1 API 650 Intro, Design of storage tanks
Summary
TLDRThis video script focuses on API 653, covering the inspection and repair of above-ground storage tanks. It outlines the design process, emphasizing the tanks' role in storing various commodities like crude oil and LPG. The script discusses design codes to prevent disasters, highlighting the API 650 code's requirements for steel welded tanks, including storage of liquid fluids, support conditions, and pressure and temperature limits. It also explores different tank roof types, their mechanical design implications, and the importance of understanding roof configurations for load determination. The script further delves into floating roofs, their types, and their role in reducing evaporation losses, concluding with considerations for material selection and tank shell thickness calculations.
Takeaways
- 📚 API 653 is a standard for inspecting and repairing above-ground storage tanks, which are crucial for storing various commodities like crude oil, LPG, and water.
- 🔍 The primary purpose of storage tanks is to hold large quantities of fluid at a relatively low installation cost, operating mostly at atmospheric or near-atmospheric conditions.
- 🏗️ Design codes, including API 650, are used to prevent disasters and ensure safety by setting minimum requirements for design, fabrication, material selection, inspection, and installation.
- 🚫 Tanks designed with API 650 can only store liquid fluids, must have a bottom supported by sand, gravel, or concrete, and must operate with internal pressure below 17 kilopascals and temperatures below 93 degrees Celsius.
- 🔧 The API 650 code is divided into two main parts: the first part contains mandatory requirements, and the second part includes annexes with good practices, recommendations, and examples.
- 🛠️ Mechanical design aspects covered by the code include materials, design, and fabrication, with a focus on understanding roof configurations to determine loads and design tank parts.
- 🌡️ Fixed roof tanks are suitable for non-volatile liquids and are the most common in industry, while floating roofs are used for volatile products to minimize evaporation.
- 🏭 Different roof types include conical, dome, and umbrella types, each with specific configurations and suitable for different tank sizes and fluid types.
- 🔄 Floating roofs come in two types: external, which rests on the liquid and is exposed to the environment, and internal, which is not in direct contact with solar radiation and reduces product contamination.
- ⚖️ The design of storage tanks must consider various loads, including operating weight of the fluid, seismic loads, and wind pressure, to ensure structural integrity and safety.
- 🛡️ Material selection for tanks is guided by best practices, client specifications, and metallurgy specialists, with carbon steel, stainless steel, and aluminum being common choices.
Q & A
What is the primary purpose of above ground storage tanks?
-Above ground storage tanks are primarily used to store large quantities of various commodities for later use, sale, or further processing.
What types of products are commonly stored in above ground storage tanks?
-Products commonly stored include crude oil and its derivatives, butane, propane, LPG, solvents, water, and more.
What are the main characteristics of above ground storage tanks?
-They are a buffer between different process stages, easy to build, operate at atmospheric or near atmospheric conditions, and are generally built in situ.
Why are design codes important for storage tanks?
-Design codes are important to avoid disasters affecting humans and include a range of experiences and good practices, stating minimum requirements for design, fabrication, material selection, inspection, and installation.
What are the specific requirements for tanks designed with the API 653 code?
-Tanks must store only liquid fluids, have bottoms supported by sand, gravel, or concrete, maintain internal pressure below 17 kilopascals, and operate at temperatures below 93 degrees Celsius, or up to 260 degrees if Annex M requirements are met.
What is the difference between atmospheric and low-pressure tanks as defined by the API 650 code?
-Atmospheric or low-pressure tanks, as defined by the API 650 code, are those that can only operate with internal pressures below 17 kilopascals.
What are the main sections covered by the mandatory requirements in the API 650 code?
-The mandatory requirements are divided into 10 sections covering the complete fabrication and installation cycle of a tank, with the most relevant parts being materials, design, and fabrication.
What are the different types of tank roofs mentioned in the script and how do they differ?
-The different types of tank roofs include fixed roofs (cone type, dome type, umbrella type), self-supporting roofs, and supported roofs. Fixed roofs are used for non-volatile liquids, while self-supporting roofs are capable of supporting themselves without any structural element, and supported roofs use a structure to support the roof plates.
