Spiral steel tubes - spiral seam submerged arc welded steel tubes for pressure fluid transport

Spiral steel tubes - Spiral seam submerged arc welded steel tubes for Pressure Fluid transport (SY5036-83)

Mainly used for transporting oil and natural gas pipelines; Spiral joint high-frequency welded steel pipe (SY5038-83) for pressurized fluid transportation, welded by high-frequency lap welding method, spiral joint high-frequency welded steel pipe for pressurized fluid transportation. The steel tube has strong bearing capacity, good plasticity, and is convenient for welding and processing. General low-pressure fluid transport with spiral seam submerged arc welding steel pipe (SY5037-83), using double-sided automatic submerged arc welding or single-side welding method for water, gas, air and steam and other general low-pressure fluid transport with submerged arc welding steel pipe.

Spiral tube material: Q235A, Q23b,0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb.Q345 L245 L290 X42 X46 X70 X80. Spiral welded steel pipe refers to the steel strip or steel plate bending deformation into the shape of round, square and then welded into the surface of the steel pipe joints. According to the weld shape can be divided into straight seam welded pipe and spiral welded pipe. Welded steel tubes are used in oil drilling and machinery manufacturing.

Now the commonly used standard of spiral steel pipe is generally divided into :SY/T5037-2000(ministry standard, also known as common fluid transmission pipe spiral seam submerged arc welded steel pipe), GB/T9711.1-1997(national standard, also known as oil and gas industry transmission pipe delivery technical conditions part I: Class A steel tubes), API-5L(American Petroleum Institute, also known as pipeline steel tubes), SY/T5040-92(spiral joint submerged arc welded steel tubes for piles).

Aiming at the three processes of electrochemical corrosion of buried pipelines, the anti-corrosion method of spiral steel pipe also starts with the inhibition of one of them. If the outer wall of the pipeline is coated with anti-corrosion coating, the circuit resistance can be increased and the corrosion current can be reduced; The addition of DC power supply can make the steel tube cause negative potential to the soil and form cathodic protection, which can eliminate the potential difference between anode and cathode and stop the process of anode and cathode fundamentally. Anticorrosive coating rule of law table, cathode protection law. But once the anticorrosive coating is broken, the exposed iron will accelerate the local corrosion. Therefore, the combination of anticorrosive coating and cathodic protection is an economical and effective method. The United States and other countries have clearly stipulated that the use of anticorrosive coating must be accompanied by cathodic protection.

However, for the urban gas system, due to the intensive underground pipe network, the external power supply of cathodic protection will cause great interference to other pipelines, which will result in the situation of self benefit and his family suffering. However, the sacrificial anode protection method with metal material with negative potential than steel tube and spiral steel tube will not appear this kind of situation. Therefore, the anticorrosive method of combining anticorrosive coating and sacrificial anode should be adopted for the main gas transmission pipe of urban gas. For other low pressure non - trunk pipe, usually direct use of anticorrosive coating method.

At present, the commonly used external anti-corrosion coatings for buried gas pipelines mainly include three layers of PE composite structure, epoxy resin powder (FBE), coal tar porcelain, epoxy coal pitch and PE tape. The three-layer PE composite structure and epoxy resin powder anticorrosive coating have excellent performance, so it is also the main anticorrosive coating for buried pipelines in European and American countries [1]. In China, from the durability of life, maintenance costs and other comprehensive economic factors, generally preferred three layers of PE composite structure anticorrosive coating.

In sacrificial anode protection, magnesium alloy is generally used as sacrificial anode to protect pipelines. Because of the damage in the process of output current, the design service life of the magnesium alloy sacrificial anode is best matched with the service life of the pipeline, neither waste nor increase maintenance costs. However, it should be noted that sacrificial anodes should not be used when the soil resistivity is too high and the protected pipeline crosses the water.

Different anti-corrosion methods have different anti-corrosion quality and cost. The anti-corrosion method and cost should be considered comprehensively according to the different pressure, different use, different environment and different gas of the protected spiral steel pipe. Two points should be paid attention to when considering the economic rationality: (1) the primary anti-corrosion investment during the construction of the gas pipe network, and (2) the maintenance cost after the operation of the gas pipe network. Because the urban gas pipeline network is located in the urban area, the maintenance and overhaul is difficult and the cost is high after the operation, so the one-time investment should be appropriately increased to reduce the daily maintenance workload of the pipeline after the operation.