‘Going to great lengths to solve the problem’
When building an active heave compensation (AHC) system to lower objects to the seafloor at a depth of up to 3,000 metres, there is more to be taken into account than just your regular waves and weather conditions. “We aim to look at the total picture by using simulations,” says Jacco Osnabrugge, Manager R&D for the IHC Motion Control & Automation cluster.
This customer needed to safely place heavy loads on the seafloor at depths of up to 3,000 metres, and so contracted Royal IHC to design, engineer and construct an AHC system fit for that purpose. “In extreme conditions such as this, you don’t want to wait until the moment the system is installed to see whether you got it right,” says Jacco.
The principle idea of an AHC system is to keep the lifting point steady in relation to the seafloor. “However, in this case, the stretching of the cable used to lower and retrieve loads poses additional challenges,” Jacco explains. “Even if the lifting point is kept steady, the load can start bouncing (oscillating) due to the spring-like characteristics the cable develops in these conditions. Over such great lengths, even the strongest cables can stretch up to an additional 8 metres in length.”
With the help of model-based engineering, Jacco and his colleagues were able to do more than just analyse the effects of the stretching cable. “More importantly, it has also helped us to develop a solution,” says Jacco. “We have improved the AHC system with additional controller programming to eliminate the effect of load oscillations.”
Problem-solving is one of the things Jacco likes most about his job at IHC. “It is very satisfying when you not only identify a problem, but also come up with a solution. I love the link between theory and practice. We get to solve challenging technological issues, and we also sometimes have the opportunity to work with some of the biggest machines and vessels in the industry.”