Regarding material deviation issues
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The new 713 steel plate negative deviation stipulates 0.3mm, and the old one seems to be 0.8mm. Now the market is quite chaotic. Question 1. When designing, how much is the general deviation calculated? 2. Is the corrosion allowance of the nozzle generally calculated as 1mm?
1. Before design, the purchasing conditions of the steel plate should indicate the grade of negative deviation, and then limit the maximum value within the grade range, that is, the minimum allowable thickness of the resulting steel plate.； 2. The corrosion allowance of the nozzle is related to the material and medium. The difference between the nozzle and the container is that the material flows. The flow of different materials has different effects on the corrosion of the nozzle. http://bbs.hcbbs.com/thread-562438-1-1.html , so specific analysis is required. Generally speaking, pipes are more cautious than containers when selecting materials. The operation and use of the entire equipment cannot be affected by takeover.
The plate deviation of the old container can be ignored, and the new one is 0.3. Of course, within a certain thickness range, the corrosion allowance of the nozzle is taken according to the body.
1. C=0.3mm 2. The corrosion allowance will not always be 1mm. The medium characteristics are different and the degree of corrosion is different. Generally, 1mm is taken for water or saturated water vapor.
In the design, the vessel steel plate C1=0.3. Of course, the corrosion allowance for the nozzle is taken for the equipment body.
1# MXYXY The commonly used plate for pressure vessels is GB/T713-2008 "Steel Plate for Boilers and Pressure Vessels". The standard stipulates that the thickness allowable deviation should be selected according to GB709B category. It can be seen that as long as you select the material standard, you can determine the material deviation. As for the corrosion margin, it is equal to the annual corrosion rate multiplied by the service life of the container. However, when we design, we generally refer to GB150 and select based on experience. They are relatively conservative, and there is only one corrosion margin for each container, without branch pipes and cylinders. The above is personal design experience.
The principle of using standards is that the latter takes precedence over the former. Of course, since the new version of the standard is released, it must be used first.