Urgent Help Need for a Deep Water Suction Hose

[yrc]

Dear All,

I am an engineering intern at a rubber company and I have been tasked with designing a 93m long adapted marine hose that is to be used as a deep water suction hose. I have run simulations with our current specifications and it seems that the current design is unacceptable. I have little experience in this field and would like suggestions on how I can reduce the dynamic loads on the hose caused by the pitching of the FPSU. Thanks!

yrc

 

[Mark62]

You need to look at the configuration of the pipe.

As I understand it you have a flexible rubber hose from a floating vessel to the seabed. The hose is used for suction, probably a form of dredging application sucking sand or silt from a sea or river bed into a hopper type vessel for removal to another location.

One important consideration is the correct length of pipe, can this be varried? is your line made up of section which are bolted together?

You can use dynamic simulation programs such as Orcaflex (

http://www.orcina.com)

to predict the motion of the pipeline due to vessel and enviromental conditions.

To change the motion of the line you could look at adding either buoyancy collars or ballast collars, have a look at CRP's site for information on this (

http://www.crpgroup.com)

 

[Zvinou]

Hello.

Why is your current design unacceptable? In most cases, problems arise in a transition area stiff -> flexible (connecting extremity for example). A solution then might be to use a bend stiffener (that smoothens the transition rigid -> flexible) or a bend restrictor (vertebrae that limit the curvature). Such pieces are generally made of polyurethane or similar materials. CRP is probably the main supplier and you can find information on their website.

 

[dwang63]

93m in deepwater off FPSO? sounds like a seawater suction hose. don't know what is not acceptable. But there are things you can do to reduce dynamic loads due to vessel motions. Hang it from mid-ship is the obvious one but may not be unrealistic. A polymer hose generates excessive dynamic loads? Most likely it resonates with a vessel motion component, such as roll, or in the close approximaty. Attach a ballast chain or something to change its natural period. Don't forget the bend stiffener at the top termination. It's a must.