Seals and Lubrication
Sanitary elastomeric seals have very good sealing capabilities and seal at a low clamping force. PTFE does not have these characteristics and the material creep even at low temperatures results in a decreased clamping force on the gasket which can produce a leak at a low pressure.
Lubrication has a noticeable effect on the pressure holding capability of the clamp unions, specifically when polymeric gaskets are used. Also, when the bolts are unlubricated there is an increased possibility that the threads will gall.
Lubricated clamp loads are 46% higher than dry loads. This will allow for higher force to be imparted onto the polymeric gasket, thus resulting in a more reliable seal.
- A ½” UNC bolt lubricated and tightened to 83.15Nm will apply a clamping load of 1448 Kg. This load will utilise 90% of the bolt yield strength.
- A ½” UNC bolt un-lubricated and tightened to 92.7Nm will apply a clamping load of 772 Kg. This load will utilise 40% of the bolt yield strength.
In addition to this; as the torque figure is increased, the chances of galling and failure of the eyebolt at the thread root increase. In order to ensure a better lifetime for your acl clamp, torque should be minimised to the correct level.
In the event that lubrication cannot be applied to the threads, a suitable bolt /nut material combination should be employed. The standard material for this application would normally be Nitronic 60 (Ref. ACL® Anti-Gall).