Top Tensioning Systems (TTS): Pull type
The ICON Top Tensioner System (TTS) can be used to either provide primary support to the conductor or provide auxiliary support to the Blowout Preventer (BOP). This is often required when conductor sizes of 13 3/8” and smaller are used.
Applied constant tension as the primary support prevents conductor buckling, controls lateral deflection and helps reduce vortex induced vibration under wave and current loading. When used to support the BOP, the ICON TTS also prevents conductor overload below should any off-centre or horizontal loading be experienced.
Jackup rig conductor tensioning systems normally tension the conductor below the wellhead. When the BOP is installed, it is only restrained by the bending strength below the conductor and above the telescopic bell nipple. Many bell nipples are not designed to support lateral loading and bending on their telescopic joint.
Stabilisation of the BOP by keeping the BOP cranes attached is not recommended since the BOP must be free to rise and fall in harmony with the conductor tensioner stroke. If the cranes remain attached, this movement could transfer the conductor tension to the BOP cranes and overload them.
The solution is to have a top tensioner system which is able to support the weight of the BOP. The TTS is attached to the handling padeyes on the top of the BOP and to the underside of the drill floor or to the spare lifting lugs on the BOP crane travellers. With a TTS, if the BOP becomes off-centre or has an accidental horizontal load applied to it, there is a restoring force which prevents the conductor below, or the bell nipple, from being overloaded.
- System A - Drill floor Padeyes (underside)
- System B - BOP Crane Rail installation
The two tensioning cylinders are designed for 50t capacity each. They have a 1m stroke which is used mainly to facilitate connection and give flexibility in the BOP position. The working stroke requirement is only 150mm typically. Durable corrosion resistant rods are provided.
The connection to the BOP is normally achieved by using chain and shackles. This can be supplied to length or supplied over length and cut on the rig when the correct length is determined.
ICON has also supplied systems with 3m stroke cylinders which do not require any chain in the connection.
- ICON TTS can be interfaced directly to BOP crown or supplied with ICON ‘Pull-up’ Gripper Clamp for connection to conductor.
- ICON TTS system is complete with connections to ICON Conductor Tensioner Control Unit (CTCU).
- Standard features of the ICON TTS includes tensioning cylinders, CTCU, interface rigging (I.e. chain, slings, shackles etc.) and underside drill floor padeyes.
- Low maintenance requirements with use of parts, materials and coatings suitable for offshore environment. Including
- Complete with easy to follow operating and maintenance instructions.
- ICON can also perform underside deck arrangement and strength checks for interface of TTS system.
- Rental and purchase options available.
The TTS utilises the ICON CTCU (Conductor Tensioner Control Unit) with the benefits of being independent and extremely simple. However a system can be supplied that utilises the rig’s existing hydraulic supply.
Technical Specifications of a Pull type Top Tensioning System:
|Design Codes and Classification||DNVGL/ABS upon request|
|Ambient Temperature||-0oC to 50oC|
|Tension Capacity||60-300Te (or as required)|
|Deck Connections||From 2 to 4 as required|
|Typical Stroke||1000mm (or as required)|
|Operating Pressure||215-230 bar|
|Nominal Weight||Variable based on 2 / 4 point|
|Hydraulic Fluid||Water Glycol|
Typical Tension Variation Vs Stroke:
Note: Control unit can be customised to suit maximum conductor tension variation allowances