FAQ - Hazardous Area Classification (HAC) Study - NFPA

FAQ HAZARDOUS AREA CLASSIFICATION (HAC) STUDY- NFPA

1.   What is the Objective of HAC?

The purpose of the Hazardous Area Classification study is to determine the extent of the hazardous areas around equipment handling or storing flammable fluids, combustible fluids and combustible dusts, both liquid and vapors in terms of Zone 0, Zone 1, Zone 2 and Division 1 and Division 2

The aim of hazardous area classification is to avoid ignition of those releases that may occur from time to time in the operation of facilities handling flammable liquids and vapors.  The approach is to reduce to an acceptable minimum level the probability of coincidence of a flammable atmosphere and an electrical or other source of ignition occurring. In Hazardous Area Classification the extent of the hazardous areas around equipment handling or storing flammable fluids, both liquid and vapors is determined in terms of Zone 0, Zone 1, and Zone 2. The hazardous area classification around the equipment handling flammable/explosive dust is determined in terms of Division 1, Division 2.

2.    What is the Scope of HAC?

The Hazardous area classification is carried out as per:

• Classification of the Hazardous area for explosive dust is carried out as per NFPA 499

• Classification of the Hazardous area for flammable liquids/ gases/ vapors is carried out by NFPA 497

3.    What reference is commonly used for HAC Study?

• NFPA-497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas.

• NFPA–499 (Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas)

4.    What is the order of precedence for HAC Study?

• NFPA 497/ NFPA 499

• As per Client Guidelines

• Other international standardsS

5.    What is the methodology for HAC Study?

• Data collection

• MSDS Sheet Preparation

• Process step and Representative Chemical sheet preparation

• Client Approval for HAC Schedule preparation

• HAC Schedule

• ·Draft Report

• Client Approval for HAC marking

• HAC marking

• Comments incorporation along with CRS (Comment Resolution Sheet)

• Final Report

6.    Different Types of Grades of Release?

• Continuous Grade release (C): A release that is continuous or nearly so, or that occurs frequently and for short periods.

• Primary Grade release (P): A release that is likely to occur periodically or occasionally in normal operation, that is, a release which, in operative procedures, is anticipated to occur.

• Secondary grade release (S): A release that is unlikely to occur in normal operation and, in any event, will do so only infrequently and for short periods, that is, a release which, in operating procedures, is not anticipated to occur.

7.   Different Types of Class of the Fluid?

Flammable Liquids vary in volatility and have a flash point below 930C and a Vapor Pressure not exceeding 2.81 kg/cm2 at 37.80C. These are divided into three classes, as follows,

Class A     :  Flammable liquids having flash point below 23° C

Class B     :  Flammable liquids having flash point 23° C and above but below 65°C 

Class C     :  Flammable liquids having flash point 65° C and above but below 93°C

8.   Area Classification (As per NFPA 497)?

• Class-1 Zone 0 Areas: A Class I, Zone 0 location is a location that meets the following conditions:

• Ignitable concentrations of flammable gases or vapors that are present continuously

• Ignitable concentrations of flammable gases or vapors that are present for long periods of time.

• ·Class I, Zone 1. Areas: A Class I, Zone 1 location is a location that meets the following conditions:

• Ignitable concentrations of flammable gases or vapors that are likely to exist under normal operating conditions.

• Ignitable concentrations of flammable gases or vapors that may exist frequently because of repair or maintenance operations or because of leakage.

• ·Class I, Zone 2 Areas: A Class I, Zone 2 location is a location that meets the following conditions:

• Ignitable concentrations of flammable gases or vapors that are not likely to occur in normal operation, and if they do occur, they will exist only for a short period.

9.   What is the steps for HAC Study?

Methodology for Flammable liquid, vapors and Combustible Dusts

The procedure of HAC involves following steps:

• Review Process Flow diagram

• Prepare separate table for liquid and solid chemical along With flammable/combustible Properties

• Classification of material as per NFPA-497

•  Selecting the Appropriate Classification Diagram

• Determine the Zone classification

• Determine Extent of the Classified Location

• Review and recommendation

To enable selection of electrical equipment appropriate to the zone classification, the apparatus sub group and temperature class is then determined based on the flammable substances that can be release.

Methodology for Combustible solids

The procedure of HAC involves following steps:

• Need For Classification

• Facility information & history

• Classification of material as per NFPA-499

• Selecting the Appropriate Classification Diagram

• Determine the Zone classification

• Determine Extent of the Classified Location

• Review and recommendation

To enable selection of electrical equipment appropriate to the zone classification, the apparatus sub group and temperature class is then determined based on the flammable substances that can be release.

10.   What are the documents required for the HAC Study?

• Scope of work

• Approved P&IDs

• List of Chemicals

• Process design basis

• Hazardous inventories and their SDS

• Process description

• MSDS or Chemical properties of RM & FG

• Equipment Design and Operating Condition /MOC

• Equipment’s & Details

• Layout & plot plan 

11.   What are documents deliverables for HAC Study?

• Executive Summary

• Document Review

• Submission of terms of reference

• HAC Methodology

• HAC Schedule

• HAC Marked Layout

• Comments Resolution sheets

• Reference

• List of tables

• List of appendix

12.   Which software will be used for the HAC study?

• AutoCAD

13.   Different guidelines for HAC study?

• IEC 60079-10-1 Explosive atmospheres Part 10-1: Classification of areas - Explosive gas atmospheres

• IEC 60079-10-2 Explosive atmospheres Part 10-2: Classification of areas – Explosive dust atmospheres

• Draft Version of EI15 Edition 4– Model Code of Safe Practice - Area Classification Code for Installations Handling Flammable Fluids. Energy Institute 2015. 3.

• EI15 Edition 3– Model Code of Safe Practice - Area Classification Code for Installations Handling Flammable Fluids. Energy Institute 2005.

• IS 61241- “Electrical Apparatus for Use in the Presence of Combustible Dust - Code of Practice”

• IS 5572- "Code of Practice for Electrical Installations of Industrial Establishments: Part 1 General Aspects"

14.   Graphical representation of Different Zones of HAC?

15.   What is the CRS Format?

 DISCLAIMER

This FAQ is provided solely for informational and educational purposes. It is advisable to verify all information presented and consult with appropriate experts or professionals before making any decisions or implementing any strategies based on the content of this blog. HSE Risk Management Services Pvt. Ltd. accept no liability for any actions taken or not taken based on the information provided herein.

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