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FBOS Transforming Mains Replacement

February 9, 2021

Steve Vick International’s ground-breaking FOAMBAG Operation on Stubs (FBOS) technique, is the long awaited solution for fully decommissioning mains of engineering difficulty, such as stranded, one way fed, stubs or those found on mains replacement schemes. The FBOS technique fully decommissions mains right up to the last transition joint on mains of 4”-6” in diameter. These sections of main and associated tee pieces into parent mains, can be impractical and costly to excavate due to the location often being under a busy junction or in a sensitive area. This makes the remote deployment of FBOS the ideal solution.

FBOS, a partnership between Steve Vick International and Cadent, and funded via Ofgem’s Network Innovation Allowance (NIA), began in April 2019. It took just fifteen months and was completed well within the project timescales, a great achievement considering the COVID restrictions that were in place during this time. The project’s aim was to allow for total abandonment of 75mm into 4” up to 125mm into 6” T1 pipes and after a number of successful field trials the FBOS technique was approved by Cadent for use across their mains replacement portfolio.

FBOS is a highly innovative technique compared to more traditional methods because it uses remote live mains insertion which can be used on both single or two way fed mains. Additionally, FBOS allows for greater insertion lengths, up to 25 metres and has an improved ability to navigate obstructions with a specially developed nosecone designed to negotiate bends, existing services and plugs. Due to FBOS’s use of SVI’s signature sealant technology, which seeks out and seals loose particles, issues relating to rust or contaminants are also reduced.

Using remote deployment, typically 10-13 metres from where the pipe intersects with the parent main, the annular space of the old metallic main can be fully decommissioned up to the final transition joint, avoiding the possibility of future leakage.

Vishal Dhanji, Innovation Project Manager at Cadent commented,

“FBOS has created a great opportunity for us to replace stranded mains or stubs that would otherwise have been difficult or costly due to their location and excavation requirements. Following our completed and successful field trials we are looking forward to adopting the technique across our network and making it available, through SVI to other gas distribution networks (GDNs).”

Steve Vick International, specialists in trenchless technology and ‘live’ remote applications, have collaborated with several gas distribution networks throughout the RIIO-GD1 period to develop products that can deliver significant benefits. One of the biggest problems facing GDNs today is the disruption caused by large excavations. Many of the SVI products, including FBOS, are designed to significantly decrease the disruption caused by mains replacement to the general public. Their techniques allow for old gas mains to be kept live throughout, therefore maintaining the gas supplies to customers, and reduce the need for complex and costly traffic management. SVI’s products also help to improve health and safety by allowing the works to take place in a safer location and reduce the environmental impact associated with excavating and disposal of soil. Successful collaborations have included, T1 ESEAL, T2 ESEAL and now FBOS.

How Does FBOS Work?

The FBOS technique is carried out by Steve Vick International’s Contract Service team. The host main is cleaned and inspected using CCTV cameras. This helps to establish the length of the pipe and for any obstructions. Once completed the FBOS nosecone is electro fused onto the PE pipe ready for insertion. There are two umbilical cords on the FBOS, the primary umbilical cord is attached to the FOAMBAG and the secondary umbilical is towed along behind and used to fill the annular space later in the process.

Once welded, the FBOS nosecone is inserted into the old main through the SVI glandbox and fed through until it meets the intersection with the parent main. At this stage the PE is squeezed off whilst the bypass remains and then tied back into the previous PE scheme. When this has taken place, a fixed volume of foam, enough to fill the bag, is pumped in using a nitrogen powered applicator gun.

When the first foam application has cured, the second umbilical is connected to the mix and inject machine and a precise amount of foam is delivered into the annular space to 100% abandon and decommission the metallic main right up to the final transition joint.

Future of FBOS

There is the potential for FBOS to be scaled up to 8” – 12”, further increasing the significant benefits this technique delivers to gas distribution networks and the public.