Written by Reporter -
For over 20 years, Rotech Subsea has been at the forefront of research and development in excavation – offering industry-leading technology and expertise.
Rotech Subsea began developing their first Mass Flow Excavation tool – the FlowDredger – in 1994, with the aim of creating a stable tool that could excavate large amounts of soft seabed quickly using a very large jet of seawater at a relatively low pressure.
The FlowDredger employed two counter-rotating impellers, operating in series, and a seawater-driven hydraulic motor. This first generation tool was capable of producing up to 8000 litres per second at a pressure of 11kPa, giving a powerful 85kW jet.
Four years later, the company built the first T-shaped excavator. This time oil hydraulics replaced the seawater drive, which greatly improved efficiency and longevity.
The patented T-shaped design of the ‘T8000’ – as this model was dubbed – also offered improved access to the internal components for offshore maintenance. It had the same performance as the original excavator and at lower flow rates the power of the jet could be increased to 130kW.
For the next decade and a half, these excavators were the best Mass Flow Excavation tools on the market for large scale projects.
In 2011, Rotech’s excavation business and worldwide fleet of Mass Flow tools were sold to Norwegian-based business REEF Subsea.
With the focus for customers changing to narrower trench profiles (for subsea cable protection) and a growing demand for more controlled tools, Rotech began to develop a new generation of excavators.
Last year, they unveiled the RS1 Controlled Flow Excavator, which was designed for the demands of the offshore windfarm market.
The new RS range delivers much greater efficiency and higher cutting capability in a more compact unit than ever before.
This means that as well as creating narrower trenches with better depth control, the RS1 can also be used to extract excavated material and pump it to a different location. Combined with Rotech’s new BackFill Box, the RS1 can offer simultaneous trenching and burial of cable.
The RS1 is a higher pressure and lower flow device than previous Rotech models. The TRS1, the twinned unit, provides 4000 litres per second at a pressure of 35kPa. For harder soils, high pressure nozzles can be fitted allow the RS1 to produce up to 100kPa of jet pressure, with a peak jet power of up to 215kW.
In 2016, the focus moved to the RS2, designed for larger scale excavations such as sand-wave clearance for freespan correction of cables and pipelines. The twinned version, the TRS2, produces 8000 litres per second at 30kPa, giving a jet power of 240 kW. The RS2 also comes in a shallow water variant, capable of working in between one and two metres of water.
In just over 20 years of development, Rotech has almost trebled the jet power of its excavators, while making them more controllable and stable.
Who knows what the next two decades will yield?