Event & target likelihood

Cause & likelihood

IPL (Integrated Protection Layers) and its PFD (Process Failure on Demand)

Mitigated likelihood

Pressure release valve between scrub tower fails to open causing product loss

1E−6

Pressure Release vale malfunctions and fails to open

1E−2

Human action

Alarms

SIS (PLC)

Design

2.6E−9

Human response to the alarm and manually close the valve before the pressure release valve

1E−1

A noticeable Alarm that would start if the flow rate kept low for a few minutes

2.6E−1

Logic in PLC once a a change in the Gas flow rate detected after the scrubber with a reasonable amount, a bypass for the scrubbing would occur and flow redirected to flare

1E−3

A manual valve would be added before the pressure release valve

1E−2