Existing Platform Inspection

INSPECTION METHOD

 

Objective :

To determine that the Platform is safe to continue its service :

1. Collect data – must be accurate
2. Evaluate data against design for any anomalies that affect the structural integrity. 

Reference :

Permen No. 18  Pemeriksaan Keselamatan Instalasi & Peralatan

API RP 2SIM - Baseline

1. Level I                     
2. Level II
3. Level III
4. Level IV
5. Special

Annual basis

Routine underwater inspection - should be carried out at an interval consistent with the SIM strategy adopted by the owner/operator.

Above Water – General scope

General Visual Inspection  - BY Inspector, covers : corrosion, permanent deformation, damage, and  modification – if any

All Jacket member :

1. All jacket structure from Splash zone up to top of Jacket
2. Crown piece
3. All weld connection

Deck member :

1. Deck Leg
2. Main Girder
3. Horizontal Brace, Diagonal Brace
4. Air gap of the bottom cellar deck and water level

Equipment layout  - to identify any modification done

CP reading - using drop cell

Personnel safety devices

Under Water – General scope

From MSL Down to  sea bed (depend on inspection level of API RP 2SIM)

1. General Visual Inspection using video
2. Scour survey
3. Debris survey
4. Anode Survey & Anode counting
5. Cathodic Protection  reading ( at the outside part of Jacket leg at each horizontal elevation)
6. Marine Growth measurement
7. Riser survey
8. Thickness measurement (at every elevation and mid between elevation)
9. MPI on selected joints

Inspection Preparation

As built drawings

1. Member identifications
2. Equipments / loadings layout
3. Anode locations

Previous Inspection Report

Data required from Design Calc.

1. Maximum Marine growth thickness
2. Corrosion allowance
3. Low fatigue life joints
4. High stressed joints
5. Additional Inspection (if any)

Inspection programs - From SIM

1. Inspection Procedures (Diving company)
2. Inspection Personnel
3. Equipment – Calibrated
4. PPE

Above Water Inspection

General Visual Inspection

By Inspector To check for any corrosion, damage,  equipment layout changes or other which can affect the integrity of the platform, this to include :

1. All above water jacket member
2. All Welds
3. Crown piece / Shim plate
4. Deck leg, main girder, beam
5. Crane pedestal
6. Barge bumper / fender
7. Boat landing
8. Conductors, risers  and riser clamps
9. Personnel safety devices
10. Handrail, grating, stairs, swing ropes, helideck, boat landings, Risers & its clamps, bridges, survival craft support, crane pedestals, etc.  (see sec. 6 0f API RP2SIM)

Under Water Inspection

General Visual Inspection

by Diver or ROV Concerned with the entire structure from top down to seabed.

Most defect found offshore are primarily due to :

1. Collision by shipping
2. Dropped objects
3. Fatigue failure
4. Corrosion
5. Debris in contact with structural member

Visual  covers :

1. Structural – for any damage.
2. Risers & clamps
3. Anode counting & depletion
4. Debris survey
5. Scour survey
6. Boat Landings & Fenders

 

Debris survey

The objective of debris survey is to find any foreign material in contact with the structural member. To prevent the structural become “sacrificial anode” due to some metal in contact with the structural more anodic compare to the structural it self.

1. To look for any Indication of fretting corrosion at the contact point location
2. To record for any debris found
3. Is the deterioration of material that occurs at the interface of two contacting surfaces due to small movements between them in the presence of a corrosive  medium

Riser Survey

Shall include :

1. General corrosion
2. Damages
3. Condition of all riser clamps (bolts, Nuts, tightness) both riser side and bracing side
4. Seabed profile
5. Marine growth, debris etc

Why :

1. Un-tight clamp may cause riser movement which can cause fretting corrosion
2. Un tight clamps can create additional load to other clamp
3. Additional load  due to un-supported riser

Scour Survey

1. Seabed soil types and a combination of current, tidal and wave forces combine to create an environment which leads to seabed sediment being lifted and transported. The result is the natural depletion of soil in one area and its aggradations in another.
2. This natural occurrence known as scour, or erosion, is exacerbated when objects are placed on the seabed, such as pipelines, platforms, protection structures, umbilical and cables.
3. Scour (seabed sediment erosion due to wave and current action) can occur around offshore piles. Scour reduces lateral soil support, leading to an increase in pile maximum bending stress. Scour is generally not a problem for cohesive soils, but should be considered for cohesion less soils.
4. The current  around seabed will pick up and transport particles will leads to erosion. This current-carried particles act as an abrasive to wear away the structural surfaces.
5. Local Scour Any fixed subsea installation will disrupt tidal flow, causing the current to first decelerate in advance of it then accelerate beyond it, to form vortices and eddies which cause sediment to be scoured, i.e. lifted from the seabed and transported.
6. Global Scour Shallower ripples and wider depressions can also form beneath and extend to some distance from the installation. This is referred to as global scour and can impact on an individual installation or form through interaction between adjacent installations.