Can hot oil pipeline work be carried out without purging and directly?
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One of our distillation towers is heated using heat transfer oil, which is 300# grade and produced in Jiangsu. Due to the long length of the heat transfer oil pipelines, re-welding is required when there are leaks in the welds of the carbon steel pipes. Replacing these pipelines is a complicated process; it is said that some manufacturers simply perform electric welding, without any accidents occurring as a result. I would like to ask an expert: Is it possible to perform welding work on heat transfer oil pipelines without first replacing the fluid?
Steam is introduced to ensure a positive pressure in the pipeline; thus, an explosion cannot occur.
Safety is of the utmost importance; replacement must be carried out, and once the replacement is approved, a hot work permit must be obtained in accordance with the regulations. Which would you choose, trouble or life? Safety is life – remember that! ! !
Why not replace it? Safety accidents often occur due to carelessness
Replacement is required. Those who manage to delay construction are just lucky. The ignition point of heat transfer oil is generally around 450 degrees, while the temperature at the center of an electric weld is around 1500 degrees. Poor replacement can easily lead to danger. Safety first; people are the most important.
Although the auto-ignition temperature of heat transfer oil is relatively high, safety requirements dictate that it be replaced, analyzed to ensure compliance, and kept under positive pressure using steam. The author has experienced working on residue oil without performing gas displacement; since no explosive gases were formed in the pipes, the residue oil merely caught fire. However, this practice is absolutely not recommended as it is indeed unsafe. There are also liquefied gas spheres that, in practice, leak due to sand holes in the root valves; skilled welders can repair such leaks by making a few welds, and this is done when the liquid level is relatively high. However, as long as the pipes or containers are filled with explosive gases, and the area where welding takes place is within that zone of explosive gases, welding must absolutely not be carried out. In other words, working on the bottom of a tank filled with diesel might be fine if there’s enough space, but when the distance is only a few dozen centimeters, problems are bound to occur. Always follow the procedures!
It cannot be generalized: 1. First, understand the properties of the material and its explosive limit range; as far as I know, its explosive range is very narrow. 2. Scope and conditions of work: Such as what the diameter of the pipe is, whether it involves grinding over cracks followed by welding, cutting the pipe open and then grinding and welding again, or using band clamps, etc., as different construction methods may require different approaches. 3. Everyone should analyze the conditions for combustion and explosion (the three elements) before defining them, and there’s no need to be overly fearful. Therefore, in light of the above conditions, the following treatment options are proposed: 1. After grinding the cracks, carry out welding repairs or apply band clamps; it is sufficient to use N2 to remove oil from the surface, and ensuring a slight positive pressure within the system is enough to proceed with welding. Of course, a special welding permit is required as per regulations, and welding can only be carried out after it is signed by the chief engineer or the factory manager. 2. Construction after cutting the thin-diameter pipes: In this case, the oil can be removed first, water is filled into the main pipeline, and a small amount of N2 is used in the branch pipelines to purge and protect the area during welding. 3. Construction after cutting large-diameter pipes: In this case, it is possible to remove oil from the pipes, wash them with water in the main pipeline, and then blow them out with steam for 8 to 24 hours; work can proceed only after explosion tests show satisfactory results. However, if the cleaning effect is not good enough, it is still advisable to fill the pipes with steam or N2 as a protective measure. Of course, blind plates should be added in appropriate locations wherever possible. Note: If the methods above do not comply with your factory’s safety regulations, your factory’s or company’s safety regulations shall take precedence.
Agree with the view from the seventh floor. As long as proper consideration is given, pressure can be maintained using nitrogen during construction
I think: 1. Apply butter to the wall for sealing； 2. Then spray dry powder at the work area, and then weld