Dilemmas in selecting fasteners for chemical processing equipment
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My branch plant has numerous chemical processing units, with media that are flammable and explosive hazardous chemicals. The operating pressure reaches up to 2.0 Mpa. Bolts for pipes (not limited to pressure pipes) should be of grade 8.8 or higher; there are single-threaded bolts of grade 8.8, but experts who came for an inspection said that such single-threaded 8.8-grade bolts are not allowed. What standard specifies this?
Petroleum bolts are divided into commercial grade and professional grade. HG20634 P438 specifies that professional-grade bolts must be used in certain areas, while 8.8 grade bolts are commercial-grade bolts; there are requirements not only regarding pressure but also regarding the type of medium involved.
8.8 can only be used in applications with a pressure rating of ≤PN16; double-headed studs are suitable for pressures up to ≤PN40, while fully threaded studs are suitable for pressures up to ≤PN160
Standard source: HG/T20613
It’s been so many years now; standards do not have retroactive effect. Projects prior to the standard modification were carried out in accordance with the design standards at that time. Those that can be implemented under certain conditions can be carried out gradually during maintenance according to the actual situation. This expert hasn’t read enough books; they only know a little about the subject