Pressurized enclosure switchgear combinations are designed for use in gas explosion-hazardous areas of Zones 1 and 2 and meet the requirements of IEC 60079-0 «General Requirements» and IEC 60079-2 «Pressurized Enclosure» or dust for the Zones 21 and 22 of the standard IEC 61241-4 «Protection by pressurization». Along with these standards, an additional test according to IEC 61508-7 «Functional safety of electrical/eletronic/programmable electronic safet-related systems – Part 7: Overview of techniques and measures (SIL 2)» according to Category 3 is required. Safety-related parts according to IEC 61508-7 (SIL 2) Category 3 must be so constructed that.
One single defect in each of these parts does not lead to the loss of the safety function and
Whenever feasible, the single defect is recognized.