: Provides detailed understanding of boundaries concerning different Zones. The intention is to reduce, to an acceptable level, the probability of coincident existence of a flammable / explosive atmosphere and sources of ignition. This approach is implemented through:

1. Minimizing the possibility of existence of flammable/explosive atmosphere.
2. Correct selection of electrical equipment to be installed in these hazardous areas. The electrical apparatus/instruments are one of the potential sources of ignition of flammable gases/vapours.
3. Ensuring that sources of ignition including electrical equipment are segregated from sources of flammable gas in accordance with code requirements.

Understanding the Applicability of Hazardous Area Classification

1. Oil and gas industries
2. Offshore platforms
3. Onshore platforms
4. FPSO
5. Oil/gas processing unit
6. Refineries
7. Gas/oil Pipelines and distribution points
8. Petrochemical industries 
9. Mining and storage areas
10. Sewage treatment plants
11. Sugar mills
12. Grain handling and processing units

STANDARDS FOR HAZARDOUS AREA CLASSIFICATION 

• API RP 500 – Recommended Practice for Classification of Locations for Electrical Installation at Petroleum Facilities Classified as Class I, Division 1 and Division 2.
• API RP 505 – Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class 1, Zone 0, Zone 1, and Zone 2
• EI 15 IP 15 Model Code of Safe Practice Part 15 Area Classification for Installations Handling Flammable Fluids 4th edition June 2015
• SP-2311 Hazardous Area Classification & Ignition Control

HAZARDOUS AREA CLASSIFICATION HAC Methodology

Technique for Area classification

The methodology adopted for Hazardous Area classification approach is based on below mentioned technique.

  Point source approach

• Installations or processes can experience variability in temperature, pressure, equipment, and ventilation, which can significantly impact the extent of flammable release.
• The extent of flammable release can vary greatly, making it necessary to conduct individual assessments for each situation.
• This approach to assessment is known as the "point source approach."
• The point source method is applicable in all situations where the release hole size is known.
• The hazard radius can be determined using the Hazard Radius Table (Annex C, Table C4) from the EI-15 standard.

  Risk Based approach

• When the ‘Release Rate’ is unknown (such as when the hole size and pressure are not determined), the ‘Risk-based approach’ should be applied as outlined in Annex C, Part-2 EI-15.
• The Risk-based approach methodology allows for adjusting the release frequency and hazard radii to match specific process scenarios.
• This methodology is applicable in situations like the failure of pump or compressor seals, leaks from valves and flanges, or operational errors.

  Direct Example approach

• Generic industrial equipment handling flammable materials can be classified based on typical examples from Annex D of EI-15.
• Common examples include drilling, workover, and wellhead sites.
• Tank storage facilities are also included, covering both upstream and downstream operations.

Importance Hazardous Area Classification (HAC) study in a process plant are:

1. To prevent fatalities and reduce the risk of fire and explosion caused by the presence of flammable atmospheres near potential ignition sources.
2. To ensure that ignition sources are eliminated or controlled within hazardous areas.
3. To accurately identify and classify hazardous areas within the facility.
4. To minimize overall risk during the design and installation phases of the facility.
5. To develop safety and operational procedures that ensure the safe operation of the plant 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