drums, vessels, & storage tanks design considerations

Drums, Vessels, & Storage Tanks

Design Considerations

The Equipment List Vessels, including Reactors

Towers

Storage Tanks See User Added Equipment

Equip # Type Tray Dia Tray Spacing Ideal TraysReal Trays Op. Pressure Max Op. Pressuremm m ft mm number number m ft KPA bar (guage)

TOWERS

Tower Dia Length or Height

VESSELS

Equip # Name Type Op. PressureMax Op. PressureOrientationMat'ls of Construction CAPCOSTBasem ft m ft KPA bar (guage) horiz/vert vessel demister Equip# Cost

Diameter Length or Height

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 UsedFab Shop

Design Pressure Excessive design pressure causes equipment

to be more expensive than is required

t = metal thickness, P = Design PressureCc = Corrosion Allowance, Ej = Joint Efficiency

5

for cylindrical shells

tP ri

S EJ PCc

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

vol dia

2

2

3 dia( )

diavol

4

3

1

3

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

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 !

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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

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Horizontal preferred when:large liquid loads are involved, consequently hold-up will set the sizethree phases are present

General - Tanks/Vessels

MeshEntrainmentSeparator

36” + 1/2 feed nozzle OD (48” min)

12” + 1/2 feed nozzle OD (18” min)

Vertical Separator13

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

Vallowable kL v

v Vdesign 75 %( ) Vallowable

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Mesh Separator

Codes Stds’ - ASME ASME - American Society of

Mechanical Engineers Section I - Fired Heaters Section VIII - Pressure Vessels Other Sections (Plastic / Fiberglass /

nuclear)

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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

12 ft

36 inLow Liq Level= 6”

Norm Liq Level = 12”

High Liq Level = 18”

M

V

X

Y U

R

D

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 TraySpace

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 TanksDesign 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 RoofConservation Vent

Tanks - Floating Roof Suitable for fluids with vapour pressures

up to about 8 psig

pontoonsEdge 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

vol dia

2

2

3 dia( )

diavol

4

3

1

3

Vallowable kL v

v

Vdesign 75 %( ) Vallowable

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)

end

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