Rima Gusriana
Subsea Inspection
Harahap, S.T., M.T.
Prodi Teknik Kelautan
Institut Teknologi Kalimantan
• Risk is defined as the potential for the realization of
unwanted, negative consequences of an event.
• The concept of a risk-based inspection (RBI) study
for subsea systems that is designed to ensure the
integrity of subsea equipment.
• A subsea equipment RBI is a method that uses
Definition equipment criticality and failure modes as criteria
for establishing the maintenance and inspection
plan for each item of subsea equipment.
Define Carefully define steps to improve facility performance.
RBI Make use of a systematically applied equipment
Make
Objectives database.
Incorporate Incorporate advances in technology promptly.
Optimize Optimize inspection, test, and maintenance work.
Eliminate Eliminate unplanned equipment failures.
Improve Improve plant performance.
Reduce Reduce costs.
Which subsea systems to inspect
What degradation modes to inspect for
RBI Planning How to inspect
When to inspect
How to report inspection results
Directions for actions if defects are found or not found.
RBI Planning
RBI Management Process
Example :
• The CO2 corrosion rate calculation
module in the Norsok code M-506 is
used to calculate the corrosion rate:
– Water cut;
– Pressure;
– CO2 concentration;
– pH;
– Temperature;
– Oxygen concentration;
– Inhibitor efficiency;
– Flow regime;
– Biological activity;
– Etc.
• The erosion rate can also be determined by the equation
below based on the following items and can be monitored
continuously:
– Fluid density and viscosity;
– Sand size and concentration;
– Sand shape and hardness;
Example : – Flow rate of fluid and sand;
– Pipe diameter;
– Flow regime;
– Geometry;
– Etc.
Inspection Plan
• When to inspect (inspection time);
• Where to inspect (which items to be
inspected);
• How to inspect (inspection methods, or
level of inspection accuracy).
Inspection Methodology
• Time-based damage causes: corrosion, An RBI assessment considers the following reasons for
erosion, or fatigue. damage to a pipeline:
• Event-based damage causes : dropped • Internal corrosion;
object, landslide, or dropped anchor • External corrosion;
• Internal erosion;
• External impact;
• Free-spans;
• On-bottom stability.
The fluid associated with hydrocarbon production from wells
is a complex multiphase mixture, which may include the
following substances :
• Hydrocarbon liquids: oil, condensate, bitumen;
• Hydrocarbon solids: waxes, hydrates;
• Hydrocarbon gases: natural gas;
• Other gases: hydrogen sulfide, carbon dioxide, nitrogen and
others;
• Water with dilute salts;
• Sand and other particles.
Inspection Assesment
Categories with a qualitative ranking system:
–Safety consequences: considers personnel injury or PLL;
–Economic consequences: considered the repair costs and business loss
due to interruptions in production;
–Environmental consequences: considers the impact of various types of
production release to the environment and the cost of cleanup.
Pigging Requirements
– Is subsea installable and retrievable without guidelines using a suitable spreader beam with rigging?
– Conforms to the same standards as the manifold header piping.
– Has a full-bore gate valve that will allow a pig to pass without hang-ups.
– This valve should be hydraulically operated.
– Provides facilities to inject chemicals/methanol through two parallel
– hydraulically operated gate valves with integral check valves mounted to either side of the full-bore gate valve.
– Is of the same material and size as the production manifold pipeline header piping.
– Is insulated to the same requirements as the production manifold pipeline header piping, with the exception
of the pipeline end connectors.
– Is constructed with bends having a minimum radius of five times the nominal pipe diameter (5D).
– Mounts on the inlet hubs of the production manifold.
– Is not required to provide anodes for its own cathodic protection.
– Electrical continuity to the production manifold will be demonstrated.
– Is coated with three-part epoxy paint with the exception of stainless steel tubing, unless otherwise specified.
Inspection Works
Inspection may be needed on a routine basis for the structures expected to deteriorate due
to flowline vibration, internal erosion, corrosion, etc. Inspection includes:
• General visual inspection, including cathodic measurements and marine growth
measurements;
• Close visual inspection additionally requiring physical cleaning for close visual inspection,
CP measurements, and crack detection by means of nondestructive testing (NDT);
• Detailed inspection including close visual inspection, crack detection, wall thickness
measurements, and flooded member detection;
• Routine pipeline inspection including tracking and measurement of depth of cover for
buried pipelines, which is also applicable for control umbilicals and power/control cables.
• Cleaning may be performed
by an ROV with brushing tools
or high- pressure wet jets and
grit entrainment
• Crack detection may be
performed by an ROV with
magnetic particle inspection
(MPI), eddy current,
alternating current field
measurement (ACFM)
methods, etc.
Maintenance activities include repair or replacement of
modules subject to wear. Maintenance is normally
performed by retrieving the module to the surface and
subsequently replacing it with a new or other substitute
module.
Retrieval and replacement have to be anticipated during
subsea equipment design. Some modules such as
Maintenance and multimeters, chokes, and control pods are subject to
removal and replacement. A completed replacement may
Repair have to be carried out due to the significant wear on or
damage to non- retrievable parts of subsea equipment.
Due to the difficulty and expense of maintenance and
repair, the operation may be continued with regular
monitoring if the damaged module is not readily replaced
and does not prevent production.
https://www.youtube.com/watch?v=Hyk4PepD9q8
https://www.youtube.com/watch?v=ETbfkvY2NBI
Video https://www.youtube.com/watch?v=lxnfqzqYJiY
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