The initial conceptual discussions have identified that utilising alternative construction methods could result in lower levels of investment and also reduced construction complexity when compared to similar projects using traditional construction techniques.
The initial conceptual designs need further development to ensure prototypes developed are suitable to all NTS CVSPs. With that in mind the project will consist of an initial feasibility and conceptual study to ascertain and mitigate existing project risks and ensure the prototypes undergo a formal process of safety assessment (FPSA) and a formal appraisal process to encompass all 37 CVSPs. A combination of a new probe design and construction techniques that take into account human factors have been identified by this project. Three prototype designs require evaluation under this proposal:
A fixed VE probe that will include Pressure Reduction Unit (PRU) separation – a regularly maintained device - from the top of the probe to an accessible location eliminating the need to install a maintenance platform and the need for the operator to work at heights.
A retractable VE probe that is to be used above ground and will also include a PRU separation from the probe and relocation to an adjacent location in proximity of the pipeline. This design configuration will also require a ball valve isolation arrangement to ensure that the probe branch can be isolated during pipeline inspection.
The below ground design solution will include a mitre valve isolation gearbox arrangement with an extension above ground; the PRU will be separated from probe. The probe retractable device and the PRU will be extended above ground and protected against 3rd party interference using reinforced plastic.
National Grid proposes that the prototypes are trialled at Churchover Multi Junction and Churchover Tee due to the site unique sample point requirements with all the proposed probe designs being required. This unique combination would also reduce construction costs with less mobilisation cost impact.
The installation of new low volume sample probes incorporating the improved design solution at the trial site.