Layers of Protection ILP

Most facilities are designed around layers of protection commonly referred to as Independent Layers of Protection (ILP). A protection layer or combination of combination of protection layers qualifies as a ILP when one of the following conditions are met (1) the protection provided reduces the risk of a serious event by 100 times, (2) the protective function is provided with a high degree of availability (i.e., greater than 0.99) or (3) it has the following characteristics - specificity, independence, dependability, and auditability. 

Most petroleum and chemical facilities rely on inherent safety and control features of the process, inherent design arrangements of the facility, and process safety ESD features as the prime loss prevention measures. These features are immediately utilized at the time of an incident. Passive and active explosion and fire protection measures are applicable after the initiating event has occurred and an adverse affect to the operation has been realized. These features are used until their capability has been exhausted or the incident has been controlled. 

The most commonly encountered Independent Layers of Protection (ILPs) are shown in Table 1  

Rank CLP Feature Typical Periods of Prime Usefulness General Level of Destruction Which May Be Occurring 

2 Basic Controls, Process Alarms, and Operator Supervision (BPCS). Continuously during operations and emergencies. None  

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Most facilities are designed around layers of protection commonly referred to as independent layers of protection (ILP). A protection layer or combination of protection layers qualifies as an ILP when one of the following is met ... 

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