Electrically speaking, these are components exposed to voltages greater than Safety Extra-Low Voltage (SELV – inherently safe against electric shock).
However, a safety component irrespective of voltage used as a risk mitigation, is a “critical component”.
Let’s consider a basic example of an interlocking guard assembly. An interlock switch rated at 12Vdc (SELV) used in conjunction with a guard enclosure to detect the state (open/close) of the guard.
The combination of interlock switch and guard enclosure prevent access to hazardous parts (i.e., thermal, moving parts, radiation, etc.). The interlock switch can either provide input signal or directly remove power to the hazardous part via a relay when the guard is opened.
In the above example, the construction and materials of the guard enclosure are also considered “critical components”. The guard construction is expected to withstand specified impact forces and resist environmental effects that may degrade the integrity of the guard.
Another example of a non-electrical “critical component” is a Caution/Warning label affixed on the product. The label is a risk mitigation to inform or create awareness of potential hazards. The label material is expected to adhere to the surface and information contained on the label remain legible throughout the intended operating life of the product.
“Critical components” are specifically identified in the certification report. The agency will normally conduct an onsite quarterly or yearly follow-up inspection to verify that the “critical components” used in production are the same as in the report.
The next post is, What are the key requirements for “critical components”?