21. Alarms And Fault Reporting

Alarm Raising

For many products it is important to indicate exceptions, failures or partial failures to users or other components of a system of products. Alarms can be indicated to people through a variety of mechanisms including audible indications (bells, whistles, sirens), visible indications (dials, printed reports, colour indicators), and other sensory stimulation.

The product definition needs to identify which (if any) mechanism for alarm raising is most suited to the needs of users. It must also indicate the implications for the users should an alarm condition be raised. The product definition should clearly identify what conditions the product may encounter, the action it should take including diagnostic indications, and the state it should be in at the conclusion of the alarm activation cycle.

Exception Or Partial Fault Reporting

Caution must be exercised with partial fault or exception condition reporting. One of the major causes of breakdown of exception or fault reporting systems themselves is system congestion caused by repeated reporting of the same condition.

Where congestion is a possibility, consideration should be given within the product definition to the ability to locally remove parts of the product from service subsequent to fault detection. This may be a user invoked or automatically activated feature of the product. The objective of such an action is to place a unit that is out of service into a normal operational condition in which it no longer reports or indicates its condition.

Caution must also be exercised to ensure that original reports are actioned or are periodically reinforced or elevated to the attention of the maintainer or other authority.

It is often worthwhile considering the provision of remote test and diagnostic facilities for the purposes of exception or fault identification in products maintained on an ad hoc problem reporting basis. Such facilities can greatly enhance the efficiency of maintenance staff and simplify spares supply and maintenance schedule optimisation. Where facilities are built into the product, the overhead cost of such facilities can often be recouped through an associated maintenance contract. Other benefits derive from the provision of such facilities such as customer perception of responsive service. Often such systems can allow a fault to be rectified before the customer has detected one.