Vacuum Suitable Screws

Vacuum compatible screwsIn vacuum technology; you basically have to differentiate two fields of application of fastening elements e.g. like screws. Vacuum compatible screws are connecting elements applicable in vacuum environment. Please find connecting components for atmosphere use for instance for flange assemblies under Standard Components.

Concepting  a  vacuum  equipment  stage  you  have  to  consider  the  special characteristics  of  vacuum  technology,  when  using  often  indispensable  screw connections. Hollow spaces in threaded blind holes, between threads and under the screw heads are traps for gas inside the vacuum chamber, which are outgassing during  the  pump  down. These  so  called  virtual  leaks  simulate  the  existence  of real leaks as extended pump down times occur and the desired ultimate pressure cannot be attained.

Rigorous requirements to the cleanliness of vacuum components forbid to lubricate bolted joints. Lubricants are mostly made from longchain organic polymers. The outgassing of these substances can contaminate the whole vacuum chamber. Many processes cannot be run under such circumstances. Even with a well-defined tightening torque on screws, non-greased threads will cause undefined pretension  forces.  Stainless  steel  screws  cleaned  for  use  in  vacuum  are  totally  oil-free,  which  will  increase  the  danger  of  galling dramatically. In consequence you will have long down times of your vacuum system in case of modification or maintenance.

  Multiple use of screws:
The repeated use of screws can lead to malfunction independent of their coating.
Coatings on screws can generate particles after multiple application. That is why we generally suggest to replace the fasteners after a one time usage. If you have questions about the multiple use of fasteners, we like to provide our advice.

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