IEC 61511 and EN 62061, respectively concern: the Safety Instrumented Systems for the process industry sector (SIS - Safety Instrumented Systems); the functional safety of the command and control systems, electrical, electronic and programmable electronic, related to the safety of the machinery (SRECS - Safety-Related Electrical Control Systems).

HINTSW - T & T Systems, for any SIL level, is able to support its clients in the definition of the most suitable HW architectures to meet the requirements of the IEC 61511 and EN 62061 related to fault tolerance, and is able to design diagnostic tests to ensure the proper diagnostic coverage, define the correct intervals for the performance of diagnostic tests and the proper frequency of the periodic test required to detect failures not detected by diagnostic tests. HINTSW - T & T Systems is also able to carry out analyzes and calculations needed to determine the chances of subsystem failure, the percentage of dangerous failures, detected and undetected, the diagnostic coverage and the susceptibility of the subsystems to the common cause failure. 

IEC 61511 and EN 62061 defines a set of requirements for fault tolerance that systems related to safety (SIS - Safety Instrumented System for the IEC 61511; SRECS - Safety-Related Electrical Control System for the Standard EN 62061) must reach, taking into account the safety integrity levels (SIL) required.

These requirements, in total, are derived from IEC 61508, General Standard on the functional safety of electrical / electronic / programmable electronic systems, with the introduction of some changes and postscripts to adapt those more to the business environment, to which the standards are referred : the process industry for IEC 61511; the machinery for EN 62061.

IEC 61511, in the definition of fault tolerance requirements in, unlike IEC 61508, distinguishes to the programmable electronic control logics by other types of logic and from the sensors and actuators, defining the minimum tolerance levels to different fault and by referring to the fraction of safe failures (fraction of the total percentage of hardware random failures of equipment that causes failure not dangerous or cause a dangerous failure detected) only for control systems with programmable electronics.

EN 62061 defines the tolerance requirements to similar failure to that of IEC 61508, however, distinguishing between four different categories of implementative technologies of safety functions (categories are those defined in ISO 13849-1), and adding a number of requirements relating to following points:
  • behavior of the SRECS on detection of a fault;
  • control of systematic failures;
  • threshold values of the probability of dangerous random hardware failures of the subsystems;
  • simplified estimate of the probability of dangerous random hardware failures of the subsystems;
  • time intervals of diagnostic tests;


Tel.: +39 02.8732.5227; +39 348.4114.771

General info: This email address is being protected from spambots. You need JavaScript enabled to view it.

Commercial info: This email address is being protected from spambots. You need JavaScript enabled to view it.
Commercial contact: +39 348.600.32.82

Registered office: I-20124 Milano, via Vitruvio 42
Office: I-20131 Milano, viale Abruzzi, 94

Read more ...



HINTSW - T&T Systems has been operating for over a decade in the field of functional safety concerning the main industrial sectors and public transport.

Read more ...



HINTSW division provides highly professional and specialized consultancy in the development of programmable electronic system used in safety-critical applications.

Read more ...

Safety certification


The safety certification of a system or equipment is often an arduous challenge to win, HINTSW provides all the support and know-how necessary to win.

Read more ...



HINTSW, drawing from their expertise, offers a wide range of services in the field of vocational training.

Read more ...

Go to top