Post on 02-Jun-2018
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Drums, Vessels,& Storage Tanks
Design Considerations
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The Equipment ListVessels, including Reactors
Towers
Storage Tanks
See User Added Equipment
Equip # Type Tray Dia Tray Spacing Ideal TraysReal Trays Op. Pressure Max Op. Pressure
mm m ft mm number number m ft KPA bar (guage)
TOWERS
Tower Dia Length or Height
VESSELS
Equip # Name Type Op. Press Max Op. Press OrientationMat'ls of Construction CAPCOSTBase
m ft m ft KPA bar (guage) horiz/vert vessel demister Equip# Cost
Diameter Length or Height
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Vessels - GeneralWall 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
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Design Pressure Excessive design pressure causes equipment
to be more expensive than is required
t = metal thickness, P = Design Pressure
Cc= Corrosion Allowance, Ej= JointEfficienc 5
for cylindrical shells
tP ri
S EJ PC
c
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Vessels - General
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General - Design
TemperaturesAllowable Stress Values are dependant on
Temperature
Temperature at Design Pressure must bestated
Materials become brittle below certaintemperatures - minimum design metaltemperature
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Reflux Drums
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Reflux Drum SizingAssume a length to diameter Ratio of 3
Therefore:
Solve for diameter
vol dia
2
2
3 dia( )
diavol
4
3
1
3
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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 fullTRAY NET VAPOR RATES AND DENSITIES
--------------- RATES ------
TRAY MW ACTUAL DENS Z FROM NORMAL
KG/M3 DENSITY K*KG/HR K*M3/HR
---- -------- ------------ -------- ----------- ----------- --
1 43.543 4.23300 0.95990 5.097E-02 2.624E-02 .
2 42.180 4.05470 0.95259 4.412 2.345
3 40.722 3.91766 0.95369 4.302 2.368
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General - Tanks/Vessels Method 2 - Hold Up Time (at half full)
2 to 32 minutes depending on quality of controlfor each outgoing stream
5 to 10 minutes is sufficient with modern controlsystems to handle minor upsets
30 minutes provides a 99% probability that anoperator can determine cause of failure
Engineering Judgement !
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Vessels - SafetyVessel that can be isolated require
Relief Valves
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Vessels - Relief Valves
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Vessels (Reactor) Sized on processing
requirements
Agitated vessels usuallyhave L/D ~ 1
Non agitated L/D ~ 3
Superficial velocitiesimportant?
Fluidization of contents?
Internal coils, external
jackets
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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
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General - Tanks/Vessels
Mesh
EntrainmentSeparator
36 + 1/2
feed nozzleOD (48
min)
12 + 1/2
feed nozzle
OD (18min)
Vertical Separator13
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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 EconomicalDesign - but not a necessity
Vallowable k L vv
Vdesign 75 %( ) Vallowable
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Mesh Separator
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Codes Stds - ASMEASME - American Society of Mechanical
Engineers
Section I - Fired HeatersSection VIII - Pressure Vessels
Other Sections (Plastic / Fiberglass /
nuclear)
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AuxiliariesManholes / inspection ports
ASME Code has minimum requirements for
these based on vessel size - See Section 8UG-46
Nozzles - velocities
max v=100/ , ft/secmin v= 60/ , ft/sec
Non-tangential inlet for easier level control
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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
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Towers Diameter - Pro II
Tray Section Height
Number of Real Trays
Ideal Trays / 0.6 * 1.1
Height = 24 x # trays
Remember - subtract condenser & ReboilerAdditional Height for Reboiler
Additional Height for V/L Separation at top
Double Tray Spacing at Feed
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Towers
6 ft
4 ft
Double Tray
Space
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Towers - Diag
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Valve Trays
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Towers Packing
Random
Structured
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Field Fabricated Vessels/Tanks Fabricate in field if shipping is impractical
Typically large atmospheric tanks
Tank TypesCone,
floating roof,
sphere,hemispheroid
Codes & Stds API, ASME
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Storage TanksDesign Pressures < 15 psig
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Tank Farm
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Tanks - Cone Roof Typically Design Pressure < 2 psig, but
usually 2.5 Inches Water gauge
Ensure Vapour Pressure of Liquid issufficiently low (suggest < half D.P.)
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Storage Tanks - Cone RoofConservation Vent
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Tanks - Floating Roof Suitable for fluids with vapour pressures up
to about 8 psig
pontoonsEdge Seal
Floating Roof
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Tanks - Spheres Suitable for Design Pressures of
2 to 15 psig
30 to 220 psig (Ludwig)
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Tanks - Bullet TanksAny Pressure
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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 feednozzle OD (48
min)
12 + 1/2
feed
nozzle OD
(18 min)
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end
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questions types of trays
horiz vs vertical reactors
lifter roof?Margin of error on flows
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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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