classification of hazardous areas - flp.co.zaflp.co.za/portals/23/documents/past presentations/2015...
TRANSCRIPT
Classification of Hazardous Areas
Schalk Kruger
Agenda
• Hazardous Area Classification Process• Flammability of Chemicals• Classification of Chemicals• Chemical Phase• Dispersion• Liquid Jet Breakup• Droplet Breakup Regimes• Dispersion Constraints• Dispersion Shapes• Solutions• Conclusion
Hazardous Area Classification
SOW, Team (SME is important), Chemicals, Operating Conditions, HAC Method (Direct Example, risk, SOR), HAC study, HAC drawings, approvals
Chemicals Flammability
Chemicals – Flammability (Methanol)
Information should be split between section 5 and section 9 of the MSDS as per Globally Harmonizing System (GHS) 5th Revised edition annexure 4
Chemicals – Flammability (Ethylene Glycol)
Information in correct section as per Globally Harmonizing System (GHS) 5th Revised edition annexure 4
Chemicals – ClassificationCAS No
Name &Formula
Rel. Dens
SG FP LFL UFL AIT MIE MESGMIC
RatioT Class
Equip.Group
67-56-1MethanolCH3OH
1.11 9oC 6% 36% 440oC 0.92 0.82 T2 IIA
107-21-1Ethylene Glycol C2H6O2
1.11 115°C 3% 7% 413°C 1.2mJ T2 IIA
• SANS 60079-10-1: flammable liquid – a liquid capable of producing a flammable
vapour under any foreseeable operating conditions
Ethylene Glycol flammability• Shell MSDS: No, product cannot ignite due to static electricity.• PHARMCO-AAPER MSDS: Flammable• NFPA 704: Classified as Code 1 i.e. materials that require considerable preheating before
ignition and combustion can occur.
Ethylene Glycol applications• Antifreeze i.e. freezing point depression• Safer alternative to formaldehyde i.e. biological specimen preservation• Treatment of dry rot in wood
P-T Phase Diagram
Dispersion - Liquid/Vapour
Dispersion type and distance
Flammability of Droplets
• Defined by the MIE
• Quenching distances i.e. distance between the droplets must allow flame propagation
• Droplets smaller than 50 µm creates a flammable atmosphere.
Liquid Jet Break-up
Change in jet break-up regime and length of solid liquid core with exit velocity
Liquid Jet Breakup
Breakup of a liquid jet, from Herrmann (2003)
Classification of droplet breakup regimes
Classification of droplet breakup regimes, from Reitz (1978), Lefebvre(1989), Faeth (1990) and Birouk and Lekic (2009).
Droplet breakup regimes
Secondary droplet breakup mechanisms, from Pilch & Erdman (1987).
Primary droplet breakup mechanisms, from Pilch & Erdman (1987).
Droplet breakup regimes
Secondary droplet breakup mechanisms, from Pilch & Erdman (1987).
Weber number
𝑊𝑒𝑔 =𝜌𝑔𝑈𝑑
2𝑑𝑑
𝜎• We = Weber number (Dimensionless)
• ρg = Gas density (typically the ambient air) (kg/m3)
• Ud = Relative velocity between droplet and air (m/s)
• dd = Characteristic length, typically the droplet diameter (m). Usually taken as Sauter Mean Diameter (SMD)
• σ = Surface tension of the droplet (N/m)
Weber number calculation to identify droplet breakup regime
Dispersion Constraints
• Congestion of SORs
• Obstacles to dispersion
• Enclosed spaces i.e. trapping of dispersion
Droplet breakup when striking a surface (any surface, liquid or solid)
Droplet Party
Dispersion Shapes
Gas/vapour with SpillageGas/vapour with Dripping
Gas/vapour
SANS 60079-10-1, Edition 2
Liquid
Video Clip of
Solutions
• IP15 - “Porous spray guards can be used around flanges and known potential leak points, causing the material to coalesce back to a liquid… rendering it non-hazardous.”
Conclusion
Legislative compliance promotes a safe and controlled environment.
“Hazardous Area Classification” is a statement that expresses an
action.
Hazardous Area Classification done properly provides multiple benefits.