×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

# Contact US

Log In

#### Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
To Your Posts
• Keyword Search
• One-Click Access To Your
Favorite Forums
• Automated Signatures
On Your Posts
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

# API shell thickness using corrected height2

 Forum Search FAQs Links MVPs

## API shell thickness using corrected height

(OP)
I make excel sheets to help me remember things I figured out before.

On my spreadsheet for tank wall minimum thicknesses, I use a corrected height H'=H+(2.31*P/G). H=actual liquid height, P=pressure, G=specific gravity. In reviewing my spreadsheet, I did not reference where I got H' from and I cannot find it in API 620, 650, or 653. It makes sense to me to use H', but do any of you happen to know where I may have found that and if you agree it should be used? Without it, it doesn't seem to matter what pressure the tank is designed for.

I use it in the shell thickness equation (1-foot method) t=(2.6*(H'-1)*D*G)/SE. D=diameter, S=design stress, E=Joint efficiency.

In summary, my question is: Where would I have found H' and should I use it in the shell thickness equation?

### RE: API shell thickness using corrected height

2
H is the design liquid depth in feet.
H' is the adjusted depth to allow for internal pressure in the vapor space per Annex F.
I don't think API-650 uses the H' terminology, it just says to include the adjustment when calculating shell thickness. In the more recent edition, they've specified to do so if pressure is over 4" water column. In older editions, I think it was only if pressure uplift exceeded the shell and roof weight.
The design pressure of a tank will normally not have a whole lot of influence on shell thickness, but does have a major effect on roof, top angle, and anchorage design.

### RE: API shell thickness using corrected height

JStephen nailed it.

### RE: API shell thickness using corrected height

(OP)
Thank you for the response.

### RE: API shell thickness using corrected height

In calculating shell thickness for Annex F tanks, H shall be increased by the quantity P/(9.8G) for SI units, or P/(12G) for USC unitsâ€”where H is the design liquid height, in m (ft), P is the design pressure kPa (in. of water), and G is the design specific gravity.
Design pressures less than 1 kPa (4 in. of water) do not need to be included.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

### Reply To This Thread

#### Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!

Already a member? Close this window and log in.