System 3 Large Diameter Bagtubes

The ALH large diameter bagtubes provide a safe and effective method for flowstopping 14” to 48” diameter gas mains.

Large diameter bagtubes are a safe, easy-to-use and cost-effective flowstopping system for maintenance, repair and modification of distribution networks whilst preserving continuity of supply. The entire procedure is totally gas-free, carried out through an arrangement of valves.

ALH supplies the complete package, including drilling machines, plug insertion equipment, flowstopping bagtubes and bags. The aluminium construction reduces weight and makes the flowstopping equipment easily transported and positioned on to the gas main.

System Parameters

  • 14” to 48” diameter mains
  • Maximum operating pressures dependent on main size
  • Ideal for use with the ALH Bond & Bolt saddle system
  • Flow rate up to 5 metres per second
  • Standard System 3 Iris Stop valve, adaptor and spool connector
  • Lightweight aluminium construction
  • Can also be used as the secondary position for Iris Stop
  • Strong bags for additional safety (GIS/E20)

Bond & Bolt Flowstopping

In 2015 the 24” to 36” bagtube was used in conjunction with the Bond & Bolt saddle to carry out its first flowstopping operation in central London. Together the system massively reduced excavation time and costs, ensuring minimal disruption to the public and a safe working environment for the operators.

Large Diameter PE Flowstopping

The large diameter Bagtube system offers an alternative to squeeze-off on polyethylene (PE) mains. On PE mains, bag insertion is via a fused branch saddle, which can be permanently plugged so that the entry valve can be removed after the operation.

 Flowstopping Bags

The E20A semi-supported bag provides a gas-free secondary seal for Iris Stop operations and large diameter flowstopping. The bag has a bladder construction conforming to GIS/E20 specification.

It is made from triple-layer calendared dry natural rubber sheet, with a high tenacity unproofed nylon cover. The bag incorporates an extended neck and a backbone, which eliminates the risk of ‘twisted bladder’.

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