SIL (safety integrity level) and PL (performance level)
Two rating scales for how reliably a safety function must perform: SIL under IEC 61508 and its sector standards, and PL under ISO 13849-1.
The network analogy
Something like an availability class, except it rates the probability of a dangerous failure, not uptime.
Why it matters for wireless
Safety protocols such as CIP Safety and PROFIsafe carry SIL and PL ratings while the wireless link inside the black channel carries none. The rating covers the endpoints and the protocol, not the availability of the radio that connects them.
IEC defines a SIL as one of four discrete levels, where SIL 4 is the highest and SIL 1 the lowest1, and IEC 62061 applies that framework to safety-related control systems on machines. ISO 13849-1 instead uses performance levels from PL a, the lowest, to PL e, the highest, each a band of probability of dangerous failure per hour. Industrial safety protocols are rated on both: PROFIsafe to SIL 3 and PL e2, CIP Safety to SIL 3 and PL e3.
A SIL is a property of a safety function, set through the risk assessment. A network engineer neither assigns it nor raises it.
About this page
Built from 6 sources: 2 standards bodies and labs, 2 protocol owners and alliances and 2 vendor documents. Researched and drafted with AI assistance, then reviewed and approved by Ben Rutter on . How pages are made
- First published
- Last updated
Cite this page
Plain
Ben Rutter. "SIL (safety integrity level) and PL (performance level)." OT Wireless, published October 5, 2026. https://otwireless.com/glossary/sil-and-pl/
APA 7
Rutter, B. (2026, October 5). SIL (safety integrity level) and PL (performance level). OT Wireless. https://otwireless.com/glossary/sil-and-pl/
BibTeX
@misc{rutter2026silandpl,
author = {Rutter, Ben},
title = {{SIL (safety integrity level) and PL (performance level)}},
year = {2026},
howpublished = {\url{https://otwireless.com/glossary/sil-and-pl/}},
organization = {OT Wireless},
}