rectangular tank design

8/15/2019 Rectangular Tank Design

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Rectangular TankDesignBasic approach and practical tips

S.Thirucheeswaran


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2Rectangular tank design

CONTENTS

► Introduction

► Main Acceptance Criteria

► Symbols and Units► Nomenclature

► List of parts or sections to be designed or c ec!ed

► Additional C ec! re"uired for t e # ole tan! and anc oring

► $esign Input and Conditions

► %eneral Notes and assumptions► Types of &ectangular Tan!s 'Classification for design approac (

► Top plate for &ectangular Tan!

► )ottom plate and )ase *rame for &ectangular Tan!

► Additional points for ad+anced design '*uture(

► ,ractical tips► Summary - &ectangular tan! types and design references

► &eferences

► Attac ments


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.Rectangular tank design

%uidelines and step-by-step design procedure is gi+en belo# for rectangulartan!s and assumptions are made for a conser+ati+e design/ T e designprocedure is an iterati+e process or c ec!ing for gi+en or assumedt ic!ness0 stiffener si1e and stiffener spacing/

Alternati+ely0 rigorous analysis using *EM or suitable structural designprocedure can be follo#ed/

Introduction


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Rectangular tank design

Main Acceptance Criteria

1) Calculated Stress shall be limited to ASM Code Allowable Stress !or" Actual corroded thickness pro#ided shall not be less than re$uired

corroded plate thickness calculated using ASM Code Allowable Stress

%) Ma&imum de'lection limited to one hal' o' the corroded plate thickness

Symbols and Units3 (anti ( Maha an !unless speci'ied"


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NomenclatureTOP EDGE STIFFENER

R1 – Unit Load (Uniform on entirespan of top edge stiffener)

ORI!ONT"L STIIFENER

R# – Unit Load (Uniform on entire span of intermediate stiffener)

$ERTI%"L STIFFENER

&' distan*e +et,een -erti*a' stiffeners (important parameterfor s.e'' p'ate t.i*/ness design)

&L – 'engt. of tan/ (important parameter for top edge stiffenerdesign)


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Nomenclature 'continued(

Primar0 Stiffener

Se*ondar0 Stiffener


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Nomenclature 'continued(

Load on 7E&TICAL STI**ENE&S3 UNI*O&ML8 INC&EASIN%

Load on S9ELL 'SI$E 7E&TICAL ,LATE( 3 UNI*O&ML8 INC&EASIN%

Load on 9O&I:ONTAL STI**ENE&S3 UNI*O&M ON ENTI& S,AN

Load on TO,;)OTTOM ,LATE '9O&I:ONTAL( 3 UNI*O&M ON ENTI& S,AN


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$esign Input and Conditions*Tank si+e, -idth & eight & /ength0 normall inside dimensions

*2nternal pressure0 i' an

*Material 3 ma&imum allowable stress #alues

*-ind loads0 seismic loads0 wa#e loads0 transportation loads etc.

*Calculate ma&imum pressure against side wall due to weight o'contents 4p5 6.788 • • s 4in psi))


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%eneral Notes and assumptions3► $esign is based on open top basis0 # ic is conser+ati+e/ T e effect of top plate is not

considered

► If top edge stiffener of sufficient si1e is pro+ided0 top side of s ell plate can be considered assupported on all edges

► Consider eit er +ertical stiffeners or ori1ontal stiffeners as primary or main stiffeners and letus call0 ot er one @secondary stiffeners 0 t at are perpendicular to preliminary stiffeners

► Selection of primary stiffeners '+ertical or ori1ontal( is based on tan! si1e and dimensions

► Secondary stiffeners are considered to reduce plate t ic!ness re"uired and to transfer load tomain stiffeners

► T ere is no simple formula or procedure to analysis or design rectangular tan! #it botori1ontal and +ertical stiffeners

► All stiffeners s all be continuous and #elded at corners

► S ell plate #elds s all be full penetration

► Tan! design can be optimi1ed on total #eig t or plate t ic!ness and;or stiffener si1e

► Tan! plate t ic!ness s all be at least .;>5B '4mm( corrosion allo#ance

► Suitable corrosion allo#ance s all be considered► Use appropriate and consistent units

► $o not combine bot +ertical stiffeners and ori1ontal stiffeners at t e same time

► If +ery large tan!0 consider internal tie-rods/ Internal baffles0 if any0 can be considered asstiffeners/ T is #ill reduce tan! plate t ic!ness;#eig t/


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Types of &ectangular Tan!s

/et us classi' the rectangular tanks into 9 t pes based on sti''eners

arrangement and design procedure.T pes 1 to 7 are simple in construction and design procedures arealso simple. Re'erence !1" or re'erence !%" can be used directl 'ordesign o' t pe 1 to 7 tanks.

