Pipe Fabrication Dimensional Errors — I Can’t See You!!!

Pipe Fabrication Dimensional Errors — I Can’t See You!!!


Can a level, square and tape measure really measure up to today’s quality standards on complex spools?

I was watching my baby girl cover her eyes as she had done something naughty. Doing this gave her the feeling that if she couldn’t see her mother or myself then she would not get into trouble. Despite her feeling of invisibility, she still ended up getting into trouble and having to apologize for what she had done.

It’s funny as this is sometimes how the Chemical, Oil and Gas industry acts when it comes to assigning appropriate project dimensional quality control for pipe spools.

Green field or brown field (based on a laser scan) projects are typically designed on a specialist CAD platform which enables the designer to design to levels where machine shops would be the only way to match the design model tolerances.

This way of designing can provide huge levels of confidence that the project has been designed correctly and that there “should” be no errors during construction. However, instead of executing the project per the model design, what happens after the piping isometrics are issued for fabrication is that the project hides their eyes and hopes it won’t get into trouble.

“Guess what? Mom and Dad are going to find you!”

Fabricators are expected to carry out appropriate dimensional QC. However, based on experience, the level of QC being offered at most fabricators is not up to the level that ensures all spools are released within PFI (Pipe Fabricator Institute) tolerances.

Having an automated digital pipe spool report generated for each pipe spool allows the project team to know what is being delivered and have confidence in the ability to successfully execute a project.

Digital dimensional control technology is available that allows the most complex pipe spools to be quickly checked to ensure fabrication tolerances are met. Any deviation from design is shown on the spool report.

“Now – No need to cover your eyes”

I’ve personally been involved with pipe fabrication inspection for twenty-one years. For the last eight years I’ve been actively promoting fabrication inspection services in the United States. It has been a challenge to have industry accept the need for digital fabrication QC. Why? Well, I hear the following responses:

Response from the project

“The fabricator is paid to fabricate correctly so we don’t need to pay for an inspection service”.

My thoughts on this statement. “The fabricator is paid to weld correctly, so why perform NDE on welds”. This is not a facetious statement. Rather it’s one that means: “Why take the chance on cutting the tested weld due to bad dimensions?…Why not carry out the adequate level of dimensional QC before delivery?”

Response from the fabricator

“We never have any rework and If we did want to bring in an inspection company we would price ourselves out of the project proposal and not get the work”.

My response to this statement: “There is rework. However, work is repaired in the field or made to fit – resulting in additional stress in the line which will eventually cause failure”.

As for the cost and the potential for losing work:  I often come across operators who have asked me who to recommend fabricators that use our service. When asked I am more than happy to mention a list of fabricators who use the service. With this recommendation the fabricator gets more opportunities to bid on the additional work with the inspection cost built in. As the client recognizes the additional commitment to quality, they understand there will be zero fabrication error when the product arrives onsite.

You can understand the arguments of both the project team and the fabricator. However, until I consistently hear of projects that are free from any rework. I will continue in my belief that Dimensional Control is essential to ensure a project is successfully executed.

happy camper becht dimensional control

Pipe spools that are inspected for dimensional compliance not only protects a fabricator’s reputation but ensures that the project is installed per the model on which the design was based.

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About The Author

Derek Paterson has joined Becht as Operations Manager of the newly formed Dimensional Control department. The department is designed to complement the services offered by the existing Laser Scan division however will stand as its own entity within Becht. Services will include any project that requires a high degree of accuracy in its measurements. Projects the department has completed with Becht since formation include: New and existing pipe verification, subsea template verification, fabricated spool QC, piping construction isometric development, flow measurement nozzle positioning and alignment. Derek has been involved in Dimensional Control (DC) services since 1997. Raised in Aberdeen, Scotland, Derek arrived in America in 2003 as lead DC surveyor on the BP Holstein project. In 2009 Derek established his own company which lead to a partnership with a major service company in 2011. Since then Derek has performed the role as DC Operations Manager. Derek is based in League City Texas and has a family of 2 boys (11&12) and a girl (3). He says there is not much time for hobbies due to work and children’s activities. However, he does try and squeeze in a round of golf and visit to the driving range when time permits and enjoys a beer and a game of corn hole with his neighbors to relax in the evenings. He attended Aberdeen College in Aberdeen, Scotland and holds a Mechanical Engineering degree.

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