-
KLM TechnologyGroup
Practical EngineeringGuidelines for Processing
Plant Solutions www.klmtechgroup.com
Page : 1 of 87
Rev: 02
Rev 1 JUNE 2010Rev 2 JUNE 2011
KLM Technology Group
STORAGE TANK SELECTION ANDSIZING
(ENGINEERING DESIGN GUIDELINE)
Author:
Rev 1 Karl KolmetzRev 2 Aprilia Jaya
Checked by:Karl Kolmetz
TABLE OF CONTENT
INTRODUCTION
Scope 5
General Design Considerations 6
TYPES OF TANKS
Fixed Roof Tanks 7
External floating roof tanks 11
Internal floating roof tanks 15
Domed external floating roof tanks 18
Horizontal tanks 20
Pressure tanks 22
Variable vapor space tanks 23
TANK SEALS AND FITTINGS 25
External and Domed External Floating Roof Rim Seals 25
External and Domed External Floating Roof Deck Fittings 32
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 2 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
DEFINITIONS 45
NOMENCLATURE 53
THEORY OF THE DESIGN 55
1. Tank Dimension 55
2. Atmospheric storage tank 59
3. Pressure Storage Tank 63
4. Refrigerated Storage 65
5. Emissions Losses 66
A. Total Losses from Fixed Roof Tanks 66
B. Total Losses from Floating Roof Tanks 69
APPLICATION 75
Example 1: Dimension of tank calculate 75
Example 2: Fixed Roof Tank Emission (Cone Roof and Dome Roof)
78
Example 3: Floating Roof Emission Losses 81
REFEREENCES 84
CALCULATION SPREADSHEET 85
Dimension of Tank Spreadsheet.xls 85
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 3 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Fixed Roof Tank Emission Losses Spreadsheet.xls 86
Floating Roof Emission Losses Spreadsheet.xls 87
LIST OF TABLE
Table 1: Maximum allowable stress value (f) 56
Table 2: Maximum allowable efficiencies for Arc and Gas welded
joints 57
Table 3: Dimension of icr, rc, and sf 58
Table 4: Size of innage and outage of tank 61
Table 5: Nozzle service for tank 62
Table 6: Paint Factors for Fixed Roof Tanks 67
Table 7: Rim-seal loss factor 71
Table 8: Average Clingage Factors (Cs) 72
Table 9: Typical Number of Columns as a Function of Tank
Diameter 72
Table 10: Deck-Fitting Loss Factors and Typical Number oF Deck
Fitting 78
LIST OF FIGURE
Figure 1: Fixed Roof Tanks 9
Figure 2: Fixed Roof Tanks 2 10
Figure 3: External Floating Roof Tanks 12
Figure 4: External Floating Roof Tanks 2 13
Figure 5: Typical List of Floating Roof Fittings 14
Figure 6: Internal Floating Roof 17
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 4 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 7: Dome External Floating Roof 19
Figure 8: Schematics of above-ground horizontal (a) and
underground tanks (b) 21
Figure 9: Scheme of Pressure Tank 22
Figure 10: Variable Vapor Space Tanks 24
Figure 11: Vapor mounted primary seals 26
Figure 12: Liquid-mounted and mechanical shoe primary seals
27
Figure 13: Secondary rim seals 29
Figure 14: Access Hatch 32
Figure 15: Gauge float 33
Figure 16: Sample ports 34
Figure 17: Rim vent 35
Figure 18: Deck drains 36
Figure 19: Deck leg 37
Figure 20: Slotted and unslotted guidepoles 38
Figure 21: Vacuum breaker 41
Figure 22: Fixed Roof Support Column 43
Figure 23: Ladder and well 44
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 5 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
INTRODUCTION
Scope
This design guideline covers the sizing and selection methods of
a storage tanksystem used in the typical process industries. It
helps engineers understand the basicdesign of different types of
storage tank systems and increases their knowledge inselection and
sizing.
The selection section contains the explanation for the
suitability of types of tanksystem used in processing industries,
which are based on the environmentalregulations, location, and
process materials involved.
All the important parameters used in this guideline are well
explained in the definitionsection which helps the reader
understand the meaning of the parameters and theterms used.
The theory section includes sizing theory and formulations for
the tanking systemsdesign.
In the application section, three cases examples are included by
guiding the readerstep by step to do tank sizing.
In the end of this guideline, example specification data sheets
for the tank system areincluded which is created based on an
industrial example. Calculation spreadsheet isincluded as well and
to aid user more understand and to apply the theory
forcalculations.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 6 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
General Design Considerations
Storage vessels containing organic and non organic liquids and
vapors can be foundin many industries, including;
(1) petroleum producing and refining,(2) petrochemical and
chemical manufacturing,(3) bulk storage and transfer operations,
and(4) other industries consuming or producing liquids and
vapors.
Liquids and vapors in the petroleum industry, usually called
petroleum liquids orvapors, generally are mixtures of hydrocarbons
having dissimilar true vapor pressures.Examples would include jet
fuel, diesel, gasoline and crude oil.
Liquids and vapors in the chemical industry, usually called
volatile organic liquids andvapor, are composed of pure chemicals
or mixtures of chemicals with similar truevapor pressures. Examples
would include benzene, styrene, and alcohols).
