Q1.What is the Objective of HAC?
A1. The objective of HAC is as follows:
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.
Q2.What is the Scope of HAC?
A2. The Scope of HAC is as follows:
The Hazardous area classification is carried out as per:
- Classification of the Hazardous area for explosive dust is carried out as per IS 61241
- Classification of the Hazardous area for flammable liquids/ gases/ vapors is carried out by IS 5572
Q3.What reference is commonly used for HAC Study?
A3. The commonly used reference for HAC study is as follows
- IS 61241
- IS-5572
Q4.What is the order of precedence for HAC Study?
A4. The order of precedence used for HAC study is as follows
- IS 61241 / IS-5572
- As per Client Guidelines
- Other international standards
Q5.What is the methodology for HAC Study?
A5. The methodology for HAC Study is as follows
- 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
Q6.Different Types of Grade of Release?
A6. Three types of grades of release are as follows:
- 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.
Q7.Different Types of Class of the Fluid?
A7. Three types of class of fluid are as follows:
Flammable Liquids vary in volatility and have a flash point below 93°C and a Vapor
Pressure not exceeding 2.81 kg/cm2 at 37.8°C. 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
Q8.Area Classification (As per IS 5572)?
A8. Area Classification as per IS 5572 is as follows:
Hazardous areas are subdivided into zones. Based on the likelihood of occurrence and duration of a flammable atmosphere Areas are classified into Zone 0, Zone 1, Zone 2 and Non-hazardous Zone.
- Zone 0 Areas: An area in which an explosive gas atmosphere is present continuously or is present for long periods. Examples are vapor space above closed process vessels, storage tanks or closed containers, areas containing open tanks of volatile, flammable liquid.
- Zone 1 Areas: An area in which an explosive gas atmosphere is likely to occur in normal operation
- Zone 2 Areas: An area in which an explosive gas atmosphere is not likely to occur in normal operation and if it does occur it will exist for a short period only
Q9.Area Classification (As per IS 61241)?
A9. Area Classification as per IS 61241 is as follows:
Based on the likelihood of the formation of potentially explosive dust/air mixtures, the area scan be designated according to Table 1
Table 1 Explosive dust area classification as per IS 61241
| Presence of Combustible Dust | Resulting Zone Classification of area of dust clouds |
| Continuous presence of dust cloud | 20 |
| Primary grade of release | 21 |
| Secondary grade of release | 22 |
Zone 20: A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is present continuously, or for long periods or frequently for short periods
Zone 21: A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is likely to occur occasionally in normal operation.
Zone 22: A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period only.
Q10.What is the steps for HAC Study?
A10. Following are the steps for HAC Study:
Methodology for Flammable liquid and vapors
- Review Process Flow diagram
- Prepare separate table for liquid and solid chemical along with flammable/combustible Properties
- Classification of material as per IS-5572
- 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 dusts
- Need For Classification
- Facility information & history
- Classification of material as per IS-61241
- 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.
Q11.What are the documents required for the HAC Study?
A11. The documents required for the HAC Study include the following:
- 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
- Equipments & Details
- Layout & plot plan
Q12.What are documents deliverables for HAC Study?
A12. The documents deliverables for HAC Study are as follows:
- 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
Q13.Which software will be used for the HAC study?
A13. Following software will be used for HAC marking:
AutoCAD
Q14.Different guidelines for HAC study?
A14. Different guidelines used for HAC study are as follows:
- 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.
- NFPA-497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous(Classified) Locations for Electrical Installations in Chemical Process Area.
- NFPA-499 (Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas)
Q15.Graphical representation of Different Zones of HAC?
A15. Graphical representation of HAC Zones are as follows:
Q16.What is the Comment Resolution Sheet?
A16. The meaning of Comment Resolution Sheet (CRS) is as follows:
A comment resolution sheet is a document used to track and address comments, feedback, or issues raised during a review process, audit, or evaluation.
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