Vacuum on Pipe 1

[Tankman650]

For large diameter pipe under full vacuum (FV) attached to pressure vessel, I always check using ASME VIII, Div 1 external pressure curves.

This may be conservative but are there other ways of verifying the vacuum loads??

 

[abeltio]

that depends, what does the specification say?
local regulations/standards?
any requirement from the insurance company that requires the parts to be certified by ASME?
If there is no requirement whatsoever... the pipe can be verified with the formulas for pipes under external pressure in text books like timoshenko's, roark & young etc...
HTH

saludos.
a.

 

[bvi]

Assuming the pipe is covered by a piping code, you need to follow those rules. For example, if it is B31.3 piping, teh Code refers to the Section VIII, Div 1 rules for design for external pressure.

 

[JoeTank]

The Steel Plate Fabricators Handbook, by SPFA, covers the design of shells for external pressure, but it is intended for thin shells, not pipe. Most piping components would have much higher D/T ratios than storage tanks. If you have the latitude, you may want to consider using the ASME VIII rules, but lower the factor of safety to something below three.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[JoeTank]

A correction to previous post... I meant to say that most piping components have a "much LOWER D/T ratio" than tanks. Sorry.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[BarryEng]

Look in 'Steel Penstocks' - ASCE Manuals & Reports on Engineering Practice No. 79.' (ISBN 0-87262-951-1)
Pages 124 to 137
Section 6.2 - Design of Steel Liners for External Pressure.
This reference is for steel tunnel liners concreted into rock.
Figure 5.1 (page 116) indicates critical collapse pressure vs ring deflection for a perfect circle & a buried pipe condition.

See also AWWA M11 (Steel pipe - a guide for design & installation) for more info.

Barry