Storm Lashing System Provides Greater Protection for Jackups

Zentech, Incorporated has developed a Storm Lashing System for jackups, which provides significant operating benefits for both existing and new-build rigs. In announcing the new product development, Zentech President Ramesh Maini explained that “with the number of jackups lost this year, we expect the rules to become much stricter in the future. Our patented concept affords benefits for jackups operating in drilling, mobile production or accommodations applications.”

Originally designed to enhance the deepwater capability and service life of shallow water jackups, the company now sees significant value from improved storm survivability of the new system. The timing for Zentech could hardly be better—their patent issued just six months before hurricanes Katrina and Rita sounded the wake-up call for offshore operators.

Zentech has a twenty-one year record of helping contractors and oil companies improve the efficiency, reliability and service life of their equipment, and the Storm Lashing System is another result of this philosophy.

The system uses radially spaced mooring lines that connect suction pile or vertical load anchors (VLA) to the jackup hull or legs at 20 to 40 degree angles, and a static tensioning mechanism to insure taut lines. Figures 1 and 2 below show this arrangement from a side and top view.

Zentech’s system can be deployed after the unit is on location. Unlike semi-submersibles, it does not need to be deployed before the jackup is on site.

The concept is more than a simple “equipment fix.” It involves an engineering evaluation of the existing rig or new-build design, followed by careful selection of the correct configuration to optimize the client’s design parameters. In a typical application, these might include:

  • Stresses in the leg members
  • Storm holding capacity of the elevating pinions of the jacking system
  • Storm holding capacity of the leg-to-hull locking system, if so equipped
  • Allowable leg footing soil reactions
  • Preload capacity
  • Overturning

Depending on client preferences, the mooring lines may be connected to strong points on the hull, jack houses, or additional jacking units that climb the leg chords, as shown in Figure 3.

In addition to generally improved storm survivability, the system enables existing jackups to be used in deeper water locations, or in situations where storm design parameters have become more restrictive. Incorporating the Storm Lashing System on new jackup designs can expand the design capabilities versus cost and enhance marketability. The system provides several other benefits for both new designs and existing rigs: longer fatigue lives, increased VDL, low dynamics and reduced preload requirements.

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