What is a floating roof and how does it function?
-A floating roof is a circular metal structure with pontoons that allow it to float on the liquid in an open or closed tank, reducing evaporation losses and preventing product contamination.
What are the considerations for selecting a type of storage tank?
-Considerations for selecting a type of storage tank include product losses, mainly due to evaporation, and the selection of the roof type, which is crucial from a mechanical design point of view to determine the loads to be supported.
What are the design conditions that need to be defined for a satisfactory design of storage tanks?
-Design conditions include ambient temperature or fluid temperature, internal or external loadings, liquid level, corrosion allowance, external requirements like wind, seismic or snow loads, capacity, diameter, height, and fabrication requirements.
Outlines
🛢️ Introduction to API 653 and Storage Tanks
This paragraph introduces the topic of API 653, which is focused on the inspection and repair of above-ground storage tanks. It emphasizes the importance of understanding the design process to ensure the tanks' adequacy. Storage tanks are highlighted as a common storage solution for various commodities like crude oil, butane, propane, and water. The tanks are designed to store fluids at low installation costs and operate under atmospheric conditions. The API 650 code is mentioned as a crucial guide for designing steel-welded tanks, with requirements such as liquid storage only, specific support for the tank bottom, and limits on internal pressure and operating temperature. The paragraph also outlines the code's structure, which includes mandatory requirements and annexes with recommendations and examples.
🏭 Types of Storage Tank Roofs and Their Applications
This section delves into the different types of storage tank roofs, their characteristics, and applications. Fixed roof tanks are common for non-volatile fluids and can have conical, dome, or umbrella configurations. The choice of roof type is influenced by factors like tank dimensions, fluid characteristics, and manufacturing methods. Self-supporting roofs are capable of bearing their own weight without additional structural support, while supported roofs require a framework due to the weight and external loads. Floating roofs are designed for tanks storing volatile products, with the ability to float on the liquid surface, reducing evaporation losses. The paragraph distinguishes between internal and external floating roofs, with the former being more effective in preventing contamination and reducing emissions.
🔩 Design Considerations for Floating Roofs
The paragraph discusses the design and functionality of floating roofs, particularly focusing on internal floating roofs and their ability to reduce gas emissions. It explains the importance of proper sealing to prevent the accumulation of explosive gases and the need for adequate venting. The design of floating roofs must ensure they can move freely within the tank without damaging the tank body or other components. The paragraph also covers different types of floating roofs, including single deck and double deck, each with specific design requirements and applications based on tank size and environmental conditions. The API 650 code's Annex C provides detailed design guidelines for floating roofs.
🏗️ Design Conditions and Material Selection for Storage Tanks
This paragraph focuses on the design conditions that must be defined for a satisfactory tank design, such as pressure, temperature, and various loads including seismic and wind. It stresses the importance of considering all loads simultaneously to determine the most stringent design scenario. Material selection is also discussed, with the API 650 code providing guidelines on allowed materials and their requirements. Common materials for tank fabrication include carbon steel, stainless steel, and aluminum. The code categorizes materials into six groups, with ASME and ASTM designations being the most frequently used. The paragraph also touches on the methods for determining tank shell thickness, with a focus on the one-foot method, which is simple and conservative.
⚙️ Calculation Methods for Tank Shell Thickness
The paragraph explains the one-foot method for calculating tank shell thickness, which is widely used due to its simplicity and safety. This method assumes the maximum stress point for each shell course is located one foot above the base, leading to a conservative calculation. It is not applicable for tanks with diameters over 61 meters. The calculation compares normal operation loads and hydrostatic test loads, adopting the greater value for determining shell thickness. Factors considered include the tank's mean diameter, liquid level, fluid density, corrosion allowance, and allowable stress.
