Safety protection method for underground metal pipeline

Abstract

A safety protection method for buried metal pipelines, which establishes a safety protection criterion for buried pipelines with the goal of protecting pipelines with good insulation. Cathodic protection is used as an auxiliary method of protection. The pipelines are divided into independent detection protection areas, and the installation can The output can also be output in the form of DC pulses, and a monitoring network can be established in the entire protection area to realize a real-time cathodic protection monitoring system characterized by detection current. By establishing a unified detection potential reference point, detection point or interval in the system If the leakage of the insulation layer is found, according to the specific position of Ohm's law, Thevenin's theorem and Kirchhoff's law, the early warning of internal damage and stress danger of the pipeline is realized, and the detection and early warning of stray current is realized according to the synchronous comprehensive current detection method. The difference between the stray current corrosion of the leakage part and the corrosion properties of the primary battery and the degree of corrosion inhibition have proposed a timely repair method that does not require major repairs of the pipeline.

Description

Technical field: [0001] The invention belongs to the technical field of pipeline safety, and in particular relates to a safety protection method for buried metal pipelines. Background technique: [0002] The use of cathodic protection to prevent corrosion of buried metal pipelines is now a well known technique. Since Faraday discovered the relationship between the amount of metal corrosion and corrosion current in 1833, which is known as Faraday's first law, in 1834, the British scholar Mr. Han David first used cathodic protection on warships. In 1928, the United States Robert J. Cohen (Kuhn) installed the first set of cathodic protection devices on a long-distance gas pipeline in New Orleans, and proposed a potential protection criterion of 0.85v, thus providing modern technology for buried metal pipeline cathodic protection Since the foundation was laid, cathodic protection technology has been widely used in the field of corrosion protection of metal pipelines. [0003] ...

AI Technical Summary

Problems solved by technology

If a certain point is used as a reference, the earth potential is different, although this difference is generally only within a few hundred millivolts, and these hundreds of millivolts are required for pipeline cathodic protection, 0.35 volts under a saturated copper sulfate reference electrode ( -0.85 volts to -1.2 volts) for the potential change interval of pressure difference fluctuations, it has seriously affected the correct judgment of the cathodic protection status of the pipeline

Therefore, it is at least not sufficient to use the earth as a reference to measure the pipe / ground potential as a criterion for judging the protection status of the pipeline

[0009] In essence, with the pipeline as the cathode, when the applied voltage to the ground where the pipeline is located is greater than the voltage of the primary battery, the primary battery will be in a suppressed state and no longer function, and the corrosion should stop. The existing tube / ground potential detection The method cannot detect the influence state of the primary battery, and of course the corrosion state of the pipeline cannot be clearly known. Especially, the potentiostat only adjusts the protection output with the potential of individual feedback points, and it is even more impossible to find the protection state of other points and other points. After the point potential exceeds the protection zone, in order to prevent corrosion, the voltage of the cathodic protection system is often pulled lower. Due to the long detection period and poor representativeness of the detection data, when the pipeline protection voltage is found to be unreasonable, it is already a leakage corrosion event that has occurred long ago. The inevitable result of low voltage is that the lowering of the protection potential of the pipe / earth stops the localized corrosion of the originally discovered part, and some new pipes undergo hydrogen evolution due to overprotection, resulting in hydrogen embrittlement of the new pipes and the peeling off of the anti-corrosion layer, forming new damage point, and then adjust the protection potential, resulting in a vicious cycle, resulting in more and more corrosion points in the pipeline, and the output power of the cathodic protection equipment is increasing. Finally, due to the limited power, the pipeline cannot continue to work, and the pipeline begins to accelerate the process of corrosion and scrapping.

[0010] Since the existing potential detection method cannot detect corrosion points in time, for the safety of pipelines, special corrosion detection must be carried out at a certain period in addition, and the parts with serious corrosion are excavated and repaired, while the places where pipelines are not seriously corroded are difficult to be found in time, and can only be done randomly. It continues to corrode, and the result is that the more the pipeline is repaired, the more corrosion spots will increase, and finally the corrosion spots will gradually increase until the pipeline finally loses its repair value

[0011] It can be seen that the maintenance method of repairing and repairing buried metal pipelines after serious corrosion and protection can not protect the pipeline well, and the periodic inspection and repair wastes a lot of money and manpower. scrapped

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