Compliance & ContractsFree referencePDF, Excel, Word exportIndustrial Machinery

ISO 13849-1 Performance Level (PL) and SIL Reference Table

Machine safety functions such as emergency stop, light curtain muting and guard interlocks are rated with a performance level (PL) from ISO 13849-1, or a SIL from IEC 62061. This table collects the bands you keep looking up in one searchable place.

Download:

Item	Group	Range or definition	Note
PL a	Performance level	PFHd 1E-5 to below 1E-4 per hour	Lowest level; no direct SIL equivalent
PL b	Performance level	PFHd 3E-6 to below 1E-5 per hour	Roughly SIL 1 band at the upper end
PL c	Performance level	PFHd 1E-6 to below 3E-6 per hour	Corresponds to SIL 1
PL d	Performance level	PFHd 1E-7 to below 1E-6 per hour	Corresponds to SIL 2
PL e	Performance level	PFHd 1E-8 to below 1E-7 per hour	Corresponds to SIL 3
SIL 1	Safety integrity level (IEC 62061)	PFH 1E-6 to below 1E-5 per hour	High demand or continuous mode
SIL 2	Safety integrity level (IEC 62061)	PFH 1E-7 to below 1E-6 per hour	High demand or continuous mode
SIL 3	Safety integrity level (IEC 62061)	PFH 1E-8 to below 1E-7 per hour	High demand or continuous mode
Category B	Structure category	Basic safety principles, single channel, no diagnostics	A fault can cause loss of the safety function
Category 1	Structure category	Single channel using well-tried components and principles	Higher MTTFd than Category B
Category 2	Structure category	Single channel with periodic testing of the safety function	Test interval must be sufficiently frequent versus demand rate
Category 3	Structure category	Redundant, single fault does not lose the safety function	Single faults detected where reasonably practicable
Category 4	Structure category	Redundant, single fault detected at or before next demand	Accumulation of undetected faults must not lose the function
MTTFd low	MTTFd per channel	3 years to below 10 years	Mean time to dangerous failure
MTTFd medium	MTTFd per channel	10 years to below 30 years
MTTFd high	MTTFd per channel	30 years to 100 years	Value capped at 100 years per channel
DC none	Diagnostic coverage	Below 60 percent
DC low	Diagnostic coverage	60 percent to below 90 percent
DC medium	Diagnostic coverage	90 percent to below 99 percent
DC high	Diagnostic coverage	99 percent or higher
CCF	Common cause failure	Score of at least 65 out of 100 required	Applies to redundant categories 2, 3 and 4 via the measures list in the standard

Summary table for orientation, not a substitute for the standard. PFHd is the probability of dangerous failure per hour. SIL values use IEC 62061 and IEC 61508 bands. Actual PL determination uses the Table 7 style combination of category, MTTFd and DC, plus software, systematic failure and validation requirements. Verify against the current edition of ISO 13849-1 and ISO 13849-2.

Link safety ratings to serial numbers

Optional: a review of how to hold safety function data against machine serial numbers in your ERP.

Optional. The tool and every export work without this. No spam.

How to use this table

Start from the required performance level (PLr) set during risk assessment, then check that the designed safety function reaches it. Find PLr in the first rows, check the PFHd limit, and confirm the category, MTTFd and diagnostic coverage rows you used in your calculation. If your customer or notified body quotes SIL, use the SIL rows for the equivalent band.

Set PLr from risk assessment first
Pick a category that can support the PL
Check MTTFd and DC band per channel
Confirm common cause failure measures for redundant designs

PL versus SIL

PL c, d and e line up with SIL 1, 2 and 3 on PFHd. PL a and b have no clean SIL counterpart. The two methods differ in how they build up the number: ISO 13849-1 uses a simplified category-based method, while IEC 62061 uses a subsystem and reliability block approach. Use the one your harmonised standard or customer references, and state it in the technical file.

Worked example

A safety door with a coded magnetic switch pair and a safety relay is assessed at PLr d. A two channel Category 3 architecture with medium MTTFd (say 20 years per channel) and high DC can reach PL d. If you use a single channel Category 2 design, you would likely fall short. Record each component's B10d value from datasheets when computing MTTFd.

Common mistakes

Treating the category as the PL is the most frequent error. Category is only one input. Another is ignoring validation: ISO 13849-2 expects fault lists and tests. Teams also forget that the PFHd of the safety function is the total of sensor, logic and actuator, not just the safety relay certificate value.

Frequently Asked Questions

What PFHd does PL d need?

PL d requires a PFHd of at least 1E-7 and below 1E-6 per hour. That is the same band as SIL 2 for high demand or continuous mode, though the two methods calculate the value differently.

Is Category 3 the same as PL d?

No. Category 3 is an architecture, and with suitable MTTFd and diagnostic coverage it can achieve PL d, and in some cases PL e is not reachable. The PL depends on category, MTTFd, DC and CCF together.

What is B10d used for?

B10d is the number of cycles at which 10 percent of components fail dangerously. Combined with your operations per year, it gives MTTFd for electromechanical parts such as contactors and valves.

Does the Machinery Regulation change this?

Regulation (EU) 2023/1230 replaces the Machinery Directive from January 2027 and adds items such as software and AI related safety aspects, but the core ISO 13849-1 method remains the common route to presumption of conformity. Check the harmonised standards list.

If you store safety function ratings in spreadsheets and want them linked to machine serial numbers and the technical file in your ERP, we can scope that connection.

Talk to an Expert Explore More Free Tools

Related Tools

Compliance & Contracts

More Compliance & Contracts tools

See all

Back to All Tools