Liquids and vapors in the bulk storage and transfer operations
can be organic orhydrocarbon in nature. Example would include all
of the above including acids andbases.
All those chemical should keep in the right storage tank. Design
and safety concernhas come to a great concern as reported case of
fires and explosion for the storagetank has been increasing over
the years and these accident cause injuries andfatalities. Spills
and tank fires not only causing environment pollution, there would
alsobe severe financial consequences and significant impact on the
future business due tothe industry reputation.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 7 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
TYPES OF STORAGE TANKS
Seven types of vessels are used to store volatile organic
liquids:
1. Fixed-roof tanks;
2. External floating roof tanks;
3. Internal floating roof tanks;
4. Domed external floating roof tanks;
5. Horizontal tanks;
6. Pressure tanks; and
7. Variable vapor space tanks.
The first four tank types are cylindrical in shape with the axis
oriented perpendicular tothe foundation. These tanks are almost
exclusively above ground. Horizontal tanks(i.e., with the axis
parallel to the foundation) can be used above ground and
belowground.
Pressure tanks often are horizontally oriented and "bullet" or
spherically shaped tomaintain structural integrity at high
pressures. They are located above ground.
Variable vapor space tanks can be cylindrical or spherical in
shape.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 8 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
1. Fixed-Roof Tanks
Of currently used tank designs, the fixed-roof tank is the least
expensive to constructand is generally considered the minimum
acceptable equipment for storing VOL's(volatile organic liquids). A
typical fixed-roof tank, which is shown in Figure 1 below,consists
of a cylindrical steel shell with a cone- or dome-shaped roof that
ispermanently affixed to the tank shell. Most recently built tanks
are of all-weldedconstruction and are designed to be both liquid-
and vapor-tight. However, older tanksmay be of riveted or bolted
construction and may not be vapor-tight.
A breather valve (pressure-vacuum valve), which is commonly
installed on manyfixed-roof tanks, allows the tank to operate at a
slight internal pressure or vacuum.Breather vents are typically set
at 0.19 kPa (0.75 in. w.c.) on atmospheric pressurefixed-roof
tanks. Because this valve prevents the release of vapors during
only verysmall changes in temperature, barometric pressure, or
liquid level, the emissions froma fixed-roof tank can be
appreciable.
For fixed-roof tanks, the nominal capacity is the geometric
volume from the bottom ofthe tank up to the curb angle, which is a
metallic angle that is welded along theperiphery at the top of the
cylindrical portion of the tank.
Additionally, gauge hatches/sample wells, float gauges, and roof
manholes provideaccessibility to these tanks and also serve as
potential sources of volatile emissions.Breather vents may be
called conservation vents, although hardly any conservation
ofvapors occurs at such low pressure settings. Generally, the term
conservation vent isused to describe a pressure setting of 17 kPa
(67 in. w.c.) or less. Vents with settingsgreater than 17 kPa (67
in. w.c.) are commonly called `pressure' vents.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 9 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 1: Fixed Roof Tanks 1.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 10 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 2: Fixed Roof Tanks 2
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 11 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
2. External Floating Roof Tanks
A typical external floating roof tank consists of an open-topped
cylindrical steel shellequipped with a roof that floats on the
surface of the stored liquid, rising and fallingwith the liquid
level. The floating roof is comprised of a deck, fittings, and rim
sealsystem. Floating roof decks are constructed of welded steel
plates and are of threegeneral types: pan, pontoon, and double
deck.
Although numerous pan-type decks are currently in use, the
present trend is towardpontoon and double-deck type floating roofs.
The two most common types of externalfloating-roof tanks are shown
in Figures 3 and 4.
Manufacturers supply various versions of these basic types of
floating decks, whichare tailored to emphasize particular features,
such as full liquid contact, load-carryingcapacity, roof stability,
or pontoon arrangement. The liquid surface is covered by
thefloating deck, except in the small annular space between the
deck and the shell; thedeck may contact the liquid or float
directly above the surface on pontoons.
External floating roof tanks are equipped with a rim seal
system, which is attached tothe roof perimeter and contacts the
tank wall. The rim seal system slides against thetank wall as the
roof is raised and lowered. The floating deck is also equipped
withfittings that penetrate the deck and serve operational
functions. The external floatingroof design is such that
evaporative losses from the stored liquid are limited to lossesfrom
the rim seal system and deck fittings (standing storage loss) and
any exposedliquid on the tank walls (withdrawal loss).
In external floating roof design. the roof is made to rest on
the stored liquid and is freeto move with the level of the liquid.
These tanks reduce evaporation losses and controlbreathing losses
while filling. They are preferred for storage of petroleum
productswith a true vapor pressure of 10.3 to 76.5 kPa
absolute.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 12 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 3: External Floating Roof Tanks 1
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 13 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 4: External Floating Roof Tanks 2
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 14 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 5: Typical List of Floating Roof Fittings
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 15 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
3. Internal Floating Roof Tanks
An internal floating roof tank has both a permanent fixed roof
and a floating roofinside. There are two basic types of internal
floating roof tanks: tanks in which thefixed roof is supported by
vertical columns within the tank; and tanks with a self-supporting
fixed roof and no internal support columns. The fixed roof is not
necessarilyfree of openings but does span the entire open plan area
of the vessel. Fixed rooftanks that have been retrofitted to employ
an internal floating roof are typically of thefirst type, while
external floating roof tanks that have been converted to an
internalfloating roof tank typically have a self-supporting
roof.
