Verification of Performance Level (SYSTEM ANALYSIS) According to EN ISO 13849-1
The ISO 13849-1 safety standard of the International Organization for Standardization (ISO) is a universal standard that aims to help create safety systems with adequate reliability in machinery. For machine builders and users, ISO 13849-1 is a guide for safe operations. As SZUTEST, we are trying to be beneficial to our manufacturers by using this guide at the highest level in the name of machine safety.
What are the stages of EN ISO 13849-1?
- Determination of Safety Functions Requirements
- Determination of Required Performance Level (PL)
- Design and Technical Implementation of Safety Functions
- Determination and Evaluation of Performance Level
- Verification
- Confirmation
How is ISO 13849-1 Applied?
ISO 13849-1:2015 provides policy-related security requirements and guidance for the design and integration of safety-related parts of controls systems (SRP/CS) of control systems, including software design. Specifies the characteristics for these parts of the SRP/CS that include the level of performance required to perform their security functions. It applies to SRP/CS for high demand and continuous mode, whatever the technology and type of energy (electric, hydraulic, pneumatic, mechanical, etc.) used for any type of machine.
In fact, ISO 13849-1 uses statistical analysis to determine the probability of failure and hazard of components and circuits over time to find a performance level (PL). The leaflet can then be used in risk assessments to ensure that appropriate safety devices are applied.
What is PL Level?
The determination of these performance levels, which are rated between PL=a and PL=e, is made with SISTEMA software within the scope of EN ISO 13849-1 and EN ISO 13849-2 standards, and the analysis of the safety-related parts of the control systems of the machines is reported.
What is Functional Safety?
Functional safety describes that part of a system’s safety that depends on the correct operation of the safety-related control system. Safety often also depends on other risk reduction measures adopted in accordance with EN ISO 12100.
Important Questions to Ask When Calculating PL
Severity of injury (S)
S1 = Mild (normally reversible) injury
S2 = Serious (normally irreversible) injury, including death
Frequency and/or exposure to a hazard (F)
F1 = Rarely, less frequently and/or short exposure time
F2 = Frequent to continuous and/or long exposure time
Probability of avoiding danger or limiting harm (P)
P1 = possible under certain conditions
P2 = Almost possible
What is MTTFd?
Reliability in ISO 13849 is given by the variable MTTFd. This means the mean time to hazardous failure. Assuming a constant failure rate, MTTFd = 1/λD, where λD is the hazardous failure rate.
| MTTFd Measure | MTTFd range for each channel |
| Low | from 3 to 10 years |
| Medium | from 10 to 30 years |
| High | From 30 to 100 years |
(MTTFd is measured according to this table)