Risk-Based Inspection Technique - Offshore Structures: Design, Construction and Maintenance - page 610

TABLE 8.33 Maximum Inspection Intervals for Default Periodic

Inspection Program

Exposure
Level

Level I
Inspection

Level II
Inspection

Level III
Inspection

Level IV
Inspection

L1 Annual 3 years 5 years Determined from level III

inspection results

L2 Annual 5 years 10 years Determined from level III

inspection results

L3 Annual 5 years Not required Not required

NDT is used when visual inspection cannot fully determine the extent of damage.
If the level I inspection indicates that underwater damage is possible, a level II
inspection should be conducted as soon as conditions permit.
A level II periodic inspection consists of a general underwater visual inspec-
tion. The inspection includes the measurement of cathodic potentials of
pre-selected critical areas. Detection of significant structural damage during a
level II inspection initiates a level III inspection. The level III inspection, if
required, should be conducted as soon as conditions permit. The level II should
also detect the following:

accidental or environmental overloading

●

scour, sea floor instability

●

damage detectable in a visual swim-round survey

●

design or construction deficiencies

●

presence of debris

●

excessive marine growth

●

measurement of cathodic potentials of pre-selected critical areas. ●

A level III periodic inspection consists of an underwater close visual inspec-
tion (CVI) of pre-selected areas and/or areas of known or suspected damage.
Such areas should be sufficiently cleaned of marine growth to permit thorough
inspection. Pre-selection of areas should be based on results of an engineering
evaluation of areas particularly susceptible to structural damage and to areas
where repeated inspections are desirable in order to monitor integrity over
time. Flooded member detection (FMD) can provide an acceptable alternative
to CVI of pre-selected areas. Engineering judgment should be used to determine
optimal use of FMD and/or CVI of joints. CVI of pre-selected areas for corro-
sion monitoring is included as part of the level III inspection.
Detection of significant structural damage during a level III inspection initi-
ates a level IV inspection where visual inspection alone cannot determine the
extent of damage. The level IV inspection, if required, should be conducted
as soon as conditions permit.