eSubsea can design and deliver standardised suction anchors or suction pile anchors, fast track and with a low cost. We provide all required structural analysis and design of suction anchors or suction caissons for your project and site specific requirements.
The holding capacity (vertical, horizontal or a combination) is typically 10 – 10,000 Tonn (100 kN – 100 MN) and it can be designed for all soil conditions.
Our suction anchors can be used as mooring and anchoring for:
- Deepwater applications
- Drilling rigs and floating offshore platforms
- TLP (Tension Leg Platforms)
- Semi Submersible
- Floating offshore wind foundations
- Semi Subs
- Buoys for electrical cables
- Aquaculture structures
- Fish farms (Salomon, Trout, Cod etc.)
- Fish cages
- Solar energy floating system
- Solar panels farms
- Underwater equipment
- Wellhead load relief systems
- Underwater monitoring
- Testing equipment
- Ships, docks, berths, pontoons and more
Design of Suction Anchors
The suction pile or anchors will be designed and calculations done for all seabed conditions and design loads such as installation, fatigue and removal loads from suction/over-pressure and levelling. Suction anchors specially designed for wellhead load relief systems or mooring for offshore wind foundations can also be provided. These will be subjected to fatigue loads.
The seabed conditions can be all from soft clay to hard sand. Geotechnical design including stability and holding capacity will be included for anchors in soft clay, hard clay and sand.
The suction anchor also known as suction piles or suction caissons can be used in many applications as shown above which will determine the design and which loads will be applied in the design analysis. It can also be an integrated part of offshore structures such as a template and manifold foundation of fixed offshore wind turbine foundation. In this case, the bearing capacity and short and long time settlement will be designed as required.
Anchor Design Codes and Loads
The anchoring foundations of suction anchors also follow the rules, technical requirements and recommendations of DNV-ST-0119 Floating wind turbine structures.
Analysis of structural collapse during suction anchor installation and retrieval (skirt buckling analysis) will be performed according to DNVGL recommended practices (DNVGL-RP-C202 and DNVGL-RP-C208). Tolerances and equivalent imperfections according to NORSOK M-101 will be included in the non-linear finite element analysis.
The penetration resistance and necessary under-pressure will be outlined calculated based on soil data available and the requirements for the suction and pump system given. Pending on the sensibility and importance of the stability and holding capacity, these geotechnical evaluations will in most cases be done by our geotechnical partners.
The suction anchor, piles or caissons can be permanent until end of field or temporary for only the duration of the specific operation whet they provide seabed support. All load conditions will be included in the engineering and design from support during fabrication on the manufacturing yard to final recovery and removal. The lifting analysis will normally be based on DNVGL-ST-E273 if not specified otherwise by the Client. This is a conservative approach and an option is to perform hydrodynamic analysis using the specific installation vessel data and limiting sea state or significant wave height.
The anchors will have main padeyes and lift points for installation lift but can also have temporary secondary padeyes for transportation and handling. Large suction anchors require significant crane lifting height and it might be more practical to weld on a temporary padeye for horizontal handling. eSubsea can perform these transportation and handling analysis with both structural design and the finite element method if required.
Subsea Anchors Corrosion Protection
The anchors will be protected from corrosion by sacrificial anode. The corrosion protection system is based on the surface area and the required time to be under water.
All required documentation such as equipment lists, fabrication drawings, design reports, corrosion protection report, lift test procedures, installation and retrieval procedure are included in the suction anchor engineering. On delivery, a certificate of conformance will be issued. If the purpose of the suction anchor is temporary, a storage and maintenance manual will be included.