Hazardous area classification and Elecrtical, Instrument and Process Engineer Responsibility

This presentation explains the Hazardous gas Classification and area Classification, and the responsibility of Electrical, Instrument and Process Engineer Responsibility.

1. Hazardous area classification By Kathiresan Nadar Process Engineer-II

2. Hazardous Area Failure Case Study On October 23 2009 Massive explosion at Caribbean Petroleum (CAPECO) Gasoline Storage area Gasoline Storage operation done without a Level Transmitter. Thus required Manual Operation and Manual Checking for predicting tank Level Error in Predicting the Level of the tank thus The Gasoline Overflow and come out of the storage tank Gasoline Vapor Covered area of 104 Acre and the atmosphere is windless (Low Ventilation) Gasoline Liquid Drained from the Containment tank to the waste water area and reached Electrical Equipment Electrical Equipment Ignited the area. The Accident Cause the Death of 2 Employee and 1 was Critically Injured.

3. Why Accident Happened ?? And Who are Responsible ?? Poor Ventilation (Natural Cause) Improper Instrumentation Poor Process Design to flow the containment liquid to Waste water area Waste water area’s Hazardous area Classification. Since Waste water has the Low or negligible source of Flammable material. The area is classified for the Zone 2. The Corresponding Instrumentation and Electrical Equipment is designed for the Zone 2 Process Safety Calculation Mistake.

4. Safety Characteristics of Gas and Vapor Flash Point Auto Ignition Temperature Explosion Limit Lower Explosion Limit Higher Explosion Limit Maximum Oxygen Concentration Vapor Density

5. Explosion Group The explosive characteristics of the air mixtures of gases, vapors, or dusts vary with the specific material involved. Group I: Electrical apparatus for mines susceptible to firedamp (for use underground). Group II: Electrical apparatus for places with a potentially explosive atmosphere other than mines susceptible to firedamp. Group III: Electrical apparatus for places with a potentially explosive atmosphere other than mines susceptible to firedamp. For Dust.

6. Grouping and Classification of Area Grouping is based on maximum experimental safe gap (MESG) minimum igniting current (MIC) ratio Groups for Gases are IIA, IIB, IIC Gas Groups Chemical/Component MESG MIC Ratio IIC Acetylene, Hydrogen, Flammable Liquid produced Vapor, Flammable Gas, Combustible Liquid Produced Vapor <0.5 mm < 0.45 IIB acetaldehyde, ethylene, Flammable Liquid produced Vapor, Flammable Gas, Combustible Liquid Produced Vapor >0.5 <0.9 >0.45 <0.8 IIA acetone, ammonia, ethyl alcohol, gasoline, methane, propane, or fammable gas, fammable liquid-produced vapor, or combustible liquid-produced vapor >0.9 >0.8

7. Temperature Classification Minimum temperature required to cause the fire without spark or flame to set a fire. T1 - 450 C T2 - 300 C T3 - 200 C T4 - 135 C T5 - 100 C T6 – 85 C For intrinsically safe it is inside temperature whereas for flame proof it is outside temperature.

8. What is Hazardous Area Classification ?? Area classification is a method of analyzing and classifying the environment. where explosive gas atmosphere may occur to allow the proper selection of electrical apparatus to be installed in that environment. Objective - The object of the classification procedure is to enable electrical apparatus to be operated safely in that environment.

9. In Situations When Explosive Gas are Present Eliminate the likelihood of an explosive gas atmosphere occurring around the source of ignition or eliminate the source of ignition Raising the flash point by substitution for e.g Adding Water Lower process temperature by cooling (water spray jet) Limiting concentration below LEL by Proper Ventilation Limit the range of explosion fames and explosion pressures to a sufficient level of safety. Explosion Proof Design Containment. In practice however, it is very difficult to ensure that an explosive gas atmosphere will never occur. In this case, apparatus with special protective measures should be used. And for proper selection we need area classification

10. Explosion Protection Avoiding fammable substances (replacement technologies) or by inerting with N2 This is done by proper venting or removing one component from the fire Triangle. For e.g Avoiding Hot Surface Avoiding Static Electricity Lightining etc provision such that the fire or explosion occurred is not transferred to the bulk system. For E.G Explosion pressure resistant construction.

