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