Subsea pipeline installation aid - Yoke Design

[FB6917]

Hi All,

Does anyone can provide me with some information or perhaps a typical example of yoke design as installation aid for the subsea pipeline vessels?

Any references?How does a yoke work and what are the important items in structural design which needs to be considered?

Thanks

 

[Ussuri]

You need to provide more information?

To what is this yoke attached?
Is this yoke used for pipelay from a vessel or towed pipeline installation?
Is it a yoke on a PLET?
Is it a yoke on an Inline Structure?
Is it for attaching a wire?
Is it for attaching buoyancy?

 

[FB6917]

Yoke is being used to prevent pipe from rotating so that inline structurs(ILT)is upright.Yoke is attached to the pipe by clamp and restraining wire.Large buoy is fixed at the end of yoke and goes down to the sea bed.
What needs to be considered in structural design of the yoke and it's footing(the clamp I suppose)?Load cases,combination and the code?Any reference or worked example?

Thanks

 

[Ussuri]

I'm not aware of any standards for the design of pipeline structures. It is usually down to experience, engineering judgement and the usual codes applied in the offshore environment.

In all the cases I have come across the buoyancy is usually above the pipeline, not below so I am not sure I understand your arrangement. Its reel lay I am more familiar with so if its S or J then the issues will be different.

Some things to possibly consider:

1) The angle and orientation of the ILT during lay, the angle of the structure will vary as it passes down the catenary.
2) There may be locked in torsion in the pipe which causes the ILT to roll during lay, so you needs to consider the orientation of the structure
3) The load on the yoke is provided by the buoyancy? (I assume) so you know what load is applied, its just that its angle of application will vary.
4) the loads applied to the yoke need to be transferred back to the structure
5) Does the installation (bending and tension in the pipe) have an effect on the structure?
6) Has there been an installation analysis completed which can tell you the loads in the pipe? What is the seastate you are laying in?
7) You are stating you have a clamp, does the clamp need to transfer the loads back to the pipe? Does the clamping pressure have any effect on the pipe when considered in conjunction with the lay forces?
8) ILTs usually need to be handled and manipulated on the back of the installation vessel so there are things to consider there

I would strongly suggest you have a word with some colleagues at your place of employment who are experienced in the design of these things. Its not something that can be learned from a web forum.

 

[FB6917]

Ussuri

I appreciate your time and advice.I reached to the same point that I need to talk with the experienced colleague.Our company is S-laying contractor.For your infromation,in chapter 20 of "Subsea Engineering Handbook" by Yong Bai,you can find useful information regarding yoke for PLET installation(not a buoyancy yoke).