Practical example – light curing in use
Rehabilitation task: Several road inlets, which were rehabilitated from the lateral sewer inlet to the main sewer.
Duration: approx. 1 hour
Material: BRAWOLINER® 3D DN 100-150
Curing method: light curing (UVRelining)
Brief description: A preliner was installed before the actual rehabilitation. The liner was then blown in and cured with the light curing unit within a few minutes. Afterwards the drain inserts were cut flush and integrated with fibreglass moulding.
The advantages of light curing are obvious here: the time window for flushing the pipe, installing the pre liner and liner and curing was approx. 1 hour.
Executing company: PKT – Pader Kanal Technik – Rohr Frei GmbH & Co. KG
The market for the rehabilitation of building and property drainage is developing dynamically. Especially due to the complexity of construction sites, the demands on sewer rehabilitation companies have increased enormously. In addition to the established curing processes (ambient temperature, steam and water) in the rehabilitation of property drainage pipes, curing with light has also established itself on the market in recent years. The rehabilitation companies are especially convinced by the short curing times and the associated economic advantages. But what are the real advantages of this system and what are the disadvantages?
Fields of application for light curing
Curing with the aid of light is particularly suitable on construction sites for property drainage where there are no or only a few inlets and branches at the connecting sewers. Good accessibility in the area of the starting point and ideally also of the destination point (e.g. shaft, inspection opening) are advantageous in order to be able to protect the connection area against penetration of water behind using e.g. collars or epoxy resin spatulas after completion of the shrinking process.
Disadvantages of light curing
Yet besides the economic advantages of light curing, there are also negative side effects.
With the systems currently available on the market, a (minimal) annular gap is created in a large number of rehabilitation projects. This is due to shrinkage processes caused by the resin used (e.g. vinyl ester resin), which means that the resin does not form a positive connection with the old pipe. The annular gap can allow water to get in behind. For example, groundwater and roots can penetrate between the outside of the liner and the inside of the old pipe. This can jeopardise the success of the rehabilitation.(see expert report “Support for sample construction sites – testing for freedom of penetration of water behind on different house connection systems” issued by the accredited testing laboratory for plastics in hose lining, Siebert + Knipschild GmbH 1)
Therefore, according to the generally accepted rules of technology, the integration of hose liners in the case of annular gap formation with e.g. liner end collars, swelling tapes or reaction resin systems is required.
(see DWA-M 144-3)
The resins used, such as vinyl ester resin, only cure on contact with light. This means that the resins do not harden in the soil and can therefore enter the groundwater when escaping into the soil. At the forefront of the hose liner process is a clean, safe and environmentally friendly rehabilitation. Environmental pollution should be avoided in any case. Against this background, the use of a preliner is particularly recommended when using light-curing equipment and light curing. This prevents uncured resin from entering the groundwater via damaged areas.
The sewer rehabilitation companies agree: light curing is an economically viable addition to the existing portfolio of curing methods used in property drainage.
To ensure the environmental compatibility of light resins, the use of a preliner is recommended. This is the only way to ensure that any impact on the body of groundwater/soil is avoided.
The challenge is to further develop the technology so that the disadvantages of the curing method are minimised. For example, light-curing, styrene-free vinyl ester resins allow significantly faster curing times than cold/temperature-curing epoxy resins, but epoxy resins have proven themselves over more than 20 years with regard to avoiding penetration of water behind and due to their good mechanical properties.
Ultimately, the requirements of the construction site still determine the choice of the rehabilitation method. Call our office or use our chatbot for more information.