💠 Bottom Plate Design and Fabrication
This section discusses the design and fabrication of the bottom plates of storage tanks, which are crucial for ensuring the tank's seal tightness. It covers the different joint types for bottom plates, with overlapped joints being preferred for their ease of assembly and cost-effectiveness. The paragraph also addresses the minimum thickness requirements for bottom plates, considering the need to withstand bending and compressive loads. The design of annular plates is also discussed, including their width determination and the factors influencing their minimum thickness as per the API 650 standard. The use of annular plates helps reduce stress concentration and increase resistance against overturning moments.
Mindmap
Keywords
💡API 653
💡Storage Tanks
💡Design Codes
💡Atmospheric Conditions
💡Internal Pressure
💡Roof Types
💡Floating Roof
💡Seismic Design
💡Allowable Stress
💡Hydrostatic Pressure
💡Annular Plate
Highlights
API 653 focuses on the inspection and repair of above-ground storage tanks, which are crucial for storing various commodities like crude oil, LPG, and water.
Storage tanks serve as a buffer in processes, are easy to construct, and operate under atmospheric conditions.
Design codes like API 653 are essential for preventing disasters and are based on collective experiences and best practices.
Tanks designed per API 653 must store liquid fluids, have a bottom supported by sand, gravel, or concrete, and operate under specific pressure and temperature conditions.
API 650 code, from the American Petroleum Institute, is divided into two parts: mandatory requirements and annexes with recommendations and examples.
Mandatory requirements cover 10 sections, including materials, design, and fabrication, which are critical for the tank's mechanical design.
Annexes in API 650 provide guidance on roof types, pressure considerations, seismic design, and allowable nozzle loads.
Storage tanks are designed to minimize product loss, primarily through evaporation, influenced by temperature variation.
The selection of the roof type is critical in the design process, as it affects the tank's ability to handle different products and processes.
Fixed roof tanks are widely used for non-volatile fluids and can have conical, dome, or umbrella configurations.
Floating roofs are used for volatile liquids, eliminating the vapor space between the liquid and the tank roof.
Internal floating roofs can prevent product contamination from environmental factors and reduce evaporation losses.
Design conditions for storage tanks include pressure, temperature, loading, and external requirements like wind and seismic conditions.
Materials for storage tanks can vary, and API 650 provides guidelines on allowed materials and their requirements.
The thickness of tank shells is determined by considering hydrostatic pressure, with methods like the one-foot method providing simplicity and safety.
Bottom plates of tanks are crucial for sealing and can be fabricated with overlapped joints or butt joints, with specific requirements for thickness and width.
Annular plates are used to support the tank's weight and reduce stress concentration, with their dimensions determined by various factors including tank diameter.
Transcripts
hi there
you are watching a video of API 653
inspection and repair of above ground
storage tanks
the contents that will be covered in
this module have been outlined to
understand the design process of this
element in order to arrive to an
adequate design
above ground storage tanks are the most
used of all types of storage facilities
storage tanks are widely used to hold
large amounts of various commodities for
later use sale or further processing
such products include crude oil and its
derivatives butane propane LPG solvents
water
Etc
what are storage tanks designed for
mainly to stock large quantities of
fluid at relatively low installation
cost
some of their characteristics are
they are a buffer between the different
stages of the process
they are easy to build compared to other
similar equipment
they operate at atmospheric or near
atmospheric conditions
generally they are built in situ
the purpose of using design codes is to
avoid disasters that can affect humans
therefore they comprise a range of
experiences and good practices
the code States the minimum requirements
for the design fabrication material
selection inspection and installation of
Tanks fabricated with steel welded
plates
tanks designed with this code must meet
the following requirements
tanks can only store liquid fluids
the bottom of the tank must be sand
gravel or concrete supported
the internal pressure in the tank must
be lower than 17 kilopascals
and the operating temperature has to be
lower than 93 degrees
going up to 260 if Annex M requirements
are met
before we start reviewing the code
organization and the minimum
requirements is convenient to establish
the main differences between the
equipment used to store products
a good comparison could be made
regarding the pressure level to which
they can operate
storage tanks designed according to the
