3 Examples of Derating

John Spacey, updated on January 12, 2017

Derating is the operation of a device, vehicle or equipment below its normal performance level when a problem is detected. The term implies an automated switch into a restricted performance mode for purposes such as reliability and safety. The following are illustrative examples.

Devices

A memory device flips into read-only mode when it encounters problems. This is done with the thought that data is often worth more than the device itself. Derating minimizes the chance of data loss as the user can read data but can't write anything new to the defective device.

Vehicles

A high speed train detects an unusual vibration from a wheel. An emergency light comes on and the train drops into a mode whereby it can no longer be operated at high speed. The train is able to make it to the next station at a safe maximum speed and is taken out for maintenance.

Equipment

An industrial robot senses low liquid pressure in one of its hydraulic actuators. The robot reports the error to controllers and slips into a limited operation mode.

Overview: Derating
Type	Reliability Engineering Safety by Design
Definition	Automatically switching a device, vehicle or equipment into a limited operation mode when a problem is detected.
Value	Reducing safety and business risks by preventing something that is broken from operating at full function. Continuing to provide limited functionality as opposed to completely shutting down to fail more gracefully.
Related Concepts	Graceful Degradation Fail Well Reliability Engineering Safety by Design