Are there any regulations regarding the use of washers on flange screws?
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I’ve seen some pipes with flange connections, or flanges at the locations where valves are installed, for which no gaskets are used on the screws. Are there any regulations regarding whether gaskets should be used? This post was last edited by lonelyghost_li on 2007-12-18 at 18:18.]
There are only specifications for the bolts used, with no requirements for washers. Think about it: pipeline maintenance is generally quite dangerous; in order to install washers, one has to get very close, which is risky. Moreover, the fit between the bolts and their holes is so tight that washers aren’t necessary.
Refer to HG/T20646.5-1999 \"Technical Specifications for the Design of Pipeline Materials in Chemical Plants\"; point 5 of section 7.6.2 states that \"Gaskets should generally not be used, and are only employed when metal bolts (shanks) and nuts are used to fasten non-metallic or non-ferrous metal fittings.\" This post was last edited by zhao*rong on 2007-12-19 13:44.]
I believe flat washers and spring washers should be used, with bolts of grade 8.8 or higher. This is the approach we follow in our construction work; it’s provided for reference only.
Pipe flanges generally do not use gaskets, whether according to national standards, chemical or petrochemical standards, or foreign standards.
Bolts for metal flanges do not require washers, whereas bolts for non-metallic flanges (such as those made of fiberglass, PPR, or CPVC) need washers.
When pressurized pipes are connected using flanges without gaskets, leaks can occur very easily. In our company’s latest projects, gaskets are used at all flange connections. It doesn’t really matter whether there are shims on the screws, but spring washers are generally used in areas subject to heavy vibration to prevent the screws from loosening