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Health, Safety, and Environment: Hazards and Mitigation

This article discusses how to identify and mitigate hazards in order to minimize environmental impact. It also emphasizes the importance of safety training programs and hazard communication in achieving a safe working environment.

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Health, Safety, and Environment: Hazards and Mitigation

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  1. 12. Health, Safety and Environment (Tasks 10 & 11) By R.A. Hawrelak for Dr. A. Prakash 19 Feb 02

  2. Today’s Objectives • Identify Hazards – Hazard Analysis. • Mitigate Process Hazards. • Minimize Environmental Impact. • Prepare a Safety and Environmental Mission Statement (RAH). • “Our group endeavored to design the safest plant possible. This included ….”

  3. Fire & Explosion & Toxic Hazards • Upper flammable limit (UFL or UEL). • Lower flammable limit (LFL or LEL). • Auto-ignition temperatures. • Flash point temperature. • Polymerization potential. • Toxic data & carcinogen rating, ca. • Spill mitigation (foam, water).

  4. Steps to Prevent Hazards • Relief devices – PSVs, PRDs, PVRVs • Leak detection – where and how. • Emergency Block Valves, EBVs. • Dikes / Drainage – away from equipment. • Flares / Ventilation – where and how. • Fire Water Supply – Looping in ISBL. • 0.25 usgpm/sf water on all hc vessels. • Reactive Chemical and PHA Reviews.

  5. Steps to Prevent Hazards – cont’d • Layout - FEI Separation Within ISBL. • Intrinsically Safe Electrical Equipment. • Harden Control Room to withstand 1 Ton of TNT at 200 ft. or 1 Ton of TNT at 100 ft. • Remote Storage for Hazardous Chemicals. • Greenbelt Separation for Municipal Planning. • Cradle to Grave Safety Training Programs. • Operating Discipline for change of command. • Emergency Response Drills – Dry Runs.

  6. Product Stewardship • Safety doesn’t end at the company fence line. • Companies with a good PS program provide safety training to their customers. • Companies must respond to LOC Spill situations for all products being delivered to their customers. • Goal No. 1: Dow ER team will be in the air within 1 hour of notification.

  7. Hazard Communication • Up-to-date process flow diagrams and P&IDs. • Proper labeling. • MSDS (Material Safety Data Sheets) • Required to include MSDS of products (AP). • Required to include MSDS of feeds. (RAH) • Required to include MSDS of intermediates. (RAH) • http://eng-dellsrv02/nioshdbs

  8. Liquid Classification - NFPA • National Fire Protection Association • Basis – NFPA 325 • Reactivity (Nr) • Flammability (Nf) • Health (Nh)

  9. The reactivity factor, (Nr), can be obtained from a qualitative description of the instability (or reactivity with water) of the substance, mixture or compound at ambient temperatures as follows: Reactivity(Nr)

  10. Flammability(Nf) • Flash point by closed-cup method. • Boiling point at standard pressure 14.7 psia.

  11. Health(Nh)

  12. Example • Ethylene Oxide • Nh = 2 • Nf = 4 • Nr = 3 • When describing a feedstock, the following description is found in many Dow reports: • “Ethylene Oxide (Nh=2, Nf = 4, Nr = 3) is a basic feed for the plant.” ….

  13. NIOSH • National Institute for Occupational Safety and Health. • Online Pocket Guide to Chemical Hazards • http://www.cdc.gov/niosh/npg/npgdname.html • Exposure limits, flash points, toxicity. • NIOSH also has a Liquid Classification

  14. Vapor Pressure • Needed to determine operating pressure of storage vessels at ambient conditions. • If Vapor pressure drops below atmospheric pressure, air can leak into vessels storing flammables. Big hazard. • To keep pressure above atmospheric pressure heat vessel, or use inert pad / depad system with safe disposal of vents.

  15. Antoine Constants • Log10(P) = A + B/(t+C) • P is in psia • T is in degrees Centigrade • Select three sets of temperature and vapor pressure in desired temperature range. • 3 Eqns – 3 unknowns. Solve for A, B, C. • Beware, there are many forms of this eqn. and the constants are not common to each eqn. • RAH CD program available to determine A,B,C.

  16. Vapor Pressure of EO

  17. The Enthalpy Chart • The engineer’s best friend. • Determine when flashing situations exist. • Know how to calculate the % flash. • Mass balance F = 100 = V + L • Heat balance = Hf(100) = V(Hv) + L(HL) • Two equations, two unknowns. • Any flash above 30% will atomize all the liquid – really big hazard.

  18. The Enthalpy Chart

  19. Hazards of Two Phase Flow

  20. Hazards of Water Hammer

  21. Maldistribution • Maldistribution of flow in lines, headers, exchangers and reactors often results in equipment failure or LOC.

  22. Entrainment • Liquid entrainment by a vapor is still one of the biggest problems in a chemical plant. • Entrainment can destroy mass and energy balances. • Entrainment leads to 2-phase flow vibration problems and ultimately LOC. • Good Knock-out pot design minimizes entrainment.

  23. Pressure Safety Valves • PSVs required by law for all pressure vessels with a Design Pressure greater than 15 psig. • PSVs and PVRVs are installed on vessels below 15 psig to prevent LOC. • Many design bases are used. Designer must follow company practice. • Design methods too complex for this course. Methods available on RAH CD.

  24. Pressure Vessels (>15 psig DP) • Select Design Pressures and Design Temperature from worst case operating conditions. Note flange rating. • Examine depressuring to 14.7 psia for minimum Design Temp & Mtls of Constr. • U.S. law requires a risk mgt plan, rmp, on worst case flammable and all toxic storage tanks. • http://www.epa.gov/ceppo/tools/rmp-comp/rmp-comp.html Free download.

  25. U.S. EPA rmp vs CDN MIACC • Major Industrial Accidents Council of Can. • Storage of 400,000 lbs of EO - toxic • MIACC 2 pt. buffer zone 293m @ 1E-06. • RAH 3 pt. buffer zone 600m @ 1E-08. • rmp endpoint is ERPG2 = 50 ppmv • rmp gives 24 km. for ER plan. • A dispersion study > 6.6 km. for ER plan. • All companies in Sarnia now use U.S. rmp.

  26. Emergency Response Data • B-M Heavy Gas Dispersion Model. • LC10 @ 320m. (2 hr exposure). • LC01 @ 535m. (2 hr exposure). • IDLH @ 1,900m. (30 min. exposure). • ERPG2 Dose @ 5.7 km by D = òC2(dt) where C = ppmv and dt = time. • ERPG2 ER Dist. @ 6.6 km for 50 ppmv.

  27. Hazard Techniques

  28. Dow Fire and Explosion Index • Dow Fire and Explosion Index is a basic standard around the world. • Dow F&EI is used for separation of adjacent unit operations to minimize probable loss. • Insurance rates determined by FEI. • CD Version – computerized FEI with 3 examples plus PowerPoint presentation.

  29. FEI

  30. Dow FEI Credit Factors

  31. Unit Analysis Summary

  32. FEI Separation Results

  33. HAZOPS • HAZOP was developed by Lawley (1974) of ICI. Based on early account by Elliott & Owen (1968). • Hazop studies are carried out by an experienced, multidisciplinary team. • Review all physicalaspects of a process (lines, equipment, instrumentation) to discover potential hazards. • PowerPoint presentation available.

  34. Example For Hazop Review

  35. After a Hazop

  36. End of Safety Presentation • Good luck in applying your safety knowledge to your final 497 report.

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