Large diameter gate valves typically do not give the water industry too much cause for concern as their sheer size protects them from damage and we typically only need to overcome seizure if not used in a long period of time.
Recently, SSI Test Inspect Consult was asked to assess the condition of a ‘dry’ valve that had been ‘released’ using a method of impact coupled with torque which failed to operate when required to do so. It became apparent that the similar metals used to manufacture both the spindle and the nut on this 48” gate valve had fused under the initial release process rendering it inoperable.
The SSI team stripped the valve and reverse engineered two new component utilising dissimilar materials which together have lubrication properties. There is nothing particular novel in this case study over and above our core activity but the point for question is as to whether we should be operating large diameter dry valves?