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Active Contributor

Join Date: Mar 2010
Posts: 18

Wind Force & Moment for API-650 Storage Tanks

05/30/2010 2:53 PM

Hi all. can any body send me the reference to calculate the wind force & moment for api-650 tanks.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

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Location: Cairo, Egypt
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#1

Re: Wind Force & Moment for API-650 Storage Tanks

05/31/2010 1:31 AM

As per API 650, Para. 3.9.6, the required min. section modulus of the stiffening ring (Top Wind Girder) shall be determined by the equation : Z = 0.0001 D2 H2 (V / 100)2

where, Z = Section modulus, in.3

D = Nominal tank dia., ft

H2 = Height of tank shell, ft, including any "free-board" provided above the max. filling height as a guide for a floating roof.

V = Wind velocity, miles/hr.

.............................

Also, the wind speed shall be used in calculating the Intermediate Wind Girder (check of tank shell against wind load as per API-650, Para. 3.9.7.1)

The max. height of unstiffened shell,in feet, shall not exceed: H1 = 6 (100 t) [√(100 t / D)3 ] (100/V2)

Where, H1 = Vertical distance between the intermediate wind girder and the top angle of the shell or the top wind girder of an open-top tank, ft.

t = Average shell thk. in height H1 in corroded condition, in.

= ( h1 t1 + h2 t2 + h3 t3 + h4 t4 + h5 t5 + h6 t6 ) / H

D = Nominal tank diameter, ft.

V = Wind velocity, mph

.............................

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Active Contributor

Join Date: Mar 2010
Posts: 18
#2
In reply to #1

Re: Wind Force & Moment for API-650 Storage Tanks

06/04/2010 2:48 PM

Thanks Mr. Abdel Halim Galala,

Your answer is for wind stiffener which are correct. But my question was how to calculate the wind force & moment for api-650 tanks. It is regading below as per api-650 11th edition add-1

5.11 WIND LOAD ON TANKS (OVERTURNING STABILITY)

5.11.1 Wind Pressure

Overturning stability shall be calculated using the wind pressures given in 5.2.1(k).

5.11.2 Unanchored Tanks

Unanchored tanks shall satisfy both of the following uplift criteria:

1. 0.6Mw + MPi < MDL /1.5

2. Mw + 0.4MPi < (MDL + MF)/2

where

MPi

= moment about the shell-to-bottom joint from design internal pressure,

Mw

= overturning moment about the shell-to-bottom joint from horizontal plus vertical wind pressure,

MDL

= moment about the shell-to-bottom joint from the weight of the shell and roof supported by the shell,

MF

= moment about the shell-to-bottom joint from liquid weight. The liquid weight (wL) is the weight of a band of liquid

at the shell using a specific gravity of 0.7 and a height of one-half the design liquid height H. wL shall be the lesser

of 0.90HD

In the above, there are Mw(Wind moment) & Wind force. How to calculate the terms of above. Is there any standard formulas are available.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

Join Date: Feb 2007
Location: Cairo, Egypt
Posts: 1746
Good Answers: 239
#3
In reply to #2

Re: Wind Force & Moment for API-650 Storage Tanks

06/04/2010 4:50 PM

Free download the attached link for a file in PDF format (10 Pages & 0.086 MB), and it will answer all of your questions.

Link: Storage_Tank_Design_Calculation - Seismic Design & Overturning Moment.

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Active Contributor

Join Date: Mar 2010
Posts: 18
#4
In reply to #3

Re: Wind Force & Moment for API-650 Storage Tanks

06/09/2010 2:41 PM

Thanks Mr. Abdel halim Galala.

It is very useful for me.

IS Appendix-V applicable for tank design external pressure having (-5) m bar(g). For that, do we provide vacuum stiffenig ring. Appendix v says as follows

V.1 Scope

This appendix provides minimum requirements that may be specified by the Purchaser for tanks that are designed to operate with external pressure (vacuum) loading as a normal operating condition. This appendix is intended to apply to tanks for which the

normal operating external pressure exceeds 0.25 kPa (0.036 lbf/in.2) but does not exceed 6.9 kPa (1.0 lbf/in.2).

Is normal operating pressure equivalent to design pressure. Can u guide me.

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Participant

Join Date: Feb 2011
Posts: 3
#5
In reply to #1

Re: Wind Force & Moment for API-650 Storage Tanks

02/14/2011 9:24 AM

Dear sir

D = Nominal tank dia., ft

H2 = Height of tank shell, ft

V = Wind velocity, miles/hr.

but we slove the equation : Z = 0.0001 D2 H2 (V / 100)2

Z = f3

Z = f2 x f x (miles/hr)/(miles/hr) = f3

How to arrive in.3

please clarify

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