Distinction between type, SIL and PL The type, Safety Integrity Level (SIL) and Performance Level (PL) are classifications of safetyrelated components.
The IEC 61496 standard series for example sets out criteria for the design and testing of electro-sensitive protective equipment (ESPE).
Modern ESPE generally takes the form of optical sensors such as light barriers or laser scanners for the detection of human beings.
The individual standards are developed in the IEC/TC 44 committee, Safety of machinery - Electrotechnical aspects. They define Types 1, 2, 3 and 4.
Type 1 is however not relevant.
In the past, users have tended to associate the numbers 2, 3 and 4 with Categories 2, 3 and 4 as specified in the previous EN 954-1 standard for safety-related parts of control systems.
The Categories have been replaced in the more up-to-date EN 13849-1 and in the IEC 61508 series of control standards by the Performance Level, PL (a, b, c, d, e) and the Safety Integrity Level, SIL (1, 2, 3) respectively.