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
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
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
