explosion design for vessel 2

[vesselguy]

Hi all,

I have never worked on off-shore design so I'm asking these questions. I'm hoping people who have designed for off-shore can help me figure out some strange requirements.

I am reviewing corporate standards from a company that primary do their work off-shore. Their vessel standard has a requirement for considering explosion loads which says,

"Unless otherwise specified, the vessel shall be able to withstand a static pressure of 0.1 bar caused by explosion. Plastic deformation on drag loads on equipment is acceptable, but deformation shall not lead to any leakage. Progressive collapse shall be preventative...."

1. How is the 0.1 bar pressure load to be used? I think the 0.1 bar (1.45 psi) is an external pressure load? If so, then if the vessel is designed for 1/2 vac or full vac would be more then enough to cover this design case, right? Also, if this load is consider to act like wind load then typical wind load case is more than this anyway. If my statements are correct, then what is the point of considering 0.1 bar? Why not just forget it?

2. What is a drag load?

3. What is progressive collapse?

 

[SJones]

See if 99:046 and 99:047 at

http://www.hse.gov.uk/research/otohtm/1999/index.htm

give any help

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JohnGP]

It's been a few years since I had anything to do with offshore equipment design, but here goes anyway.

1. Blast load is not the same as vacuum design. Under a vacuum, force is applied uniformly over the shell, and the worst that can happen is that the shell can collapse if not supported adequately. A blast pressure will generally act on the surface from one direction, giving rise to external overturning and bending moments. It is somewhat like a wind load, as you suggest, but my experience with wind loads is that they don't approach the 0.1 bar that you are talking about.

2. Drag load arises from the resistance to flow caused by the vessel in the flow stream created by the blast.

3. I'm guessing here, but progressive collapse could be the total collapse of vessel supports, rather than just plastically deforming - i.e. a little vessel movement is acceptable, provided there is no leakage, but not significant collapse with other serious knock-on effects.

Cheers,
John

 

[gr2vessels]

vesselguy,
The blast load is a common topic, but you need some reading in order to evaluate/understand the whole concept of blast loading on mechanical and civil structures. Do a bit of "google" on the 'design blast loads', perhaps the civil sector is better informed (and applied) than the mechanical equipment (vessels, tanks, etc).
Cheers,
gr2vessels