COMPANY: EMAS-AMC
PROJECT TITLE: Chevron 2012-2014 Installation Campaing Platforms & Pipelines Installation
CLIENT: Chevron Thailand
LOCATION: Thailand
YEAR: 2012
VESSEL: Derrick Lay Barge (DLB) Lewek Champion
SCOPE OF WORK: Installation of the Erawan 2 FSO Mid Water Arch.
MY INVOLVEMENT: I was on-board to install the Mid-Water Arch + Pipeline End Manifold.
INTRODUCTION
EMAS AMC Pte Ltd has been contracted by Chevron Thailand to perform the installation of platforms and pipelines as part of the 2012 – 2014 Chevron Installation Campaign. The works involve installation of wellhead platforms and associated pipelines for the further continuous development of the Chevron Thailand Oil and Gas fields in the Gulf of Thailand.
EMAS AMC shall mobilize its installation barge, the Lewek Champion, on or about the 13 February 2012 for an infield date of 01 March 2012. The installation activities are estimated to last approximately 6 months / 180 – 200 days. The installation program shall be split between pipeline installation phases and platform installation phases. A mode change involving mobilization of required equipment and personnel will be required when switching between pipelay and platform installation mode.
The preliminary main scope of work requires installation of up to 13 pipelines and 12 platforms for 2012 Campaign with additional job scope of FSO hook up/stabilization column installation and E&I room installation. Details on 2013 and 2014 Campaign will be further updated in due course.
CARGO BARGE LOAD OUT AND TRANSPORTATION
General
Erawan FSO II MWA is to be loaded out on 280 Class barge, it is to be loaded out in a transverse arrangement with the tether base on the port side and MWA on the starboard side, this is such that it can be lifted off in a stern condition and the crane will only have to boom up to lift each individual package. For the MWA load out refer to drawing: MWA-INS-FAB-403-S01 in appendix-1.
Sea Fastening Access
The MWA will be adequately seafastened with seafastenings positioned such that there are no obstructions caused by chain/rigging laying on top of them. This, along with adequate supervision of the load out, will help ensure that no further movement of these items is required prior to cutting and lifting the MWA. It will also assist in reducing the chance of any seafastening still being attached when the lift is made.
Cargo Barge Load out and Manifest
The following table provides a typical list of the major components and materials that are to be loaded out onto the cargo barge.
| ITEM | DESCRIPTION | QTY |
| 1. | Mid Water Arch, pre-rigged to tether base and lift rigging (including spreader bar) | 1 unit |
| 2. | Tether base, pre-rigged to Mid Water Arch | 1 unit |
| 3. | Piles c/w 4 each pile locking pins, 36” x 38.1mm WT, 38.9M long | 2 each |
| 4. | Lift rigging and spreader bar from MWA to hook | 1 unit |
| 5. | Riser clamp bolts and spares (for riser installation) | 4 length |
Barge Arrival and Demobilization
When the material transportation spread enters the COMPANY concession area, management of the spread will become the responsibility of the LCP. Prior to this, the LCP will provide instruction via email to the transportation spread a few days in advance to give sufficient time to transit to rendezvous point. The instruction shall include essential information like the point of contact, radio frequency, field entrance protocol and etc. LCP admin, barge master, superintendent & field engineers will be included in the distribution list for tug DPR.
A standing instruction will also be provided by COMPANY’s EPC Contractor to inform the tug master of their responsibilities offshore. The responsibility of the tow tug is to tow the material barge to site and back, The responsibility of the LKT is to bring the material barge alongside the LCP during installation. However, if site condition requires, the tug may be called to assist LKT in bringing the material barge alongside.
Upon arrival of the cargo barge at site, the tow tug master will report immediately to LCP and should not approach within 8 km of any vessel or structure in the area before contacting the barge superintendent.
The barge superintendent on LCP will take control of the tow within 8 km of the derrick barge and instruct the tow master accordingly.
