If inline isolation tools are used on the NTS then the extent of the isolation will be significantly reduced due to the downstream block valves not requiring to be used. With a reduced isolation length the amount of natural gas that is vented to atmosphere will be reduced having an environmental and financial impact each time the tool is used.
Insulation Joint (IJ) replacement example from above
Existing case
- Assumed 15km between the IJ and the next operational ball valve downstream
- This would be taken down to 7 bar(g) using a recompression rig ~£80k
- Venting cost
7bar/km = 4 tonnes of gas/km, total = 60 tonnes
£2,157/km - Cost of gas = £32,355
Use of an Inline flow stop tool
- Assumed the tool could be stopped 10m downstream of the IJ
- No requirement for recompression rig
- Venting cost
Venting cost 70bar/km = 43 tonnes of gas/km, total = 0.43 tonnes
£25.5k/km – Cost of gas = £255
Total savings = 59.57 tonnes of gas and £32,100
According to the RIIO 2 business plan for NGGT it is planned that 41 IJs will be replaced over the 5 year period, therefore across RIIO 2:
Total savings = 2,442 tonnes of gas and £1,316,100, additionally the recompression rig will not be needed for the 41 jobs across RIIO 2 so £3,200,000 could be added as well.