Why are no elastic gaskets used for the bolts of chemical processing equipment, pipes, and valves?

Thread Content

On many chemical processing equipment, as well as on pipe flanges and bolt connections for valves, there are no flat washers or spring washers. Everyone is puzzled: there are many measures to prevent bolts from loosening, so why isn’t the simplest solution, namely spring washers, used in the chemical industry? There are many explanations; the most common one is that in chemical processing environments, the high corrosivity leads to corrosion of elastic gaskets, resulting in connection failure and leaks ； But such an explanation lacks normative support. In fact, such a point in the mechanical manual can explain this clearly: since anti-loosening measures (not just spring washers) result in a significant loss of preload, anti-loosening measures need not be employed in the following situations: when the bolt is subjected to axial forces, for bolts of grade 8.8, when the clamping length is more than three times the bolt diameter; and for bolts of grades 4.8, 5.6, and 5.8, when the clamping length is more than five times the bolt diameter.