Upon completion of installation and approval from COMPANY CAR, the tug master will receive instruction from LCP admin that the barge spread can be released from field. A cargo manifest detailing the balance materials on board the barge spread will be forwarded to COMPANY’s EPC Contractor yard engineer, and at the same time COMPANY CAR will notify COMPANY’s EPC Contractor of the release of the barge spread.
Tow tug is to inform satun marine control & benchamas offshore marine coordinator when departing the chevron field (area of operational control).
MARINE EQUIPMENT
Marine Spread
The LCP is a non-self-propelled DP2 combination heavy lift pipelay barge, designed to effectively operate in hostile weather conditions. The barge measures 143m long by 40m wide, with mean operating draft of 6.5 m.
The barge is equipped with two amclyde pedestal cranes. These cranes have a maximum capacity of 68MT with a boom length of 48m. The main crane is a 900 MT huisman crane with boom length of 70m, and a main block capacity of 900 MT.
The LCP will have on board air and SAT diving support as well as a work class ROV.
All of the barge accommodation is located above the main deck, and is fully air conditioned with a mess hall and recreational facilities. A helideck is located over the bow superstructure and is capable of accommodating an S61 helicopter.
The following are the anticipated support vessels assisting the LCP during MWA installation operation:
LCP Tow Tug – by EMAS-AMC
Contractor Material Barge and Tow Tug – by EMAS-AMC
Material Barge and Tow Tug – by COMPANY
Supply Boat – by COMPANY
Crew Boat – by EMAS-AMC
LCP MWA Installation Equipment
| ITEM | DESCRIPTION | Name of Barge / Vessel | QUANTITY |
| Major Work Barge | |||
| 1 | MWA Installation Barge | Lewek Champion | 1 unit |
| 2 | AHT #1 | Lewek Kestrel | 1 unit |
| Capital Asset Barge | |||
| 1 | Material Barge | Crest 2801 | 1 unit |
| 2 | Towing Tug | Crest Ocean | 1 unit |
| Hammer spread | |||
| 1 | IHC S-280 Pile Driving Hydraulic Hammer, Modified with Subsea hammering Sleeve for underwater work c/w associated power pack and control van | – | 1 unit |
| 2 | 24” – 42” IHC Internal Pile Lifting Tool, Set at 36” | – | 2 unit |
| Survey & Positioning | |||
| 1 | DGPS Units | – | 2 unit |
| 2 | Barge Heading Gyro Unit | – | 2 unit |
| 3 | USBL Beacons | – | 10 unit |
| 4 | Subsea Bullseye, Mounted to Tether Base | – | 1 unit |
| Remotely Operated Vehicle (ROV) | |||
| 1 | 150HP ROV System c/w 3” wire cutter | – | 1 unit |
| 2 | Control Shack | – | 1 each |
| 3 | 20ft Equipment Container | – | 1 each |
| 4 | Launch & Recovery A-Frame | – | 1 unit |
| Diving Spread | |||
| 1 | Saturation Diving System | – | 1 lot |
| 2 | Air Diving System | – | 1 lot |
SITE SPECIFIC SURVEY
Pre-Installation Survey
A Pre-Installation Debris Survey will be conducted, consisting of the following:
- The Survey Area will consist of the Tether Base footprint and a corridor of 10 metres around the perimeter.
- Parallel lines run at a spacing of 5 metres, covering the Tether Base seabed footprint & perimeter.
- Video and Sonar (~20m Range & 150° Sonar)
- Water depths at the four corners of the structure and at the pile locations shall be recorded to determine slope.
Any debris or abnormalities discovered during the pre-installation survey shall be reported to CAR and CMR and remedial works discussed and suitably risk assessed prior to being performed.
Survey during Installation
Survey for positioning, orientation, elevation and level of the MWA will also be conducted meanwhile during installation, as hold points to confirm that tolerances are met. Refer to document: 16002-EMA-QA-ITP-0003 “Inspection and Test Plan (FSO System Installation)”.
Final Surveys after installation
Post installation the following surveys will be performed.
As-built Position and Level Survey
Subsequent to completion the MWA Installation, a set of subsea surveys will be Performed to check the following:
Position and orientation of the MWA and Tether Base, by use of USBL Fixes
Level of the Tether Base, by use of subsea Bullseye.
