As part of planned work on the National Transmission System (NTS), all obsolete gas analysers were replaced to improve the accuracy of these calorific value calculations. The new analysers needed more efficient sample systems, that required smaller vented gas volumes. This meant the gas sample probes needed replacing as well.
Alongside this, the existing gas sample points found across the network were installed with plug valves or small isolation points which were unable to accommodate low volume probes. This required the sample pits to be altered, to include above ground platforms and below ground access.
In July 2013, we launched a project to trial an alternative design to eliminate the need for working at height or within the confined spaces of the sample pit. As part of the project, we developed and tested three different probe designs to determine which was most suitable for use on our network, with the new sample pit design.
Traditionally to take a gas sample, technicians were required to climb into the sample pit, isolate the valve and remove the probe. This was a two-man operation requiring specific training.
The new sample pits meant the maintenance points were relocated above ground, making it safer and more cost effective. The amount of costly excavation work was reduced, as was the quantity of construction material needed.
The new probes can reduce the pressure of the gas sample to meet the gas handling requirements of the new analysers, making it safer and easier to use.
Following testing, the new sample pits were installed across all 37 calorific value sample points found across the network. This delivered a total saving of £1.3m. The new probe installations cost about a quarter of the previous sample pit and platform method, which cost around £120k each.
Alongside these cost benefits, the installation of the new sample pits resulted in reduced project delivery times, improved working conditions for technicians and reduced quantities of concrete, resulting in carbon savings too.