Resources
IPL
Independent protection layer or layers. This refers to various other methods of risk reduction possible for a process. Examples include items such as rupture disks and relief valves which will independently reduce the likelihood of the hazard escalating into a full accident with a harmful outcome. In order to be effective, each layer must specifically prevent the hazard in question from causing harm, act independently of other layers, have a reasonable probability of working, and be able to be audited once the plant is operation relative to its original expected performance.