As-built Pile Penetration Survey
Tether Base pile as-built penetration will be performed after the pile driving.
Post Installation Riser Clamp Survey by ROV
The ROV will perform the survey to confirm the clamp has not been damaged.
Post Installation Debris Survey by ROV
The final seabed debris survey will be carried out by ROV, once all construction activities have concluded on MWA installation.
Any debris or deformities discovered during the post-installation survey shall be reported to CAR & CMR and remedial works discussed and suitably risk assessed prior to being performed.
Anode Survey
Divers or ROV will perform the survey to confirm if all of the anodes are still intact on both the Tether Base and Mid Water Arch.
Mudline Survey
Divers or ROV will perform the survey to find out how much the MWA has settled into the seabed after installation by the level of the mud relative to the skirt of the MWA
Limiting Weather Criteria / Weather forecasting
Limiting weather criteria for all critical lifts for MWA includes lifting MWA from cargo barge, lowering through splash zone, position the tether base on the seabed, pile lifting from cargo barge, stabbing into tether base pile sleeve, pile driving and normal operations are as follows:
| Condition | MWA Lift | Normal Operations |
| Significant Wave Height | 0.6m | 1.5 m |
| Wind Limitations | 18kts | 20 Kts |
| Current Limitations | 0.8 kt | 1 Kt |
However barge operation shall remain the discretion of the barge superintendent, in consultation with Chevron CAR.
The LCP shall receive local weather information from OWS provided by COMPANY. Weather forecasts shall provide the basic tabular forecast as well as surface weather charts drawn with isobaric lines identifying wind force/direction, swell & wave height/direction/period. Weather radar & real time weather data (wind speed, wave heights, etc.) are also available.
Before critical lifting operations, a suitable weather window will be required to be confirmed by weather reports. This weather window should be 48 hours for the Mid Water Arch, so as to allow enough time to get both piles into the Tether base after placement of the Mid Water Arch.
MWA INSTALLATION
Safety
It is to be noted that the MWA Buoy is a pressurized vessel that is filled with nitrogen to a pressure of 5.1 Bar, please exercise caution when working around the buoy.
PLEM 9, which is located 76.5m to the east of the MWA is a live gas PLEM, caution must be exercised while lifting piles, vessel is to be setup in such a way that no lifting over pipelines is to be performed.
General
The MWA will be lifted in a single piece off the deck of the material barge, at the stern of the LCP, a stern lift being utilised so as to maximize the hook height, this will reduce the need for any Handshake rigging, thereby increasing the efficiency of the installation and reducing the weather window required
Installation Location
The MWA design location is based on the PLEM9 as built location which has been the basis for the whole field design.
MWA Location is as follows:
| Field Location | Erawan | |
| Coordinates of MWA Centre (Design) | 744,274.1 m E | 1007557.5 m N |
| Water Depth / Mudline Elevation | 60m / 196.85’ | |
| Design Orientation | 6” Riser section to north, 10” to South* Tank Centre Line to 0° Grid. | |
* Design orientation is to be clearly identified on MWA prior to installation.
Orientation is to be controlled by two separate means, firstly there is a docking frame on the ROV with associated docking station on the MWA, this allows the ROV to mate with the MWA and use its thrust (150 Horsepower). Secondly there is a holdback padeye on the spreader bar which can be used for bulk orientation, however spreader bar orientation is to be used only if required as there is a large distance between the spreader bar and the tether base which will be susceptible to twist.
Whilst ROV is assisting in final positioning, all fixes must be taken from the tether base not the ROV, this is because the Docking station is offset from the centre of the tether base.
However for guidance the ROV can use the following offsets:
Docking Station Orientation offset : Perpendicular to centreline of tank, offset +90°.
Docking Station Location Offset : 9200mm south (in line with tank centre line)
543.7mm west (to face of docking recepticle)
Installation Tolerances
The installation tolerances given for the MWA are:
Position : ± 1.5m of design position
Orientation : ± 5° of designed orientation.
Verticality of Tether Base (Level Tolerance) : ± 5° of designed verticality.
