Mooring Line Monitoring in the Gulf of Mexico

The challenge

The Appomattox FPSO has a total of 16 anchoring lines that ensure that it is held in the right place in the more than 2,000 m deep water. MacGregor Pusnes has supplied eccentric fairlead chain stoppers which are the connection point between the anchoring lines and the FPSO. The chain stoppers are located underwater at the bottom of the hull, ensuring that the forces are transmitted safely.

A variety of sensors, cables, hydraulic hoses and connections are needed to measure load forces, angles and positions, as well as the ability to open and close the chain stopper.

An offshore delivery is typically characterized by very demanding specifications and tough quality requirements for design, production, testing and documentation. This project was no exception. For example, the life expectancy of all equipment is a minimum of 25 years, equipment must be interchangeable by divers and the bundle of cables and hydraulic hoses must cross a moving area and be able to withstand enormous forces.

The solution

Scanmatic worked very closely with MacGregor Pusnes in designing the solutions that met the challenges that were presented, and took advantage of good collaboration to solve the puzzle. Scanmatic’s delivery consisted of:

  • Redundant inclinometers for measuring the angle of the chain stoppers relative to the direction of gravity
  • Redundant proximity switches for monitoring the position of the chain stopper arm
  • Oil-filled subsea cables and connectors
  • Hydraulic hoses for hydraulic cylinders
  • Fixing solutions to hold the bundle of cables and hydraulic hoses to each side of the moving area
  • Bend stiffeners to ensure safe and even movement of the bundle with cables and hydraulic hoses in the moving area
  • Test case for testing, verification and data logging of the sensor package on each chain stopper

The delivery was a success and underlines Scanmatic’s ability to handle really demanding projects and deliver on the quality expected in this market.

Figure 1 Scanmatic’s redundant inclinometer with diver changeable connector

Figure 2 Scanmatic’s redundant proximity switch (2 sensors in unit) with diver changeable connector