API 650 code are also known as
atmospheric or low pressure tanks
since they can only operate with
internal pressures below 17 kilopascals
the API 650 code from the American
petroleum Institute is divided in two
main parts
in the first part of the code the
mandatory requirements are found where
the scope definitions and Main contents
are included
in the second part we find the annexes a
set of good practices recommendations
and examples
[Music]
the mandatory requirements are divided
into 10 sections covering the complete
fabrication and installation cycle of a
tank
from the mechanical design perspective
the most relevant parts are
materials
design and Fabrication
in the other hand the code has 27
annexes
covering the different roof types
internal and external pressure
considerations seismic design and
allowable nozzle loads among others
until aspect to consider When selecting
a type of storage tank are product
losses
main product losses are those produced
by evaporation that is temperature
variation
therefore the aspect that governs the
design of the tongue is the selection of
the roof type
as observed in the picture there are
different types of tank roofs mainly
depending on the process and side
requirements
from the mechanical design point of view
it is mandatory to fully understand the
roof configuration in order to design
the parts of the tank but more
importantly to determine the loads to be
supported
fixed roof tanks are used for the
storage of a large number of products
usually non-volatite fluids at
temperatures close to ambient
it can be said that the largest number
of applications in the industry use
fixed roof tanks
when the fluid to be stored is a product
that tends to evaporate at operating
temperature of the tank
a vapor chamber is created between the
level of the liquid and the tank roof
to eliminate the vapor chamber between
the liquid level and the roof floating
devices resting on the liquid are used
storage tanks with fixed roofs are used
to store non-volatile liquids with a low
content of light non-flammable products
such as water diesel asphalt crude oil
Etc
[Music]
its roofs can adopt different
configurations depending on the
dimensions of the tongue the fluid to be
stored the tag material and the
manufacturing method among other things
the three configurations accepted by the
API 650 code are
cone type
Dome type and
umbrella type
at the same time the roof can be
self-supporting or supported
clinical roofs are characterized by
their easy construction
the configuration of this type of roof
is a cover with the shape of us and
surface of a straight cone
Dome type roofs are less used than
conical roofs because of the complex and
difficult manufacturing process
each sheet and segment should conform to
the radius of curvature of the roof thus
increasing the cost and delivery time
umbrella type roofs are a variety of the
Dome type
which only keeps the curvature on the
vertical axis on the circumferential
axis the umbrella type roof is similar
to The Cone type roof
self-supporting roofs consists of a set
of overlapped or bad welded plates
because of their physical shape they are
capable of supporting themselves without
any structural element
they are supported at the outer part of
the roof by the Tongue shell
the thickness of the roof blades must be
calculated undesigned so that the roof
can be self-supported
self-supporting groups can adopt any of
the three configurations mentioned
earlier conical Dom type or umbrella
type
supported roofs share the same
characteristics as the supporting type
although in this case a structure is
used to support the roof plates
the main reason for using a frame is due
to the fact that the weight of the
plates to be supported and the external
loads apply to the roof on weight
mechanical elements snow
Etc
depending on the diameter of the tank
and the loads to be supported the roof
will be designed with or without columns
a floating roof is a circular metal
structure provided with a floating
capacity because of the pontoons
included in this structure
the pontoons allow the roof to float on
the liquid
in an open or closed tank
there are two types of floating roofs
the external ones which rest on the
store liquid and are in contact with the
environment
and the internal ones those not in
direct contact with the solar radiation
on rain
the process of sending and receiving the
stored liquid is the same for both
configurations
the main differences between internal
and external roofs are the following
can reduce evaporation losses
[Music]
internal floating roofs can effectively
prevent the store product from being
contaminated by winds and rain snow or
dust
[Music]
tanks with internal floating roofs are
easy to build and maintain
in addition materials of the seal
element have longer duration because
they are not in direct contact with
solar radiation
in large diameter tanks where the fixed
roof would have to be supported by
columns
making the sale between this and the
floating roof complex
in addition
the cost of tanks with external floating
roof is generally lower
