Selection of FEA package for offshore structures (Oil & Gas) 1

[Thedraffy]

I manage the offshore engineering teams for a an Oil and gas services company in Scotland. At the moment we use a combination of 3D space frame analysis (STAAD Pro) and CSC/Tekla packages for 2D frames and bolted moment connections (TEDDS & Fastrak)

We need to evaluate FEA packages for designing complex fabricated items, plated structures, welded assemblies etc for fixed and floating offshore structures (topsides/hull structures/subsea) with a view to implementing it this year (we also need to consider training/user friendlyness)

Before I give the Ansys sales people a call, can any structural engineers / naval architects give me the low down on its pros and cons, and generally what it's limitations are... As in my experience it's only once you buy and implement a package you discover what it can't do... Any and all help is appreciated?



TheDraffy

 

[Crannog]

I'm not trying to teach you to suck eggs but I'll give a pretty low-level/general reply:
Ansys and Abacus are common enough in the industry, and there are plenty of Ansys users in the Aberdeen area. Typically both their sales reps will tell you both can do the job and both are probably right. At the end of the day it will come down to what experience your staff have and what interfaces you may need to have with clients/suppliers (ie whether you would need to share analysis files), first of foremost that would drive my choice.

I'm sure you appreciate that being able to find the buttons isn't the same as knowing how to get the right results out of the software so I would look never to put in a system where I don't have at least on user who is experienced with general-FEA (which is sounds like what you have) and knows the foibles of that software suite.

Also a driver for me would be the size of the structures you're analysing, eg whole topsides down to brackets and frames on gantries? Do you need plate modelling as shells or solids? Do you need to model welds or will you be looking at matching welds to plate thickness? Is fatigue analysis required?

I use Ansys for a lot of medium (1-10m) offshore-structures and it can go bigger but without answering the above questions, I wouldn't recommend it to you Cart-Blanche - though it certainly can do a/the job.

If I was in your place:
I would get a list of the above, and everything you need it to do.
Then get the sales-reps in and see what they say vs your list (taking everything they say with a pinch of salt).
Whilst they are in get them to demo the software with the biggest model you want running and see whether it can handle the analysis, with your actual geometry.

Give us a shout if you have any particular questions.

-Drew

 

[TezzaTwo]

You need someone with years of experience to drive the software effectively. Their salary is larger than the price of the software. So to repeat the person you choose will probably dictate the software package. Solve the experienced driver problem first.

"so I would look never to put in a system where I don't have at least one user who is experienced with general-FEA (which is sounds like what you have) and knows the foibles of that software suite"

 

[TezzaTwo]

A word of caution stepping into the finite element analysis business. People believe the pretty pictures they get.

https://www.ima.umn.edu/~arnold/disasters/sleipner.html

The sinking of the Sleipner A offshore platform

The conclusion of the investigation was that the loss was caused by a failure in a cell wall, resulting in a serious crack and a leakage that the pumps were not able to cope with. The wall failed as a result of a combination of a serious error in the finite element analysis and insufficient anchorage of the reinforcement in a critical zone.

It cannot be emphasized enough that you need an experienced finite element analyist together with hand calculations as order of magnitude checks on any finite element results. This is one of the conclusions of the many reports into this large failure.

Also your implementation is more than just the software you need a quality assurance system for checking and verifying FEA models. This does not come with any software package. Proper QA of the finite element model would have caught Sleipner A.

 

[SDMAX]

From my experience, the main FE packages used for offshore structures are SACS, SESAM and ANSYS (ASAS), they all have their own plus points and negatives.

As TezzaTwo has noted you will need to get someone experienced on board to run the software as its only too easy for a new user, no matter how experienced an engineer they are, to set or not set a controlling parameter and obtain results which look good but aren't worth the paper they are written on (or electronic version of that cliche).

If you have no one on board at present with the experience needed to run the software, it may well be worthwhile interviewing a few likely candidates and seeing what packages they have experience of and using that to drive your decision.

Another point to bear in mind is that a number of the software companies are moving from a purchase license option to a pay and play option where you pay for each instance of usage or on a per user/per hour basis. This can be beneficial if you don't need the software all the time, but can lead to some substantial bills if use is not controlled.

Let us know what route you go down and why?