Types of Failures Based on the Mode of Failure

• Sudden Failures

These types of failures occur in items after giving some period of desired service rather than deterioration while in service. This period of giving desired service is not constant but follows some frequency distribution, which might be progressive, retrogressive or random in nature.

• Progressive Failure

If the probability of failure in the beginning of an item is less and gradually increases in its life, then such failure is called progressive failure. For instance, light bulbs & tubes fail progressively.

• Retrogressive Failure

If probability of failure in the beginning of the life of an item is more but as time passes the chances of its failure become less then such failure is said to be retrogressive.

• Random Failure

In this type of failure, the constant probability of failure is associated with items that fail from random causes such as physical shocks, not related to age. For instance, vacuum tubes in air burn equipment have been determined to fail at a rate of the age of tube.

• Gradual Failures

A gradual failure is progressive in nature, i.e. as the life increases, its operational efficiency also deteriorates resulting in increased running (maintenance and operational) costs. They also cause decrease in the resale or salvage value. Mechanical items as pistons, bearings, ring, etc. and automobile tyres fall under this category.