Why are so few people using looper stainless steel flanges?
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I recently went to a newly built chemical company, which is basically equipped with normal pressure equipment and material pipelines with pressures lower than 1.0MPa.； The materials are mainly isooctane, pentane, butane, acrylonitrile, etc. which are weakly corrosive. However, all the stainless steel parts on site are fixed flanges. I asked the person in charge of the company and the equipment personnel why they did not use loose flanges, which can not only reduce investment costs but also facilitate construction and maintenance. The other party said they had never heard of it. It's really strange.
Personally, I think the difference in cost between some small flanges, integral 304 flanges, and loose-threaded flanges is not obvious. After being used for a long time, loose-threaded flanges will be affected by factors such as the environment, leakage, leakage, and insufficient anti-corrosion, and their appearance will be poor.； For slightly larger flanges, you can choose loose sleeves or bushing rings, which can indeed save a lot of costs.
Are you a new graduate? There is no advantage in using a looper with such a small diameter for low pressure. In addition, there is everything in the air in chemical plants, and carbon steel loopers are severely corroded. The loops we use to make titanium equipment are also made of 304. We went to construction and made a device for two months, but the work was not finished yet. Many of the steel parts on site had not had time to be painted, and they were rusty as if they were old.
If we use loopers on site for a long time, on-site maintenance will be more difficult, and leakage and leakage will become more serious.
Because the use of loop flanges is not recommended and the requirements are relatively high. People don’t explain it, but you don’t know it yourself.
Wastewater can be used, but others are not recommended. First, familiarize yourself with ASME B 16.5, JIS B 2220-2004, HG 20592, these common specifications. There are too many lacking.
Judging from the pictures, the construction of the device is not professional, and the welds have poor appearance and have not been pickled.； Stainless steel flanges are equipped with stainless steel bolts. Regular design institutes rarely match them like this. At least from the maintainability aspect that the poster is concerned about, the stainless steel screws are easy to get stuck and are quite troublesome to handle.
The low cost of the loop flange is also due to the lower material of the flange, and the sealing surface only has a thin layer. It is troublesome to maintain for a long time and is rarely used now.