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FSM TA HOME PAGE > ADDRESSING YOUR CHALLENGES > HOW DO YOU KNOW IF YOUR SIS WILL PERFORM SUCCESSFULLY FOR 20 YEARS OR MORE?

 

 

Addressing your challenges

 

 
 

How do you know if your SIS will perform successfully for 20 years or more?

 

What does 'device useful lifetime' mean?

A device hardware failure rate changes as the operating time increases. The simplified methodology is that the rate of failures in time can be approximated by a ‘Bathtub’ shaped curve. As such, three regions can be distinguished in such a pictorial representation.

In the earliest part of device ‘life’, the failure rates are high (weaker units in the population usually during or shortly after completion of the manufacturing process). Then the failure rate remains flat as a function of operating time and so finally, the strength of the product declines and the failure rate increases rapidly (this is called the “end of life” or “wear-out” phase of the Bathtub). To simplify hardware random failure reliability calculations, it is usually assumed that a device failure rate will be constant. What this requires is that a device shall be removed from service before the end of its useful life to make the SIL verification calculations valid.

It should be noted that useful life applies for hardware only and we usually do not consider end of useful life terminology for the software.

 

1. Where can I find the necessary information about useful life of a product? 

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2. What is the difference between a device and a component?

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3. How do you detect the end of life status of a device?

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4. Can I really use my safety devices for 20 years? 

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5. How can ABB FSM TA help?

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