When the bonnet flange of a bolted bonnet valve is leaking, what should you do?

When dealing with a leaking bonnet flange on a bolted bonnet valve, the appropriate first step is to tighten the bonnet bolts. Over time, these bolts can become loose due to vibration, thermal expansion and contraction, or normal wear and tear. By tightening the bonnet bolts, you help to restore the proper compression of the gasket material between the bonnet and the valve body, potentially eliminating the leak without the need for replacement or additional interventions.

This action is often the quickest and least disruptive solution, offering a practical means to address the leak while maintaining the integrity of the valve. If tightening the bolts does not resolve the issue, then further assessments may be required, such as checking for corrosion or considering replacement or sealant application, but those steps would typically follow the basic maintenance of tightening the bolts first.