Tanks initially constructed with both a fixed roof and an
internal floating roof may be ofeither type. An internal floating
roof tank has both a permanently affixed roof and aroof that floats
inside the tank on the liquid surface (contact deck) or is
supported onpontoons several inches above the liquid surface
(noncontact deck). The internalfloating roof rises and falls with
the liquid level. A typical internal floating roof tank isshown in
figure below
Contact-type decks include (1) aluminum sandwich panels with a
honeycombedaluminum core floating in contact with the liquid; (2)
resin-coated, fiberglass-reinforcedpolyester (FRP), buoyant panels
floating in contact with the liquid; and (3) pan-typesteel roofs,
floating in contact with the liquid with or without the aid of
pontoons. Themajority of contact internal floating decks currently
in VOL service are pan-type steelor aluminum sandwich panel type.
The FRP decks are less common.
Several variations of the pan-type contact steel roof exist. The
design may includebulkheads or open compartments around the
perimeter of the deck so that any liquidthat may leak or spill onto
the deck is contained. Alternatively, the bulkheads may becovered
to form sealed compartments (i.e., pontoons), or the entire pan may
becovered to form a sealed, double deck, steel floating roof.
Generally, construction is ofwelded steel.
Noncontact-type decks are the most common type of deck currently
in use, andtypically consist of an aluminum deck laid on an
aluminum grid framework supportedabove the liquid surface by
tubular aluminum pontoons. The deck skin for thenoncontact-type
floating decks is typically constructed of rolled aluminum
sheets(about 1.5 meters [m] [4.9 feet (ft)] wide and 0.58
millimeter [mm] [0.023 inches (in)]thick). The overlapping aluminum
sheets are joined by bolted aluminum clamping barsthat run
perpendicular to the pontoons to improve the rigidity of the
frame.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 16 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
The deck skin seams can be metal on metal or gasketed with a
polymeric material.The pontoons and clamping bars form the
structural frame of the floating deck. Deckseams in the noncontact
internal floating roof design are a source of emissions.Aluminum
sandwich panel contact-type internal floating roofs also share this
designfeature. The sandwich panels are joined with bolted
mechanical fasteners that aresimilar in concept to the noncontact
deck skin clamping bars. Steel pan contactinternal floating roofs
are constructed of welded steel sheets and therefore have nodeck
seams. Similarly, the resin-coated, reinforced fiberglass panel
decks have noapparent deck seams. The panels are butted and lapped
with resin-impregnatedfiberglass fabric strips.
The internal floating roof physically occupies a finite volume
of space that reduces themaximum liquid storage capacity of the
tank. When the tank is completely full, thefloating roof touches or
nearly touches the fixed roof. Consequently, the effectiveheight of
the tank decreases, thus limiting the storage capacity. The
reduction in theeffective height varies from about 0.15 to 0.6 m
(0.5 to 2 ft), depending on the typeand design of the floating roof
employed.
All types of internal floating roofs, like external floating
roofs, commonly incorporaterim seals that slide against the tank
wall as the roof moves up and down. Circulationvents and an open
vent at the top of the fixed roof are generally provided to
minimizethe accumulation of hydrocarbon vapors in concentrations
approaching the flammablerange. Flame arresters are an option that
can be used to protect the vessel from fire orexplosion. When these
are used, circulation vents are not provided. Tank ventingoccurs
through a pressure-vacuum vent and flame arrestor.
The design features of internal floating roof can be summary as
follow
1. A truly vapor tight metal to metal clamp beam develops the
full strength of thedeck skin itself
2. A patented pivot joint eliminates stress at pontoon ends by
allowing flexurewhere it is needed
3. Pontoon saddles support the clamp beams on the pontoon and
distribute theconcentrated load to assure against localized
buckling
4. Bolted connections are corrosion resistant 300 series
stainless steel fixings5. Reduces emissions from fixed roof tanks
by up to 97% & meets VOC control
and Environmental Protection Standards
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 17 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 6: Internal Floating Roof
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 18 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
4. Domed External Floating Roof Tanks
Domed external floating roof tanks have the heavier type of deck
used in externalfloating roof tanks as well as a fixed roof at the
top of the shell like internal floating rooftanks. Domed external
floating roof tanks usually result from retrofitting an
externalfloating roof tank with a fixed roof. A typical domed
external floating roof tank isshown in Figure 7.
As with the internal floating roof tanks, the function of the
fixed roof is not to act as avapor barrier, but to block the wind.
The type of fixed roof most commonly used is aself supporting
aluminum dome roof, which is of bolted construction. Like the
internalfloating roof tanks, these tanks are freely vented by
circulation vents at the top of thefixed roof. The deck fittings
and rim seals, however, are basically identical to those onexternal
floating roof tanks.
