In recent years, many cities in China have built sewage treatment plants. Most of the water pipelines in urban sewage treatment projects are buried in steel pipes. Corrosion is a major problem in sewage treatment projects. The quality and life of the underground water pipeline directly affect the whole project. Therefore, it is very important to protect the underground pipeline in the city sewage treatment project.

1. buried pipeline characteristics

1.1 Corrosion Characteristics

The corrosion of buried pipelines in urban sewage treatment engineering is mainly soil corrosion, which is characterized by scattered pipeline layouts and complex soil conditions, so the corrosion mechanism is complex.

Soil corrosion includes electrochemical corrosion and microbial erosion of steel tubes composed of salt, water, and oxygen in the soil. Due to the dense underground electrical facilities and cables in the city, the corrosion of stray current is also serious, and the pipelines passing through the vicinity of the factory may even be subjected to chemical corrosion by acid or alkali media.

1.2 Mechanical characteristics

Urban buried pipelines often pass through roads, buildings, rivers, etc., resulting in complex compression conditions. In addition, the pipeline may be impacted and crushed by stone sand in the process of buried backfilling.

1.3 Maintenance Difficulties

Once the buried pipeline is damaged by corrosion, it is not easy to inspect and maintain, so corrosion is aggravated. During maintenance, environmental damage is often caused. Because of this feature, the design life of the buried pipeline and its anti-corrosion is generally required to be more than 20 ~ 30A.

2. anticorrosive layer requirements

According to the characteristics of urban buried sewage pipelines, the anti-corrosion layer of the pipeline should meet the following basic requirements:

(1) It has good chemical corrosion resistance;

(2) Good insulation performance and compactness, prevent electrochemical and stray current corrosion;

(3) Bacterial corrosion resistance;

(4) It has a certain mechanical strength to prevent mechanical damage in the process of handling and burying;

(5) The construction is simple and safe and meets the requirements of site construction.

In addition, there are some special requirements in special areas, such as cold resistance.

3. commonly used anti-corrosion methods

There are several anti-corrosion methods that can be used for urban sewage-buried pipelines:

3.1 Petroleum asphalt - glass fiber cloth coating

This anticorrosion method used to be used in oil pipelines, but is now being phased out. Its advantage is a wide source of raw materials and low cost. Disadvantages are not resistant to bacterial corrosion, poor physical properties, and a poor construction environment.

3.2 Chlorosulfonated polyethylene coating - glass fiber cloth coating

This method has a good anticorrosion effect and a wide construction temperature range and can be used in conjunction with cathodic protection. However, the surface treatment requirements are high, the coating is thin, and the mechanical strength is low. It was used in the water diversion project of the Huangpu River in Shanghai.

3.3 Epoxy coal tar pitch coating - glass fiber cloth coating

This method has good chemical and electrochemical corrosion resistance, bacterial corrosion resistance, high mechanical strength, and a wide application range. Can be used in conjunction with cathodic protection. The disadvantage is that it can not be constructed at low temperatures (below 0℃), and the surface treatment requirements are high. At present, it is widely used in urban sewage treatment engineering.

3.4 Coating the anticorrosive layer with polyethylene insulation tape

This method is convenient to construct, easy to repair and has good anti-corrosion performance. However, the mechanical strength is low, the resistance to cathodic stripping performance is poor, and should not be used with cathodic protection, and the sealing performance is poor in special-shaped parts. It is widely used in oil and gas pipelines.

3.5 Fused epoxy coating

The advantages of fused epoxy coating are good corrosion resistance, high mechanical strength, high construction efficiency, and good coordination with cathodic protection. However, the coating construction should be carried out in the workshop, and other methods (such as liquid epoxy resin) should be used in the field repair. Fused epoxy coating is widely used in foreign countries.

3.6 Cathodic protection

It is an advanced anti-corrosion application technology with a good anti-corrosion effect, long and predictable life, and monitoring of pipeline operation and corrosion condition. It must be used together with an anti-corrosion coating. Industrial water pipeline and long-distance pipeline application, and the effect is good.

Cangzhou shenlong pipe manufacturing co., ltd. Is engaged in oil, gas, water, coal slurry mixing medium steel pipeline coating operations, anti-corrosion, insulation, piping is set in a body's specialized pipeline engineering precast construction enterprises, products used in an oil pipeline, chemical piping, electrical, pipe, gas pipe, heat pipes, sewage pipes, etc. Anti-corrosion processing of straight pipe and bend pipe DN40-3000 three-layer structure polyolefin (PE, PP, TPEP,3LPE) steel pipe coated with anti-corrosion, DN40-3800 steel hot stewed bend pipe and pipe fittings coated with FBE, epoxy resin coating anti-corrosion, DN40-3800 steel pipe inner wall resistance reduction, solvent-free epoxy steel pipe, epoxy paint anti-corrosion, Coated plastic steel pipe, dip plastic steel pipe. Lined with plastic steel pipe PE, PO, PP, PTFE, HDPE, polymer polyethylene corrosion. The company is in strict accordance with China Petroleum and Natural Gas SY/T0413-2002, national GB/T23257-2009, German DIN 30670, American AWWA C210, and other international and domestic anti-corrosion standards.