We tap the clamp with a plastic mallet before tightening the nut. Is this the recommended way to install sanitary clamps?

Tapping the clamp with a plastic mallet is a good practice to ensure that the proper torque is achieved when tightening. After ferrules are welded, there is a deviation in the flatness (depending on the ferrule length). The addition of manufacturing variances in the clamps also adds to the tolerance build-up on assembly. Tapping the clamp in place with a hammer to align the ferrules should ensure that the union settles into place prior to tightening the nut. This technique is also useful in light of the fact that in a thermal environment, materials expand and become tighter, so a quick tap is part of many companies’ maintenance best practices.