Which resins are used in pipe rehabilitation?

Our range includes various resins for successful pipe and sewer rehabilitation. Read on to find out more about the different types of resin and their areas of application.

Epoxy Resin for CIPP Applications

The CIPP (Cured-In-Place Pipe) method enables fast and comparatively cost-effective sewer rehabilitation. Especially for longer pipe sections, it quickly becomes apparent that effort and costs remain manageable with trenchless rehabilitation. Instead of excavating soil and breaking through walls, a hose made of durable fabric material is impregnated with a special resin and inserted into the pipe via a manhole. Using pressure, the liner is pressed against the inner pipe wall and cures in place. After just a few hours, the sewer pipe is permanently sealed again, and the rehabilitation is completed following a corresponding inspection. In contrast to partial CIPP repairs (short liners), full-length CIPP rehabilitation can renew sections of twenty to thirty meters or more at once.

Two types of resin are used in CIPP applications: epoxy resin for house connections and interior pipelines, and epoxy resin for mainlines. It is important to distinguish between in-house rehabilitation and municipal sewer rehabilitation. As soon as the pipe leaves the property boundary, it falls under the municipal domain, where mainline resin is used.

Epoxy Resin for House Connections and Interior Pipelines

Epoxy resin for house connections and interior pipes is available with higher viscosity. This is necessary because house connections often involve shorter pipe sections and many bends. The viscous resin can better navigate around these tight curves.
The resin is also available in different subtypes with varying curing and working times. The term "pot life" refers to the period during which the reactive resin system can be processed during CIPP installation — meaning the carrier material can be sufficiently saturated and the liner reliably positioned.
Pot life depends on the formulation of the reactive resin, the processing temperature, and the quantity being mixed. Typically, pot life values are specified at a resin temperature of 22°C. Higher ambient and resin temperatures shorten the pot life, while lower temperatures extend it:

If only one or two metres of pipe need to be rehabilitated, a resin with a shorter working time can sometimes be selected. For longer sections with many bends, however, a resin with a longer working time is recommended. Seasonal conditions and temperature are also important factors that influence curing speed. During the summer months, it is common to use a resin that cures more slowly, because the higher the temperature, the faster the resin reacts. Many rehabilitation technicians use the trick of placing the resins in tubs of cold water beforehand to counteract the temperature effect and slow down the reaction time.

Epoxy Resin for Mainline Applications

The epoxy resin used for mainline rehabilitation is less viscous than the epoxy resin for house connections and interior pipes. It is tougher and therefore better suited for larger diameters and longer distances that need to be rehabilitated. As with the interior resins, various versions are available, differing in their working and curing times:

The processing time and curing time must be adapted to the construction site. Inexperienced users should initially choose resins with a long processing time so that they can react more easily in the event of errors. Bends in pipes in particular are difficult to renovate at the beginning. With a short processing time, there is hardly any time to react if the packer gets stuck in the bend or something else unforeseen happens.

Silicate Resins for Short Liner Applications

Short liner methods are used to repair localized damage. They are classified as repair techniques and are primarily aimed at sealing sewer sections that have been damaged by

• leaking pipe joints,
• radial cracks,
• holes,
• fragmented pipe sections, or
• longitudinal cracks.

For this purpose, a synthetic resin made of two or three components is mixed according to the manufacturer's specifications. A fiberglass mat or synthetic fiber felt, cut to fit the damaged area, is then impregnated with the liquid resin mixture. The saturated carrier mat is placed onto an inflatable packer that is sized to match the nominal pipe diameter. Under camera observation, the packer is pulled or pushed into position at the damaged section. Installation is carried out after thorough cleaning and with maintained flow diversion (bypass pumping if necessary). At the damaged site, the packer is inflated with compressed air, pressing the impregnated short liner fully and overlapping onto the old pipe. During this process, the resin also penetrates into pipe joints, cracks, and spaces between pipe fragments. After curing — depending on the resin system used, between 45 minutes and ten hours — the packer is deflated and removed.

(c) CarboLith PL Spot Repair System, 2022, S. 4

Three-Component Resin

Silicate resins are primarily used in the short liner process. There are two types of silicate resin used in this process. The first type is a three-component resin. For instance, CarboLith PL silicate isocyanate resin is made up of components A (white, water glass component), B (black, isocyanate component) and C (white, catalyst), which are mixed together according to the instructions. The advantage here is that components A and B remain unchanged, while component C acts as the catalyst. I can therefore determine the processing time by adding more or less of component C. The more component C I add, the faster the resin hardens and the shorter the processing time.

