Pipe lining

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Hose lining (also: hose relining) is a common method for trenchless rehabilitation of underground, pressureless drainage networks such as sewers . It is often called no-dig method ( English no-dig , no digging ), called so grave-contact method. A plastic hose ( hose liner or inliner ) impregnated with synthetic resin is pulled into or turned into the channel, which then hardens.

tube

See main article: Hose liners

The hose usually consists of a polyester needle felt (non-woven fabric), polyamide or GRP (glass fiber) fabric. It is for the sewer to be restored assembled . The length and diameter correspond to the old pipe and the wall thickness is based on the static specifications and is calculated. The hose is impregnated with the resin in the factory (UP needle felt / GRP) or in a mobile impregnation system on site (especially EP needle felt because of the faster, non-controllable reaction of the EP resin). The resin is mainly an unsaturated polyester resin (ISO-NPG) or an epoxy resin . In special cases (temperature, pH value ) other resins are used.

Installation

The impregnated liner is drawn into the sewer to be rehabilitated through existing manhole openings ( manhole cover ) ( inverted or inverted ). After the impregnation of the Eversion, the beginning of the hose is stretched over a frame on a 2–3 m high scaffold above the initial shaft. The hose is "turned inside out" and filled with water. This causes the hose to pull (roll itself up) into the canal. The advantage here is that the friction with respect to the old pipe can be neglected; the hose that slips down slides through the water and lies against the old pipe in a form-fitting manner. The viscous resin reacts (hardens) when heated (with warm water) in an exothermic reaction and a solid, fiber-reinforced "pipe in a pipe" is created.

There are methods that eversize with compressed air or pull in the hose with a cable winch and then set it up. The reaction of the resin can be stimulated and supported with steam or UV light. The advantages of this process are the short hardening time and lower energy consumption, as the entire volume of water in the hose does not need to be heated. The disadvantage is the limited range of possible uses, the rehabilitation of pipes in the groundwater or in culverts is often not possible. In addition, the practicable limit for such pull-in methods is currently approximately above DN 900 or above a wall thickness of approximately 14 mm. Larger diameters can be produced, but the process technology and the tightness in the standard manhole present the sewer workers with greater technical and physical challenges.

The liner has to harden for some time (depending on the diameter and length between 2 hours and several days) before the canal can be used again. It then has a wall thickness of at least 3 mm to typically 12 mm (or more depending on the nominal size), depending on the statics . The existing house connections are then milled out using sewer robots and should be connected to the rehabilitated sewer using so-called "hat profiles".

development

Such procedures were first used in accessible canals (so-called collectors) in England in 1971 and initially referred to as in-situ procedures ( Latin in situ, meaning the treatment of the damaged pipe on site). In the 1990s, these methods were increasingly developed.

Areas of application

In addition to the "standard market" of common main sewer nominal sizes (DN 200 to around DN 1200), the market has developed in the direction of house connections and underground pipes (DN 200 and smaller) with particularly curved liners.

Channels larger than DN 1200 have already been renovated (record: 427 m DN 2500 at San Diego Airport, California). This is primarily a capacity problem. The pipe liners are hardened with thermal hot water hardening. Large providers have to bring together several heating systems for this. The logistical problems with such large canals are usually enormous, since operations must be secured during the work.

Norms and standards

  • ISO 11296-4 - Plastic piping systems for the renovation of underground pressureless drainage networks (gravity lines) - Part 4: Pipe lining hardening on site

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