Aluminum dome roof have some advance features :
1. The Clear Span design eliminates the need for interior
support structures whilehigh strength aluminum alloys and corrosion
resistant materials provide for a longservice life.
2. Properly designed tension rings ensure that the lateral force
generated by thedome is not translated to the tank shell,
eliminating the need for additional tankshell reinforcement or
modifications.
3. Beams are designed with an extruded continuous threaded
bolting slot. Thisbolting slot provides more thread engagement area
and more pull resistance thanin conventional designs.
4. The overlapping panels naturally shed water and are secured
in place with apatented Batten Bar and hidden gasket system. This
deign allows the roof panelsto flex while keeping sheets from
puckering and bolts from leaking.
5. Aluminum Dome reduces wind induced vapor losses, aids in odor
abatement andprovides significant emission credits.
6. Floating roof and seal maintenance are drastically reduced
due to the lack ofrainwater and UV exposure.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 19 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 7: Dome External Floating Roof
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 20 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
5. Horizontal Tanks
Horizontal tanks are constructed for both above-ground and
underground service.Figures 8 present schematics of typical
underground and above-ground horizontaltanks. Horizontal tanks are
usually constructed of steel, steel with a fiberglassoverlay, or
fiberglass-reinforced polyester. Horizontal tanks are generally
smallstorage tanks with capacities of less than 75,710 L (20,000
gallons).
Horizontal tanks are constructed such that the length of the
tank is not greater than sixtimes the diameter to ensure structural
integrity. Horizontal tanks are usually equippedwith
pressure-vacuum vents, gauge hatches and sample wells, and
manholes
to provide accessibility to these tanks. In addition,
underground tanks may becathodically protected to prevent corrosion
of the tank shell. Cathodic protection isaccomplished by placing
sacrificial anodes in the tank that are connected to animpressed
current system or by using galvanic anodes in the tank. However,
internalcathodic protection is no longer widely used in the
petroleum industry, due tocorrosion inhibitors that are now found
in most refined petroleum products.
The potential emission sources for above-ground horizontal tanks
are the same asthose for fixed-roof tanks. Emissions from
underground storage tanks are mainlyassociated with changes in the
liquid level in the tank. Losses due to changes intemperature or
barometric pressure are minimal for underground tanks because
thesurrounding earth limits the diurnal temperature change and
changes in thebarometric pressure would result in only small
losses.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 21 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
(a)
(b)
Figure 8: schematics of typical above-ground horizontal (a) and
underground tanks (b)
Product discharge Product delivery line
Fit pipeVent line
Float vent valve in ventline for over protection
Dielectric bushing providingelectrical insulation betweentank
and all connecting lines
Cathodic monitoring systemAccess manway
Striker plate below fill pipe
Submergedproduct deliverypump
Sacrificial anodes
Cathodically-processed epoxycoasted steel
Compacted bed of sand or gravel
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 22 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
6. Pressure Tanks
Two classes of pressure tanks are in general use: low pressure
(2.5 to 15 psig) andhigh pressure (higher than 15 psig). Pressure
tanks generally are used for storingorganic liquids and gases with
high vapor pressures and are found in many sizes andshapes,
depending on the operating pressure of the tank. Pressure tanks
areequipped with a pressure/vacuum vent that is set to prevent
venting loss from boilingand breathing loss from daily temperature
or barometric pressure changes.
The pressure tank allows the pump to run occasionally instead of
every time a faucetis opened. The basic system is often enhanced,
either by necessity or for improvedperformance, with a constant
pressure delivery system.
Figure 9: Scheme of Pressure Tank
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 23 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
7. Variable Vapor Space Tanks
Variable vapor space tanks are equipped with expandable vapor
reservoirs toaccommodate vapor volume fluctuations attributable to
temperature and barometricpressure changes. Although variable vapor
space tanks are sometimes usedindependently, they are normally
connected to the vapor spaces of one or more fixedroof tanks. The
two most common types of variable vapor space tanks are lifter
rooftanks and flexible diaphragm tanks. Lifter roof tanks have a
telescoping roof that fitsloosely around the outside of the main
tank wall. The space between the roof and thewall is closed by
either a wet seal, which is a trough filled with liquid, or a dry
seal,which uses a flexible coated fabric.
Flexible diaphragm tanks use flexible membranes to provide
expandable volume.They may be either separate gasholder units or
integral units mounted atop fixed rooftanks. Variable vapor space
tank losses occur during tank filling when vapor isdisplaced by
liquid. Loss of vapor occurs only when the tank's vapor storage
capacityis exceeded.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 24 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 10: Variable Vapor Space Tanks
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 25 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Types of Floating Roof Perimeter Seals
External and Domed External Floating Roof Rim Seals
Regardless of tank design, a floating roof requires a device to
seal the gap betweenthe tank wall and the deck perimeter. A rim
seal, or in the case of a two-seal system,the lower (primary) rim
seal, can be made from various materials suitable for organicliquid
service. The basic designs available for external floating roof rim
seals are
(1) mechanical (metallic) shoe seals,
(2) liquid-filled seals, and
(3) (vapor or liquid mounted) resilient foam-filled seals.
Figures below depict these three general types of seals.
