thin walled tube 1

[leisure17]

Is the calculation for tube thickness with a negative internal pressure the same as for posative internal pressure(pd/f). Can't remember this one and all texts only do formulaes for posative internal pressures, nothing showing an external pressure.
Cheers
Mick

 

[leisure17]

sorry pd/2f

 

[blacksmith37]

Try to find API Bul 5C3; it will have collapse calcs.

 

[Yobbo]

Hi,

This formula is the same. The p is just the pressure difference. Fact is though, that you will have to check stability against imploding as well. For this a different criterium is necessary. I haven't got that in my active mmemory, but you should check a technical handbook or the internet on that. In german the term is "beulen" in english I do not know.

Karel Postulart, The Netherlands
Nuon Power Generation

 

[btrueblood]

In Americanese, we'd call it buckling.

 

[blacksmith37]

API Bul 5C3 has all 4 modes; tensile, burst, buckle and collapse (2 methods depending on D/t ratio). Does Barlows' formula have a new name?, It is hard keep up with technology.

 

[leisure17]

Thanks for the replies. my "tube" is actually ducting 300mm dia with an negative internal pressure of -0.3bar. A bit bigger than the API piping specs.

 

[BigInch]

See API-RP-1111 Design Construction Installation and Maintenance of Offshore Pipelines - Section 4.3.2.1 Collapse Due to External Pressure. (Use absolute pressure and positive external pressure is physically the same as negative internal pressure).

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[waterpipe]

It seems that API is your standard, however, AWWA M11 "Manual-Steel pipe Design and Installation" has a full coverage of buckling calculation for circular cylindrical shells under external loads, buckling.

 

[blacksmith37]

API 5L goes to 2032mm diameter; The 5C3 strictly speaking only applies to API casing/ 508mm max.