The re'erences !1" : !%" do not gi#e direct procedures 'or t pe ; to ". T pe 9 Tank is designedwith Tie?rods and re'erence !1" gi#es a procedure.

@esign o' rectangular tank shell plate 4side #ertical plate) is critical

and procedures are gi#en below. @esign procedures 'or top plate0bottom plate0 bottom 'rame etc. are e&plained separatel . Re'er tosketch showing di''erent t pes o' tanks with sti''ener arrangementcommonl used.


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Types of &ectangular Tan!s 'Type-> to ('Classification for design approac (

Type-> Type-2

Type-. Type-


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Types of &ectangular Tan!s 'Type - 4 to


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Types of &ectangular Tan!s 'Type - =('Classification for design approac (


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>6Rectangular tank design

Type-23 Tan! #it Top Edge Stiffener and;or #it top plate

2' top edge sti''ener o' su''icient si+e is pro#ided or top plate is welded to shellplates with or without top edge sti''ener0 all 7 edges ma be considered assupported 'or shell plate design and Roark s Case 1 4e) can be used tocalculate re$uired shell plate thickness 4tr) and ma&imum de'lection 4 ma&).

Acceptance criteria shall be stress and de'lection.* Calculate uni'orm load on entire span 4R1) acting on the top edge sti''ener.

Consider top edge sti''ener as a beam 'i&ed both ends* Top edge sti''ener 2min5R1 • bD7 319% • • ta and select sti''ener with 2

more than 2 min calculated0 howe#er the sti''ener angle shall not be lessthan %.;E & %.;E & 6.%;E

* Recalculate shell plate thickness0 de'lection Roark s Case 14d). Selectthickness 4ta)

* Recheck top edge sti''ener si+ing 4step?%.%)


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> ori1ontal stiffener &2

* Calculate moment o' 2nertia re$uired 'or sti''eners and select sti''ener si+e

* Recalculate shell plate thickness0 de'lection Roark s Case 14d). Selectthickness 4ta)

* Recheck sti''ener si+ing 'or latest plate thickness selected


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>=Rectangular tank design

T8,E- 3 Tan! #it Top Edge Stiffener and one or more+ertical stiffeners

* Calculate R1 and si+e top edge sti''ener. se length o' tank F/E assti''ener length !@o not use sti''ener spacing FlE as length o' sti''ener"

* Calculate moment o' 2nertia re$uired 'or sti''ener and select sti''ener.se height o' tank as #ertical sti''ener length and uni'orml increasing

loading on the #ertical sti''ener * Recalculate shell plate thickness0 de'lection Roark s Case 14d). Select

thickness 4ta)



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2?Rectangular tank design

T8,E-43 Top Tan! #it Top Edge Stiffener0 oneori1ontal primary stiffener and one or more +ertical

secondary stiffener Same as type-. and calculate secondary +ertical stiffener si1econsidering uniformly increasing load bot ends fiDed '&oar!Jscase 2'd( Table-


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2>Rectangular tank design

T8,E-53 Tan! #it Top Edge Stiffener0 one or more+ertical primary stiffeners and one or more ori1ontal

secondary stiffener Same as type- and calculate secondary ori1ontal stiffener si1econsidering uniform load on entire span bot ends fiDed '&oar!Jscase 2'd( Table-


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T8,E-63 Top Tan! #it Top Edge Stiffener and 2 or moreori1ontal stiffeners

* Similar to t pe?80 howe#er the loads on hori+ontal sti''eners arecalculated using re'erence !>".

* Calculate load 4uni'orm load on entire span) on each sti''ener R10 R%0R8 etc. Re'er Attachment 'or sample calculation.

* Calculate moment o' 2nertia re$uired 'or each sti''ener0 select sti''ener

* Recheck plate thickness : de'lection Roark s Case 14d). Selectthickness 4ta)



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2.Rectangular tank design

T8,E-


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T8,E-= Open Top Tan! #it Tie-rod supports

'*or +ery large rectangular tan!s0 internal tie-rods can

be considered to reduce plate and stiffener si1e and#eig t0 if permitted for ser+ice or process re"uirements/Internal baffles or partition plates can be considered astie rods;stiffeners(


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Top plate for &ectangular Tan!