11. Hazardous area Defined by The type of hazard (groups). The AIT of the hazardous material (temperature or T rating). The likelihood of the hazard being present in flammable concentrations(zones/ Class and Division) Type of Hazard Group I, II, III and its subdivision. NFPA Publication 70, National Electrical Code (NEC) defnes the type of hazardous substance Class and Division – Followed in North America Zones – Followed in the Rest of the World

12. What are Classes, Division and Zones Class I – Flammable Gases and Vapor may present. Class II – Location in which combustible dust may be present. Class II – Location in which Ignitable fibre may be present. Division Defines the probability of the hazardous materials being able to produce the hazardous mixture Division 1 – The mixture has the high probability of forming the explosive atmosphere at normal operating conditions. Division 2 – The Mixture has low probability of forming the explosive mixture at normal operating conditions. Zone 0, 1, 2 – Zones where hazardous vapor and Gas will be present Zone 20, 21, 22 – Zones where hazardous dust or fibers will be present.

13. Sources of Release Identify the Source of Release Process Item such as Tank, Pump, Pipeline, Vessels etc are the source of release Welded pipeline are not considered as the source of release.

14. Next Important thing is the Grade of Release The Release is Continuous, Primary or Secondary Grade should be estimated based on operating conditions (T and P) at Normal or Abnormal situations. Continuous – A Release that is expected to occur for longer period of the time For E.g Surface of a flammable liquid in a fixed roof tank Surface of an open reservoir (e.g., oil/water separator) Primary – A Release that occur Periodically or Occasionally during normal operation Seal of Pump, Compressor, Valves, Water draining point, Sample Collecting Point, Relief Valve, Vent during normal operation. Also changing filter cloth. Secondary – A Release that occur infrequently or if it occur the duration is low Seal of Pump, Compressor, Valves, Water draining point, Sample Collecting Point, Relief Valve, Vent during abnormal condition

15. Extent of Zone Extent of Zone Depend on the following factor Release Velocity or Release Rate Concentration of flammable gas in the released mixture Ventilation Obstacles Boiling Point of the flammable liquid LEL Flash Point Relative Density Liquid Temperature

16. Ventilation

17. Why Ventilation effect the Zone type and Zone Extent ? Ventilation Promote Dispersion thus Hazardous material fall below LEL. Availability of Ventilation Good – Ventilation is present continuously (Wind speed 0.5 m/s) Fair – Ventilation that occur during normal operation and interruption is permissible Poor – Ventilation that did not meet standard and interruption is not expected. Ventilation Degree High Ventilation – Reduce the Source of release below LEL Instantaneously. Medium Ventilation – Ventilation that provide stable Zone Extent once the Hazard Release and reduce concentration below LEL when Release is stopped. Low Ventilation – Cannot control the concentration when release is in progress

18. Who are responsible for Area Classification ?? Process Engineer (Process Safety Engineer ) For Extent of Zones, Type of Zones and Hazard Group Electrical Engineer and Instrumentation Engineer Proper selection of instrument or electrical Equipment based on Zone selected.

19. What effects ?? Locations of Vessels or potential release point location may change Guide the location of Flare, LPG connection etc. Location of Motors or other electrical and Electronic instrument changes. Thus effect the cost of wiring and Electrical Tray. Type of Electrical and Electronic Equipment Changes. This add the cost variations. Defines the number of Fire and Gas Detectors, type and Locations Defines the type and safety requirements of Fire water. Safety and Operational Manuals and Procedures.

20. Process Engineer Responsibility Plant and Installation at which hazardous material being handled such a way that Zone 0 and Zone 1 are kept to minimum and mainly area should be Zone 2 Try mostly to make the secondary source of release. If primary source is unavoidable than try to minimize the quantum of release Process Equipment relocation is needed to fit the requirements. Most Area classifications are generated in the FEED stage itself.

21. Electrical and Instrument Engineer Responsibility Engineers work on the principle that Hazard as defined by the Process is always present Select the Equipment to avoid the Explosion or Fire Hazard Choose Explosion Proof Housing when Process is not critical. Choose Intrinsically safe or Increased Protection When the Process is SIL Critical.

22. Instrument for Different Zones. Equipment Protection Level The EPL is a level of protection assigned to equipment based on its likelihood of becoming a source of ignition EPL Ga – Equipment with Very high level of protection that is not the source of ignition during normal operation EPL Gb - Equipment with high level of protection that is not the source of ignition during normal operation EPL Gc - Equipment for explosive gas atmospheres having an enhanced level of protection that is not a source of ignition in normal operation Zone 0 Category 1 Zone 1 Category 2 Zone 2 Category 3

23. THANKS