Festo - Sicurezza dei Sistemi Comando:
Determinazione del B10 di componenti pneumatici in accordo con ISO 19973(*) e conversione nel MTTFd di EN ISO 13849-1: esempio
Determining B10 values for pneumatic components according to ISO 19973 e converting a B10 value into an MTTFd value EN ISO 13849-1
Definition of the B10 value Statistically expected value for the number of cycles at which 10% of the components have exceeded the limit values defi ned for the test (switching time, leakage, switching pressure etc.) under specifi c conditions.
But: a component can also fail before the B10 value is reached.
The service life cannot be guaranteed.
The B10 values are defi ned on the basis of the results from longterm tests with at least 7 test objects.
The B10 value may be used for the safety specific evaluation and for establishing the preventive maintenance of systems (TPM = Total Productive Maintenance).
Dangerous failures
Only dangerous failures are relevant to the safety of machines according to ISO 13849-1.
Whether a failure is a dangerous failure depends on the application.
If no information is possible or available on the number of dangerous failures, ISO 13849-1 permits the assumption that every second failure is dangerous.
This results in: B10d = 2 x B10 For which products do I need a B10d value?
For all products which are subject to mechanical wear and are used in safety-related parts of a control system.
Furthermore, they must contribute to the execution of the safety function, such as valves or clamping cartridges.
This does not apply to fittings, tubes, angle brackets, fixtures, etc. Drives are not normally part of the safety function and do therefore not have to be evaluated either.
For which products do i need an MTTFd value?
For all electronic products which are used in safety-related parts of a control system and directly contribute to the execution of the safety function, such as controllers, fieldbus nodes for the detection of dangerous situations, such as sensors in the test channel of category 2.
ISO 19973-2:2007
Pneumatic fluid power -- Assessment of component reliability by testing -- Part 2: Directional control valves