Hermetically seal is type of instrument device sealing which is designed to avoid hazardous gas ingress therefore preventing contact with sources of ignition such as arcing contacts. Instrument device with hermetically sealed design is suitable for use in Zone 2 or Division 2 and unclassified locations. The seal shall also be able to protect inside equipment from moisture and humidity to prevent corrosion.
Hermetically seal must be constructed with certain material so that the instrument device seal must be strong and permanent. It also shall withstand to harsh environment or severe weather, and chemical substance spill.
Instrument switches installed in process facilities mostly requires hermetically seal requirement, unless noted otherwise.