Container / basket Load on Piping Supports

[PIPING3984]

hi friends

here i got a small assignment which something new to me,but i feel it interesting and challenging. i am facing problem in the intial stage.

My assignments is as follows.

Its an Oil and gas platform,where the containers / baskets (app maxi weigh 10-15 T) shifted to a laydown area from a height of 15m lifting with a crane. Unfortunately under this laydown platform there is compressor house with full of piping and these pipes are supported(maxi spring supports are used) with this laydown structural platform.

Now the question is when the 20 foot standard container / basket(Dims in inches: 232"L x 92"W x 93"H) is dropped from a height of 50feet (worst case), what could be the impact on platform and especially on piping supports.

 

[mizzoueng]

This is more of a structural question, first you would have to look at the beams supporting the platform and the associated load bearing members that are supporting your pipe hangers.

If you are using constant force (CF) hangers or rigid rod (RR) hangers, more than likely those will move with the steel and if the pipe doesn't (but sounds like it is small OD pipe so ti should) then the RR hangers will probably be loaded with the pipe movement forces AND the beam deflection. This would probably cause bending in the RR as they are not designed for this. CF hangers are only designed for downward movement. When the platform is hit, it would cause the steel to deflect downwards, and the pipe would probably not move initally. Looking at the movements, the pipe would essentially be going "up" by the resultant movement of the hanger going down with the steel. This couls seriously damage you CF hanger. The loss of support would then cause the pipe to drop and then you would be placing a shock load on your hanger when the pipe moves. The only hangers designed for shock loading are mechanical or hydraulic snubbers.

Under this scenario, your hangers are just not designed for this. Even snubbers would not be designed for this. To counteract this scenario, you would have to install flex connections around the perimeter of the platform to enable the piping to move with the steel if this ever happened. The piping would still be under great stress if it ever happened, but the flex connections would allow the entire pipe sections to move with the steel without worrying about the rest of the system.

If you foresee this happening more than once, then I would get the structural steel reviewed (as its probably not large enough unless it has some beams tied to the sea bed) and then run a 3D pipe analysis. CeaserIII, Autopipe, and others allow you to put in steel and platform to tie the piping to. Then you can apply the impact load to see how it affects hangers and piping.

 

[PIPING3984]

Hi mizzoueng , thanks for ur valuble information.
by reading your reply i got some idea to start.

i have few queries on our reply, you speak about flex connections. what do u mean by that ? A flexable connections on the platform , is it something like spring bed where a container can sit and create on impact on the platform directly.

My approach would be something like your last para, getting the deflections from structural department for the supports and using this displacements i will run in Caeser II and check the results.please comment on my approach.

you mentioned this statement "CF hangers are only designed for downward movement". till now i feel that springs hangers are designed to take the upward movements. please throw some light on your statement.

reagdrs
ASK

 

[BigInch]

Its not clear how the compressor building "under" the laydown area of a platform would be affected by a container dropped on the laydown area of the platform. Is the building somehow in contact with the laydown platform?

I doubt that this is a design case for any of the pipe, so just consider those destroyed and evaluate the consequences.

http://virtualpipeline.spaces.msn.com

"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein

 

[PIPING3984]

hi biginch

Its unfortunale that they made a new laydown area just above the compressor house (old)platform.The question is when the container is dropped from a height what impact it creates on deck and piping supports which are taken from the laydown deck. so u mean to say it doesnt effect the pipe supports.

 

[BigInch]

No. They need to be considered, its not (or wasn't) clear to me exactly what mode of impacts are to be considered.

I would think that the piping system is not designed for direct impact loads, so I discounted that possibility of a direct hit, if not, then you will have to evaluate those.

Similar to what missou says,

If it is direct impact to the pipe that you are interested in, the pipe system needs to be designed for those loads, or, first assume they are destroyed and evaluate the consequences. If the consequences are significant, then the systems might need to be designed for those loads, in which case rerun the stress program with the new impact loads on the pipe, and/or also consider support displacements and vibrations to the pipe from a hit on the platform, if the results of the impact from a dynamic structural analysis show significant vibration or support movements.

http://virtualpipeline.spaces.msn.com

"We can't solve problems by using the same kind of thinking we used when we created them." -Albert Einstein