You can achieve the proper degree of clamp tightness by using an approved torque-tightening tool. Tighten the hygienic clamp jaws to ensure that neither over- nor under-tightening occurs. Also include inspections of ferrules, gaskets, clamps, and piping as a part of regular maintenance procedures; changeovers and cleaning routines may mean that conditions have changed. Additionally, equipment may travel as a result of vibration, moving pipelines out of alignment.
Always tighten clamps according to the appropriate torque specifications. Currently there is not a list of definitive torque values; however your clamp supplier typically can cite a torque value. Elastomer gaskets need no more than
4Nm of torque on the clamp to seal correctly and maintain ASME-BPE Cat 2 intrusion. However, end users must perform their own compression and intrusion tests to ensure that the consistency between batches of components is in line with the torque guidelines.
Due to the reasons stated above, clamp manufacturers normally recommend similar torque values for different styles of clamps at the same flange size. However, gasket intrusion can be more pronounced on a single-hinge clamp than on a double-hinge clamp. It’s common to find the same torque value specified for different types of fasteners (e.g. spring-loaded, dome nut, wing nut etc.) on the same clamp.
As for how often you should re-torque sanitary fittings, rechecking a union now is much cheaper than losing product later. As an example, for some gaskets, it’s common to find that a single post-SiP re-torque back to
4Nm is acceptable after the first SiP experienced by the gasket. The re-torque can be applied with either a torque wrench or by application of approximately one half-turn of the nut, with additional tightening recommended after the first SiP.