Vessel motions during pipelaying

[cavatina]

I am starting my graduate research.
It should be something about subsea pipelines.

Is it common to consider Vessel motions during pipelaying?
Or are the stresses during installation considered in an unrealistic static condition?

Do you think the considering vessel motions will result in very different stresses?

Do you think this is a good topic for a PhD?!

PS. Please inform me if you have some nice ideas/topics other than the mentioned one, regarding subsea pipelines.

 

[civilperson]

Tiny boats are affected by sea motions, not much effect on ships. If giant seas are encountered, not much pipeline laying will be accomplished.

 

[Ussuri]

Vessel motions are considered. We use this software, among others at my work.

http://www.orcina.com/SoftwareProducts/OrcaFlex/index.php

The lay analysis you would do depends on the type of lay you are doing (S-lay, J-Lay, Reel Lay, Flex Lay etc). Different vessels have different responses to a given seastate. We use RAO data to simulate that response and then the affects on the lay. A large semi lay barge will be more stable than a smaller monohull. But it will still have an effect. The motions will generate hydrodynamic load on pipe which need to be assessed.

Andrew Palmers subsea pipeline book would be worth a look. Its not a topic I know much about as we have a department of analysts who do all this stuff for us.

 

[narenr]

Cavatina, Indeed this is a good subject for a Phd, we can then look for you after Robert Mahalay who is the guru of pipelay analysis.

Static analysis is performed for various configurations of pipelaying and worst case is selected to perform the dynamic analysis which will include the RAO for the barge and the hydrodynamic loading on the pipeline itself. This analysis will determin the safe sea state for pipelaying.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.

 

[jfduroch]

Vessel motion are of critical importance in pipelay and month of engineering are dedicated to such analysis particularly with regards to fatigue.

the oldest software package is called OFFPIPE
more recent and also 3D models can be designed now with either Orcaflex as mentionned in previous answer or competitor Deepline

http://www.principia.fr/eng/logiciels/deeplines/

The way analysis proceed today particularly in deepwaters is to identify the limiting seastate for installation and each vessel will have its limitations which will be very dependant also of the type of pipe to install.

An interesting field of research for your PhD would be to develop a method that would provide a better decision making aid during installation rather than just weather forecast, superintendant experience or gut feeling, and hundreds of analysis. For instance by linking directly the actual vessel motions to the constraints effectively supported by the pipeline beeing laid.

 

[sy123]

Narenr, who is Robert Mahalay, any specfics on where to look for his work?

 

[cavatina]

sy123:

Ive seen Robert Malahy's name on the OFFPIPE software (OFFPIPE.com). I guess he has developed the program...

 

[narenr]

Yes Robert Mahalay is the developer of OFFPIPE software. It was the first commercial offshore pipelay and the most popular one. He had done a lot of work on pipelay analysis. His OTC papers are avialable.

Narendranath R
Pipeline engineering is made easy with state of the art computer software, visit

http://www.narendranath.itgo.com.