One major difference in seal system design is the way in which
the seal is mountedwith respect to the liquid surface. Figure below
shows a vapor space between theliquid surface and rim seal, whereas
in second Figure, the seals rest on the liquidsurface. These
liquid-filled and resilient foam-filled seals are classified as
liquid- orvapor-mounted rim seals, depending on their location.
Mechanical shoe rim seals are different in design from
liquid-filled or resilient foam-filled rim seals and cannot be
characterized as liquid- or vapor-mounted. However,because the shoe
and envelope combination precludes contact between the annularvapor
space above the liquid and the atmosphere (see below), the emission
rate of amechanical shoe seal is closer to that of a liquid-mounted
rim seal than that of avapor-mounted rim seal.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 26 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure `11: Vapor mounted primary seals
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 27 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 12: Liquid-mounted and mechanical shoe primary seals
Mechanical Shoe Seal.
A mechanical shoe seal, also known as a "metallic shoe seal"
(Figure above), ischaracterized by a metallic sheet (the "shoe")
that is held against the vertical tank wall.Previously the
regulations did not specify a height for mechanical shoe
seals;however, shoe heights typically range from 75 to 130
centimeters (cm) (30 to 51 in.).
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 28 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
The shoe is connected by braces to the floating deck and is held
tightly against thewall by springs or weighted levers. A flexible
coated fabric (the "envelope") issuspended from the shoe seal to
the floating deck to form a vapor barrier over theannular space
between the deck and the primary seal.
Liquid-Filled Seal
A liquid-filled rim seal (Figure above) may consist of a tough
fabric band or envelopefilled with a liquid, or it may consist of a
flexible polymeric tube 20 to 25 cm (8 to 10in.) in diameter filled
with a liquid and sheathed with a tough fabric scuff band.
Theliquid is commonly a petroleum distillate or other liquid that
will not contaminate thestored product if the tube ruptures.
Liquid-filled rim seals are mounted on the liquidproduct surface
with no vapor space below the seal.
Resilient Foam-Filled Seal
A resilient foam-filled rim seal is similar to a liquid-filled
seal except that a resilientfoam log is used in place of the
liquid. The resiliency of the foam log permits the sealto adapt
itself to minor imperfections in tank dimensions and in the tank
shell. Thefoam log may be mounted above the liquid surface
(vapor-mounted) or on the liquidsurface (liquid-mounted). Typical
vapor-mounted and liquid-mounted seals arepresented in the Figures
above respectively.
Secondary Seals on External Floating Roofs
A secondary seal on an external floating roof consists of a
continuous seal mountedon the rim of the floating roof and
extending to the tank wall, covering the entireprimary seal.
Secondary seals are normally constructed of flexible
polymericmaterials. Figure below depicts several primary and
secondary seal systems. Analternative secondary seal design
incorporates a steel leaf to bridge the gap betweenthe roof and the
tank wall. The leaf acts as a compression plate to hold a
polymericwiper against the tank wall.
A rim-mounted secondary seal installed over a primary seal
provides a barrier forvolatile organic compound (VOC) emissions
that escape from the small vapor spacebetween the primary seal and
the wall and through any openings or tears in the sealenvelope of a
metallic shoe seal (Figure below). Although not shown in Figure
below,a secondary seal can be used in conjunction with a weather
shield as described in thefollowing section.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 29 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Another type of secondary seal is a shoe-mounted secondary seal.
A shoe-mountedseal extends from the top of the shoe to the tank
wall (Figure below). These seals donot provide protection against
VOC leakage through the envelope. Holes, gaps, tears,or other
defects in the envelope can permit direct exchange between the
saturatedvapor under the envelope and the atmosphere. Wind can
enter this space throughenvelope defects, flow around the
circumference of the tank, and exit saturated ornearly saturated
with VOC vapors.
Figure 13: Secondary rim seals
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 30 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Weather Shield
A weather shield may be installed over the primary seal to
protect it from deteriorationcaused by debris and exposure to the
elements. Though the USA EPA does notaccept the installation of a
weather shield as equivalent to a secondary seal, there area large
number of existing tanks not affected by high VOCs that have
thisconfiguration. Typically, a weather shield is an arrangement of
overlapping thin metalsheets pivoted from the floating roof to ride
against the tank wall. The weather shield,by the nature of its
design, is not an effective vapor barrier. For this reason, it
differsfrom the secondary seal. Although the two devices are
conceptually similar in design,they are designed for and serve
different purposes.
Internal Floating Roof Rim Seals
Internal floating roofs typically incorporate one of two types
of flexible, product-resistant rim seals: resilient foam-filled
seals or wiper seals. Similar to those employedon external floating
roofs, each of these seals closes the annular vapor spacebetween
the edge of the floating deck and the tank shell to reduce
evaporative losses.They are designed to compensate for small
irregularities in the tank shell and allowthe roof to freely move
up and down in the tank without binding.
Resilient Foam-Filled Seal
A resilient foam-filled seal used on an internal floating roof
is similar in design to thatdescribed for external floating roofs.
Resilient foam-filled seals are shown in Figuresabove. These seals
can be mounted either in contact with the liquid surface
(liquid-mounted) or several centimeters above the liquid surface
(vapor-mounted).
