Cathodic protection range of PCCP pipeline

As early as 1984, in the study of the cathodic protection of the Gaeping-Yingkou water supply line, the literature indicated that the protection potential was -0.50V(CSE) when the concrete protective layer was not damaged. When chloride has been applied to the steel bar, the value is -0.71V. Has eroded steel bar, using -0.77V; In Japan's "Guidelines for Preventing Erosion of Concrete Structures in the Ocean", the protection potential is defined as -0.77V~-0.85V; To sum up, negative offset -0.10V is adopted for cathodic protection of Geping-Yingkou water supply line; And -0.77V~-0.85V.

In the protection section of THE PCCP pipe, in order to ensure the service life and protection range of the sacrificer anode, each 20 PCCP pipes (about 100 m) are used as a protection unit for electrical continuity bonding; There is no electrical continuity bonding between each protection unit.

The above text is quoted from "Cathodic Protection of Concrete Pipe of Prestressed Steel Cylinder" by Hu Shixin et al.

The scale of NACE RP 0100-2004 requires that after the cathodic protection system of PCCP pipeline is put into operation, the polarization potential difference of pipeline should not be less than 100mV; The minimum negative potential should be no less than -1000mV(minus the IR drop).

Electrical insulating

Both cathodic protection and stray current protection measures for reinforcement assume an electrical continuity extending through the reinforcement. The maximum protective potential was below the hydrogen evolution potential, which was -1.170V. This scale is derived from laboratory test results and successful cathodic protection empirical data. This code is applicable to cathodic protection and erosion control of PCCP pipelines. To this end, the measuring cables are connected to the reinforcing bars after the concrete has been removed from the different points at long distances.

Cathodic protection criterion

In order to prevent the interference of stray current and the loss of the protection current of THE PCCP pipe, insulation measures should be installed at the head and end of the protection pipe, branches and connections with the external pipe for electrical insulation. The practice in foreign countries tells us that cathodic protection is an effective corrosion prevention technology for buried PCCP pipe, and it has been popularized in foreign countries. For example, the Great Artificial river project in Libya adopted cathodic protection on the basis of summarizing the experience and lessons of the first phase of the project. If measured resistance value & GT; 1 ω, indicating that electrical continuity is not fully achieved. During the design, the cathodic protection method and detection period can be determined according to experience to meet the requirements of similar scale.

PCCP pipe water supply and drainage engineering provides high quality and long life pipe materials, for large diameter and long interval has great wind, in recent years in the sea has made rapid progress in the development, but because the PCCP pipe in the sea application time is short, the erosion of this kind of pipe has not caused people to face up to.

According to the requirements of NACE RP 0100 scale [8], electrical continuity shall be made between the prestressed reinforcement and the steel cylinder in the PCCP pipe to ensure the electrical continuity of the cathodic protection current between the prestressed reinforcement and the steel cylinder. At the same time, to ensure the electrical continuity between THE PCCP pipes, each PCCP pipe should be electrically continuous bonding. To avoid the influence of contact resistance, rust should be completely removed from the contact points. Although the technology of PCCP pipe started late in China, the starting point is higher. The CATHOdic protection of PCCP pipe in the south-to-north water transfer project has been designed and is being put into practice, which is the first time in China. Its experience will bring a qualitative surge to the construction of PCCP pipe in China in the future. The steel bar should then be short-circuited to the rest of the reinforcing steel bar of the mesh which has achieved complete electrical continuity.

If the protection section of PCCP pipeline contains steel pipe fittings such as (manhole) exhaust valve well, drain valve well and connecting measures, electrical continuity should be connected at both ends of (manhole) exhaust valve well, drain valve well and connecting measures steel pipe fittings to ensure the continuity of cathodic protection current. This is the case for most reinforced concrete structures with steel bars, but this is verified by measuring the resistance of the reinforcing mesh.

Electrical continuity requirement