Subsea 7's New Hot Tap Technology Sucessfully Tested Offshore
Subsea 7 Inc (OSE Symbol: SUB), one of the world's leading subsea engineering and construction companies, has announced that following a 3 year development, testing and qualification programme, its new subsea hot tap technology - Subsea Grouted Tee (SSGT)*, has successfully completed offshore trials in the North Sea and further demonstrated the technology's deepwater, diverless potential.
Following an extensive DNV approved onshore testing programme in test tanks and laboratories, the offshore trials of the SSGT technology involved the mobilisation of a subsea grout mixing and injection unit, complete with test tee assemblies, on Subsea 7's Seven Pelican dive support vessel (DSV). The skid mounted mixing unit was developed to enhance diver based hot tapping operations and also allows the SSGT technology to be utilised in deep water, where pumping from the surface could be challenging.
During the trials, the mixing unit was deployed to the seabed where divers carried out the installation and hook up operations. After grout injection into a test tee assembly followed by a 24 hour grout curing period, the unit was recovered to the vessel where the grout quality test was successfully performed.
John Mair, Global Technology Manager for Subsea 7, commented:
"Subsea 7 has developed the capability to deliver this technology over the past three years because we believe it offers a safer and more cost-effective solution to traditional hot-tap intervention methods. The successful completion of the offshore tests further demonstrated the benefit and quality of mixing the grout on the seabed as opposed to pumping from the surface providing further evidence that the technology can also be considered for deepwater, diverless applications.
This again demonstrates Subsea 7's commitment and capability related to technology development and our aim to be the Subsea Partner of Choice in our sector."
Subsea 7 will present a technical paper on the subject of Subsea Grouted Tee on Thursday 10th September at the Offshore Europe Conference in Aberdeen, Scotland. "The development of Subsea Grouted Tee for Subsea Live Pipeline Intervention", will be presented as part of the Facilities and Infrastructure session in the Gordon B room at 11.30hrs by Paul Booth (Engineering Manager) and Dan Vu (Project Engineering Manager) of Subsea 7.
*Further Info: Subsea Grouted Tee (SSGT)
Subsea Grouted Tee technology enables intervention activities to be carried out on high and low pressure subsea pipelines, without the need for major hyperbaric welding operations. Typical intervention scenarios are repairs, valve by-pass/replacements, removal of blockages and branch connections. These activities are frequently performed with the assistance of highly experienced welder divers which are not required with SSGT. Utilising the SSGT also presents the opportunity to intervene into pipelines whilst still under internal pressure, negating the requirement for costly production shutdowns.
Subsea Grouted Tee consists of a tee which incorporates a top half shell with a branch which is either welded or extruded onto the shell during fabrication. The tee branch contains a high pressure Hydrogenated Nitrile Butadiene Rubber (HNBR) seal, qualified for hydrocarbon applications, which is energised when the tee is clamped in position around the pipeline. The lower half of the shell is split into two parts to create a door arrangement which is operated hydraulically once the tee is positioned on the pipeline to ease the subsea installation. The tee, deployed in an installation frame, is sized to produce an annular gap between tee and pipeline. The annular gap is dried and injected with epoxy grout which once cured creates the mechanical bond between pipeline and tee, allowing full transfer of load between tee and pipeline.
Due to its unique design, Grouted TeeTM technology can tolerate much greater pipeline ovality than some other bolt-on mechanical fittings. It is a ‘no welding' solution which offers mechanical integrity with an ability to take considerable loads, typically equal to or in excess of those tolerable by the main pipeline.
The Grouted TeeTM technology was originally developed by Advantica, now GL Industrial Services UK Ltd (GL), in the 1990s and used on cross-country high-pressure onshore pipelines and distribution networks worldwide. In 2006, Subsea 7 realised the benefits that the technology could potentially bring to its clients and, in support of its own development programme, embarked with GL on an industry-sponsored Joint Industry Project (JIP) to qualify the technology for subsea applications.
