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.
Objectives
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
Learnings
Outcomes
Research and modelling work that took place with regards to carrying out D/3 drillings proved successful in confirming its feasibility without impacting integrity of pipelines up to a minimum of 18”. NGN will carryout a further internal review of the findings before progressing to live field trials.
Due to unsuccessful independent laboratory testing of the saddles at Rosen, live field trials were not undertaken during the project. ALH Systems will proceed with independent development & further validation testing prior to re-engaging with NGN to proceed to field trailing the final product.
Lessons Learnt
Testing carried out by ALH Systems proved that by exploiting the use of advancements in resin technology, traditional methods of carrying out live operations on the gas network can be significantly improved, resulting in Opex efficiencies for network operators and overall reductions in disruption for customers.
Due to challenges with ensuring the area of the main where the resin is to be applied to is kept clear of debris prior to siting of the saddle, it is essential the operatives receive specialist training and maintain competence in installing the Bonded Saddle. Failure to ensure the resin remains clear of debris can risk the possibility of the resin not achieving the required levels of adhesion to prevent the saddle from detaching off of the parent main.
As identified during this project, significant benefits for NGN can be achieved throughout GD2 due to the enabling of flow stopping and STASS operations through the Bonded Saddle (v2) on NGNs 18” diameter network, future project work could involve assessing the potential workload for additional diameters within NGNs Tier Two population that could benefit from having a Bonded Saddle solution developed that is suitable for deployment on those smaller diameter pipelines, however, it is generally assumed that there is a limit at which the use of the Bonded Saddle on smaller diameters can negatively impact productivity due to the time required for resins to cure vs traditional methods.
