pushing back the boundaries of uncertainty
DESCRIPTION
TRANSCRIPT
Pushing back the boundaries of
uncertainty
Overview - uncertainty
Uncertainty should be avoided in any engineering project
Lack of certainty will often cost money and reputation
This discussion outlines how reducing the levels of dimensional uncertainty can save significant time and money for a given engineering project
Example No 1
Double jointed pipes
Must be straight
Why? To reduce stress at joint, to ensure fit in JLay tower, to ensure pipe ends are square for welding
How straight and how measured?
How could such a simple thing involve any uncertainty?
Description of uncertainty
Typically pipes are measured in two locations at 90 degrees apart
Unfortunately the actual out of straightness can be 1.4 times larger
Pipes are flexible
Support of pipe is also important
Solution
Better understanding by engineers
Better specifications
Better tools
Example No 2
Pipe shape
Pipes are accepted by a welding contractor as fit for welding
A Hi-Lo mismatch is specified
Pipes are measured using a ruler graduated in mm
Pipes to all be welded offshore Africa
Description of uncertainty
UOE pipes have many shape features (flatter sections, peaking, more curved sections, ovality, expander marks)
Pipes also have a different average diameter and each end of the pipe is usually different
Sample measurements are taken
Solution
Measure the pipes
Understand the problem using simulation
Provide an on-board solution
Save several days at $500k per day
Example No 3
Land pipe project in the US
Several hundred miles of pipe
Pipes supplied with many defects
All pipes required rebevelling
Client unwilling to pay for this additional work
Description of uncertainty
Number, quantity and degree of defects not understood
Level of inspection carried out was not sufficient to resolve dispute
Solution
Deployment of qualified team
Traceable equipment for every measurement (ovality, pitting, paint overspray, gouges, bevel land thickness, bevel angle)
Client wins case worth $10M+
Example No 4
Owner/Operator
Problems with contractors working to the letter of the specification
Specification leaving gaps for contractors to exploit leaving client with a bill or an issue
Description of uncertainty
Contractors and suppliers not always supplying requirements
Some areas not specified properly
Some tools not appropriate or used inappropriately
Accuracy of tools not specified properly
Solution
Supply of educational material
Top quality clear diagrams
Simple specifications
Tools specified
Reporting
Qualification tests identified
Accuracy specified rigorously
Example No 5
Pipe welding can be compromised by poor pipe fit-up
A poor fit-up can result in a poor weld which has to be cut out or reworked
Each welding problem slows production and costs the client or the contractor money
Description of the uncertaintyPipe shapes are very variable
When fitted together the mismatch can be large
It is uncertain which pipe joint is going to be a problem
θ1
θ2
Solution
Measure each pipe end
Rotate the pipes to fit if possible
Sort the pipes into a better order
Implement this system on-site prior to welding
Conclusions
Uncertainty can exist in many areas
There is usually a cost to each uncertainty
Good specifications are required to eliminate areas of ambiguity
OMS has provided many unique solutions (services and tools) to the problems that arise
The amounts of money saved total far more than the cost of using OMS’s tools and services