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The Structural Inspection Work Engineering Essay

Subsea integrity management (SIM) is a continuous process throughout the lifecycle of subsea/offshore facilities. As the requirement for the effective implementation of the business's Integrity Management (IM) program, Remotely Operated Vehicle (ROV) underwater inspection work will be completed on subsea structures and pipelines. The goal of this Scope of Work document is to define the scope of inspection, equipment types, personnel role and competence, and quality of work for the Contractor.

The Company requires the underwater inspection services operated from a Remotely Operated Vehicle (ROV) support vessel equipped with Work and Observation ROVs and other ancillary equipments. The Contractor shall supply all resources essential to perform the task. This shall include without limitation the vessel necessary to perform the Work, the ROVs, all necessary certification, personnel, equipment, machinery, consumables, materials, logistics, tools, spare parts, management, engineering, and other services required to effectively perform the Work. Contractor shall ensure all his employees comply with all Company HSE standards.

Structural Inspection Work

4. 1 Objective and Methodology

The purpose of this inspection is to examine the integrity of the jacket structure and other structural components mounted on the jacket. This will be attained by the ROV visually inspecting all jacket structural members, connections, clamps and other fitting. The inspection will be performed in conjunction with continuous CP measurements on all structural members surveyed and irregularities recorded. Data out of this Inspection Survey would be used by Company to examine the deterioration rate of the health of the structure and the corrective actions required.

4. 2 Scope of Work

The scope of inspection shall cover the following jacket segments and other structural components:

Jacket members in splash zone.

All horizontal, vertical, diagonal structural members.

CP measurement of all structural members.

Installed Galvanic anodes

Structural clamps and connections.

Mud mat and leg pile scour.

4. 3 Inspection Deliverables

The inspection shall establish and report the next details:

Major or minor structural damage such as dents, cracks, flooded members, buckle, weld defects, gouges etc.

Thickness and nature of marine growth on jackets and shall carry out immediate work to eliminate growth.

Impact damage from dropped objects, coating damage, loose members.

Condition of Mud mat and pile scour (look for settlement, stability)

Performance of the CP and anode wastage.

Condition of riser, umbilical and structural clamps and other structural connections.

Flooded member detection

5. 0 Pipeline inspection work

5. 1 Objective and Methodology

The reason for this inspection is to evaluate the integrity of the pipeline and identify any potential threat to it. This will be attained by the ROV moving above and across the pipeline, inspecting visually and recording of pipeline system irregularities using underwater video cameras. At the same time, continuous cathodic potential measurements will be taken, measurement of the burial depth, free spans etc. Data obtained would be used by Company to determine the deterioration rate of the external condition of the pipelines and the corrective actions required. The survey will be performed for the whole pipeline lengths.

5. 2 Scope of work

The scope of inspection shall cover the next pipeline segments and other subsea facilities:

Pipeline riser in the splash zone and below splash zone.

Riser Clamps in splash zone and in submerged zone.

Umbilical carrying electrical, hydraulic and fibre optic cables.

Submarine pipelines fittings such as flanges, spools, supports, induction bends etc.

Subsea structures components (pipeline end terminal, valves, instruments etc)

5. 3 Inspection deliverables

The inspection shall establish and report the following details:

Major or minor pipe damage.

Pipeline settlement/displacement along the complete length.

Pipeline exposure and burial depth.

Identification of where upheaval buckling or excessive lateral buckling occurs.

Identification of where excessive free spans occur including length, height and end support conditions.

Assessment of pipeline and riser expansion loops, support and protection.

Assessment of sea bed scour and sand wave movement affecting pipeline integrity.

Assessment of health & evidence of damage to pipeline external attachments such as valves, flanges, induction bends, end termination etc.

Assessment of the performance of the CP.

6. 0 ROV Requirements

The ROV shall have capability to work in all depths and under weather conditions normally experienced in the location of the business assets. IMCA Code of practice for safe and efficient procedure of ROV's is classified below as:

Class I - Pure Observation

Class II - Observation with payload option

Class III - Work class vehicle

Class IV - Towed or bottom crawling vehicles.

Class V - Prototype or development vehicle.

Class I, II and III will be utilized. ROV's shall have sufficient thrust and controllability allowing positioning at any required orientation to the structure and pipeline without their performance being affected by action of the sea current or wave. ROV will be of high power rating. As the very least, the Contractor's ROV shall have the following equipments and specification:

Pay Load Capacity - should be sufficient to execute the activities indicated in Sections 4. 2 and 5. 2

Flotation module and tethering capability

Propulsion System - thrusters should be capable of producing speed to operate a vehicle the payload capacity.

