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Telescopic joints

A telescopic joint is defined directly from the properties table and is not placed in the model graphically.

Telescopic joints characteristics can be grouped as follows :

  • Global data

  • Outer Barrel (OB) data

  • Element partitioning (for Inner and Outer Barrel)

  • Connection points definition

These groups are described in detail below:

Global data:

  • Name of the Telescopic Joint

  • Length at mid stroke: The length is important to define the static configuration of the model.

  • Total mass: Including all the parts associated with the moving element (TJIB+TJOB+Tensioner ring), telescopic joint empty

  • Total apparent weight (full of water): This must be provided from catalogue data.

Outer Barrel [TJOB]:

  • Length: The joint length of the outer barrel only (in order for the software to calculate effective masses per unit length)

  • Outer diameter: steel wall diameter of the barrel

  • Hydraulic diameter: used for drag calculation when the OB is below the water free surface, and thus should account for peripheral lines, goosenecks and other acccessories.

  • Wall thickness: steel wall thickness of the barrel, for stiffness and stress calculation purposes.

  • Dry weight (empty): this should include the mass of the tension ring and other accessories.

  • Wet weight (full of water): this should include the mass of the tension ring and other accessories.

  • Drag coefficient: Cd applied to the hydraulic diameter to compute the drag load (Morison)

  • Inertia coefficient: Cm applied to the hydraulic diameter to compute the inertia load (Morison), Cm = Ca + 1 where Ca is the added mass coefficient

Partitioning:

  • Partitioning for IB: Number of beam elements used to model the IB (default = 4)

  • Partitioning for OB: Number of beam elements used to model the OB (default = 4)

Connection points:

Three primary points are associated with the Telescopic Joint:

  • The IB top point, named TopIB by default. (This is the connection point at the upper flex joint).

  • The OB top point, named TensRing by default

  • The OB bottom, named BotOB by default

The coordinates of the primary points are displayed but cannot be modified because the position is deduced from components that already exist in the model. The connected component is selected using "Linked to". On the selected component, a connection point is chosen via the selection box Attach point. The boundary condition is defined through the connection type box: Pin, clamp, user defined, flexjoint and spring boundary conditions are available.

  • The telescopic joint is connected at the top (first primary point) to the upper flex joint [UFJ] .
  • The coordinates of the two other primary points are then derived from:
    • The first primary point coordinates
    • The Telescopic joint length at mid stroke
    • The OB length
    • The OB may be connected to other objects from these objects own definition windows (i.e. the last marine riser joint).

Note

1) A telescopic joint is an integrated device whose detailed characteristics are rarely known. The outer diameter and wall thickness of the OB are however required in order to estimate its stiffness.

2) The sliding mechanical function of the Telescopic joint is provided with a pipe-in-pipe contact/sliding modeling between IB and OB.

3) IB characteristics are deduced from the given input data, for modeling purpose only (no results are available), in particular for contact with OB.

4) For the calculations (preliminary API RP16Q, static, dynamic), the fluid inside the telescopic joint becomes the mud of the drilling riser to which the TJ is connected.

5) Once the Telescopic joint has been created, the following entities are automatically created and added in the Types and Model trees :

  • One Rigid pipe properties type for the IB,
  • One Rigid pipe properties type for the OB,
  • One object telescopic joint which name has been previously defined,
  • One object IB,
  • One object OB.