Drums, Vessels, & Storage Tanks Design Considerations

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

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

Design Pressure Excessive design pressure causes equipment to be more expensive than is required t = metal thickness, P = Design Pressure C c = Corrosion Allowance, E j = Joint Efficiency 5

Vessels - General

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

Reflux Drums

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

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 half full

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

Vessels - Safety Vessel that can be isolated require Relief Valves

Vessels - Relief Valves

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

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

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

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

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/ft 3 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

Mesh Separator

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

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

Auxiliaries Thermowells Steamouts Maintenance blinds Drains Level Gauges

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

Towers 6 ft 4 ft Double Tray Space

Towers - Diag

Valve Trays

Towers Tray Flows VIDEO

Towers Packing Random Structured

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

Storage Tanks Design Pressures < 15 psig

Tank Farm

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.)

Storage Tanks - Cone Roof Conservation Vent

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

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

Tanks - Bullet Tanks Any Pressure

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

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

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