Lighting - should be sufficient to conduct all the operational sequences.

Camera - ROV should be equipped high quality video camera (monochrome and coloured) that can record, transmit and take pictures.

Handling system and controller

Manipulators

Launching and recovery system - "A" frame and winch system

ROV console, umbilical and power cables

Topside PC based control with diagnostic monitoring system.

Telescopic boom showing both sides of pipeline

Special tools - metal cleaning and cutting wheel, air grit blasting system, water jet system and hydraulic steel brush, Ultrasonic test, Magnetic particle test etc

Sensors for temperature, leak detection, trench profile, pipe burial, cathodic potential, marine growth and acoustic measurements.

Spare and tool kits

ROV procedure and procedure manuals

7. 0 Personnel Requirements

7. 1 Personnel type

The following personnel shall be required for the task:

ROV supervisor

ROV pilot

ROV maintenance technician

Data recorder

Surface support personnel

7. 2 General qualification

Contractor shall supply fully qualified and experienced personnel to undertake the inspection Work. All personnel shall have experience in the field of subsea inspection for jacket structures and pipelines. They will be computer literate with sufficient skills to produce electronic reports, input to databases and have good communication skills. Personnel shall be familiar with the primary coal and oil industry codes and standards in general use, including all relevant CSWIP codes and standards and shall comply with HSE procedures. All personnel shall have current and valid offshore medical/visual fitness and offshore survival certificate.

7. 3 Personnel role and qualifications

The personnel job functions and minimum qualification are highlighted below:

7. 3. 1 ROV/Inspection supervisor

Role

The ROV supervisor shall be responsible for, however, not limited to the next:

Integrating all the required ROV functions with topside support activities which are associated with planned operations.

Shall be familiar with the structures and pipelines to be inspected.

Shall determine how businesses are accomplished, their means of documentation, and the actions of those personnel necessary to assist operations.

Shall work closely with the Inspection/Data Recorders to ensure a competent inspection operation.

Shall be responsible for the entire safety of the ROV businesses including coordination of vessel activities.

Shall be competent in piloting the ROV and perform basic checks and maintenance on the vehicle.

Shall ensure that the ROV is maintained in good working condition.

Qualification

Shall possess the next minimum qualification:

Desirable degree in engineering (mechanical, electrical, electronic) or its equivalent.

Shall possess evidence of ROV related trainings.

Shall have good leadership, interpersonal, capacity to work under pressure, result oriented skills.

7. 3. 2 Remote Visual Inspection (RVI) Inspector

Role

Shall be responsible for, but not limited to the next:

Shall be able to perform specific calibrations, interpret test outcomes and make final evaluations.

Shall carryout subsea qualifications for minor or major defects, CP, FMD and other NDT.

Shall prepare subsea inspection reports filled with structural sketches

Shall are accountable to ROV/Inspection supervisor.

Qualification

Hold a qualification in a relevant engineering or science subject, HNC or above.

Current CSWIP 3. 4. u or other relevant CSWIP documentation or equivalent.

Shall have offshore experience in supporting ROV structural/pipeline inspection, corrosion monitoring, underwater NDT, FMD and data processing.

7. 3. 3 ROV Pilot/technician

Role

The ROV pilot/technician shall be knowledgeable in both piloting and maintenance of the ROV. His role shall include the following:

Shall be accountable for the actual flying and control of the ROV.

Shall use the data recorder.

Shall be responsible for the maintenance of the ROV including pre-dive and post-dive maintenance checkout of ROV components

Shall report to ROV/Inspection supervisor.

Qualification

Shall possess the next minimum qualification:

Engineering degree, trade apprenticeship or school education in mechanical, electrical, electronic or hydraulics.

Shall own proven background in operating, maintaining and repair of ROV.

Shall be skilled at solving problems and troubleshooting, open minded, work under great pressure, team player and result oriented.

7. 3. 4 Data Recorder

Role

The Data recorder will be responsible for the following:

Shall be responsible with the management of information acquisition and recording during ROV operations.

Shall use the ROV pilot to obtain required information.

Shall be in charge of keeping records of structural and pipeline drawings, inspection data, photographs and all video documentation.

Shall report to ROV/Inspection supervisor.

Qualification

Shall possess the next minimum qualification:

Trade apprenticeship or college education in mechanical, electrical, electronic or hydraulics.

Shall own proven track record in subsea inspection work and recording of inspection results.

Shall be knowledgeable in identifying and classifying and different damage types.

