Fluoroelastomer Specialists
Sealing is a very complex science by itself as it involves many physical aspects, including mechanical design, materials science, surface science and fluid behaviour. Armin Reicharz reports.
For applications requiring hermetically sealed connectors – like vacuum processing equipment, pressure vessels or continually immersed devices – some parameters need to be carefully taken into account to achieve hermeticity.
Different levels of sealing exist. They should be adapted to the operating conditions, in which the equipment will be used. Installations having to withstand dust or water ingresses usually need to be environmentally sealed. Applications requiring gas tightness need a higher degree of protection; they are generally hermetically sealed.
To be referred to as hermetic, a system has to be designed to avoid its content leaking out or gas leaking in over an extended period of time. The effectiveness of a hermetic barrier is calculated in leakage rate values. Leak rates quantify the amount of gas flowing through the barrier every second and are expressed in mbar.l/s or atm.cm3/s. Hermeticity typically concerns leakage rates below 10-6mbar.l/s.
A typical hermetic connector requires several sealing barriers. Some advanced sealing techniques, like the ones developed by Fischer Connectors and described below, enable to exactly adapt the sealing performance of a connector to the level of protection it needs. To achieve such flexibility, each critical area of a connection – the panel interface, the contact block and the connectors interface – is protected by its own independent seal.
The panel seal (A ) is placed at the interface between the receptacle housing and the panel or equipment housing. It plays an important role for hermeticity because it covers a large cross section.
The protection of the contact block is ensured by a combination of two seals (B and C), a gasket sealing the junction between the contact block and the receptacle housing, and an advanced polymer compound covering the rear of the block and sealing the contacts.
Finally, the connectors interface is also protected by a seal (D). Not participating in making the system hermetic, it is dedicated to prevent ingress of water or harmful particles in the connecting area where male and female contacts mate.
Testing enables to guarantee that a connector is hermetic. For instance, all Fischer hermetic connectors are submitted to a 100 per cent quality screening test, using helium as tracer gas.