due to Manufacturing tolerances in the
construction of large circular
structures the diameter of floating
roofs is smaller than the Tank's
internal's diameter
this Gap allows the roof to travel up
and down without any interference with
the tank wall
the space between the floating roof and
the inner tongue wall is closed by means
of a set of mechanical seals divided on
primary seals
and secondary seals
the requirements and design guidelines
for this type of roofs are contained in
Annex C of the API 650 code
the design of the roof and its
accessories should allow the roof to
travel to the upper and lower liquid
operation level
without damaging the attack body
the roof itself or any other vertices
[Music]
single deck floating roofs consists of a
flood Central cover
surrounded by pontoons floats which are
divided radially into compartments
since the roof is exposed to the
environment the design must warranty
adequate drainage
the central cover is formed by a
membrane formed by Steel plates
overlapped and welded by means of
affiliate weld usually only in the upper
part and connected to the inner part of
the pontoon
the different parts of this type of roof
are shown on the screen
[Music]
this type of roofing is used for tanks
up to 65 meters in diameter
for larger diameters fatigue caused by
wind has been experienced due to the
excessive flexibility originated in the
central part of the tongue
[Music]
the double deck floating roof consists
of two decks covering the entire roof
the Pontoon has an upper and a lower
membrane separated by a number of ribs
between these two decks defining the
compartments of the roof
the outer ring with the compartments
represent the main buoyancy element of
the roof
this type of roof is of much heavier
construction than the previous one and
also more expensive however
a more rigid construction allows better
drainage from the top of the roof
[Music]
the different parts of this type of roof
are shown on the screen
this type of roof is preferred for small
tanks under 10 meters in diameter
the to use Simple Roofing the central
cover would be very small
double decks roofs are also prepared for
tanks with diameters above 65 meters
its use is recommended in those areas
where the load on the roof due to
rainfall and debris is very high
internal floating roofs are used inside
fixed roof tanks to reduce gas emissions
since this type of roof is not in direct
contact with the atmosphere its
construction is much lighter compared to
external floating roofs
the requirements for internal floating
roofs are limited only by safety and
durability factors
[Music]
allowed configurations and minimal
requirements are included in Annex age
of the API 650 code
there are different types of internal
floating roofs as shown on the screen
going from bulkheaded type
still pontoon type 2 aluminum sandwich
type
internal floating roofs can directly
rest on the store product
this way there is no Vapor space between
the roof and the product
[Music]
the free space above the floating roof
must be adequately vented to the
atmosphere to avoid the accumulation of
potential explosive gases
[Music]
the adequate definition of the design
condition is a stepping stone of any
satisfactory design in some cases the
real difficulty of the calculation
process lies with definition of the
design conditions
pressure and temperature are just two of
the many design constraints that should
be taken into account
some of them are
ambient temperature or fluid temperature
requirements either internal or external
loading Us in self-loads live or dead
loads
liquid level corrosion allowance
external requirements side conditions
such as wind seismic or snow
capacity
diameter height
and Fabrication requirements
[Music]
due to the large quantities of product
that could be stored in this type of
equipment load's definition is one of
the fundamental aspects to be evaluated
prior to any development
the loads that generally govern the
design of storage tanks are the
operating weight of the fluid
seismic loads and the wind pressure
these two last conditions depending on
the site
all loads acting simultaneously upon the
tongue must be taken into account
therefore the different design scenarios
are determined
checking the tank against every possible
case
until the most stringent is found
[Music]
the code does not recommend or suggest
any material for any particular
application
the code merely States what materials
are allowed and the requirements they
have to comply with
to select a material for an application
the following should be consulted
best practices and Lessons Learned
authors of reference
current Publications like API or Nays
client specifications
and Metallurgy specialists
storage tanks can be fabricated from
different materials carbon steel
stainless steel aluminum Etc
the API 650 code divides materials in
six groups as it can be seen in the
picture
it is worth mentioning that some of the
elements of storage tanks such as the
annual plate are defined according to
these groups
[Music]
the most used materials in the
manufacture of storage tanks according
to the API 650 code are those
