Often, the functionally safer a system is built, the less reliable it becomes. In a continuing discussion of how to handle independent protection layer alarms, this article demonstrates the concepts using the example of a refinery furnace.

There is no way around it: The functionally safer a system is built, the less reliable it becomes. Typically, process control systems are built with one or more independent protection layers (IPL).

Industrial fired heaters are known to be the oldest and most common industrial process devices. Many manufacturing processes (if not all of them) involve heat exchange in some way or another, and the use of fired heaters is a way to provide such energy exchange.