×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Storage Tank API 650 - Design External Pressure

Storage Tank API 650 - Design External Pressure

Storage Tank API 650 - Design External Pressure

(OP)
Hello,

I have a SS-304 storage tank with 1" insulation (ID=14 feet X 20 feet High and self supporting cone roof). I am using Tank software for analysis purpose. In Tank software, under external pressure analysis - specify external pressure (Pe)in lb/ft^2.

I have a client with 40 Yrs old tank. The drawing did not have any design condition so what is the best guess?

Please, Can some one explain regarding design external pressure. What will be the value?

I am using -1.73 inch of water OR -8.999 lb/ft^2. Is it correct??

I appreciate it.

Thanks - Mayur

RE: Storage Tank API 650 - Design External Pressure

Why are you concerned about the external pressure?

RE: Storage Tank API 650 - Design External Pressure

Under the current standard, the external pressure is taken as 1" of water column if not otherwise specified, or zero for tanks with circulation vents.
With the 1" of water column, no calculations are required for the vacuum condition.
In the current standard, the 1" vacuum is accounted for in the roof loading (with 40% factor) and in the shell stability calculations/ wind girder calculations.

For a 40-year old stainless tank, it was built prior to Appendix S, so it may not comply with Appendix S.

RE: Storage Tank API 650 - Design External Pressure

bimr, I don't believe you are correct. For tanks, pipes, rods, etc, strength in tension is far stronger than compression, hence worst case is nearly always compression / collapse or essentially vacuum conditions where inside pressure is > outside.

Think of your humble Coke can. It can handle high internal pressures, but with much much less than 1 bar across it it will crumple inwards very easily

For a tank this only relates to instances when the tank is empty usually, but on any negative pressure compared to atmospheric pressure, the strength of a tank is very low.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Storage Tank API 650 - Design External Pressure

LittleInch, you are correct and I deleted it. The tank walls are much more flexible than an egg. In regards to that matter, I was looking at the Saturn 5 rocket last year and it is probably a better example. The designers had to pressurize the kerosene fuel tanks as fuel was spent, otherwise the thin rocket walls would collapse.

Don't understand why the OP is concerned about the external pressure unless he is planning to steam clean or make a boat.

RE: Storage Tank API 650 - Design External Pressure

(OP)
All,

I appreciate your input and time.

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!


Resources