Corrosion hazard and control measures of buried gr

Corrosion hazards and control measures of buried grounding wires in oil depots at present, the corrosion detection and anti-corrosion technology of oil tanks and pipelines is gradually maturing. However, the corrosion of buried grounding wires is still ignored. On the one hand, because the corrosion of buried lines does not affect the leakage of media, and the degree of attention is not enough, there are generally no basic anti-corrosion measures for buried lines, which is very easy to cause serious corrosion in the short term; On the other hand, due to the particularity of its burial, it is difficult to judge the degree of corrosion and maintain the corrosion, so the corrosion problem can not be dealt with in time. As far as the current buried grounding system is concerned, there are still many disadvantages in practice and design. If these unsafe factors cannot be paid attention to, they will leave hidden dangers for future safety work

I. hazards of corrosion of buried grounding wires in oil depots

(I) there are generally no basic anti-corrosion measures for buried grounding wires, which brings great inconvenience to future maintenance work. According to the general practice, the buried grounding trunk line and branch line are directly exposed underground, which is not done according to the same anti-corrosion grade of the buried pipeline. On the one hand, the buried grounding wire is generally made of carbon steel, and the structural and structural changes of the material itself, such as welds and heat affected zones, are easy to cause structural changes and aggravate corrosion. On the other hand, the corrosion degree of the grounding wire is closely related to the resistivity of the surrounding soil and other factors. The soil with low resistivity is highly corrosive, and vice versa. According to relevant data, if the oil hole of the buffer is blocked, the resistivity of 14 kinds of soils in China is measured. The annual corrosion rate of metals ranges from 0.005 to 0.085mma-1. The corrosivity varies greatly in different regions, and some areas with serious corrosion can reach 1mma-1 or more. According to the current standard, the grounding material is 40 × 4mm Flat steel or Φ The vast majority of 16mm round steel adopts galvanized flat steel. In areas with severe corrosion, it is likely that the overflow area will be greatly reduced in a few years. At the same time, in areas with less corrosion, local severe corrosion may also occur. However, the existing grounding systems of oil depots in our army were built earlier, and the corrosion of buried lines was easy to be ignored during use, and the corrosion parts could not be treated in time. Even if some grounding wires need to be replaced after passing the test, it is difficult to replace them because of the strict regulations in the oil depot area, and hot work is prohibited in the bending test of cemented carbide. At the same time, considering safety, economy and other factors, it is difficult to replace them

(II) safety problems caused by the corrosion of buried grounding wire during the use of gear testing machine in friction and wear testing machine. The purpose of the grounding system of the oil depot is mainly to make equipotential connection between electrified bodies such as oil storage equipment and the ground, accelerate the dissipation of charges, and prevent explosion caused by static electricity accumulation or lightning strike. Taking the electrostatic grounding system of oil tank as an example, the usual practice is to connect the tank with the grounding body through the grounding trunk line, and judge whether the electrostatic system meets the safety standard according to the resistance value of the grounding body. However, if the buried trunk line or branch line is seriously corroded, even if the measured resistance of the grounding body meets the requirements, it cannot play the role of equipotential connection with the tank body, but creates the illusion of safety and increases the risk. In addition, other grounding systems are quite different in structure, such as oil pipelines, pump rooms, gas stations, etc., which also have the same problems