ii) Modifying the conventional risk priority number (RPN) model, which is the product of the three risks factors, occurrence (O), severity (S), and detection (D), to make it more rational for ranking the priority of failure modes: the modified RPN value is based on many theories like the fuzzy set theory [16, 22, 23], the grey theory , the Monte Carlo method , the evidence theory [23, 26, 27], and so on [28-30].
In Step 4, the risk priority number (RPN) offers a useful way to assess the risk level of each failure mode.
As mentioned before, Risk Priority Number
(RPN) is the product of Severity (S), Occurrence (O), and Detection (D) and is calculated by formula1:
Abbreviations: CVC, central venous catheter; Feb, February; LLT, laboratory liaison technician; RPN, risk priority number
Key Words: - Failure mode and effect analysis (FMEA), Cause and Effect Diagram, preliminary hazard analysis, Risk priority number
, ISO 22000, Prerequisite programmes
Calculate Risk Priority Number
(RPN) = E S * O * D 8.
d] denote the chance of undetection and S denote the severity, then the risk is measured by the risk priority number
(RPN) given by:
As the analysis progresses, the team will identify the potential causes and effects of failure, present controls, determine critical characteristics (Delta), recommend corrective action, assign a risk priority number
(RPN) and identify key personnel.
Computation of risk assessment was done by calculating the risk priority number
for each step.
The risk priority number
provides a qualitative numerical estimate of the design risk.
The FMEA team will identify high Risk Priority Numbers
(RPN) as the basis for the development of written quality procedures and controls.
They identified failure points and assigned Risk Priority Numbers
(RPNs) based on the potential impact of each failure.