Offshore pipeline riser calculation

Universidad de los Andes

Introducción a la ingeniería offshore – Subsea Infrastructure

Sergio Antonio Muñoz Pinzón

November, 2015

1.    The drillship Transocean Deepwater Discovery has a drilling riser with the following properties:

Length: 2000 m

External diameter: 21,25”

Wall width: 0,812”

Young’s modulus: 2,07e+11 Pa

Axial force: 9e+6 N

Assuming the whole riser is immersed in fresh water in a water depth of 2000. A constant current (same direction and velocity) of 2 knots is loading the whole riser. It is necessary to take in account the axial force. However, the effects of    gravity, internal and external hydrostatic pressure can be neglected.

Plot the graphs of (i) deflection, (ii) angle of rotation, (iii) shear force and (iv) bending moment along the whole drilling riser for the following cases:

a.       Riser with both ends fixed

b.      Riser with both ends equipped with ball joints

For both cases a. and b. the riser can be assumed to be a tensioned beam,

Cable "welding" for cathodic protection systems in pipelines and electrical connections in structures.

Recently I was talking with a welding engineer about a new method used for joining the cable from the rectifier to pipeline, this method has been proved to be satisfactory in Australian pipelines and is called Pin Brazing.

Traditionally those joints have been made through TW or thermite welding i.e. Cadweld and others, the main advantage of pin brazing is that this can be welded in overhead and others positions than flat