Secure, Recover & Install Caissons Safely
Platform caissons face severe corrosion in the offshore environment. Left unaddressed, a failing caisson risks becoming a dropped object, threatening subsea infrastructure and platform safety.
Our Internal and External Lifting Tools (ILT/ELT) enable the safe, secure lifting of damaged caissons and provide a controlled, planned recovery, engineered to the caisson's as-found condition. The same tooling is then used to install the replacement caisson.
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Case Study - 41" Caisson Recovery After Two Decades Of Repairs - North Sea
After more than 20 years of repairs, a 41" caisson faced a real risk of severing during recovery. STATS combined an ILT bridging the weakened sections with ELTs to secure and control the extraction.
Webinar - Safely Securing and Recovering Caissons
Discover how STATS’ Internal and External Lifting Tools safely secure and recover corroded offshore caissons without shutting down production. Watch now to eliminate dropped-object risks and protect your assets.
Caisson Damage
Securing In Place, Recovery and Removal
Caisson recovery is a two-stage process. STATS' lifting tools secure a failing caisson in position the moment corrosion is identified, stopping it becoming a dropped object. Once secured, the lifting tools (ILT or ELT or a combination of both) carry out the controlled removal - cutting and lifting away the damaged sections on your schedule, not in response to a failure in progress.
Stage 1: Securing in Place
ELT (External Lifting Tool)
ELT: What You Need to Know
- MECHANISM: Hydraulically actuated taper-locks grip the wall of the caisson under vertical load. Once pre-tension is applied, the lock holds independently of hydraulic pressure - if one hydraulic circuit is lost, the tool keeps its grip.
- INSTALLATION: The split-section design allows each half to install independently - useful where external supports restrict access, or where overhead height and lateral clearance are restricted.
- TYPICAL DEPLOYMENT: Two ELTs are generally used together - one lower on the caisson, one higher. The upper ELT is used to lift the caisson; the lower ELT is used to support the dead weight while the upper section is removed. The caisson is fully supported during all lifting and cutting activities.
- CERTIFICATION: Designed and tested in accordance with DNV 378, with a client- or third-party-witnessed Factory Acceptance Test (FAT) completed prior to mobilisation.
Stage 2: Recovery and Removal
Internal Lifting Tool (ILT)
Once the caisson is secured, STATS' Internal Lifting Tool carries out the controlled removal - cutting and lifting away the damaged sections for disposal, on a schedule the operator controls rather than reacting to a failure in progress. The same tooling is then used to install the new caisson.
ILT: What You Need To Know
- MECHANISM: The same fail-safe taper-lock mechanism as the ELT, in a compact design that passes through bore restrictions and adapts to varying wall thicknesses within the same caisson.
- INSTALLATION: For ILTs used to bridge a cracked or severed caisson, the linked length between the ILTs can be configured to a client's exact requirements, allowing easy installation even in areas of restricted access.
- TYPICAL DEPLOYMENT: Two ILTs are used to lift the cut caisson sections away once the ELTs have secured the caisson.
- CERTIFICATION: Designed and tested in accordance with DNV 378, with a client or third-party witnessed Factory Acceptance Test (FAT) completed prior to mobilisation.
Alternative: Final Extraction
Pin Lift Approach
Some operators prefer to complete the final extraction using a pin-lift approach rather than relying on the ILT alone, once the caisson has already been secured with the ELT.
Pin Lift: What You Need To Know
- METHOD: Holes are drilled either side of the caisson and a bar is fitted through, allowing the final lift to be carried out on the bar rather than the ILT.
- WHEN IT'S USED: ypically selected for the final extraction stage, after the caisson has already been secured and stabilised using the ELT.
- FLEXIBILITY: STATS supports both the ILT and pin-lift methods, and can advise on which suits the condition of the caisson and the client's preferred approach.
Specifications
Engineered to Every Caisson's Condition
Standard specifications for the ELT/ILT range are set out below. Every tool is engineered and DNV 378 certified to your caisson's exact condition, so dimensions outside this range are available on request.
ELT/ILT Specifications
- SIZE RANGE: 24" - 48" as standard
- DESIGN/SAFE WORKING LOAD: 55 Tonne
- CERTIFICATION: DNV 378 (DNV Standard for Certification of Lifting Appliances)
- LOCK MECHANISM: Hydraulically actuated taper-lock, fail-safe once pre-tensioned
- TOOL CONFIGURATION: Up to 4 tools per recovery (2x ELT + 2x ILT)
- TESTING: Client or third-party witnessed Factory Acceptance Test (FAT)
Caisson Damage
Local Everywhere
Instead of flying people and equipment all over the world, we've set up fully-functional bases in nine strategic locations. These bases enable us to employ local technicians, work with local manufacturers, and invest in local economies. They're a significant investment, but our regional bases are key to delivering the best possible service for our clients - and minimising the environmental impact of our work.
