Discussion on the flange types used for vinyl chloride pipes
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In the design documents provided by the design institute, there are various types of flanges used for vinyl chloride pipes, as follows: 1, 2.5 MPa, RF； 2, 2.5MPa, M ； 3, 1.6MPa, RF ； 4, 4.0 MPa, M. Please discuss which type would be more suitable.
These forms are established according to needs and relevant standards and specifications. For example, the fourth type should be used on the vent pipeline of the polymerization reactor; it’s not needed elsewhere on the monomer feeding pipes. Use whatever the design institute designs; there’s no need for detailed discussion.
The designs produced by some design firms may be overly conservative, which has a significant impact on the owner’s construction costs, causing them to spend much more money. Moreover, some overly generous designs can also lead to increased difficulty and workload in future maintenance. This post was last edited by shizhiyong001 on 2009-2-23 at 10:33.]
In PVC production, the maximum operating pressure of the vinyl chloride monomer pipelines and equipment does not exceed 20 KG/CM2. Flange: 300bar RF (20KG/CM2). Gasket: 300bar metal+PTFE or 300bar asbestos+PTFE. Answer completed
In my opinion, it is more appropriate to use male-female (MFM) flanges (PN6.3 or 300LB) for the polyvinyl chloride feeding pipes. The cost may be higher, but considering safety factors, it is still worth it; after all, the losses resulting from accidents caused by flange issues are much greater than the cost of purchasing those flanges.
2.5MPa, RF； 2.5MPa, RF ； The accompanying metal wound gasket should be fine!
Currently, in design projects carried out by design institutes, the materials used are generally selected with a margin for safety, as a precautionary measure, especially in new factories. Of course, it is still necessary to consider the actual situation; safety comes first in the chemical industry, and good materials ensure higher performance.
It should depend on the specific situation: 2.5 MPa is used for polymerization reactors, while 1.6 MPa is sufficient for RF and other applications
**There are mandatory requirements: Vinyl chloride is considered an extremely hazardous substance; therefore, the flange pressure rating must be 2.5 MPa or higher, and the seal surface type should be either a male-female surface or a keyway surface. It wasn’t chosen arbitrarily; everyone can check the relevant design specifications.
The flange type depends on the design pressure; temperature, pressure, and the medium are key factors, and temperature cannot be ignored
Xiling Xue’s choice is correct, but the reason given is not entirely accurate: vinyl chloride is considered a medium-hazardous substance – as stated in HG20660, and there are also explanations provided in that document