Pre-Lift Checks
The MWA lift shall not take place until the following items have been checked and found acceptable. For the pre-lift check list refer to Appendix 2: 16002-EMA-OP-PCL-0001 “Pre-lift check list for critical lift”.
- Pre-lift/JSA Meeting
Prior to commencement of any work or task, a Job Safety (risk) Analysis (JSA) shall be completed for the operation at hand, and toolbox talks held including all involved personnel.It is to be noted that the MWA buoy is a pressurized vessel that is filled with nitrogen to a pressure of 5.1 Bar, please exercise caution when working around the buoy. - Debris Survey
An ROV debris seabed survey at the design location must be completed to ensure that the installation site is free of debris. A pre-installation debris survey will be conducted, consisting of the following:
– The survey area will consist of the Tether Base footprint and a corridor of 10 metres around the perimeter.
– Parallel lines run at a spacing of 5 metres, covering the Tether Base seabed footprint & perimeter.
– Video and sonar (~20m Range & 150° Sonar)
– Water depths at the four corners of the structure and at the pile locations shall be recorded to determine slope.Any debris or abnormalities discovered during the pre-installation survey shall be reported to CAR and CMR and remedial works discussed and suitably risk assessed prior to being performed. - Cargo Barge
Check the draft of the barge and ensure that no damage has been sustained to the barge or the permanent equipment during the tow. - ITP
Confirm that ITP is reviewed and all ‘HOLD’ points reviewed before proceeding with the installation. Refer 16002-EMA-QA-ITP-0003 for FSO ITP. - Structure
Review the general condition of the MWA and examine for damage to or loss of any components with particular attention given to the following; - The MWA buoyancy tanks should be checked for any dents or damage to flanged fill-nozzles. It will indicate potential loss of internal pressure from the buoyancy tanks.
- Riser Clamp is fully intact
- No anodes are damaged
- No Damage to Anti Foul Paint on Mid water Arch
- Tether Chain is fully rigged up as per its drawing (112-G-S-50011-01), chain should have NO twists and safety pins in all shackles.
- Concrete ballast blocks are fully intact and secured on MWA Tether base.
- Rigging and spreader bar are completely rigged up and loaded out as per drawing, all shackles have safety pins attached. Refer to drawing: MWA-INS-FAB-403-S01 in Appendix 1.
- Trunnions which are to be used for lifting the MWA have correctly got ROV friendly pins attached (to be checked by ROV supervisor). Refer to drawing: 16002-EMA-OP-FSO-DWG-0057 “Sling keeper pin on trunnion Mid Water Arch” in Appendix 1.
- Weather Forecast
Review the prevailing and forecasted weather conditions. The final decision for the lift to proceed will be made by the Barge Superintendent after consultation with the CAR and Satun Weather Station.
- MWA Familiarity
The ROV and Diving Supervisor’s are to review the MWA structure to gain familiarity with the overall configuration. Any Spray paint for reference purposes is to be applied at this point
Weight Control Report
The Weights of the packages vary based on what items are picked up and what is in water at any one time, the expected non dynamic loads are listed as below.
| Details: Lift Weights, Including Rigging (Non Dynamic, For Reference) | ||
| Weight MWA only | 122.605 | MT |
| Weight MWA Before Tether Base Up | 130.378 | MT |
| Weight MWA + Tether Base In Air | 390.049 | MT |
| Weight MWA + Tether Base In Water | 285.259 | MT |
| Weight MWA In Water | 60.407 | MT |
Maximum Expected Weight
The maximum expected weight is based on a DAF of 1.56, this is a conservative DAF based on a 1.3 DAF multiplied by a additional 1.2 DAF for Slamming loads.
