ULO in association with Coflexip developed a ”Continuous Grout Operating Placing System” for placing mattress in situ subsea, which is placed and grouted in continuous length of, up to 500 meters per reel. The development started in 1983 and execution of projects progressed in 1984 to 1990.

The system adopted a ULO patented opening and closing device, to open and close the joint and grout at the same time, so a cable, umbilical or flexible pipeline can be encased in the mattress or the mattress can be placed on top, during the laying process.

The Continuous System was a remotely operated crawler unit that was preloaded and lowered subsea over the cable umbilical or small diameter pipeline. The crawler was hydraulically operated and could develop and lay rate of 30 – 50 M per hour.

The grout material was mixed and pumped at the same rate as the mattress was laid. Several projects were executed of which the longest section of continuous laying was in excess of 5 Kilometers.