Inspection procedures are produced to make sure that relevant information is correlated to determine the need for further inspection, or determine the equipment needed to obtain more information, for an engineering assessment of the damaged pipeline. This would determine the method of repair of the pipeline that will be used.
REPORTING REQUIREMENT
Consistency, accuracy and completeness of the inspection tasks are extremely important, as the information provided will aid engineers and the emergency response team to plan for the next corrective action.
Reports are to include all work carried out by the vessel. Additional reports may be requested to cover specific activities, which are needed to formulate later planning for work scopes.The main aims of producing standard procedures for inspection and investigation of damage to pipelines are as follows:
- To assist engineers and emergency operation team in the scope of work.
- To standardise the format and correlate the procedures into an easy reference for the repair manual.
- To specify to the contractor the method and standards to which the work is to be performed.
- To specify personnel qualifications necessary to carry out the specified works
- To carry out all works in a safe and efficient manner.
The detailed inspection of a damaged area on a submarine pipeline caused by impact. Anchors wires trawl boards dropped objects etc. The work would normally include cathodic potential measurements, cleaning, UT wall thickness measurements, dimensional survey, mould profiles, video survey, photography survey and NDT methods. During the initial damage assessment the following inspection techniques could be utilised:
GVI
(General Visual Inspection)
DVI (Detailed Visual Inspection)
CVI (Close Visual Inspection)
UT (ultrasonic Inspection)
MPI (Magnetic Particle Inspection)
Pipeline preparations would have to be accessed during GVI for burial and any need to excavate to locate the damage/leak area. Once the damage/incident area as been located the following information needs to be addressed.
- Pipeline identification confirmation.
- Survey coordinates.
- Water depth.
- Severity of damage.
- Field joint number.
- Anode joint.
- Closes other Subsea asset.
- Closes Platform (manned & unmanned).
- ROV survey along pipeline route for any other signs of damage (the distance covered will have to be determined by reasons for the inspection /investigation such as trawl board, anchor dragging from other vessels).
- Pipeline free-spans.
- Debris associated with damage or hazard for divers/ROV.
The inspection procedures should be capable of identifying the following:
- Damage to, or defect in, the pipeline.
- Change in the position of the pipeline.
- The extent of marine growth on the pipeline.
- The condition, or change in condition, of the seabed in the vicinity of the pipeline with particular reference to the presence of debris, boulders and scour.
- The presence of, and extent of, unsupported spans.
- The presence and extent of any loss of cover in buried lengths.
- The presence and extent of any loss of weight coating.
- Loss of wall thickness in the pipeline.
- Loss, movement or failure of any protection placed over or around the pipeline.
- Verification of satisfactory working of cathodic protection systems.
- Leaks from the pipeline.
- Deterioration in support and protection at pipeline crossings.
DAMAGE INSPECTION
The ROV would locate and fix the positions of the incident/damaged area. Confirmation that no pipeline leaks or hazards that could endanger divers are evident, prior to deployment of the divers and DSV direct set-up over location.
On completion the ROV would carry out, and fully video record, viewing both sides of the pipeline. An initial GVI (General visual inspection) or survey of the area of interest highlighting the area of damage, items of debris which may have caused the damage or any other assignable cause.
Concrete removal equipment
It is labour intensive work by divers to chip a large area of concrete weight coating away, time consuming and expensive for the duration of a DSV. Equipment is available for the efficient removal of concrete coating, thus saving vessel time and quickening the investigation and/or repair operation.
Protective coating removal.
The removal of the protective coating after the concrete as been removed will have to be carried out under certain circumstances for some pipeline repair procedures, and for certain inspection techniques. The following techniques can be used for removal of the protective coating and completed to a bare metal finish.
- Diver operated Low-pressure air grit system.
- Auto HP water jet set-up on guide
The removal of the pipeline coating for inspection or repair would be for the following reasons:
- NDT inspection MPI/CVI of welds.
- Damage assessment on dents and gouges
- Remedial grinding.
- Repair sleeve installation for sealing
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