Risk Matrix

  • Initial Risk Matrix is based on the CoF and PoF levels already established.
  • Dimensions of the Risk Matrix may vary from client to client.
    Below is an example:

Probability of Failure
Consequence of Failure (Severity) Level
0
A
B
C
D
E
1
5
5
11
17
  
2
5
5
5
 
  
3

 

 

 
11
  
4
 
 
48
4
 
5
 
2
34
39
  
   
LOW RISK
TOLERABLE RISK
INTOLERABLE RISK

Confidence Risk Matrix

  • Confidence levels are defined for each Asset Failure/Threat combination.
  • Confidence is a measure of the quantity and quality of integrity information, e.g. historical inspection data.
  • Risk Based Frequency Factors (used during RBI) are derived from the combination of Consequence and Confidence level.
    Below is an example:
Confidence Level
Consequence of Failure (Severity) Level
0
Good
High
Medium
Low
Poor
1
N/R
N/R
N/R
N/R
N/R
2
0.95
0.9
0.85
0.8
0.7
3
0.9
0.85
0.8
0.7
0.6
4
0.85
0.8
0.7
0.6
*
5
0.8
0.7
0.6
0.5
**
   
0.7
0.6
0.5
**
**
   
- Numeric values indicate Risk-Based Frequency Factors
- Single asterisk indicates insufficient predictability
- Double asterisk indicates unacceptable condition

Risk Mitigation

All Risks Should be Mitigated except those falling in the low-risk category (considered to be ALARP)
3 ways to mitigate risk:
Reduce Consequence of Failure

  • Done through preventative and corrective maintenance and confirming that controls and barriers are in place. (methods such as redesign, decommission, replacement etc, can be considered but only in cases where intolerable risk cannot be reduced to tolerable levels by other methods).
  • (methods such as redesign, decommission, replacement etc, can be considered but only in cases where intolerable risk cannot be reduced to tolerable levels by other methods).

Reduce Probability of Failure

  • Done through preventative and corrective maintenance and confirming that controls and barriers are in place. (methods such as redesign, decommission, replacement etc, can be considered but only in cases where intolerable risk cannot be reduced to tolerable levels by other methods).
  • (methods such as redesign, decommission, replacement etc, can be considered but only in cases where intolerable risk cannot be reduced to tolerable levels by other methods).

Increase Confidence (in probability assessment)

  • By inspection, monitoring, trending and verification.

Defining Mitigation Strategy

  • Mitigation options (typically inspection, routine maintenance or monitoring activities) are allocated to each Asset Failure/Threat combination.
  • Each mitigation option shall have a designated frequency type.

Five Frequency types for mitigation options:

Risk Based
Should be used for all high-cost inspection and maintenance options.

Time Based

Used for routine maintenance and inspection where prescriptive requirements exist.

Continuous
Used for monitoring options where data are collected and analysed electronically on a daily or more frequent basis.

Ad Hoc
Used for unplanned, event-triggered inspection and maintenance.

Condition Based

Not normally used, instead the more appropriately focused risk-based frequencies are favoured.