Mar 2021
Gas Distribution
Bonded Saddle V2
Mar 2021
Mar 2022
Northern Gas Networks
Ben Gill
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Network Innovation Allowance
GD - Repair and GD - Mains Replacement
Gas Distribution Networks
This project is to further develop the ALH bonded saddle to allow it to be used for flow-stopping and STASS robot
mains entry as well as challenging the current D/4 drilling regulations.
Northern Gas Networks (NGN) have fully implemented the use of Bond and Bolt saddles as part of the STASS operation, which is attached to the metallic main using a resin based adhesive and bolts.
The technology allows a number of benefits including increased safety to operatives and general public and cost savings on excavation and reinstatement
The D/4 drilling regulations mean that NGN are only allowed to drill a hole ¼ the size of a main to gain access (a 5 mm hole in a 20 mm pipe for example) as the current train of thought is that anything bigger will undermine the stability of the main. There is no substantial evidence available to accurately dispel this
legacy regulation and as such an investigation and findings need to take place (as a part of this project) to ensure we can change regulation safely.
One limitation of the current method, Bond and Bolt, is that the resin used requires a 24-hour cure before any ALH System 3 drilling operations can take place. The resin utilised in the new technique, Bonded Saddle, only requires a 90-minute cure time prior to drilling, albeit the drilling uses an ALH System 1 drill
rather than a System 3.
The D/4 challenge is that we are unable to access some mains with our robotic technology due to not being able
to drill a hold big enough to launch the robot. A specific example here is that STASS requires a 6” drilling to
launch the robot, therefore for any main less than 24” diameter we are required to excavate fully around the main and install and encirclement clamp to facilitate drilling. A key example here is that 18” mains is the primary work basket for STASS and is the largest volume of repairs undertaken on Tier 3 pipes.
The objectives of the project are:
  • Development of a suite of technical reports to support the in-house manufacturer testing of the resin
  • Carry out physical tests at 3rd party partner to validate in house testing and therefore offer assurance for network approval
  • Carry out live, G23 Field Trials to confirm anticipated reduction in time taken to carry out operations are proven and thereby validate the Cost Benefit Analysis
  • Clearly identify the cost savings against traditional alternatives for using Bonded Saddle technology
  • Utilise existing saddles to remove the need for additional tooling