Reference

API RP 1111 - Recommended Practice for the Design, Construction, Operation and Maintenance of Offshore Hydrocarbon Pipelines (Limit State Design)

CSWIP-DIV-13-04 Registration Scheme for Underwater (Diver) Inspectors - Grade 3. 1U, 3. 2U, ROV Inspectors (3. 3U) and Underwater Inspection Controllers (3. 4U)

Corrintec Cathodic Protection Survey Methodology - ROV Survey Methodology [online]

Available from: http://www. uniquegroup. com/images/attachment/87_ROV1%20Survey%20Method%20ROV. pdf [Accessed 17 November 2010]

IMCA R 002 rev 2 - May 2009 Entry Level Requirements and Basic Introductory Course Outline for New Remotely Operated Vehicle (ROV) Personnel

IMCA R 004 - Code of Practice for the Safe and Efficient Operation of Remotely Operated Vehicle

ISO 13628 - 8: 2002 Petroleum and GAS Industries - Design and Operation of Subsea Production Systems - Part 8: Remotely Operated Vehicle (ROV) Interfaces on Subsea Production Systems

NOAA Cooperative Institute for Ocean Exploration, Research, and Technology - Remotely Operated Vehicle Operations and Procedures Manual, [online], Available from:

http://uncw. edu/nurc/pdf/rov_operations_manual. pdf [Accessed 17 November 2010]

Ricci, F (1990), Use of ROV's functioning of EAN Underwater Installation in the North Sea, [online], Available from: http://archimer. ifremer. fr/doc/1990/acte-1164. pdf [Accessed 17 November 2010]

Question 10

More than a quarter of the North Sea oil & gas production pipeline network were first commissioned in 1960's and 70's. Other 23% was built during the 80's. These pipelines were actually made to operate around twenty years. Identify the main element threats to the integrity of the pipeline in later life.

1. 0 Introduction

Generally, pipeline whether onshore or offshore continues to be the most cost effective and relatively safest way of transporting oil and gas from production field to users. Most of the offshore pipelines in the North Sea are well past their at first design life of twenty years. Some are even over thirty to forty years. Some of these pipelines may be required to operate to get more years beyond their design life as the North Sea continues to provide oil and gas. Identifying the threats to the integrity of the pipeline in later life is paramount in designing a highly effective Pipeline Integrity Management (PIM) system.

2. 0 Threats to the Integrity of Pipeline in Later Life

Some of the main element threats to the integrity of an pipeline in later life are discussed below using section 2. 2 of ASME B31. 8S - 2004: Managing System Integrity of Gas Pipeline as a guide.

2. 1 External Corrosion

External corrosion is a common phenomenon in offshore pipeline. This result because of the galvanic cell formed on the pipe surface. The seawater acts as the electrolyte, while anodic and cathodic areas are formed on the pipe surface. The steel pipe wall also acts as the conductor for electrons. The cathodic areas with high oxygen absorption receive electrons from the anodic areas and this causes metal loss at the anodic region. The pipe is usually coated with materials such as asphalt, fusion-bonded epoxy, polyethylene, polypropylene etc to isolate the pipeline steel from seawater and soil. This provides sort of resistance between the anodic and cathodic areas on the pipe surface. A cathodic protection system using sacrificial anode or impressed current is also installed to complement the coating system.

As pipeline ages the pipeline surface coating breaks down little by little and allows oxygen to the bare metal pipe causing metal loss. The cathodic protection system is usually devote place to replace coating defects and degradation as time passes. As the coating wears out more cathodic current is necessary and this reduces the effectiveness of the cathodic protection system. If the degradation of the coating and cathodic protection is not mitigated the pipeline metal surface is exposed and corrodes quickly, therefore constant monitoring of coating and CP system is necessary.

Internal Corrosion

Corrosion on the internal wall of an pipeline occurs when the pipe wall is exposed to water and contaminants such as oxygen, carbon dioxides, sulphides and chlorides present in the pipe fluid. The operating conditions of the pipe can further lead to the concentration of the corrosive elements; internal corrosion process is determined by the service of the pipeline. For example sweet and sour corrosion is caused by the presence of dissolved carbon dioxide and hydrogen sulphide in the fluids respectively.

Activities of some micro-organisms living on the inner wall of pipes may influence corrosion this is recognized as Microbiologically Influenced Corrosion (MIC). A few of these micro organisms can handle producing metal dissolving products such as organic and natural acids that happen to be detrimental to the pipe metal surface by accelerating corrosion.

