BE-13 Renovation: Lining with Cured-In-Place Pipes - Final Work, Accep...

Lining Observations

Surface Irregularities (Folds)

The goal of the renovation is the installation of a fold-free liner. Folds / Wrinkles can occur due to special conditions on site, such as access possibilities, changes in cross-section, displaced joint, but also due to unsuitable membranes (foils) in the construction of the lining tube errors in manufacturing process of the lining tube, faults during the winched-in-place process, insufficient or not constant inflation pressure, incomplete curing, etc.

The following limit values apply to wrinkled lining:

On straight sections and bends with a radius RBend > 10 × DN, the limits of EN ISO 11296-4 apply: "The CIPP liner shall not introduce surface irregularities in addition to those of the existing pipeline, which exceed 2 % of the nominal diameter or 6 mm, whichever is the greater."

The DWA-A 143-3 supplements this:

  • In bends with a radius of 5 × DN ≤ RBend ≤ 10 × DN the following limits must be observed:
    → In circular profiles max. folding up to a size of 3 % of DN or 2 cm. The larger value applies.
    → In ovoid cross-sections max. folding up to a size of 3 % of the hydraulic equivalent circle or 2 cm.
    → In bends, the smaller value applies up to DN 600 (equivalent area circular pipe), and > DN 600 (equivalent area circular pipe) the larger value applies.

  • In bends with a radius RBend < 5 × DN, the limits of folding shall be specified separately.


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