Page 372 - Pipelines and Risers

Pipeline Inspection, Maintenance and Repair 343

18.4.2 General Maintenance Repair
This section deals with those non-critical repairs which in the short term will not jeopardize
the safety of the pipeline and hence, can form part of a planned maintenance program.
Examples include:

Corrosion coating repair;
Submerged weight rectification;
Cathodic protection repair;
Span rectification procedures;
Installation of an engineered bacWill (rock dumping).

Corrosion Coating Repair
Repairs carried out on the corrosion coat of a submarine pipeline may be undertaken under
two differing environments. They are:

Marine conditions - coating applied in seawater.
Hyperbaric conditions - coating applied in dry conditions inside a habitat.

The need for any major repairs at a particular site usually dictates the conditions in which the
coating repair is carried out. Repairs to a subsea pipeline that involve only repairs to the
corrosion coating is unlikely.

Submerged Weight Rectification
In a submerged pipeline system the concrete weight coating provides negative buoyancy. If a
loss of concrete weight coating occurs at locations where a pipeline is exposed on the seabed,
the stability and structural integrity of the system may be affected. If the condition worsens it
may be that some rectification measures are necessary to stabilize and protect the pipeline
system. These remedial measures may include:

Installation of concrete sleeves;
Installation of engineered backfill;
Installation of sand or grout bags;
Installation of stabilization mattresses or saddles.

For each situation which arises the requirements for stabilization and protection of the
pipeline due to its exposure or loss of weight coating should be analyzed to assess its weight
rectification requirements.

Installation of Concrete Sleeves