Learnings

Outcomes

The monitoring equipment that has been installed will give Wales & West Utilities a strong indication that odorant is reaching all areas of the mid system. Physical sampling continued to March 2021 to give us assurance that the Spectra systems are reporting accurately. Rhinology will continue as per usual.

We typically inject 6mg/m2 of odorant into the pipeline network to ensure desired levels are reached throughout the network. In the first quarter of 2016 we witnessed that despite injecting 12mg/m2 at Maelor works, the desired levels of odorant were not being achieved across mid Wales and the coastal region covered by this injection point. The solution was to increase the injection levels to 15mg/m2 to reach desired levels of odorant. The initial phase of this project has demonstrated that both nominated sites are achieving between 10-20mg/m2. As these sites are at the extremity of the regions covered, early indications suggest that the injection levels can comfortably be reduced by 10 to 20% as outlined in the project initial plan, 960kg to 1,080kg per month (12 to 13mg/m2). During the final inspections, the odorant was reduced from 15mg/m2 to 12mg/m2. The Spectra site at Wem reacted to this, circa 25 miles away. However, this site at Aberystwyth did not respond, this is approximately 150 miles away. We followed the data for a few weeks after and although there were slight variations, we believe that the line of flight of the gas could have affected this. It is worth noting that 2 days after the reductions of odorant at Maelor works it had to be increased back to 15mg/m2 as the primary Rhinology point on Maelor site reported a failure of odorant. This location is only 50m away from the injection point. It is believed that the pipe configuration on site could be affecting the flow of odorant through the network and needs investigating further. 

Benzene levels have also shown consistency at both sites around the region of 90mg/m2. Although these levels are higher than anticipated they are within the desired safety levels of exposure to humans 160–320 mg/m3 (50–100 ppm). This aspect of the equipment demonstrates a useful safety mechanism for WWU moving forwards to ensure that staff know that levels are safe prior to entering site. It is worth noting that throughout the duration of the project some abnormal peaks were noted at the Aberystwyth site, although not noted at Wem. It is worth noting that the equipment was factory calibrated for Odorant only. It has been recommended that WWU should consider having set equipment in place where Benzene is typically reporting high. The spectra system can then be calibrated to analyse these peaks more accurately and focus closer on Benzene results to give WWU more accurate data.    

Remote monitoring of TBM and Benzene levels has been demonstrated, with TBM levels in the range that was expected. Benzene levels were more variable and subject to rapid spikes of short duration which require further investigation. 

The trial has highlighted some initial calibration issues with Benzene which were addressed by in field calibration using gas cylinders with a known concentration of Benzene. As the laboratory calibration technique utilized in the initial stages proved unreliable, the investment in calibrated gas cylinders was a more cost-effective approach. Due to the small amounts of product required from the cylinders during calibration they will last for 5 years on the Benzene and 2 years on the TBM.

All data gathered throughout the course of this project is accessible through software readily available to WWU, the seamless access to the software has allowed quick analysis of site levels. 

The TRL moved from  7 to 8

Lessons Learnt

Despite the multiple delays of the project due to covid, all members of all teams stayed in regular contact throughout this period. All parties knew their tasks within and around the installation which made the task much more seamless when arriving at site. Calibration was performed by comparing the signal detected by Spectra on a gas sample with the concentration of analytes of interest measured by an independent lab on an equivalent gas sample; this calibration technique was chosen instead of using standard gas cylinders because of logistic obstacles faced for cylinder shipping in site.

The use of laboratory testing as a calibration technique was found to be unreliable, the team agreed the use of pre-defined concentrated calibration cylinders for both odorant and benzene. This offered a reliable source for calibration and better-quality data on which to assess results upon. It should be noted that the use of separate hoses should be used for each cylinder as the benzene may cause a sample contamination error.