Satisfy customers and users
The customer/user requires a system/product/service to perform as expected and to consistently perform as expected for a satisfactory period. Dependability concentrates on the “consistently” aspect. When comparing systems etc. this consistency can be qualitative and dependability can be expressed as a rating or as an index. Where more precise quantitative terms are necessary, reference should be made to IEC 60300-3-4 and its associated standards.
A design engineer is concerned with designing an item so that it performs as defined within its requirements. A dependability engineer is concerned with what can go wrong and how this can be resolved. Implementing IEC 60300-3-1 early in the design will improve the design. If the system is required to be repaired during its operational life, then additionally, early implementation of IEC 60300-3-10 and 60300-3-14 will also provide added benefit.
A dependability programme will cost money, but the old adage – “you have to spend money to save money” is certainly true in this case. A correct dependability programme will reduce costs by: catching early design errors/faults failures thereby reducing costly re-design; catching early manufacturing errors/faults/failures thereby reducing expensive major strip-downs; optimising maintenance and support which are major cost drivers in the life cycle; giving confidence to the user and thereby reducing marketing and sales costs of a company.
Risks are the consequences and their likelihoods that might occur as a result of defined but uncertain events. For a system to operate consistently, system risks are important and dependability has to consider possible events. Many of the tools used by dependability can be modified and used for risk assessment and can be found within IEC/ISO 31010.
It is recognised that current systems are highly flexible, permitting changes such as enhancements, extensions and changes in its useable boundaries. These may affect one or more measures; however, the dependability processes are sufficiently robust to enable these measures to be re-assessed to ascertain the suitability of the system for its revised purpose/requirement.
Dependability considers the wider aspects of sparing such as recoverability, upgrades, impact of downtime, maintenance and support to provide the best sparing solution from which a spares provisioning programme can be established.
IEC TC56 have established a number of standards for dependability. To obtain the benefits mentioned above, it should be recognised that the tailoring necessary to enable an effective and efficient dependability programme requires personnel with the necessary skills to enable its implementation.