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The Role Of Polyurethane Spraying In Pipeline Trenchless Repair

December 21, 2021

1. Definition of polyurethane spraying

An emerging trenchless pipeline repair technology that sprays the lining material onto the inner surface of the existing pipeline to form a lining covering layer to improve the pipeline’s pressure resistance, corrosion resistance, and wear resistance.

2. Scope of use

(1) Structural repair or chemical protection of reinforced concrete pipes, brick pipes, cast iron pipes, steel pipes, clay pipes, etc.;
(2) Pipelines with a diameter greater than 800mm, trench boxes with a width and height greater than 800mm, etc., especially those projects that are affected by traffic conditions and the surrounding pipeline network and other complex environments, and excavation methods cannot achieve the goal.
(3) Check the tightness of the well and repair the structural integrity.

3. Process

1) Precipitation and drainage;
2) Check well for ventilation or forced drainage;
3) The inspection well is cleared;
4) Pipeline dredging;
5) Polyurethane plugging and seepage water treatment;
6) The high-pressure cleaner cleans up all the residues or impurities on the base of the shaft wall; smoothes the shaft wall with cement mortar or modified epoxy mortar; uses indirect heaters to dry the surface.
7) Adjust the equipment to the temperature and pressure coefficient required by various materials for preheating.
8) After the test spray quality of the test block meets the requirements, the spraying operation can be performed.
9) Continuously work in the order of detail first and then the whole, and cross spraying to the thickness required by the design for multiple passes at a time.
10) After the spraying construction is completed and passed the inspection, if there are special requirements, a protective layer can be applied to the surface. For example, anti-ultraviolet ability, you can apply topcoat on the coating surface.

4. Process characteristics

1. Polyurethane lining has the characteristics of rapid formation, strong toughness, corrosion resistance and wear resistance, and any desired thickness can be obtained with only one spray application;
2. The polyurethane inner lining cures quickly, starting to cure in 2 seconds, reaching a non-shedding state in 2 minutes, and fully curing in 4-6 hours, and water can be passed 30 minutes after application;
3. Because its construction method is spraying, it has strong adaptability to irregular base surfaces, and is suitable for adhesion of various corners and uneven contact surfaces;
4. After the lining is repaired, the surface roughness is low, with a Manning coefficient of 0.009, which is the same as that of the PE pipe; the anisotropic strength is more uniform after repair;

5. Process advantages

Some scholars used ANSYS to establish a three-dimensional finite element numerical simulation of the pipeline-asphalt pavement structure, and analyzed the force characteristics of the underground pipeline. High strength. And can improve the wear resistance, pressure resistance, corrosion resistance of the pipeline, and increase the service life of the pipeline.

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