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Drums, Vessels, & Storage Tanks

Drums, Vessels, & Storage Tanks. Design Considerations. The Equipment List. Vessels, including Reactors Towers Storage Tanks See User Added Equipment. Maximum Allowable Working Pressure (MAWP)- Actual Metal Thickness Used. Fab Shop.

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Drums, Vessels, & Storage Tanks

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  1. Drums, Vessels, & Storage Tanks Design Considerations

  2. The Equipment List • Vessels, including Reactors • Towers • Storage Tanks • See User Added Equipment

  3. Maximum Allowable Working Pressure (MAWP)- Actual Metal Thickness Used Fab Shop Design Pressure (Relief Valve Set Pressures, Minimum Required Metal Thickness) Process Engineer Maximum Op. Pressure (Controls, S/U , S/D ...) Normal Op. Pressure (Pro II) Vessels - General • Wall Thickness • determined by required pressure • Process Engineer Determines Design Pressure • See Web Notes

  4. Design Pressure • Excessive design pressure causes equipment to be more expensive than is required t = metal thickness, P = Design Pressure Cc = Corrosion Allowance, Ej = Joint Efficiency 5

  5. Vessels - General

  6. General - Design Temperatures • Allowable Stress Values are dependant on Temperature • Temperature at Design Pressure must be stated • Materials become brittle below certain temperatures - minimum design metal temperature

  7. Reflux Drums

  8. Reflux Drum Sizing • Assume a length to diameter Ratio of 3 • Therefore: • Solve for diameter

  9. Reflux Drums (PRO II) • The Volume - Method 1 • Determine Liquid Rate Into the Drum - Careful of your simulator flows • Give 20% excess for start-up • Size for 5 to 10 min @ half full

  10. General - Tanks/Vessels • Method 2 - Hold Up Time (at half full) • 2 to 32 minutes depending on quality of control for each outgoing stream • 5 to 10 minutes is sufficient with modern control systems to handle minor upsets • 30 minutes provides a 99% probability that an operator can determine cause of failure • Engineering Judgement ! 11

  11. Vessels - Safety • Vessel that can be isolated require Relief Valves

  12. Vessels - Relief Valves

  13. Vessels (Reactor) • Sized on processing requirements • Agitated vessels usually have L/D ~ 1 • Non agitated L/D ~ 3 • Superficial velocities important? • Fluidization of contents? • Internal coils, external jackets

  14. Vessels (Reactor) • Plug Flow Reactor Issues • Residence Time / Volume - Pro II • Pressure Drop - packed beds - ergun eqt. (Perry’s) • Back Mixing - Testing, CFD - L/D > 5

  15. General - Tanks/Vessels • Horizontal vs. Vertical • Vertical preferred when: • small liquid load • limited plot space • ease of level control is desired • Horizontal preferred when: • large liquid loads are involved, consequently hold-up will set the size • three phases are present 12

  16. 36” + 1/2 feed nozzle OD (48” min) Mesh Entrainment Separator 12” + 1/2 feed nozzle OD (18” min) Vertical Separator General - Tanks/Vessels 13

  17. General - Tanks/Vessels • Liquid levels • norm liq level at 50% • show low liq level at 25% • provide low, low liq level for pump shut offs • Vapour Disengagement (vertical flash vessel) • Diameter Calcs; v = ft/ sec; density = lb/ft3 • No Mesh k=0.16; Mesh Separators k = 0.35 • Length to Diameter Ratio - 3 to 5 for Economical Design - but not a necessity 13

  18. Mesh Separator

  19. Codes Stds’ - ASME • ASME - American Society of Mechanical Engineers • Section I - Fired Heaters • Section VIII - Pressure Vessels • Other Sections (Plastic / Fiberglass / nuclear) 14

  20. Auxiliaries • Manholes / inspection ports • ASME Code has minimum requirements for these based on vessel size - See Section 8 UG-46 • Nozzles - velocities • max v=100/ , ft/sec • min v= 60/ , ft/sec • Non-tangential inlet for easier level control 14

  21. Auxiliaries • Thermowells • Steamouts • Maintenance blinds • Drains • Level Gauges

  22. Towers • Diameter - Pro II • Tray Section Height • Number of Real Trays • Ideal Trays / 0.6 * 1.1 • Height = 24” x # trays • Remember - subtract condenser & Reboiler • Additional Height for Reboiler • Additional Height for V/L Separation at top • Double Tray Spacing at Feed

  23. Towers 4 ft Double Tray Space 6 ft

  24. Towers - Diag

  25. Valve Trays

  26. Towers • Tray Flows VIDEO

  27. Towers • Packing • Random • Structured

  28. Field Fabricated Vessels/Tanks • Fabricate in field if shipping is impractical • Typically large atmospheric tanks • Tank Types • Cone, • floating roof, • sphere, • hemispheroid • Codes & Std’s – API, ASME

  29. Storage Tanks Design Pressures < 15 psig

  30. Tank Farm

  31. Tanks - Cone Roof • Typically Design Pressure < 2 psig, but usually 2.5 Inches Water gauge • Ensure Vapour Pressure of Liquid is sufficiently low (suggest < half D.P.)

  32. Storage Tanks - Cone Roof Conservation Vent

  33. Tanks - Floating Roof • Suitable for fluids with vapour pressures up to about 8 psig Floating Roof pontoons Edge Seal

  34. Tanks - Spheres • Suitable for Design Pressures of • 2 to 15 psig • 30 to 220 psig (Ludwig)

  35. Tanks - Bullet Tanks • Any Pressure

  36. 36” + 1/2 feed nozzle OD (48” min) 12” + 1/2 feed nozzle OD (18” min) Vap Rate: Liq Rate: Vap Density: Liq Density: Workshop • Size the Flasher • Size 50% Liq Hold-up for 10 min

  37. end

  38. questions • types of trays • horiz vs vertical reactors • lifter roof? • Margin of error on flows

  39. Reflux Drums (HYSYS) • The Volume • Liquid Rate Into the Drum - Careful of your simulator flows • Give 20% excess for start-up

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