The maximum expected lift weight will be at the point where the Tether base is being lowered through the splash zone, this is demonstrated as below
| Maximum Expected Lift Weight | ||
| Weight MWA + GB In Air | 364.171 | MT |
| Grommet Weight (2 Grommets) | 7.396 | MT |
| Spreader Bar Weight | 13.894 | MT |
| 400MT Shackles Weight | 0.944 | MT |
| Spreader Bar Slings Weight | 3.644 | MT |
| Total Weight | 390.049 | MT |
| DAF (@1.56) | 218.427 | MT |
| Maximum Expected Lift Weight | 608.476 | MT |
Mid Water Arch Installation Sequence
- As the MWA is installed after a MODE CHANGE from previous work, conduct tool box talk onboard vessel with all relevant crew members including riggers, crane operators, deck foremen, superintendent, field engineers, ROV crews, divers and vessel captain.
- Following procedures to be followed by the LCP when entering or departing a new field / location:
· Marine control to be contacted when the LCP first arrives at the outside boundary of COMPANY fields (project start).
· Marine control to be informed when the LCP arrives at/departs from EFSO 2 location.
· Field OIM/radio room to be informed when the LCP arrives at/departs from EFSO 2 location.
· Marine control to be contacted when the LCP departs the outside boundary of COMPANY fields (project end).
· DP check list to be completed
Before arrival of LCP and spread in field, a kick off meeting shall be held. - At the beginning of each shift a toolbox meeting is to be performed, this will involve all direct crew involved in work. Continual updates of scope of work and JSA’s are to be discussed during these meetings. All attendees are to sign an attendance sheet.
- Hold a pre lift meeting with all relevant parties, at which decision is to be made on which barge heading as per sea conditions. Set up barge nearby to final placement position whilst not placing the barge over or adjacent to any in field assets.
Safety:
It is to be noted that the MWA Buoy is a pressurized vessel that is filled with nitrogen to a pressure of 5.1 Bar, please exercise caution when working around the buoy. The MWA is to be installed in close proximity to PLEM 9, which is located 76.5m to the east of the Mid Water Arch. All pipelines to PLEM 9 are in an easterly direction from PLEM 9.
Note:
· Meanwhile LCP (barge admin/barge foreman/superintendent) give instruction to material barge tug to stand by at rendezvous point.
· LCP will be set up with prevailing conditions (mainly current) to port forward quarter.
· Visual inspection and ITP of pressure vessels are to be performed prior to cut seafastening. - Deploy ROV to perform debris survey and recover any hazardous objects. ROV to check the seabed profile for slope issue COMPANY CMR and FE are to be present during survey.
Note: Debris recovery (If required) will be discussed with field engineer and CAR / CMR before any decision is made to remove it. ROV will read the water depth at proposed corners of the tether base (4 positions) to visualize sea bed profile. - By use of LKT and if required, the material barge tug, bring material barge alongside the stern of the LCP. Refer to attached DWG 16002-EMA-OP-FSO-DWG-0042 in Appendix 1.
Note: Barge Foreman to ensure that yokohamas are in position on the stern of the LCP. - INSTALLATION NOTE: The following activities shall be performed once the gangway is installed between the material barge and the LCP.
Perform post-towing survey with FE and COMPANY CAR. - Install the Subsea Bullseye on the MWA Tether Base. Install USBL Beacons on the corners of the MWA Tether Base.
- Start cutting seafastening to 75% after approval from CAR and ABS.
- Rig-up main lift slings and the tugger lines to the spreader bar
Note:
· All rigging installed will be inspected by CONTRACTOR’s field engineer at yard during load out to confirm installed rigging complies with approved engineered lift drawings.
· Visual inspection and checking of relevant ITP points on MWA and Tether Base to be performed prior to cutting
· MWA Buoy is pressurized at 5.1 bar, exercise caution whilst cutting - Conduct Pre-Lift Meeting with all concerned parties.
- Get approval from CAR onboard to proceed with the lift.
- Cut the remaining 25% sea fastening.
- Once seafastening completely cut 100% to ensure un-authorized personnel move away from MWA location on cargo barge prior to perform MWA lifting operation.
Refer to attached drawing ‘16002-EMA-OP-FSO-DWG-0054, FSO ERAWAN-2 field layout’ in Appendix 1 which shows the pipelines, PLEM and MWA gravity base target location.