4common 'or all t pes o' tanks)

► $esign top plate0 if applicable0 edges simply supported0 uniformload o+er entire plate - &oar!Js Case > 'a( Loads to be consideredself #eig t0 maintenance load0 sno# load etc/ Use 2??? !g;m20 as adefault uniformly distributed load on entire surface of top plate andadd internal pressure if any/

► ,ro+ide stiffener for top plate by connecting all +ertical stiffeners0as a default/ T is is mainly re"uired for transfer of load from+ertical stiffener0 unless special stiffener arrangement is designed/

► C ec! bottom plate t ic!ness for maDimum un-stiffened area


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)ottom plate and )ase *rame for &ectangular Tan!'common for all types of tan!s(

* Gro#ide base 'rame co#ering all 7 sides o' the tank

* Consider simpl supported both ends 'or si+ing the long side 'rame member and loadhal' o' the ma&imum design weight @/ 4uni'orml distributed along the entire length)0pro#ide same si+e 'or short side 4no calculation is re$uired 'or short side?conser#ati#e)

* Gro#ide sti''eners 'or tank bottom plate 4connecting long side members o' base 'rame)load ma be calculated 4- 5 p & spacing) kg3mm 4uni'orml distributed load3unit length).Sti''ener si+e can be o' smaller than outer base 'rame member si+e

* 2' re$uired0 pro#ide additional sti''eners in perpendicular direction 4smaller in si+e thanouter base 'rame member si+e) in order to reduce the bottom plate thickness.

* Check bottom plate thickness 'or ma&imum un?sti''ened area ? Roark case 14a) Table?%>

* Minimum thickness shall be 6.%;E 4> mm) plus corrosion allowance0 i' entire sur'ace o'the bottom plate is supported.


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)ase *rame 'common for all types of tan!s(


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2? times plate t ic!ness(

► Selection of primary stiffeners '+ertical or ori1ontal( based on tan! si1e anddimensions0 relation bet#een tan! lengt -L and 9eig t-9

► )olted rectangular tan!s0 bolted top plate

► Consideration of design pressure0 usually a small pressure li!e ?/?4 bar

► Loading3 seismic0 transportation0 #a+e etc/

► Top plate loading 2??? !g;s"/m► No11le loading

► Lifting lugs0 lifting analysis

► Spacing of ori1ontal stiffeners 'une"ual0 increasing spacing from bottom to top(

► eig t estimation0 optimi1ation of #eig t0 plate t ic!ness0 stiffener si1e;spacing etc/

► Types of loading U$L0 uniformly increasing loading

► elding of stiffeners to plate and end connectionsK elding of plates


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2=Rectangular tank design

,ractical tips* Gre'erred t pe o' welded oints 4corner weld oining shell plates)* Sti''ener arrangements* @o not e&trapolate the design procedure o' one t pe to other t pe

without proper consideration

* n?sti''ened tanks ma not be larger than 86 't8 46.


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,ractical tips 'continued(


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..Rectangular tank design

Summary - &ectangular tan! types and design references


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&eferences3

>/ Eugene */Megyesy 0 ,ressure 7essel 9andboo!0 ,ressure 7essel,ublis ing Inc/0 >2t Edition 2??> 'C ec! for latest edition(

2/ anti Ma aPan0 $esign of ,rocess E"uipment0 ,ressure 7essel9andboo! ,ublis ing0 Inc/ T ird Edition >==? 'C ec! for latestedition(

./ anti Ma aPan0 A met od for designing rectangular storagetan!s0 C emical Engineering0 Marc 2=66 pp >?6->>2

/ arren C/ 8oung0 &ic ard %/ )udynas/ &oar!Js *ormulas forStress Strain0 6t Edition

4/ Omer / )lodgett0 $esign of #elded Structures0 T e Qames

*/Lincln Arc elding *oundation0 *ifteent ,rinting Marc ->==55/ M/Starc1e#s!i0 Non-Circular ,ressure 7essels R Some guidance

notes for designers0 )ritis Engine Tec nical &eport >= 7olumeI7 pp 52-


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rectangular tank design

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