Rehabilitation and Maintenance of Drains and Sewers / Prof. Dr.-Ing. D. Stein, Dipl.-Ing. R. Stein (2004)

Shrink hoses

For some years the shrink hoses to DIN 30672 [DIN30672-1a], also called shrink sleeves [Opitz85], that have proven themselves in the gas and water sectors have also been used in the sewage sectors for sealing pipe joints up to DN 1200 [FI-Raych].

Shrink hoses consist of jet soaked polyethylene with an inner coating of thermoplastic sealing adhesive.

Jet soaked plastics, especially when they are specially mixed with stabilisers, possess the following properties [Opitz85] :

  • The resistance to aggressive media is increased. They have a high degree of chemical resistance to oils, acids, alkalis, aggressive soils, ozone and ultra-violet rays;
  • The material is extremely crack resistant (cold flow resistance);
  • The resistance to ageing is increased;
  • The brittleness is reduced.

The longitudinally split shrink sleeve suitable for repair work (Image 5.2.4.2.2-1), is laid around the previously cleaned and pre-warmed pipe joint to be sealed and closed with a suitable closing system - sealing clip or flexible rail of chrome-nickel steel.

Spiral formed sealing strips of plastics are placed around the respective pipe region for provisional sealing of the leaking pipe joint and also for filling of cavities during the installation.

During the heating of the socket with an open, soft propane gas flame, shrinking forces are released, which squeeze the permanently plastic seal adhesive into possible cavities and unevenness so that a fixed and leak tight pipe joint is created which, nevertheless permits angular changes and longitudinal movement.

The working sequence in the sealing of a pipe joint with the aid of a shrink sleeve is shown in (Image 5.2.4.2.2-2). (Image 5.2.4.2.2-3) and (Image 5.2.4.2.2-4) as an example on a cast iron pipe.

The shrinking process has been properly executed when

  • the shrink sleeve is fully shrunk onto the pipe joint;
  • it lies smooth without cold spots or air bubbles and the seal adhesive has been pressed out at both ends [FI-Raych].
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Image 5.2.4.2.2-1:  Separated shrink wrap with closing rail for sealing socket joints to DN 350 [FI-Raych]
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Image 5.2.4.2.2-2:  Working sequence with sealing leaking pipe joints of cast iron piping with the shrink hose [FI-Raych] - Warming the surface to be enclosed to approx. 60 °C
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Image 5.2.4.2.2-3:  Working sequence with sealing leaking pipe joints of cast iron piping with the shrink hose [FI-Raych] - Applying the shrink hose
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Image 5.2.4.2.2-4:  Working sequence with sealing leaking pipe joints of cast iron piping with the shrink hose [FI-Raych] - Shrinking the shrink hose with a soft yellow propane flame

Rehabilitation and Maintenance of Drains and Sewers / Prof. Dr.-Ing. D. Stein, Dipl.-Ing. R. Stein (2004)