1 API 650 Intro, Design of storage tanks

Summary

This 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

00:00

🛢️ 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.

05:00

🏭 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.

10:03

🔩 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.

15:04

🏗️ 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.

20:04

⚙️ 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.

25:05

💠 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.

Keywords

💡API 653

API 653 is a standard set by the American Petroleum Institute for the inspection and repair of aboveground storage tanks. It is a crucial reference for professionals in the industry to ensure the safety and integrity of storage tanks. The video script outlines the importance of adhering to this standard to prevent disasters and ensure the tanks are designed, fabricated, and maintained according to the collective experiences and best practices.

💡Storage Tanks

Storage tanks are large containers used to hold various commodities such as crude oil, propane, and water. They are designed to store large quantities of fluid at relatively low installation costs. The script discusses the different types of storage tanks, their design considerations, and the materials used in their construction, highlighting their importance in the storage and processing of various products.

💡Design Codes

Design codes are a set of minimum requirements for the design, fabrication, material selection, inspection, and installation of tanks. They are essential to avoid disasters that can affect humans and the environment. The script emphasizes the role of design codes in ensuring the tanks are built to withstand various loads and conditions, thus maintaining safety and reliability.

💡Atmospheric Conditions

Atmospheric conditions refer to the normal air pressure and temperature conditions at sea level. The script mentions that storage tanks operate at atmospheric or near-atmospheric conditions, which means they are designed to handle pressures and temperatures that are typical of the environment where they are located.

💡Internal Pressure

Internal pressure is the pressure exerted by the fluid stored within the tank. The script specifies that tanks designed with the API 653 code must have an internal pressure lower than 17 kilopascals, indicating the tanks are designed to handle low pressure and are not suitable for pressurized service.

💡Roof Types

Roof types are the different configurations of the top part of a storage tank. The script discusses various roof types such as fixed roofs (cone, dome, and umbrella) and floating roofs (internal and external). The choice of roof type is critical for the design of the tank as it affects the tank's ability to contain the stored fluid and its resistance to environmental factors.

💡Floating Roof

A floating roof is a type of tank roof that floats on the surface of the liquid stored in the tank. The script explains that floating roofs are used to reduce evaporation losses and can be either internal or external. They are designed to move up and down with the changing liquid level, which is crucial for tanks storing volatile products.

💡Seismic Design

Seismic design refers to the consideration of earthquake effects in the design of structures. The script mentions that seismic design is one of the annexes in the API 650 code, which means that storage tanks must be designed to withstand the forces generated by seismic activity to ensure their stability and safety.

💡Allowable Stress

Allowable stress is the maximum stress that a material can withstand without permanent deformation or failure. The script discusses how the thickness of the tank shell is determined based on allowable stress, ensuring that the tank can support the loads it will experience without exceeding the material's strength limits.

💡Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by a fluid at rest due to the force of gravity. The script explains that hydrostatic pressure increases with depth, which is why the bottom of the tank shell requires a thicker plate to withstand the higher pressure at the bottom compared to the upper parts of the tank.

💡Annular Plate

An annular plate is a ring-shaped plate used at the base of a storage tank to distribute the load from the tank shell and roof. The script mentions that the annular plate helps to reduce stress concentration at the shell-bottom joint and increase the tank's resistance to overturning moments induced by external loads.

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