MTTFd value  according to DIN ISO 19849-1:2008-12 / BGIA-Report 2/2008:

We provide comprehensive support for the integration of VELOMAT products into safety-related parts of machines and systems.

If required, we can supply the characteristic values for determining the MTTFd value (mean time to dangerous failure) and the maximum service life T10d. Depending on the specific load situation in the application, it is possible to determine the specific values.

How is the MTTFd value determined?

The MTTF is a key figure used in reliability engineering to describe the average time until the first failure of a system or component. The MTTF value is primarily used for irreplaceable systems where no repair or recovery is possible after failure and the system must be replaced.

The MTTF value is usually calculated using the following formula:

Where:

• T1,T2,...,Tn is the service life (the time to failure) of the individual units tested.
• n is the number of units tested.

What steps must be taken to determine the MTTF?

1. Determine the test period: Determine how long the test period will last or how long the components will be operated.
2. Measure service life: Measure the time to failure for each component tested.
3. Calculate average: Add up all measured lifetimes and divide the total by the number of units tested.

The MTTFd value is an expected value of the mean time to dangerous failure. This categorises the respective component or assembly into the following levels:

The MTTFd value is a statistical mean value and not a guaranteed service life.

It is used to assess the reliability of individual components or assemblies in an overall system. VELOMAT uses the "Parts Count Method". This takes into account the worst-case scenario with a safety factor of 10.

The user must define the application characteristics of the products.

To calculate an MTTFd value within the application used, the value is required, which is made up of the cycles, the number of operating days per year, the number of operating hours per day, the cycle time and the B10d value.

A calculation specification for the MTTFd and T10d value of a VELOMAT component or product can be provided on request.

This considers "heavy and light duty" operation in accordance with DIN EN 280. Other operating cases can be determined individually by the customer using the calculation examples provided.

Important points:

• The MTTF is a statistical indicator and indicates when a failure is expected to occur on average, but not when it will actually occur.
• The MTTF is particularly important for components that are not repaired after failure, such as many electronic components.

We recommend the use of the SISTEMA programme of the "Institute for Occupational Safety and Health of the German Social Accident Insurance" for the creation of complete system documentation.

Please contact us if you have any questions about the safety-related integration of VELOMAT products into your system.