How is MTTFd (mean time to dangerous failure) determined for pneumatic components?
The MTTFd for each channel is specified in three stages and must be observed individually for each channel (e.g. individual channel or each channel of a redundant system). The maximum MTTFd which can be specified is 100 years. MTTFd Designation for each channel Range for each channel Low 3 years ≤ MTTFd < 10 years Middle 10 years ≤ MTTFd < 30 years High 30 years ≤ MTTFd ≤ 100 years MTTFd values for individual components can be calculated or estimated. In accordance with good engineering practice, the MTTFd or B10d value for a pneumatic component be assumed with B10d = 20 000 000 switching cycles, if certain properties remain constant. To calculate MTTFd according to DIN EN ISO 13849-1, Appendix C, proceed as follows: With B10d and nop, the mean number of annual actuations, the MTTFd for components can be calculated as follows: where with the following specifications which are met in relation to the component: - hop is the mean operating time in hours per day - dop is the mean operating