Resilient foam-filled seals work because of the expansion and
contraction of a resilientmaterial to maintain contact with the
tank shell while accommodating varying annularrim space widths.
These seals consist of a core of open-cell foam encapsulated in
acoated fabric. The elasticity of the foam core pushes the fabric
into contact with thetank shell. The seals are attached to a
mounting on the deck perimeter and arecontinuous around the roof
circumference.
Polyurethane-coated nylon fabric and polyurethane foam are
commonly usedmaterials. For emission control, it is important that
the mounting and radial seal jointsbe vapor-tight and that the seal
be in substantial contact with the tank shell.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 31 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Wiper Seals
Wiper seals are commonly used as primary rim seals for internal
floating roof tanks.This type of seal is depicted in Figures above.
Wiper seals generally consist of acontinuous annular blade of
flexible material fastened to a mounting bracket on thedeck
perimeter that spans the annular rim space and contacts the tank
shell. Themounting is such that the blade is flexed, and its
elasticity provides a sealing pressureagainst the tank shell. Such
seals are vapor-mounted; a vapor space exists betweenthe liquid
stock and the bottom of the seal. For emission control, it is
important thatthe mounting be vapor-tight, that the seal extend
around the circumference of the roof,and that the blade be in
substantial contact with the tank shell.
Three types of materials are commonly used to make the wipers.
One type consists ofa cellular, elastomeric material tapered in
cross section with the thicker portion at themounting. Rubber is a
commonly used material. All radial joints in the blade arejoined. A
second type of wiper seal construction uses a foam core wrapped
with acoated fabric. Polyurethane on nylon fabric and polyurethane
foam are commonmaterials. The core provides the flexibility and
support, while the fabric provides thevapor barrier and wear
surface. A third type of wiper seal consists of overlappingsegments
of seal material (shingle-type seal). Shingle-type seals differ
from the wiperseals discussed previously in that they do not
provide a continuous vapor barrier.
Secondary Seals for Internal Floating Roof Tanks
Secondary seals may be used to provide some additional
evaporative loss controlover that achieved by the primary seal. The
secondary seal is mounted to an extendedvertical rim plate, above
the primary seal, as shown in Figure above. Secondary sealscan be
either a resilient foam-filled seal or an elastomeric wiper
seal.
For a given roof design, using a secondary seal further limits
the operating capacity ofa tank due to the need to maintain contact
with the tank shell or keep the seal frominterfering with IFRT
fixed-roof rafters when the tank is filled. Secondary seals are
notcommonly used on internal floating roof tanks that are not
affected by the EPAregulations.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 32 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
TYPES OF FLOATING ROOF DECK FITTINGS
External and Domed External Floating Roof Deck Fittings
Numerous fittings penetrate or are attached to an external
floating roof deck. Thesefittings accommodate structural support
components or allow for operational functions.These fittings can be
a source of emissions in that they must penetrate the deck.Other
accessories are used that do not penetrate the deck and are not,
therefore,sources of evaporative loss. The most common fittings
relevant to controlling vaporlosses are described in the following
sections.
Access Hatches.
An access hatch consists of an opening in the deck with a
peripheral vertical wellattached to the deck and a removable cover
to close the opening as shown in Figurebelow. An access hatch is
typically sized to allow workers and materials to passthrough the
deck for construction or servicing. The cover can rest directly on
the well,or a gasketed connection can be used to reduce evaporative
loss. Bolting the cover tothe well reduces losses further.
Figure 14: Access Hatch
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 33 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Gauge Float Wells
Gauge floats are used to indicate the level of stock within the
tank. These usuallyconsist of a float residing within a well that
passes through the floating deck, as shownin Figure below. The
float is connected to an indicator on the exterior of the tank via
atape passing through a guide system. The float rests on the stock
surface within thewell, which is enclosed by a sliding cover.
Evaporation loss can be reduced bygasketing and/or bolting the
connection between the cover and the rim of the well. Thecable
passes through a bushing located at the center of the cover. As
with similardeck penetrations, the well extends into the liquid
stock on noncontact floating decks.
Figure 15: Gauge float
Gauge Hatch/Sample Ports
Gauge hatch/sample ports provide access for hand gauging the
level of stock in thetank and for taking samples of the tank
contents. A gauge hatch / sample port consists
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 34 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
of a pipe sleeve through the deck and a self-closing gasketed
cover, as shown inFigure below. Gauge hatch/sample ports are
usually located under the gaugersplatform, which is mounted on the
top of the tank shell. The cover may have a cordattached so that it
can be opened from the gaugers platform. A gasketed coverreduces
evaporative losses.
Figure 16: Sample ports
Rim Vents
Rim vents are found on tanks equipped with a rim seal system
that creates a vaporpocket, such as a mechanical shoe seal or
double wiper seal system. The rim vent isconnected to the rim vapor
space by a pipe and releases any excess pressure orvacuum that is
present (Figure below). The rim vapor space is bounded by the
floatingdeck rim, the primary-seal shoe, the liquid surface, and
the primary-seal fabric. Rimvents usually consist of weighted
pallets that rest on the gasketed surface.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 35 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 17: Rim vent
Deck Drains
Deck drains permit removal of rainwater from the surface of
floating decks. Two typesof floating roof drainage systems are
currently used: closed and open. Closeddrainage systems carry
rainwater from the surface of the deck to the outside of thetank
through a flexible or articulated piping system or through a
flexible hose systemlocated below the deck in the product space.