corresponding to the designation asmi
ASTM
the most used materials are indicated on
the screen according to the groupings
mentioned
there are different methods accepted by
the API 650 standard to determine the
thickness of tank shells
next we will review the different
considerations to bear in mind to
calculate this element
it is clear to observe that the
hydrostatic pressure will be maximum at
the bottom of the tongue due to higher
static head
therefore the bottom shell course will
require a thicker plate
decreasing moving upwards in the tank
shell
circumferential stresses induced in the
tongue shell due to the hydrostatic
pressure are not linear
mainly due to the presence of welded
joints having higher allowable stresses
than plates
consequently the stresses in one shell
course is not linear either
having its maximum value at a certain
height
in order to establish the tank shell
thickness the different calculation
methods Define the height at which the
maximum stresses are located in every
shell course
stresses that must be lower than the
allowables
there are three methods to determine the
tongue shell thickness accepted by the
storage tanks standard API 650. these
are
the one foot method
the variable design Point method
and the elastic analysis in other words
infinite element analysis
from all these three methods we will
study the one foot method in this module
from all three methods aforementioned
the one foot methods is most widely used
mainly due to its Simplicity and due to
the fact that the results are in the
safe side
[Music]
this method determines the Shelf
thickness considering that the design
point for each core's maximum stress
point is located at one foot
304.8 millimeters above the base of the
shell course
this simplification in the calculation
process is on the safe side
the one foot method cannot be used for
tanks with diameters larger than 61
meters
the tank shelf thickness calculation
according to the one foot method
Compares two loads combinations
normal operation loads
and hydrostatic test loads
the bigger value of these two afford
mentioned will be adopted for the tank
shell thickness
its thickness is a function of
the mean diameter of the tank
the liquid level
the specific density of the fluid
the corrosion allowance if required and
the allowable stress
the bottoms of vertical cylindrical
storage tanks are generally welded
fabricated using steel plates
plates used for bottoms can be joined
according to the following
using overlapped joints with fillet
welds
or with butt joints where a full
penetration weld must be used
overlapped joints are the preferred
alternative for the fabrication of
bottoms of off storage tanks mainly due
to its easy assembly and reduce cost
the arrangement of plates should
warranty a minimum overlapping of 305
millimeters
[Music]
the main purpose of the bottom plates is
to guarantee the seal tightness of the
tank
and considering that these plates do not
have to withstand the hydrostatic
pressure of the fluid they require
significantly smaller thicknesses than
the shell plates
a 1.5 millimeter thickness metal sheet
or less will be able to withstand the
bending and compressive loads generated
in the outside part of the tank by the
weight of the shells resting on this
section
however to prevent deformations when
welding plates with a minimum thickness
of 6 millimeters according to a
requirements of the API 650 standard
shall be used
[Music]
depending on the tank diameter
the bottom plate Arrangement May adopt
different configurations
the main aspect to bear in mind when
defining the fabrication procedure is
the fact that plates will suffer a
deformation after welding
unless otherwise stated plate for bottom
fabrication must be at least 1 800
millimeters wide
the weight of the tank mainly the shell
and roof could be supported either by
bottom plate or by an annular plate
unrolled plates are used mainly to
reduce the effect of stress
concentration at the Shell bottom joint
the use of a thicker annular ring plate
under the tongue shell is prescribed by
the API 650 standard
[Music]
with this plate the effect of
differential settlement of the bottom of
the tank is reduced and the resistance
against overturning moments induced by
external loads is increased
externally another plates must adopt a
circular shape while internally they can
adopt circular or polygonal
configurations
generally unreal plates follow the
polygonal approach for the internal site
when annular plates are required the
width shall be determined by using the
equation shown in the picture
but not less than 600 millimeters
between the interior of the tank and the
nearest welded joint
leaving a 51 millimeter projection
outside of the tank
the recommended width of the annular
plate is a function of
the annual plate thickness
the maximum liquid level
and their specific gravity of the fluid
depending on the tongue Shell First
course thickness and depending on the
induced stress in this same element
the IPA 650 standard indicates the
minimum thicknesses of annular plates
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