Stripper pressure transmitter problem
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This post was last written by wwxxss_1 Editor on 2009-12-16 07:41 The weather has suddenly become colder recently, and there have been more problems. One of them is particularly difficult to deal with. In the hydrogenation workshop of the factory, the top pressure of the stripper tower is inaccurate. After going up, there was a height difference of 11M between the pressure gauge and the top of the tower. When I checked the zero point, it was only 5KPA. The night shift staff replaced all the antifreeze inside (ours was glycerin mixed with water) and replaced it with gasoline. I was very depressed. I felt that changing gasoline was wrong and brought a lot of inconvenience to our work. . . When I was draining the oil, I found that the pipeline was a little blocked. I suspected that the oil and gas inside were mixed with water and had frozen and there were signs of blockage. I used steam to purge it clean. When I filled the antifreeze, the problem came. After it was full, the transmitter only showed 24.1KPA. This was obviously wrong. There was air in it and it couldn't be filled anymore. I had no choice but to let it go. Set the zero point to zero, and it worked for one day, but it was clogged again the next day. After blowing and filling, it was still the same. I had no choice but to lift the pressure tester up and hit it from bottom to top. It was OK. The meter showed 98KPA (later I changed to the kind of antifreeze used in cars, which has a smaller density), and it was normal after it was put into use. . . But why can't it be poured down from above? Do you have any good solutions? A senior sister of mine insists that hydrogen sulfide causes ammonium salts to crystallize. I think she is an idiot. Hydrogen sulfide does not contain N elements, so how can ammonium salts be produced? But in fact it is blocked. I think it may be that after oil vapor and water vapor enter the pressure guide pipe, and after condensation, the temperature is low and the water freezes, causing the blockage. . . I don’t know it very well, so I can’t explain it to others. . . Please experts help solve it. . . One more question, what exactly is antifreeze? What are generally used in chemicals? Can’t anything that can prevent freezing be called antifreeze? It should be the kind mixed with glycerin and water, but one of my senior brothers thinks that it is the kind that is added to cars, and the people in the warehouse also said so. . . I'm not very clear. Sometimes I really can't explain my work. I hope someone can give me an answer. . . My QQ270964252
It's not necessarily the condensate that's frozen. As far as I know, the pressure guide pipes of hydrogenation pressure and differential pressure instruments are often blocked, and it's caused by some polymers. There is no other way but to replace the pressure guiding pipe during maintenance and add two primary valves. If they are usually blocked, close the two primary valves. Use a hacksaw to cut off the pressure guiding pipe and then dispose of it. Antifreeze (ours is glycerin plus water, 50% each), with a freezing point of -35 degrees, or ethylene glycol (36%) plus water, with a freezing point of -51 degrees.
For this kind of problem, I think the designers did not consider the on-site conditions and chose the pressure-guiding tube type differential pressure transmitter. If your instrument management department (such as the measurement office) has a flange-type differential pressure transmitter (can have a capillary tube), replacing it will not cause so many problems. However, the flange-type differential pressure transmitter is much more expensive than the pressure-guiding tube type. I once did construction, and an instrument construction team replaced the flange-type transmitter with a pressure pipe, which saved a lot of costs, but the maintenance of the manufacturer increased a lot.
You can propose rectification during maintenance and replace it with a single-flange pressure transmitter, which can save a lot of antifreeze and is easy to maintain. Otherwise, change the pressure gauge to the gas phase pipe and reduce the length of the pressure guiding pipe. The length of your pressure guiding pipe is 11 meters, which is too long.
Glycerin plus water is also antifreeze. The one used in cars should be ethylene glycol. If there are crystals, it is recommended to use a flange transmitter. 4#nap6
Will the medium at the top of the tower freeze? If the medium is frozen, it is best to use insulation and heat tracing, or it is best to replace it with a single-flange pressure transmitter during maintenance. Ethylene glycol mixed with water or glycerin mixed with water can be called antifreeze.
Thank you everyone for your answers. It has been cold recently and the heat tracing in the factory has frozen a lot. I am too busy to come to Haichuan. . . I asked a process engineer and he also said it might be ammonium salt crystallization. . . I added insulation to the root valve that induces pressure, and now there is no problem. . . Yes, the 11M pressure guiding tube is too long. . . We use the Rosemount pressure change. Someone upstairs asked us about the differential pressure transmitter. What type is it and how do we measure it? Is it the same as our pressure change? I also found that the negative pressure chamber of some transmitters is blocked, and the air only enters from the positive pressure chamber. Can differential pressure be used to measure pressure in this way? What is the density of 50% glycerol mixed with water? What about the boiling point? The steam in our factory may be too strong, and some may seem to be boiling, resulting in inaccurate measurement. . .
The poster is still too young. Let me vindicate your senior sister. There are two types of hydrogen sulfide, one of which can cause ammonium salts to crystallize. I don't know what your situation is. If the heat tracing is done well, there will generally be no problem.
Please note that the poster: 1. The stripper pressure measurement will not be too high. 2. Is it absolute pressure (negative pressure operation)? 3. The measuring pipeline is 15m, which is too long and will affect the normal use of the instrument. 4. Insulate the pressure point. As long as these problems are addressed (solved), the instrument will be "forgotten".
The main job of the instrument in winter is to keep it warm. If you keep an eye on the hot wire, there will usually be no problem.
study* Yes, I am not an instrument student, but I will soon take an instrument class. I don’t know how to manage it. Can you guys give me some advice?