Cement mortar within the coating of spiral steel pipe

Municipal water supply pipe, spiral steel pipe in addition to outside the anti-corrosion, the need for internal anti-corrosion disposal. At that time the most use of cement mortar fabric corrosion, the method is evenly coated in the steel pipe wall layer of cement mortar leaving the pipeline to be protected. Cement mortar within the coating can not only avoid the corrosion of the inner wall of the pipeline, extending the use of pipeline life, and to protect the water quality, adhere to or improve the pipeline water supply, with significant economic and social benefits.

Spiral steel pipe to do the common sense of cement mortar inside the coating as follows:

(1) Spiral steel pipe material required
Cement should use more than 42.5 grade grade silicate, usually Portland cement or slag Portland cement. Sand should be used to consolidate, clean, graded with excellent natural sand, no debris, the amount of its blur is not greater than 2%, the maximum particle size of not more than 1.2 mm, gradation should be based on construction technology, diameter, site construction conditions to determine. Mixing water is necessary to clean, do not have the soil, oil, acid and alkali and other effects of cement mortar strength, durability of the material, usually use drinking water.

(2) Spiral steel pipe coating construction conditions
Cement mortar fabric construction, usually under the pipeline should be completed, the test pressure and according to the plan needs to be compacted after compaction. Fabric construction process, the pipeline is necessary to be in a stable situation. If the first fabric after the next layer of anti-corrosion, the steel pipe wall will be thin, small stiffness, in the construction of lifting, transportation, soil is also a large deformation and damage to the coating. Before the construction of the fabric, the inner wall of the pipe is necessary to clean, remove the soft oxide, floating rust, dirt, grease, welding slag and other attachments; steel pipe wall protrusion shall not be greater than the thickness of the coating plan 1/3; Vertical deformation shall not be greater than the planning rules, and not more than 2% of the pipe diameter.

(3) Spiral steel pipe coating construction
Cement mortar coating can be used mechanical spraying, artificial pressure relief, dragging drum or centrifugal prefabrication method construction. If it is necessary to use prefabricated method to do the inner coating, the spiral steel pipe in the transport, installation, backfill process should be used to protect the protective coating. Construction, the main mix of cement mortar, cement and sand quality cooperation ratio of 1: (1-2), cement mortar slump of 60-80 mm, cement mortar compressive strength should not be less than 30MPa. Mechanical coating method of cement mortar within the coating surface smooth, fine, uniform thickness, the role is better. Foreign 1930s began to use mechanical spraying construction, China since the 60's has successively in Shanghai, Qingdao, Dalian and other cities. When the mechanical spraying method is used, the elbow, the tee, the special pipe and the gate valve are close to the pipe section, etc., and can be smudged by hand and the smooth splitting section is connected with the mechanical spraying cloth. In addition, the towel or centrifugal prefabrication method is also widely used, no longer elaborate here. Spiral steel pipe regardless of what method of construction, protection processes are to ensure that the cement mortar coating does not occur cracks and hollowing the key link. Therefore, the cement mortar within the coating after forming, it is necessary to immediately block the pipeline, shall not constitute air convection; after the final condensate wet protection, usually Portland cement protection time should not be less than 7d, slag cement should not Less than 14 d; water should continue to block before, adhere to the wet.

(4) The construction quality of the coating in the spiral steel pipe
The quality of the coating in the cement mortar shall comply with the following rules.
1) The width of the crack shall not be greater than 0.8 mm and shall not be longer than the length of the pipe and shall not be greater than 2.0 m.
2) The thickness of the coating error and pitting, empty dots and other surface defects should be consistent with the depth of the rules, spiral steel pipe defect area should not be greater than 5cm2.
3) Flatness need to 300 mm long ruler, along the direction of the vertical axis of the pipe attached to the wall, measuring the surface of the coating and the gap between the ruler should be less than 2mm.
4) Hollowing area per 1m2 shall not exceed 2, each shall not be greater than 100cm2.