The MWA is to be lifted from the cargo barge and lowered through splash zone as far as reasonably possible from the PLEM and pipelines. - Release material barge and tow clear of LCP location with LKT
- Boom down Tether Base until at least 15m clear from stern of LCP (radius approx. 22m)
- Lower Tether Base through splash zone.
- Continue lowering until MWA is fully through splash zone
- Once MWA is through splash zone, deploy ROV to monitor lowering of Tether Base to bottom.
- Rotate Tether base using ROV as required, the tether base has been set up with a ROV stab in bucket for orientation. The ROV is to mount into the buckets then by use of its compass change the heading of the tether base, under instruction from barge foreman / superintendent.
- Slowly lower down the tether base until 5m (approx.) clearance from the seabed and check the tether base orientation and position.
Once Tether base is confirmed by COMPANY CMR to be on target based on ROV orientation and position, place Tether base on seabed. - Take Fixes from Survey to ensure Tether base is within position and orientation tolerances
- Once position is confirmed to be accepted by CMR, fully slack the rigging, ROV to proceed to trunnion location.
- ROV to remove sling keeper pins and guide out all lift grommets out from MWA trunnions.
- Once all grommets are removed from the trunnions, return spreader bar to surface and derig from crane
- Preliminary position and orientation shall be recorded by ROV. It also takes initial surveys of level and mudline at this point.
PILE INSTALLATION
The Tether base is designed for two piles to be installed so as to anchor it further after placement. These piles are 36” diameter X 38.923m long and designed for interchangeable positioning.
- The sequence proposed below is a guideline only, under the discretion of barge superintendent the sequence may be changed to suit conditions and to optimize operations.
- Specific attention to be given to the on-bottom stability of the tether base
- The pile guide casings have sufficient strength to self-support the pile under minimum pile self penetration.
- Review of drivability assessment shall be performed before commencement of work. The pile drivability report to be referred and included in appendix-3 Rev-0.
Level Tolerances For Stabbing Piles
Tolerances have been defined as to the maximum angle the Tether Base can be on to install piles without risk of geotechnical failure.
The following level tolerances have been defined for the longitudinal axis:
Maximum Tilt for tether base stability : ± 1.5° of design tilt
Pile Details
| Pile Make-up | O.D. | W. T. | Length (including Cut-off) | Cut-off | Weight | Max Stick up length |
| mm | mm | m | m | MT | m | |
| Lead Section (P1) |
914.4(36”) |
38.1mm | 38.923 m (75’) | – | 32.05MT | Full Length |
Pile Drivability
A site specific pile drivability study report has been included in the appendix 3. This includes both the estimations of pile movement during stabbing and self-penetration of the piles and the expected energy requirements for pile driving.
Weight Control Report
The maximum expected weight of Piles plus rigging is as follows
| Maximum Expected Pile Lift Weight | ||
| Weight of Pile (Factored) | 35 | MT |
| Rigging Weight | 2.5 | MT |
| Total Weight | 37.5 | MT |
| DAF (@1.3) | 11.25 | MT |
| Maximum Expected Lift Weight | 48.75 | MT |
The maximum expected weight of the hammer plus rigging is as follows:
| Maximum Expected hammer Lift Weight | ||
| Weight of hammer (Factored) | 51 | MT |
| Rigging Weight | 2.5 | MT |
| Total Weight | 53.5 | MT |
| DAF (@1.3) | 16.05 | MT |
| Maximum Expected Lift Weight | 69.55 | MT |
Pile and Pin Installation Procedure
PLEM 9, which is located 76.5m to the east of the MWA is a live gas PLEM, caution must be exercised while lifting piles, vessel is to be setup in such a way that no lifting over pipelines is to be performed. Refer to drawing: 16002-EMA-OP-FSO-DWG-0054 “FSO ERAWAN-2 Field layout” in appendix 1.
- At the beginning of each shift a toolbox meeting is to be performed, this will involve all direct crew involved in work. Continual updates of scope of work and JSA’s are to be discussed during these meetings. All attendees are to sign an attendance sheet.
