YUHONG GROUP - Application of fin tubes in the petrochemical industry

High-frequency welding finned tube is increasingly used in various fields of petroleum, chemical production, the most commonly used is the convection section of the ethylene cracking furnace, according to past experience, finned tube in the use of the process, if due to manufacturing, improper use, damage occurs, the finned tube can not play the role of convection to strengthen the role of heat transfer, so that the temperature of the exhaust smoke from the furnace to increase, affecting the heat recovery of the furnace.
Several common forms of damage to the finned tube are:

(1) finned tube fins off: that is, there are manufacturing welding reasons, but also operational reasons. Finned tube in the winding welding process due to improper selection of process parameters, resulting in welding is not secure or fins, tube surface oil caused by ‘virtual welding’; fin welding surface cooling water or other solvent oil as a coolant improper use of weld cracks. Especially when the operation is not when the finned tube before blowing ash condensation is not complete, a large number of condensate into the repeated rapid cooling and heating, resulting in weld thermal fatigue cracks, or the furnace on, stopping the process of frequent temperature rise and fall, will also cause fatigue of the fins weld fall off, like a spring-like heap together. Therefore, to avoid the fins off the method is to choose the appropriate welding process parameters to ensure that the welding, and operation to avoid repeated raising and lowering the temperature;

(2) fin local melting, ablation: furnace combustion ash and fuel furnace combustion is not sufficient, the carbon is brought into the convection section, accumulated in the fins, secondary combustion occurs, which burns the finned tube. The method to avoid secondary combustion is to strengthen the convection section of the stove pipe blowing ash, increase the number of blowing ash;

(3) local thinning of the finned tube elbow, burst: in the process media flow path in the elbow structure of the sudden change in the operation of the use of the process by the high temperature, high pressure gas flow scouring, it is easy to cause local thinning, thinning to a certain degree will cause bursting. In addition, the elbow in the hot push manufacturing process, there may be local thinning or micro-cracks, welding process, such as the impact of heat-affected zone may cause damage to the elbow in the use of the process;

(4) finned tube due to corrosion thinning or long-term service state, the material performance deterioration and burst: such as carbon steel pipe operating at 500 ℃ for a long time at high temperatures, it is very easy to occur pearlitic spheroidal tendency, resulting in the material of high-temperature strength becomes low, plasticity deterioration, bursting and so on. In addition, especially for stainless steel materials, in the start of cooking furnace alkali solution in the chloride easily caused by corrosion damage to the pipe, such instances in the petrochemical system has occurred many times, should pay attention to.