Pushing Back The Boundaries Of Uncertainty
- 1. Pushing back the boundaries of uncertainty
- 2. 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
- 3. 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?
- 4. 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
- 5. Solution Better understanding by engineers Better specifications Better tools
- 6. 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
- 7. 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
- 8. Solution Measure the pipes Understand the problem using simulation Provide an on-board solution Save several days at $500k per day
- 9. 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
- 10. Description of uncertainty Number, quantity and degree of defects not understood Level of inspection carried out was not sufficient to resolve dispute
- 11. 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+
- 12. 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
- 13. 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
- 14. Solution Supply of educational material Top quality clear diagrams Simple specifications Tools specified Reporting Qualification tests identified Accuracy specified rigorously
- 15. 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
- 16. Description of the uncertainty Pipe shapes are very variable θ1 When fitted together the mismatch can be large It is uncertain which θ2 pipe joint is going to be a problem
- 17. 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
- 18. 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