Hazardous Area Classification

Schalk J. P. Kruger

2

Agenda

• Legislation

• Scope of Work (SOW)

• HAC team

• Chemicals

• Operating conditions

• Method/s of HAC

• HAC study

• HAC drawings

• Practical

3

Legislation

Constitution

Rights

ACTs

Who and Why

Regulations

What

Standards

How

• Your right to be safe

• Employer, employee - safety

• Regulation of the things

• Specific procedure on the how

4

Scope

5

Team

6

Chemicals - Flammability

7

Chemicals - Flammability – SDS - Methanol

8

Chemicals - Classification – Standard - Methanol

SANS 60079-20-1: Material characteristics for gas and vapour classification — Test methods and data

Gas Group: IIA

Auto Ignition Temperature (AIT): 440 oC

Temp class: T2

LEL: 6%

Flash point: 9 oC

Relative Density: 1.11

X

Zone

IIA

T2

X

Zone Distance

9

Chemicals – Compositions! (VL-Bottoms)

Chemical Vol. % Relative

Density

AIT oC Flash

Point oC

LEL % Group

(MESG)

Propanal (C3H6O) 39% 2.00 188 -26 2.0% IIB (0.86)

Butanal (C4H8O) 21% 2.50 205 75 1.7% IIA (0.92)

Water (H2O) 14% 0.017 N/A N/A N/A N/A

Ethyl Acetate (C4H8O2) 9% 3.04 470 -4 2.0% IIA (0.99)

2-Methyl Propanal (C4H8O) 5% 2.50 165 -22 1.6% IIA (0.92)

2-Methyl Butanal (C5H10O) 1% 2.97 240 -5 1.3% IIC (H10)?

3-Methyl Butanal (C5H10O) 1% 2.96 207 -5 1.3% IIA (0.98)

Ethanal (CH3CHO) 1% 1.52 155 -38 4.0% IIA (0.92)

Result (Inference) >1 165 (T1) -26 1.6% IIB (39%)

Calculated 1.97 165 (T1) 2.093% IIB (0.87)

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Area Classification - Direct Example

SANS 10089-2: Electrical and other

installations in the distribution and marketing

sector

• American Petroleum

Institute (API) – API RP

500: Petroleum Facilities

• Energy Institute – IP15:

Flammable liquids

IIA

T2

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Area Classification - Direct Example Challenges

A - Pump Rate, flashback

arrestor, safety release

valve, operational

conditions, ambient

temperature changes

B - Relative density

C - Relative density, liquid

leaks, sampling flushing

D - Lots of applications i.e.

Zone 1, over classification

E - Only for these

chemicals

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Source of Release - Operating Conditions - PFD

Major vessels, major process streams,

pressure, temperature, composition, flow

directions

13

Source of Release - Sources of Release - MFD

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Area Classification - Grades of Release

Equipment Example of Leak Grade of Release

Pumps Seal Secondary

Compressors Seal S

Vents Full Bore Primary

Valves Gland/Seal S

Pressure relief valves Full Bore P

Small bore connections Fitting Leak S

Piping systems Gasket S

Flanges, blinds Gasket S

Pig receivers and launchers Full bore or Partial Release P

Liquid pools Vaporisation Continuous

Sumps Vaporisation C

Drains (Open) Vaporisation C

Drain Points Full bore or Partial Release P

Sample points Full bore or Partial Release P

15

Area Classification – Degree of Ventilation

Ventilation

Grade of

release

Degree

High Medium Low

Availability

Good Fair Poor Good Fair PoorGood, fair or

poor

Continuous

(Zone 0 NE)

Non-

hazardous a

(Zone 0 NE)

Zone 2a

(Zone 0 NE)

Zone 1aZone 0

Zone 0

+

Zone 2

Zone 0

+

Zone 1

Zone 0

Primary

(Zone 1 NE)

Non-

hazardous a

(Zone 1 NE)

Zone 2 a

(Zone 1 NE)

Zone 2aZone 1

Zone 1

+

Zone 2

Zone 1

+

Zone 2

Zone 1 or

zone 0c

Secondary b

(Zone 2 NE)

Non-

hazardous a

(Zone 2 NE)

Non-

hazardous a

Zone 2 Zone 2 Zone 2 Zone 2Zone 1 and

even zone 0c

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Area Classification - Zones

• Zone 0: Continuous release - All the time

• Zone 1: Primary release - During normal

operations

• Zone 2: Secondary release - During

abnormal operations

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Source of Release - Dispersion Liquid / Vapour

Dispersion: PHAST Pamphlet from Det Norske

Veritas (DNV)

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Source of Release - Dispersion Equations

Witlox, H W M and Holt, A 1999, A unified model for jet, heavy and passive dispersion

including droplet rainout and re-evaporation, Det Norska Veritas, London UK

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Source of Release - Dispersion – CFD

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Source of Release - Dispersion - Concentration

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Source of Release – Meteorological conditions

• Solar Radiation

• Evaporation

• Precipitation

• Wind speed, height and direction

• Relative humidity

• Barometric pressure

• Topography

• Ambient air temperature

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Area Classification - Dispersion – Pool Heat

Transfer

23

Area Classification - Dispersion –

Meteorological Conditions - Wind

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Area Classification - Dispersion - Other

• Congestion of SORs

• Obstacles to dispersion

• Enclosed spaces i.e. trapping of dispersion

25

Study

• Traceable i.e. references, calculations, reproducible

• Approved by accountable persons

• Defendable arguments

26

Drawings

• Top view

• Side views

• Cuts

• Different levels of structures

• Chemical products table

• SOR table (Zones 0 and 1 only and perimeter zone 2)

• Approvals

27

Dispersion Shapes - Standard

28

Area Classification results - Direct Example

29

Area Classification Result - Source of Release

Method

30

Area Classification - Scenarios

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Area Classification - Scenarios

32

Conclusion

Legislative compliance provides a safe and controlled environment.

Area Classification provides the basis for a number of actions e.g.

permit to work controls, selection of equipment and inspections

“Hazardous Area Classification” is a statement that expresses an action.