Process Safety Event Rates PSE per million hours Process Safety Event Rates
Tier 3 Events
Tier 1 Tier 2
1.4
1.2
1
Number of High-High alarms in 2021 1 A high-high alarm is defined as failure of the trip sensor on tanks when filling resulting in a Tier 3 loss of primary containment.
0.8
0.6
0.4
0.2
0
2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
Source: UKPIA
As refinery and terminal operations increased in 2021, the process safety event rate for both Tier 1 and Tier 2 events increased. There was just one Tier 3 event in 2021, down from two such events in 2020. Note that as Tier 3 events occur as the result of an alarm being triggered, it is possible that the accidental triggering of this alarm is recorded in these statistics. The process safety event rate is represented as the number of events normalised per million hours worked.
43 | Statistical Review | 2022
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