Issues with manhole gasket standards
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Question: 1) HG/T21516-2005 RFⅠs-35CM (WC-1220)-600-0.6; 2) HG/T21520-2005 RFⅢs-35CM (WD-2323)-500-1.0. What are the standards for the gaskets of these two types of manholes? If anyone knows, please tell me, thank you! The issues are: 1) In HG/T21516-2005, it specifies non-metallic flat gaskets, and C-1220 is not mentioned; 2) The wound gaskets used in HG/T21520-2005 are of PN16 grade
Multiple types of gaskets can be used for manholes, such as non-metallic gaskets and wound gaskets. Currently, manholes use European standard flanges and gaskets; as specified in HG/T21514-2014, gasket symbols starting with W followed by A, B, C, or D correspond to those defined in HG/T20610 \"Wound Gaskets for Steel Pipe Flanges\". It seems that the standards applicable to your manholes are outdated.
WC-1220, WD-2323 refer to gasketing materials. According to the standards for installing manholes, non-metallic flat gaskets or PTFE-lined gaskets should be used.
For non-metallic flat gaskets or PTFE-lined gaskets, it’s sufficient to specify the standard; then why are there codes like C1220 and D2323? I can’t understand this Isn’t that contradictory?
Once this issue is understood, non-metallic flat gaskets or tetrafluoroethylene can be used, as well as wound gaskets. If wound gaskets are used, the type will be C/D, the material will be 1220/2323, and the dimensions will follow those of non-metallic gaskets. (In other words, the gasket is custom-made.) Thank you all for the reminders.
The standard for metal wound gaskets is at least PN16; gaskets of lower stress classes are generally not used. However, if the client insists on using a wound gasket, explain to them that it can only be manufactured as a special order. For manhole flanges of the 0.6MPa class, the sealing surface is very narrow, and the gasket designed for them is even narrower.