Offshore Bridge Linked Platforms 1

[compo]

Does anyone know of any specific codes/standards or have experience that covers offshore oil and gas platforms which are bridge linked, with process piping containning hydrocarbons going to/from the platforms. I am specifically interested in knowing if there are code requirements for shutdown/isolation valves for the hydrocarbon piping at the bridges. I have never comes accross anything to date and have seen with and without. My view is that it should evaluated on a risk basis considering the factors such as bridge impact, excalation potential etc. I'd appreciate any info.

thanks

 

[Nosey]

I haven't come across a standard relating to isolation around a bridge.

I agree with you about the evaluating each case individually on the risks. A good HAZOP and risk analysis should provide you with the answers you require.

There are lots of bridge linked platforms around the world to consult with, but it may be useful to talk to Phillips about their Ekofisk facility in the Norwegian Sector as it is a massive facility with lots of bridges.

Regards

Nosey

 

[jay165]

I don't there are any. In the US, Freeport Sulfur's Main Pass 299 facility is an example of multiple platforms linked by bridges (I believe it is currently shut down due to the low price of sulfur). You may want to contact the MMS and ask them.

 

[mgp]

I agree with Nosey that any requirement for shutdown valves should be evaluated from a HAZOP Study.

I have worked on several offshore projects with interconnecting bridge piping have been involved. In all of these cases it has been a requirement to analyze bridge crossing lines in order to be able to absorb relative platform movements which can be very significant if the platform movements are out of phase. This is off course a normal operational requirement. There were no requirement for additional ESD valves.

However I also I remember another case where a monotower platform was connected to a 4-leg platform via a combined process module/pipe bridge. In this case we had to do additional stress analysis to cover the ship impact case (which was not an unrealistic event with a supply vessel around the monotower). The piping was allowed to have plastic deformation in this case, but was not allowed to burst.

As far as I remember the decision of what to evaluate was in each case related to the probability, and consequence of failure - i.e. HAZOP.

One other thing to remember is that a flanged connection (ESD VALVE) near the bridge landing will be more likely to leak due to pipe movements, meaning higher risk during normal operation. Since many of the lines are most likely already isolated by ESDV's not too far away from the bridges, it may not improve safety much if valves are added.

regards
Mogens