Stress Corrosion Cracking (SCC)

Stress corrosion cracking occurs consequently of combined actions of stresses in the pipe metal and the existence of a corrosive environment. It could occur internally or externally in the pipe. The stresses are either created from operational cyclic loads or residual stresses introduced during manufacturing or installation. The corrosive environment is the seawater or maybe it's in the existence of a specific chemical such as hydrogen sulphide present in the pipe fluid. The more the pipe is exposed to these agents of SCC the higher the probability of failure. Palmer and King (2008, pp 95) mentioned that the cracking starts at pits and crevices, plus they gave two hypotheses to describe the propagation of cracking. The first hypothesis is that if the pit is over a certain depth, there is certainly stress amplification. This causes a plastic yield at the crack tip which progressively damage the oxide film and there is a severe anodic dissolution at the crack top. The second hypothesis relates to brittleness of the material at the crack tip due to hydrogen concentration which causes material failure. An effective CP of the system can help reduce the effect of SCC.

Manufacturing Related Defects

Pipe manufacture refers to the way the pipe pieces are created in the mill. Pipe defects may occur at the melting, forming or heat treatment of steel such as microstructure anomalies, non metallic inclusions, surface decarburization and segregation amidst other. It could also occur by improper storage that can lead to surface defects such as corrosion, cracks, grooves and scabs or during subsequent processing. API Specification 5L provides standards for pipe well suited for use within conveying gas, water and oil in both the oil and natural gas industry. Pipe could be seamless or welded. Seamless pipes are made by hot working steel to create a tubular product with out a welded seam. If possible, the hot worked tubular product may be subsequently cold finished to produce the desired shape, dimensions, and properties.

Seam welded pipes are produced by joining the sheets together by using filler or non filler metal and seams are formed on the pipe. Exemplory case of seam pipe formed by using filler metals are continuous, electrical and laser welding. Non filler metal methods such as submerged arc welding (SAW) and gas metal arc welding (GMAW) are also used. Defects may arise through the joining of the pipe sheets resulting to weak seam lines, leakages, cracks etc. These defects should be eliminated when proof test is carried out on the pipe in the mill. Section 7. 8 of API specification 5L gives limit of acceptable defects, which sets the standard for detection during manufacture of pipes. The likelihood of failure of pipes in service to fail because of this of these manufacturing defects increases as the pipe ages.

Fabrication/Construction Related Defects

These are defects introduced into the pipeline during fabrication, construction or installation. It may occur during transportation, handling or welding of the pipe on site. They mostly result into mechanical damage such as dents, gouges, bends, buckle, broken pipe, defective fabrication weld and girth weld defects (causes cracks, burns and undercut). Critical defects could be detected using radiographic test, ultrasonic testing or hydro testing of the pipeline. If these defects aren't eliminated as the pipe ages they propagate and finally lead to failure of the pipeline. Residual stresses introduced during fabrication and construction of the pipeline contributes to SCC which also leads to pipeline failure.

Equipment Failure

Equipment failure is the failure of the pipeline ancillary facilities such as valves, pumps, compressors, pig traps, meters, regulators etc. A few of these facilities wear out with time. For instance failure of pressure and relief valves can cause pipeline rupture and explosion. Vibration consequently of poorly installed pump or compressor contributes to cyclic loading on pipe flange connections and as time passes this cause fatigue and eventual cracking or fracture of the pipe.

Third Party Damage

Over the lifespan of a pipeline, third party interference is quite typical. This could be accidental or intentional (vandalism). The result of third party interference creating pipeline damage reaches times catastrophic. Impact damage on pipeline could occur due to dropped object from platform or ship impact on risers. Anchor drag during construction and supply boat activity, trawl board/net drag could also seriously damage the pipeline in later life. External coating of the pipe if damaged causes accelerated corrosion and a potential for future fail (delayed failure mode) or direct cut in to the pipe thereby leading to leaks and sometimes explosions (immediate failure). Pipeline may be vandalised by economic saboteurs and terrorist, and this usually lead to environmental problems, lack of life and property.

Incorrect Operational Procedures

This threat is caused by incorrect operating procedures or failure to stick to procedures. You will discover time when pipe leakages are reported and due to poor communication and bureaucratic procedures such leakages are left unattended to promptly. Abnormal or inconsistent operating conditions of the pipe can lead to the concentration of corrosive elements in pipe leading to internal corrosion or formation of hydrates, wax deposition and erosion problems. Inconsistent past pipeline incidents reporting, data collection and management brings about data duplication, accuracy variations or data loss. It has a huge negative effect on the pipeline integrity management programme as insufficient, inaccurate or non option of data leads to deficient integrity management.

Weather Related and Outside Forces

Submarine pipeline which is quite typical in the North Sea have been put through cyclic loads from sea waves, vortex induced vibrations and thermal stress over time and these could result into fracture. Earth movement triggering natural hazards in form of earthquake, mudslides, faults, soil liquefactions, storms amongst others has high likelihood of occurrence with time and these poses threat to the integrity of pipelines.

