Special grade hot fire - electric welding with material
Thread Content
Today, the stirring reactor of a certain workshop in our unit broke, and the fracture was outside the reactor. There are Class C flammable liquid formic acid and other materials (viscous) in the kettle, which cannot be transferred ； Moreover, the smell of formic acid is so strong that it is difficult to open the kettle and stir it. Make a good seal, use negative pressure in the kettle, and for stirring cutting, electric welding, the neutral line of electric welding is directly welded to the welding joint. I have always been afraid that sparks would be generated in the kettle during welding, but luckily I have been fine. ask: Is this dangerous?
Not ordinary danger, but considerable danger.
It's very dangerous. Fortunately, your ignition point is not on the cauldron. If that were the case, the negative pressure would directly draw the sparks in and explode!
I think the safety measures are okay. The dangerous properties of formic acid.: Combustible. Its vapor and air can form an explosive mixture, which can cause combustion and explosion when exposed to open flames or high heat. Chemical reactions may occur on contact with strong oxidizing agents. It is highly corrosive. Since the sealing is done and there is negative pressure in the reactor, according to the three elements of combustion and explosion, there is no element of mixing flammable gas and air to reach the explosion limit, so it is still relatively safe. Please correct me in my personal opinion.
This approach is quite thrilling, and it belongs to the bold type of people with high skills. If the safety control is changed, it may not be possible to play well. It is better to be cautious, and be careful to sail the boat for thousands of years.
Personally, I think it's very dangerous, especially in a negative pressure state. Send some information (some incomplete) for reference: When welding operations are carried out in flammable and explosive material systems or production systems, the system should be effectively isolated, which includes two aspects. One is the isolation of flammable and explosive materials, that is, the isolation of flammable and explosive materials from flammable parts. ； Second, the welding circuit itself is electrically isolated from the flammable and explosive system. Through years of fire practice and accident lessons, the importance of isolation in these two aspects has formed a consensus in the fire management of chemical systems. However, it should be pointed out that not everyone understands the importance of two isolations. Some even object to the necessity of isolating the welding circuit from the flammable and explosive system. Often, the welding operation measures completely ignore the problem of complete isolation of the welding system itself or the system that may form the welding circuit from the flammable and explosive system. During welding operations, the current of the welding machine is generally around 60-70A. The spark energy generated by the resistance heat generated during the welding operation or the impact current during arc ignition is incomparable to any static spark. The energy generated is enough to ignite any kind of combustible vapor and cause a fire and explosion accident. Sparks are not only generated in the ground wire of the welding machine, but can be generated in any part connected to the welding circuit, even inside the equipment, as long as the conditions are met. As we all know, although gas welding (cutting) operations and electric welding operations are both called hot operations, due to their own characteristics and the different conditions of the objects subject to fire, the safety measures taken are also different. For example, in gas welding (cutting) operations, as long as the materials are isolated from the hot spots with blind plates to ensure that there are no flammable and explosive materials in the hot parts and the hot environment, the isolation measures are It is considered reliable, but the welding operation process is completed through electron transfer, that is, as long as there is resistance anywhere where electrons can pass, sparks may be generated in these places. Therefore, the first thing to consider is to completely disconnect the circuit. The method is to remove a section of the pipeline or isolate it with a non-metallic blind plate (non-metallic fixture). First, it is necessary to confirm that the oxygen content in the system does not exceed 1%, and analytical means and methods must be available ； The second is to ensure that the operation is under positive pressure and no tempering is allowed under any circumstances. ； Third, the welding process ensures that the heated weldment is locally heated and does not cause the temperature of the entire equipment to rise.
1# dhmao I admire the bravery of a talented artist. . . . . . . . :hug: :hug: :hug: Speaking of safety measures, the vacuum in the kettle makes it easier for air and welding slag to enter, making it more dangerous. I would never dare sign a fire permit like this.
This kind of fire is indeed very dangerous. I don't think any accidents are accidental. I definitely don't advocate such risky work. I have worked in flammable and explosive enterprises for many years and have been in charge of safety. There have been countless fires in explosion-proof areas and equipment, and I have never started a fire like this. Even with the signature of the factory director, no one would dare to do such a fire here. Negative pressure belt welding, personally think that even if it is absolutely necessary to start a fire, it should be protected by slightly positive pressure or filled with inert gas.
I agree with the point above that slightly positive pressure is better. Negative pressure is just a measure to prevent the leakage of combustible gases. However, it is really brave for a skilled person to sign such a fire permit. 8#lvye0218