Safety Note: Lever Type Chain binders shall not be used for pile seafastening. - Piles shall be handled using the ILT which is suitable for subsea operating mode. Handling of hydraulic hose may require assistance from starboard side crane. There will be a safety sling in case of ILT failure.
- Twin Crane upend first pile and overboard. During pile lowering, ROV is to monitor the clearance between pile and the buoyancy tanks. This pile over-boarding operation shall be monitored and to be performed away from any structures. Note: PLEM 9, which is located 76.5m to the east of the MWA is a live gas PLEM, caution must be exercised while lifting piles, vessel is to be setup in such a way that no lifting over pipelines is to be performed.
- Using ROV as a guide to keep it away from MWA, lower pile and stab into tether base
- Stab and self-penetrate 1st pile on the highest pile guide, FE to note down self-penetration of pile. ROV to note the self-penetration of piles.
- Repeat Steps 3-5 to place the 2nd pile into the Lowest Pile Guide
- Deploy S280 Hydraulic hammer over the starboard side and lower to Tether Base.
Note: Hammer shall be set up for subsea operating mode. Hydraulic hoses deployment shall require assistance from starboard side crane - ROV to monitor Clearance between piles and MWA Buoyancy tanks during Lowering operation
- Stab hammer onto highest Pile and commence hammering while monitoring with the ROV, ROV to perform checks on hammer hoses intermittently to ensure no tangle with the MWA Buoyancy Tank. The hydraulic hoses properly secured to crane wire on running shackles.
- Hammer pile to full penetration of 30m (30m Calender Passes below lip of Pile Sleeve). Pile driving needs to be monitored all the times to avoid the piles are over-driven and ensure a risk of fouling the hammer with the sleeve and getting it stuck.
- Recover hammer and stab on other side pile
- ROV to check that all hoses and lines are clear, then recover hammer to surface
- Deploy saturation divers to Tether Base
- Locate pin installation hub and hole, Check that Cutting protection coupling is installed and fully intact.
- Broco hole through pile, hole is to be 90mm diameter to allow the screw in locking pin to grip onto it.
Note: Ensure broco area is clear of mud and other debris prior to commencing broco - Remove Protection coupling, inspect hole cut, if hole cut is the correct dimension, install locking pin. Check Locking pin fit. If not fully installed, remove and touch up hole as required
- Install the locknut, remove Pin Eyebolt and screw in earthing strap
- Repeat steps 14-16 for the 7 remaining pin locations
- Recover divers to surface and perform final as built survey with ROV. Final pile penetration to be recorded and made part of the final report.
Key Information
Pile Refusal Criteria
The point where the pile driving with a proposed hammer has to be stopped and other methods instituted (e.g. drilling system or using a powerful hammer) is defined as per following refusal criteria that has been established considering the recommendations of the pile hammer manufacturers (e.g. IHC) in order to provide safe use of CONTRACTOR’s equipment.
The pile refusal shall be as per pile drivability report, Hammer manufacturers recommendation as follows:
Pile driving refusal is defined as the point where pile driving resistance exceeds either
a. An average of 250 blows per 25 cm pile penetration over 6 consecutive calenders (150 cm)
Or;
b. 650 blows per pile penetration.
If there has been a delay in pile driving operations for one hour or longer, the above shall not apply until the pile has been driven at least 25 cm following resumption of pile driving.
However in no case shall the blow count exceed 1000 blows for 25 cm of penetration.
Pin Installation
Divers are to install pins in the piles to secure the piles to the Tether Base, the pins are designed such that they screw into a welded hub on the tether base sleeve. So that the hub threads are not damaged during the cutting of the pin hole, a protection coupling will be provided which when screwed into the welded hub will prevent arc out / unintentional burning of the threads.
There is one protection coupling supplied for each hole to be cut, ensure that all protection couplings are installed prior to installation of the MWA.
As built documentation requirements
The following documents are to be provided as as-built documents and will require all the relevant survey to be completed prior to the end of the installation works.
- MWA Position & Orientation
- MWA as built level and elevation.
- QA/QC Records and documents
- ITP Documents
- ROV Survey Videos, including debris
- Pile traceability sheet (attached in appendix 3)