Reference

Andrew, P. and Roger, K. (2008). Subsea Pipeline Engineering. 2nd Ed. Tulsa: PennWell Corporation.

API Specification 5L (2004) Specification for Line Pipe. 43rd Ed. Washington: American Petroleum Institute

ASME B31. 8S (2004) Managing System Integrity of Gas Pipelines. New York: American Society of Mechanical Engineers.

DNV Technical Report No. 44811520 (2009). A Guideline Framework for the Integrity Assessment of Offshore Pipelines. [online], Available from:

http://www. boemre. gov/tarprojects/565/565aa. pdf [Accessed: 19 November 2010]

Martin, T (2005) Quantitative Pipeline Risk Assessment. Conference Proceedings, Geospatial Information & Technology Association, India. [Online], Available from:

http://www. gisdevelopment. net/proceedings/gita/2005/papers/84. pdf

[Accessed: 19 November 2010]

Kirkwood, M and Cosham, A (2000) Can the Pre-service Hydrotest Be Eliminated? Pipes and Pipelines International, [Online] vol. 45, No. 4, July - August, pp 1-19

Available from: http://www. penspenintegrity. com/downloads/HydrotestEliminated. pdf

[Accessed: 19 November 2010]

Tan, H (2010) EG55F7/G7 Lecture 4-2: Subsea Corrosion, Aberdeen: School of Engineering

Tan, H (2010) EG55F7/G7 Lecture 7-2: Environmental Assisted Cracking, Aberdeen: School of Engineering

Question 9

Prepare a set of questions and information requirements that you could present to an asset owner who's in need of a sacrificial anode retrofit for a subsea pipeline.

1. 0 Introduction

Sacrificial anode retrofit on subsea pipeline is usually required by asset owners to keep the integrity of these pipeline. It involves the installation of sacrificial anodes to replace or augment the depleted cathodic protection (CP) system set up. The reason why for retrofitting a subsea pipeline CP may be due to the following:

To keep up with the integrity of the pipeline when the original CP system is inadequate or depleted.

To boost the service life of the pipeline so that it can serve way beyond its design life.

When there's a coating harm to the pipeline.

2. 0 Information Required for Sacrificial Anode Retrofit for a Subsea Pipeline

The following questions must be answered and the information obtained can be used to effectively design a sacrificial anode retrofit for the subsea pipeline.

Location of pipeline

Where is the pipe located?

Where will be the termination points?

How far is it from platform or shore?

Is there any pipeline route survey drawings or alignment sheets?

Pipe properties

What material is the pipe manufactured from?

Is it seam welded or seamless?

What is the strength of the pipe?

What is the exterior and internal diameter?

What is the pipe wall thickness?

What is the pipe length?

Subsea environment

What is the depth of seawater?

What is the seawater temperature at seabed?

What is the velocity of seawater at seabed?

What is the concentration of dissolved oxygen at seabed?

What is the concentration of dissolved salt at seabed?

What is the PH of the Seawater at seabed?

What is the electrical resistivity of seawater at seabed?

What is the soil resistivity of the seabed?

How is the seabed topography/terrain?

What is the burial status of the pipeline?

How does soil erosion affect the pipeline?

Has there been any incidence of ground movement, for example mudslides, earthquake, subsidence etc?

Has there been any adverse weather related problems, for example storms, hurricane, Tsunami etc?

External coating assessment

Does the pipeline have any external anti corrosion coating?

If yes,

What material is it made of?

What is the thickness?

Does it have any defect?

How effect could it be?

Is there any thermal insulation?

If yes,

What material is it made of?

What is the thickness?

Is it damaged in any place?

Is there concrete coating?

If yes,

What is the strength?

What is the thickness?

Is it damage in virtually any place?

To what extent would it cover the pipeline

Are there any other styles of coatings? Please specify.

Assessment of Existing CP system

How is today's CP system performing?

What is the range of current output of existing anodes?

What is the pipeline current density demand/requirement?

What is the level in the offing?

Pipeline fittings and connections

What is the health of the flanges?

What is the condition of the bends?

What is the health of the valves?

What is the condition of the tees?

What is the condition of the expansion loops?

What is the health of the riser connection?

What is the condition of the tie in spools?

Are there some other fittings? Please specify.

Operating procedures

Can the CP operating and maintenance data be provided?

Was there any deviation from specification/procedures?

Is the electrical power system set up always available?

Was there any record of accident on the CP system?

Does the operating procedure adhere to Company's HSE procedures?

Does the operating procedure comply with legislation?

How are other CP systems performing in the region?

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