Since product does not enter this closeddrainage system, there is
no associated evaporative loss. Open drainage systems,consisting of
an open pipe that extends a short distance below the bottom of the
deck,permit rainwater to drain from the surface of the deck into
the product. Since thesedrainpipes are filled with product to the
product level in the tank, evaporative lossoccurs from the top of
the open drainpipes. Two types of roof drains are commonlyused in
open drainage systems: flush drains and overflow drains. Flush
drains (Figure
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 36 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
below) have a drain opening that is flush with the top surface
of the double deck. Theypermit rainwater to drain into the
product.
Overflow drains (Figure below) consist of a drain opening that
is elevated above thetop surface of the deck, thereby limiting the
maximum amount of rainwater that canaccumulate on the deck and
providing emergency drainage of rainwater. They arenormally used in
conjunction with a closed drainage system. Some open deck drainsare
equipped with an insert to reduce the evaporative loss.
Figure 18: Deck drains
Deck Legs
Deck legs prevent damage to fittings underneath the deck and
allow for tank cleaningor repair by holding the deck at a
predetermined distance from the tank bottom. Thesesupports consist
of adjustable or fixed legs attached to the floating deck as shown
in
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 37 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure below. For adjustable deck legs, the load-carrying
element passes through awell or sleeve in the deck.
Figure 19: Deck leg
Slotted and Unslotted Guide Poles and Wells
Anti-rotation devices are used to prevent floating roofs from
rotating and potentiallydamaging roof equipment and rim seal
systems. A commonly used antirotation deviceis a guide pole that is
fixed at the top and bottom of the tank (Figure below). The
guidepole passes through a well in the deck. Rollers attached to
the top of the well ride onthe outside surface of the guide pole to
prevent the floating roof from rotating.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 38 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
The guide pole well has a sliding cover to accommodate limited
radial movement ofthe roof. The sliding cover can be equipped with
a gasket between the guide pole andthe cover to reduce evaporative
loss. The guide pole well can also be equipped with agasket between
the sliding cover and the top of the well to reduce evaporative
loss.Openings at the top and bottom of the guide pole provide a
means of hand-gaugingthe tank level and of taking bottom
samples.
In the slotted guide pole/sample well application, the well of
the guide pole isconstructed with a series of drilled holes or
slots that allow the product to mix freely inthe guide pole and
thus have the same composition and liquid level as the product
inthe tank. Evaporative loss from the guide pole can be reduced by
modifying the guidepole or well, or by placing a removable float
inside the pole. Deck fitting factors forslotted guide poles
without pole sleeves were determined from test data on
fittingswhere the float top or float wiper was positioned at or
above the sliding coverelevation.
Tests were not conducted with floats where the top of the float
or wiper was below thesliding cover elevation (short floats);
emissions from such a configuration areexpected to be somewhere
between those for guide poles with and without floats,depending
upon the float height. When a pole sleeve is used, the evaporative
loss willnot be affected by the height of the float within the
well, since the purpose of the polesleeve is to restrict the flow
of vapor from the vapor space below the deck into theslotted guide
pole.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 39 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 20: Slotted and unslotted guidepoles
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 40 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Vacuum Breakers
The purpose of a vacuum breaker is to allow for the exchange of
vapor and airthrough the floating roof during filling and emptying.
Vacuum breakers are designed tobe activated by changes in pressure
or liquid level, or strictly by mechanical means.
Mechanical vacuum breakers are activated when the deck is either
being landed on itslegs or floated off its legs to equalize the
pressure of the vapor space across the deck.This is accomplished by
opening a deck penetration that usually consists of a wellformed of
pipe or framing on which rests a cover (Figure below). Attached to
theunderside of the cover is a guide leg long enough to contact the
tank bottom as theexternal floating deck approaches the tank
bottom. When in contact with the tankbottom, the guide leg
mechanically opens the breaker by lifting the cover off the
well.When the leg is not contacting the bottom, the penetration is
closed by the coverresting on the well.
The closure may or may not have a gasket between the cover and
neck. Since thepurpose of the vacuum breaker is to allow the free
exchange of air and/or vapor, thewell does not extend appreciably
below the deck. The gasket on the underside of thecover, or
conversely on the upper rim of the well, provides a small measure
ofemission control during periods when the roof is free floating
and the breaker isclosed.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 41 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 21: Vacuum breaker
Internal Floating Roof Fittings
Numerous fittings penetrate or are attached to an internal
floating deck. These fittingsserve to accommodate structural
support components or to allow for operationalfunctions. The
fittings can be a source of evaporative loss in that they
requirepenetrations in the deck. Other accessories are used that do
not penetrate the deckand are not, therefore, sources of
evaporative loss. The most common fittings relevantto controlling
vapor losses are described in the following sections.
