Introduction
C-lok is a simple diverless subsea structural connector activated via a single hot stab operation using a standard Class III (3,000 psi) Work-class ROV. The device is offered in three basic capacities. The C-lok 900 offers a higher load connector capacity, the C-lok 300 provides for mid range and the C-lok 150 for lighter duty applications. The patented C-lok technology for all three is described in the C-lok 900 product notes.
The C-lok Connector provides robust and reliable resistance in all 6 degrees of freedom.
This system is operable at any water depth and may be activated at any pile penetration depth so pile refusal is of no concern.
This permanent connection is available over the full range of API standard diameters as well as diameters well beyond. Uniquely C-lok may be released permitting equipment/structure recovery. The structure may then be redeployed and the C-lok re-activated at any stage.
C-lok is offered with two types of locking mechanism. The Self Locking Wedge option may be used where restrictive access is an issue or the Twin Locking Screw option maybe preferred using a simple ROV manipulator operation. Both methods are field proven and offer equally reliable locking methods that may be tailored to suit the application.
As a result the locking operations may be used to suit an unlimited range of diameters and capacities using a standard ROV interface in both ROT and ROV ‘Fly to Place’ formats.
The Removable Hydraulic Unit (RHU) tool is available in a range of sizes to suit the application. The lighter fly to place tool has a submerged weight that is within standard Class III Work Class ROV assisted lifts whereas the Remote Operating Tool (ROT) version is intended for vessel assisted deployment.
Both C-lok formats are field proven and LRS (Lloyds Register of Shipping) approved designs.
Application
C-lok is the general purpose connector for all subsea tube to tube structural applications. Equally suited for multi-pile (post driven) and monopile (pre and post driven) arrangements. It is also ideal for attachment of subsea structural modules where release and recovery of the module is either a planned or contingency event.
C-lok is a fully adaptable and patented clamp connector that not only offers the widest range of fully diverless ROV based applications but is also available in a diver assisted alternative.
Conventional oil and gas subsea structures have submerged self weight in the region of 50 Te to 150 Te. Allowing for typical operational and environmental loads the maximum pile loads for a four pile structure will often range from 30 Te to 80 Te and for extreme environmental loads and fishing interaction may increase to 100 Te. For a nominal operational capacity of between 100 Te and 120 Te the C-lok 150 is available. For more onerously loaded subsea structures the C-lok 300 is available. For the highest loaded structures or for typical monopile connections the C-lok 900 is typically recommended.
The key advantages of the diverless C-lok 300 is its ability to guarantee full engagement at any water depth and at any depth of pile penetration regardless of soil type or characteristics. This version of C-lok has been developed to suit the widest range of applications and structure sizes whilst using the compact ‘fly to place‘ tool.
Key features and advantages
- Diverless
- Quick, engagement complete in less than 5 minutes
- Releasable, allowing disengagement and re-engagement in less than 15 minutes
- Fully caters for pile refusal ensuring connection regardless of pile penetration achieved
- Single tool may be used repeatedly for a wide range of pile sizes
- Operates at any water depth
- C-lok Connector has full qualification testing and is a field proven LRS approved design
- Operated by a standard Workclass ROV (Class III) without specialist ROV tooling
- Common ‘Fly to Place’ tool (60 kg) available for C-lok 300 and C-lok 150 versions
- Suitable for full range of API pile sizes and fabrication tolerances
- Allows repetitive use of the hydraulic tool with a full redundancy
- All hydraulic equipment is recovered to surface using a simple vertical lift
- Suitable for impact or vibrohammer and suction piles
- C-lok unit may be integrated into the main structure fabrication sequence at any stage
- The connector is able to accommodate a wide range of seabed inclinations
- No additional deck space required
- Tools preset on the C-lok (PCU) avoiding need for separate tool deployment
- Tools self centering using self-weight and may be recovered by a simple lift off
- Allows full FAT testing in the shop along with load tests if required
- Permanent works all carbon steel – with full dedicated CP anodes
- High capacity device (example 290 Te for a 610 x 25.4 WT pile)
- Resists all load types (6 DOF) including torsion.
- Ideal for pre-piling post piling, multiple and monopile foundations
- Range of RRU tool capacities available (C-lok 300, C-lok 750, C-lok 900)
- Lloyds Register Approved Design
Outline offshore procedure
The following procedure is based on a post installed pile for a conventional multi-pile subsea structure foundation:
- Lower structure with ‘Fly to Place’ tools pre-mounted and land on seabed
- If levelling operation required see Subsea Structure Levelling product details
- Lower pile and penetrate through pile sleeve allowing pile to self penetrate into seabed
- Remove dummy hotstab and placed into dummy receptacle
- Stab hotstab into receptacle
- Deliver ROV supply (max 3000 PSI)
- Confirm required analogue pressure reading on C-lok tool interface (typically 18,500 PSI)
- Insert Locking Pin actuator and rotate clockwise noting number of turns
- Open valve to relieve cylinder pressure
- Insert Locking Pin actuator into Cylinder Release Pin and rotate anti-clockwise two turns
- Lift off ‘Fly to Place ‘ tool and recover to vessel
- Repeat above procedure for each pile
Fabrication
Units are fabricated, adjusted and machined prior to leaving the workshop. Each unit is subject to a complete FAT and optional load tests before shipping
Fabrications and design are carried out under a fully implemented BS EN ISO 9001 approved Quality Management System
All components, including control interface operators are detaile designed in house to ensure a robust offshore and in place performance
Testing
BECL provide full FAT and optional Load Test facilities to demonstrate both functional performance and perform hydraulic pressure testing and qualification load testing of the C-lok units
Design and Documentation
Video – C-lok 300 SIT Operations
Video – C-lok 300 ‘Fly to Place’ Tool
Video – outline offshore procedure