Northern Gas Networks
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Network Innovation Allowance
GD - Mains Replacement
Gas Distribution Networks
The Internal Live Service Insertion (ILSI) project seeks to extend the completion date of the project following complications during initial field trials.
Currently, service renewals to properties are carried out using several techniques, one of which is the ‘Live Service Insertion’ (LSI) method. The standard LSI technique requires a small excavation in the customers private land or garden. The relining of the service is carried out from this excavation towards the parent main and back towards the customers property to the existing meter position.
Internal LSI has been designed for use from within a customer’s property, permanently abandoning the annular space between the existing metallic service and the new PE liner, allowing the undertaking of excavations within the customer’s land boundaries to be avoided.
Reason for extending the project
Field trials were undertaken to assess the newly designed ILSI system against the project success criteria. Field trials are the last phase of the ILSI project and carried out under G23 documentation.
Selected field trial sites were found to be unsuitable. The services selected had a substantial amount of Dupont service pipe connecting the existing service to the parent main. This prevented the passage of the Nosecone system. CCTV inspection revealed that all the remaining field trial sites were of the same design and therefore not suitable for ILSI.
To continue with the project, the project timeline requires extending to undertake minor modification of the nosecone system and carryout the intended field trials. There will be no impact to the project cost.
The projects original drivers and anticipated forecasted benefits remain current. Although delays to the original project timeline have occurred, it will not attract any additional Capex costs. However, internal overhead cost will be impacted, but are expected to be minimal.
Continuing with the project is deemed a credible option, therefore It is recommended the project completion date is extended to 30th December 2019.
The agreed sealing length will have an impact upon the final design for the Nosecone used in the system as well as all other tooling including sealant injection and pipe pushing systems. SVI will use their extensive knowledge of sealants and injection techniques to help determine the best possible solution.
The standard sealant application systems will not be suitable for use inside a customer’s property. They are inherently bulky and are not clean enough to be transferred from an external scenario to an interior one. A new applicator system will be able to inject sealant via the service head adapter port with a steady flow. SVI will aim to incorporate a self-mixing system into the applicator gun, this will remove the potential risk of spillages inside a customer’s property when mixing a two-part sealant by hand in buckets or within a sealed sachet. Powering the applicator will require discussion between NGN and SVI to establish an acceptable power source. It is thought that the agreed power source may also be used to power the PE pipe pushing system.
Alternative Mixing - Options
In order for a clean and simple injection of LC14 sealant to be carried out, it will be necessary to investigate and produce a system with the capabilities to mix the LC14 sealant as it is injected. This will reduce the risk of spillage within a customer’s property.
A redesigned nosecone will be required in order for the new system to negotiate an increased number of bends and increased length of service. It will be necessary to carry out gas flow testing on the new Nosecone to assess its performance when compared to the original Nosecone design. A redesigned Nosecone should outperform the original Nosecone design in all aspects with minimum pressure loss once installed. It may be decided that the Nosecone design will incorporate a ‘lead in’ or extended nose portion to allow the easy insertion of PE into the metallic service. Design consideration will be made to allow the easy reconnection to the new PE parent main.
PE Insertion Device
It is expected that the increase in service length and the increased number of bends will have a detrimental effect on the ability to insert a Nosecone and PE pipe. There is also the distinct possibility that the area in which a skilled service layer is required to work in will be dramatically reduced. It is therefore necessary to investigate a new method/machine that will enable the insertion of the new service from a confined space within a customer’s property and be able to overcome the requirement for additional force to be applied during insertion.