The access hatches, deck legs, vacuum breakers, and automatic
gauge float wells forinternal floating roofs are similar fittings
to those described earlier for external floatingroofs.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 42 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Column Wells
The most common fixed-roof designs (Figure below) are normally
supported frominside the tank by means of vertical columns, which
necessarily penetrate the floatingdeck. (Some fixed roofs are
entirely self-supporting and, therefore, have no
supportcolumns.)
Columns are made of pipe with circular cross sections or of
structural shapes withirregular cross sections (built-up). The
number of columns varies with tank diameterfrom a minimum of 1 to
over 50 for very large tanks. A typical fixed roof supportcolumn is
shown in Figure below. The columns pass through deck openings
viaperipheral vertical wells. With noncontact decks, the well
should extend down into theliquid stock. Generally, a closure
device exists between the top of the well and thecolumn.
Several proprietary designs exist for this closure, including
sliding covers and fabricsleeves, which must accommodate the
movements of the deck relative to the columnas the liquid level
changes. A sliding cover rests on the upper rim of the column
well(which is normally fixed to the deck) and bridges the gap or
space between thecolumn well and the column. The cover, which has a
cutout, or opening, around thecolumn, slides vertically relative to
the column as the deck raises and lowers. At thesame time, the
cover slides horizontally relative to the rim of the well. A gasket
aroundthe rim of the well reduces emissions from this fitting. A
flexible fabric sleeve sealbetween the rim of the well and the
column (with a cutout, or opening to allow verticalmotion of the
seal relative to the columns) similarly accommodates limited
horizontalmotion of the roof relative to the column.
A third design combines the advantages of the flexible fabric
sleeve seal with a wellthat excludes all but a small portion of the
liquid surface from direct exchange with thevapor space above the
floating deck.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 43 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
Figure 22: Fixed Roof Support Column
Sample Pipes or Wells
A sample well may be provided to allow liquid stock sampling.
Typically, the well isfunnel-shaped to allow for easy entry of a
sample thief. A closure is provided, which istypically located at
the lower end of the funnel and which frequently consists of
ahorizontal piece of fabric slit radially to allow thief entry. The
well should extend intothe liquid stock on noncontact decks.
Alternately, a sample well may consist of aslotted pipe extending
into the liquid stock equipped with an ungasketed or
gasketedsliding cover.
Ladder Wells
Some tanks are equipped with internal ladders that extend from a
manhole in the fixedroof to the tank bottom. The deck opening
through which the ladder passes is
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 44 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
constructed with similar design details and considerations to
those for column wells. Atypical ladder and well are shown in
Figure below.
Figure 23: Ladder and well
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 45 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to develop the final design.
The guidelines are a training tool foryoung engineers or a resource
for engineers with experience.
This document is entrusted to the recipient personally, but the
copyright remains with us. It must not be copied,reproduced or in
any way communicated or made accessible to third parties without
our written consent.
DEFINITIONS
Above Ground Storage Tank (AST) - any one or combination of
tanks, includingpipes connected thereto and any ancillary equipment
and containment system, that isused to contain an accumulation of
liquids or gases, and the volume of which,including the volume of
connected piping.
Accuracy - The ability of a measuring instrument to indicate
values closelyapproximating the true value of the quantity
measured.
Atmospheric Storage Tank a storage tank which has been designed
to operate atpressures from atmospheric through 0.5 psig
Autoignition Temperature - The temperature to which a flammable
mixture of vaporand air in the explosive range must be heated for
ignition to occur spontaneouslywithout external source of
ignition.
API Gravity (Relative Density) - A means used by the petroleum
industry toexpress the density of petroleum liquids. API gravity is
measured by a hydrometerinstrument having a scale graduated in
degrees API. The relation between API gravityand relative density
(formerly called specific gravity) is:
API Gravity at 60 Deg. F. = 141.5 - 131.5Relative Density
60F/60F
Ballast Water - Oil contaminated water contained in the cargo
compartments ofmarine vessels. Ballast water is taken aboard empty
or near empty vessels to providea safe level of stability for the
vessel. Tankers arriving at a shipping dock to take onproduct,
discharge ballast water into a shore side storage tanks for
subsequentwastewater treatment. This operation is known as
de-ballasting.
Barrel (BBL) - A unit of volume equal to 42 U.S. gallons or
9702.0 cubic inches.
Blocked Operation - The use of a single process unit alternately
in more than oneoperation to manufacture various grades of product.
Lube oils and certain chemicalssuch as linear paraffins are often
made in blocked operation.
Breathing Loss - Loss associated with thermal expansion and
contraction of thevapor space, resulting from the daily temperature
cycle or any such temperature cyclethat can be induced by weather
conditions such as rainstorms.
-
KLM TechnologyGroup
Practical Engineering Guidelinesfor Processing Plant
Solutions
STORAGE TANK SELECTION ANDSIZING
ENGINEERING DESIGN GUIDELINES
Page 46 of 87
Rev: 02
JUNE 2011
These design guideline are believed to be as accurate as
possible, but are very general and not for specific design
cases.They were designed for engineers to do preliminary designs
and process specification sheets. The final design mustalways be
guaranteed for the service selected by the manufacturing vendor,
but these guidelines will greatly reduce theamount of up front
engineering hours that are required to