Add Criticality Rating
Explanation
Use this activity to add a new Criticality Rating to perform FMECA Analysis. In FMECA the criticality rating is performed to prioritize failure modes based on their potential impact and likelihood of occurrence.This process involves defining a normalized rating for Severity, Probability, and Detectability from basic data for a defined Failure Mode. Based on the RPN (Risk Priority Number) normalized rating from the Criticality Selection, it becomes easy to define maintenance actions, including preventive maintenance, corrective actions, or allowing the equipment to run to failure, depending on the nature and severity of the failure mode.
First, select a CM Risk Category (e.g., Personal Injury, Environmental Impact, or Production Loss) from the drop-down for the defined CM Standards in basic data.
Note: The CM Risk Category field cannot be edited once updated; only the CM Severity, CM Probability, and CM Detectability fields are editable. If an incorrect CM Risk Category is selected, delete it, and add the correct one as a new CM Risk Category.
It is possible to define a CM Risk Category without updating the CM Severity, CM Probability, and CM Detectability fields. When these fields are defined, the RPN normalized value is calculated by multiplying all the values and dividing by 10,000. If only two ratings are defined, they are multiplied and divided by 100. If only one rating is defined, the RPN Normalized value is null.
Next, select the CM Stand ID for CM Severity, CM Probability, and CM Detectability fields from the drop-down defined in basic data for the selected CM Risk Category.
Note: If CM Severity and CM Probability are defined for a CM Risk Category in the CM Standard basic data, it is mandatory to select these values from the drop-down in the CM Severity and CM Probability fields in Criticality Selection, or an error message will appear. However, CM Detectability is not mandatory. Severity ratings can be defined with a value between 0 and 100.
Severity Normalized Rating, Probability Normalized Rating, and Detectability Normalized Rating fields will be filled by default according to what was defined in CM Standards Basic Data. A color code will appear for these fields based on the ratings for defined CM Severity, CM Probability, and CM Detectability.
The RPN Normalized Value field will be updated automatically based on the normalized rating values of CM Severity, CM Probability, and CM Detectability.
For example, for a crane with a Failure Mode of reduced trolley speed, select "Movement Failure" as the CM Risk Category. Choose the appropriate values for CM Severity, CM Probability, and CM Detectability. If CM Severity is 40, CM Probability is 50, and CM Detectability is 20, the RPN Normalized Value is calculated as (40 * 50 * 20) / 10,000 = 4. Based on this RPN Normalized Value, decide on the maintenance action, such as "Preventive Maintenance."
Prerequisites
- FMECA Analysis must be prepared in Prepare FMECA page.
- The Functions, Functional Failures & Failure modes must be defined.
- Ensure the following data are defined:
- CM Standard
- CM Risk Category
System Effects
As a result of this activity, a new Criticality Selection is created.