Discussion on the flange types used for chlorine pipelines
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This post was last edited by sunjl1981 on 2013-1-6 at 20:12. In the chlorine pipelines designed by the design institute, the operating pressure ranges from 0.15 to 0.2 MPa; however, there are several types of flanges available for these pipelines, namely those rated for 1.6 MPa/RF and 2.5 MPa/M. Please share your opinions on which type is more suitable. Personally, I think 2.5 MPa is more appropriate. This post was last edited by haining on 2009-2-25 at 11:07. ] # ， ， &
Personally, I think 2.5 MPa with M is more appropriate
What is used more frequently in our unit is 1.6MPa, RF
According to HG20583-1998, these are media with extremely high hazards; the nominal pressure is not less than 1.6 MaP, and welded flanges with necks should be used whenever possible.
A 2.5MPa MFM necked weld flange should be used. Chlorine is also highly toxic; it is classified as a highly poisonous substance in the list of highly toxic materials. This post was last edited by busuanshou on 2009-2-24 08:19.]
However, the recognition of chlorine as a highly toxic substance is a recent development; as a result, many chlor-alkali plants still use the former method when dealing with chlorine. It’s easy to construct and the cost is low; I wonder if that means it doesn’t meet the standards or violates the Work Safety Law, haha. This post was last edited by limingshuguang on 2009-3-2 09:53]
During his inspection of the Shenhua coal-to-oil project, the Premier emphasized eight words – “quality, technology, safety, efficiency”. Among them, technology refers to excellent technologies developed through independent innovation, while also incorporating advanced foreign technologies. He also pointed out that Shenhua is an enterprise with production capacities in the hundreds of millions of tons; it is an important part of the energy security strategy, as well as a significant scientific and technological endeavor and exploration. At present, direct coal liquefaction is fully industrialized worldwide, with Shenhua being the first. And the “high-pressure self-tightening flange” is indeed an excellent technology resulting from independent innovation.
Use a welded flange with a neck at 1.6 MPa; no specific requirements are specified for the sealing surface, so an RF surface is convenient to use.
I think 2.5 MPa is a suitable value for RF. Last edited by yzhms on 2009-2-25 20:08.]
Our company uses 1.6MPa RF equipment, but the flanges connected to it have M-type sealing surfaces, as the flange sealing surfaces for pressure vessels are of the FM type.
The equipment interfaces in our facility are of PN1.6 MFM standard; valves specifically designed for chlorine are used on the pipelines, and if the PN rating is too low, leaks can occur and the valves cannot be closed properly. Our company uses PN2.5 M flanges and fittings. The flange comes with the valve.
It turns out that the manufacturers originally supplied titanium welding rings about 5MM thick to be used as flanges, and these were generally sufficient to meet the sealing requirements. However, after use, many manufacturers reported slight leaks at the flange area after a certain period of operation. It was not possible to replace the flanges without stopping the machine; one could only tighten the screws. But applying too much force could cause cracks in the titanium welding rings. Since the flanges were held in place by swivel fittings, it was easy to over-tighten them, yet if not tightened enough, the leaks would worsen. Later, the manufacturers made adjustments by increasing the thickness of the welding ring flanges to 10MM, which helped to alleviate the aforementioned problems. Therefore, the person asking for advice should purchase welding rings with a thickness of 10MM. Of course, welding techniques are equally important as well; even the best equipment is useless if not welded properly.
I agree with the opinion expressed on floor 8. In the past, liquid chlorine was packaged and transported using either a vaporizer for pressurization or gas pressure, which required a high pressure in the storage tanks (1.1 MPa); therefore, flanges with a pressure rating of 2.5 MPa were commonly used. Nowadays, submersible pumps or canned pumps are employed for pressurizing the liquid during packaging and transportation, and the pressure in the storage tanks is usually the pressure at the compressor outlet. As the original poster mentioned, 1.6 MPa is already more than one pressure level above the maximum required value; thus, a pressure rating of 1.6 MPa is sufficient. (It’s just my personal opinion – I think a rating of 1.0 MPa would be more appropriate, while 0.6 MPA is slightly too low.) As for the flange sealing surfaces, some experts suggest that flanges with uneven surfaces have poorer sealing performance compared to flat flanges, and their use at this pressure level is not recommended. Proponents argue that flat flanges are easier to install and replace, while the uneven surfaces present disadvantages; I have also seen flanges with grooved surfaces – it’s extremely difficult to manufacture gaskets for those! I think a flat one is better). As for high-neck flanges, since they are used to connect with equipment, high-neck flanges should be chosen – it looks better, doesn’t it? Hehe! (Actually, it’s well known that high-neck flanges are easy to inspect for defects during welding, right!) It’s better to be safe, especially since there are no valves at the front. ）
Generally, the flanges used on chlorine pipelines are rated for 2.5 MPa, with a concave sealing surface (FM type), while valves typically use the LCBJ41F type at -2.5 c/M pressure (with a convex sealing surface on the flange).
The maximum pressure is 0.2 MPa; 1.6 MPa can be used with RF flanges. If safety requirements are followed, operation becomes impossible. Our company carried out a safety assessment, and they insisted that we build a cofferdam around the saltwater storage tank, which really annoyed us. This is what regulatory authorities are like: if you don’t comply, they won’t issue you a permit. Who can you turn to for justice then?