Bolt material issue
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Recently, in our distillation unit, the bolts of the atmospheric tower top cooler have broken multiple times during operation, causing difficulties in operations and maintenance. In the past, materials such as bolts, 316L, 20#, and Q235 were all unsatisfactory. I would like to ask all fellow sailors for advice on what to use
The main issue is the large temperature difference; 8 can be used. Grade 8 strength bolts. What kind of condenser is yours? The condenser bolts have broken multiple times during operation. What medium are you using for distillation? What is the temperature at the top of the tower? And what is the cooling medium? Circulating water? For frozen saline, can a floating-head type be used?
Floating head bolts in the cooler; the medium flowing through the shell side is gasoline, oil-gas, water vapor, and H2S. Piping medium: circulating water.
Bolts made of 35CrMoA and nuts made of grade 35 steel should work fine!
35CrMoA/35# GB3077/GB/T699, with two type II hex nuts
Bolts of grade 10.9 made of 35CrMoA can be used. If the operating temperature of the bolts is around -20°C, low-temperature alloy materials should be employed, such as 10.9-grade bolts made from Q345D.
The low-temperature resistance of 304 bolts is not as good as that of the aforementioned types