How to choose the flange of this equipment
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There is a low-pressure, medium-high-impact tower kettle, which is designed as a type three container according to its capacity. There is an air outlet on the upper part of the container, which is connected to the distillation tower. The flange used is the equipment flange in the JB/T4700 standard. Which type of flange should I choose for this equipment? (The design pressure is 0.15MPa, the design temperature is 40 degrees, the medium is hydrofluoric acid, and the corrosion margin is 3mm)
Choose JB403 long-neck flange + metal gasket + high-strength stud combination.
Is it hydrofluoric acid or anhydrous hydrogen fluoride? The material selection for anhydrous hydrogen fluoride is okay, but you have to be careful if it is hydrofluoric acid. The corrosion allowance is only 3...you need to choose the material carefully. As for the flange, I also think it should be a butt welding flange.
It is anhydrous hydrogen fluoride. Since the equipment of this process can only be used for more than two years before being forced to be scrapped, a corrosion margin of 3mm is enough. Of course, users are not willing to make the cost too high. For Class III containers with highly hazardous media, the standard regulations do not mandate the use of high-neck butt welding flanges for equipment flanges, but only stipulate that Class C and D welds must be penetrated, so does the structure of the JB/T4702 flange count as a penetration structure? Some senior engineers who have been approved strongly require the use of high-neck butt welding flanges. We young people think it is too wasteful and unnecessary. JB/T4702 flanges can be used.
Personally, I think JB/T4702 is not a fully welded structure, and when HG 20583 introduces take-over flanges, when the medium is highly extreme, hazardous and Class III pressure vessels, necked butt welding flanges should be used as much as possible. I think as equipment flanges, butt welding should be used.
For hydrofluoric acid, I remember that the material used in a previous piece of equipment was Monel 400. I personally think it is best to use long-neck butt welding flanges.
Leakage prevention is also an important aspect. Use tongue-and-groove and other high-sealing flanges, and the material must be resistant to hydrofluoric acid.
It is recommended to use high-neck flange. Sometimes experience is still very important. As a design unit, you do not need to take this risk.
1. For Class III containers with highly hazardous media, the standard regulations do not mandate the use of high-neck butt welding flanges for equipment flanges. They only stipulate that Class C and D welds must be penetrated, so does the structure of the JB/T4702 flange count as a penetration structure? 2. Some senior engineers who have been approved strongly require the use of high-neck butt welding flanges. We young people think it is too wasteful and unnecessary. JB/T4702 flanges can be used. reply: 1. It is obvious that the structure of JB/T4702 flange is not a penetration welding structure (look at the picture in the structural form). 2. High engineering basis: HG 20583 media for highly extreme, hazardous and Class III pressure vessels should use neck butt welding flanges as much as possible. Article 1 overturns your conclusion. According to Article 1, only butt welding flanges can be used, and it is not inconsistent with Article 2. There is no way to choose one with a diameter.
This issue is not a matter of waste or waste. As a designer, safety is the most important. This has nothing to do with the length of time the equipment is used. This is not just for the designer himself, but for the safety of users and operators. If I were to do it, I would also choose JB/T4703.