Risk-Based Inspection Technique - Offshore Structures: Design, Construction and Maintenance - page 579

TABLE 8.8 Additional Boat Landings

Number of Boat Landings Score

0 0

1 5

2 8

≥ 3 10

No data 10

scores gives the total score. The total score can vary from 0 to a maximum of
13.6. The overall weight of the total score is 5.
Risers and conductors do not have any interdependence with others, as the
appurtenances do not directly contribute to the redundancy or strength of a plat-
form. On the other hand, riser failure increases the overall risk in a platform.
Damages to appurtenances are usually detected through different levels of
inspection. The causes of damages are mainly internal or external corrosion,
external impact, vibration or natural hazards.

Boat Landings
Both excessive marine growth and additional boat landings, for which the jacket
has not been designed, increase the global loading on the structure, increasing the
likelihood of failure. Corrosion and uncontrolled modifications may result in
boat-landing failure, creating a dropped-object hazard to the jacket. The score
for the effect of boat landings is presented in Table 8.8 .
The number of boat landings should be identified, because the score for this
factor depends on this number and ranges from 0 to 10. The overall weight of
the total score is 5.

Grouted Piles
Grouting is usually used to fill the annulus between the leg and pile and
increases the effective wall thickness of the leg, since it is then be a combined
section of leg, grout and pile together, which increases the capacity of the joints
of braces that frame into the leg. In many areas, particularly older Gulf of Mex-
ico platforms, the weak links in the platform design are these joints. Therefore,
grouting of the annulus between the leg and pile of some platforms is a reason-
able measure for reducing the likelihood of failure.
The 1975 threshold date is meant to capture the impact of API RP2A factors
at that time that resulted in better joint design, and hence a lower score, since
after 1975 the joints may be well designed and grouting will not provide much