Today operators are faced with the challenges of ageing offshore installations and the consumed fatigue lives of their structural details. As contracts of offshore installations are renewed or extended, engineers are faced with the challenge to extend the fatigue life of assets for a new required period of time. This training will help engineers and naval architects to tackle these challenges,

3. www.lets-global.com

4. IIW Document XIII-2430r1-12

5. Specimens sprayed with artificial salt water
Specimens

6. Specimens

7. The As-welded corroded specimens exhibited a slight improved
fatigue strength compared to the As-welded non corroded
specimens.

8. The surface layer with detrimental residual tensile stresses may
be removed by the corrosion process
and/or
Possible stress concentrations such as weld toe notches and
corrosion pits are ‘softened’ by corrosion

9. The reduction of the compressive layer (induced by the Ultrasonic Peening treatment) due
to corrosion is detrimental to the fatigue life improvement.
Only a improvement factor of 1.6 was observed after 7.5 years of corrosion

10. Compare real situation to drawings and/or finite element models

12. A bracket, which had not been taken into account in the FE model had
been installed at the fatigue hot-spot after a crack repair
The original planned extent of Ultrasonic Peening:
Is this extent of treatment sufficient?

13. Just because something is written in ink does not mean it is true

14. Just because something is written in ink does not mean it is true

18. Visual inspection of fatigue hot-
spots is strongly recommended
prior to planning of work.
Difficulties with access can easily
be assessed on site, but can be
hard to predict from a drawing
and/or from a picture.

19. ASSET INTEGRITY
Is a result of optimizing the combination of:
• understanding of plant or structure criticality
• degradation mechanisms
• appropriate design
• construction
• plant operation
• maintenance

20. ASSET INTEGRITY MANAGEMENT
Actions to ensure that a critical equipment or
structure is:
– designed
– constructed
– and operated
so that it remains safe and fit-for-purpose
throughout its entire intended life

21. ASSET INTEGRITY ASSURANCE
is a combination of many factors of
which Risk Based Inspection
is one important component

22. Is the optimized application of appropriate
inspection methodology to equipment or
structures based on the risk and consequence of
their failure in such a manner as to provide
reliable information on condition and
deterioration rates
RISK BASED INSPECTION

23. • Helps understanding the current condition
• Provides information about rate of degradation
when baseline data as
– design philosophy
– operating conditions
– maintenance regimes
– other such data
are also known and linked in to the condition
assessments and prediction.
Benefits of Risk Based Inspection

24. RBI is an evolution from
• prescriptive regulations
• is a method for optimizing the inspection process
• supports good Asset Integrity Management
It relies on knowledge of other factors in order to
design the RBI programme and,
• to interpret the results
• to predict future condition

25. Designing a RBI System for an FPSO
• define the key stakeholder objectives
• agree on key project issues such as
– data availability
– baselines
– database selection
– database inputs and outputs.

26. RBI system depends on
• complete and accurate data
• at the set up stage
• throughout the asset life.
• This data includes:
– Line / Vessel Lists
– Material of construction
– Operating temperatures and pressures
– Design temperatures and pressures (if operating values not available)
– Insulation / lining / cladding details
– System criticality information
– Basic fluid composition
– Heat and Material Balance
– Process System Description
– Materials selection basis
– Fabrication drawings, Datasheets etc
– Plus many others

27. RISKScreeningMatrix

28. SCREENING
• Screening can be performed at any level such as a
complete facility or process unit, down to multiple
or individual pieces of equipment. It is
recommended to do a good quality risk screening
where data is readily available such as a complete
process line list/vessel list.
• If data is less readily available a risk screening by
system/structural component may be more
appropriate.

29. Structural Integrity Life Extension
for FPSO

30. a) b)
d)
c)

31. a) b)
d)
c)

32. a) b)
d)
c)

33. a) b)
d)
c)

34. a) b)
d)
c)

35. 1 2 3
?
4
Possible number of people in a confined space
- Alternative escape route
- Escape route length
- Company policy
- Not a exact science….
5

38. A temporary platform is spot-welded
into a bulkhead.
All personnel continuously secured
with Rope Access methods
No extensive testing/safety measure of
the platform itself is necessary before
work can start.
Advantages:
-Quick to set up
-Improves working quality
Drawbacks:
-Hot-work

40. malcolm.hedmar@lets-global.com
LETS Global Ultrasonic Peening
Procedure
Lloyd’s Approval

41. - Fatigue hot-spots found in four FPSO cargotanks
- Bulkhead and bracket welds treated by UP rope access team
- January 2011 to February 2012
malcolm.hedmar@lets-global.com

42. Transverse cargo tank bracket; 6 hours required
Ultrasonic Peening treated area;
- 300mm on each side of bracket

43. Transverse cargo tank bracket

44. Bulkhead connection; 8 hours required

45. Scenario
Fatigue hot-spot located in cargo oil tank
Weld improvement method; Ultrasonic Peening

46. 12m

47. -Quick to install
-Good access to fatigue hot-spot
-Equipment can rest on platform

48. Fatigue hot-spot

49. Drawings recieved from client;
Planned extent of Ultrasonic Peening