Process for spraying polyurethane on inner wall of nodular cast iron pipe

Abstract

The invention relates to a process for spraying polyurethane on the inner wall of a nodular cast iron pipe, in particular to the process for spraying the polyurethane on the inner wall of the DN100-DN300 nodular cast iron pipe. The steps of the process are as follows: 1. processing the inner surface: (1) removing rust and oxide skins; (2) shot-blasting, further removing the rust on the surface of the nodular cast iron pipe, and eliminating stress; (3) removing floating dust; 2. heating and drying; 3. preparing for the spraying: (1) storing coatings; (2) stirring the coatings; (3)_heating and heat-preserving the coatings; (4)_spraying for trial; 4. spraying the polyurethane: polyurethane components A and B are heated, filtered and heat-preserved according to the volume ratio of 1:1, are conveyed into a special mixer under high pressure for high-speed collision mixing or spiral mixing, and are then sprayed onto the surface of the nodular cast iron pipe by a spray gun or a spray cup at high speed in an atomized manner; 5. cleaning the mixer and the spray gun or the spray cup. The thickness of a film formed in one step can be up to 3mm and the adhesive power of the coatings is high, so that the invention can meet the demand for spraying the polyurethane on the inner wall of the small-caliber nodular cast iron pipe.

Description

technical field [0001] The invention relates to a process for spraying polyurethane on the inner wall of a nodular cast iron pipe, in particular to a process for spraying polyurethane on the inner wall of a DN100-DN300 ductile iron pipe. Background technique [0002] Ductile iron is widely used in the production process of water treatment. With the development of human beings and the needs of the environment, more and more water treatment projects have put forward higher requirements for the pipes used and their coatings. Polyurethane coating has the advantages of wear resistance, corrosion resistance and small resistance coefficient. It is very suitable for pipelines with special requirements for the inner wall coating of ductile iron pipelines, so it is favored by users. At present, the most widely used internal and external coatings of ductile iron pipes at home and abroad are mostly asphalt paint, epoxy resin, and cement lining. Foreign countries have developed polyuret...

AI Technical Summary

Problems solved by technology

Foreign countries have developed DN300 and above ductile iron pipes to spray polyurethane coatings. However, due to the complex process, difficult control, low pass rate and low production efficiency of DN100~DN300 ductile iron pipes, there are only a few such as France and Switzerland in the world. The state has mastered the technology of spraying high-density polyurethane coating on the inner wall of small-sized ductile iron pipes

[0003] Ordinary asphalt coating technology is simple, but its anti-corrosion ability is poor, and serious pollution is not conducive to environmental improvement

[0004] Lined cement coating is widely used, but its anti-corrosion ability is poor, its strength is low, and special anti-corrosion pipelines cannot be used, and its hydraulic resistance coefficient is large and energy consumption is high.

[0005] The anti-corrosion ability of epoxy coating technology is relatively high, but the maximum film thickness does not exceed 500 microns, and it needs multiple coatings, and the coating adhesion is poor