Two-Component Resin

The second type of resin used in the short liner process is a two-component system. There are different variants of this resin, including winter, summer and turbo resins. In this system, component C is fixed directly into the overall system.

The summer resin hardens slowly and has a longer processing time. The winter resin hardens faster, resulting in a shorter processing time. Turbo resin hardens very quickly. It has the shortest processing time of all. With turbo resin, it only takes a few minutes from mixing to pressing the resin into the pipe.

Customer Requirements and Weather Conditions Determine the Choice

The decision as to whether a customer selects a two-component or a three-component resin is usually based on personal preference. If the customer wishes to control the curing speed themselves, a three-component resin is preferred. If, however, the customer relies on fixed processing times, a two-component resin is typically selected. Moreover, depending on the specific site conditions and the weather forecast, the choice of silicate resin may vary. During the summer months, a "summer resin" is generally used, as high temperatures significantly reduce the available processing time. "Turbo resins" are commonly employed for small-scale repairs. Experienced professionals tend to use turbo resins, whereas beginners often opt for slower-curing resin types.

In both CIPP (long liner) and short liner rehabilitation methods, the choice of repair technique largely depends on the customer's requirements. The sewer rehabilitation engineer is familiar with all available rehabilitation and repair systems and determines the appropriate method based on the site-specific conditions, bearing in mind that they may be held accountable for any rehabilitation defects. The site supervisor must thoroughly review the technical specifications and tender documents, compare them with the actual site conditions, and, as part of the preparatory work, clarify whether the short liner method is technically feasible for the repair of the existing pipeline.

Prior to installation, essential site conditions — such as access to manholes, storage space, and flow management — must be assessed. Incorrectly selected base materials can lead to corrosion, exposed carrier fabrics, an insufficient resin matrix, incomplete curing, and poor adhesion to the host pipe. Consequently, only material combinations approved by the manufacturer may be used. Ideally, the selected system should hold a general building authority approval (e.g. DIBt certification) or an equivalent recognised certification.

Injection Resins for Manhole Rehabilitation

In addition to silicate and epoxy resins used in CIPP and short liner procedures, special resins are also employed for manhole rehabilitation and robotic sewer repairs. These resins are fast-reacting two-component injection resins, designed to seal and consolidate water-bearing zones, particularly under pressurised water conditions.

When repairing cracks in manholes and sewer pipelines, or when sealing leaking joints to prevent groundwater infiltration and minimise the entry of extraneous water, polyurethane injection resins are typically used. The resin is injected into the cracks. These injection resins are rapid-setting two-component systems that foam upon contact with water. There are also lower-foaming polyurethane resins, which are used where the manhole already contains high levels of moisture.

A third variant exists: flexible resins, which are applied when significant mechanical stresses, such as vibrations from heavy goods vehicles, act on the structure. Flexible resins are capable of compensating for such stresses and ensuring the long-term stability of the repair. The grouting resins are inserted into the shaft by hand. Robots can provide support in the pipe area that cannot be entered.

Here's how it works: To seal cracks, a 12 mm hole is drilled approximately every 10 centimetres and dowels are inserted. You then have the resin in a gun and this is injected into the holes and the crack. If the crack was just sealed, it would leak again after years, which is why these holes are drilled. Manhole renovation is done by professionals. Customers are, for example, homeowners whose inspection chambers have groundwater inlets that do not pass a leak test and who want their chambers repaired.

Please refer to the safety data sheets for the resins

In summary, epoxy resins are used in the CIPP method (long liners), while silicate resins or polyurethane resin systems are applied in the short liner method and in injection resin systems for manhole rehabilitation. Epoxy resins differ from silicate and polyurethane resins in that they generally contain ingredients that are more irritating to the respiratory system and skin, which may be released during processing. Therefore, greater attention must be paid when handling epoxy resins. However, it is always essential to carefully study the relevant technical data sheets and safety data sheets for all resins prior to processing and to wear the appropriate personal protective equipment when working with these materials.

Would you like to learn more about resins and their application? We would be pleased to advise you.

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