Duo Bag 12

The Gastech Duo Bag 12 is a double-balloon pipeline isolation machine for low-pressure gas networks from DN 3″ to DN 12″, rated to a maximum operating pressure of 50 mbar. The system uses two guided insertion tubes — visible in the image as two parallel vertical stainless rods rising from a blue flange clamp base mounted on the pipeline — each carrying an inflatable sealing balloon that is inserted from opposite sides of the isolation section. The guide tubes feed the balloons through the pipeline bore along perfectly smooth inner surfaces, eliminating the risk of balloon puncture from the cut burrs left by the hole saw during the tapping operation — a critical issue on steel pipelines where sharp internal burs are produced at the tapping point. The full assembly uses standard polyethylene fittings readily available on the market, reducing spare parts dependency. A central ball valve with green lever handle provides the inflation and venting control between the two balloon positions. Product code: DA.0800.0300.0001.

The double-balloon architecture allows one balloon to be inserted on each side of the work zone simultaneously, creating a dual-seal isolation barrier. Water can be injected between the two balloons to form a hydraulic lock — an additional safety layer on steel pipelines where the consequence of a single balloon failure would otherwise allow gas to reach the work zone. Gas flow is stopped with zero gas escape at any point during insertion or extraction — the guide system fully contains the balloon from entry to full sealing position without any gas discharge. The robust but lightweight construction allows single-operator handling during insertion and extraction procedures, reducing the crew requirement at each isolation point.

The Gastech Duo Bag 12 is deployed by gas network operators and pipeline contractors for live-line isolation of low-pressure steel, cast iron, and polyethylene gas distribution mains from DN 3″ to DN 12″ — during repair work, fitting replacement, network extension connections, and any maintenance operation that requires a section of the live low-pressure gas network to be safely isolated without interrupting upstream gas supply or venting the network to atmosphere.

Leader Infra supplies this double-balloon guided pipeline isolation machine for gas network operators — enabling zero-escape live-line balloon isolation from DN 3″ to DN 12″ at up to 50 mbar with simultaneous dual-balloon insertion and optional hydraulic lock for maximum safety on steel gas mains.

FAQ — Why is the hydraulic water lock between the two balloons an important safety feature on steel gas pipelines? Steel pipe interiors produce sharp cut burrs at the tapping point that increase the risk of balloon puncture during inflation. Filling the space between the two balloons with water creates a hydraulic barrier — if one balloon is punctured or deflates unexpectedly, the water column between the two balloons prevents gas from reaching the open work zone immediately, giving the crew time to respond safely before the second balloon is also compromised.