Task Analysis, Failure Modes and Effects Analysis

Task Analysis Purpose Take modeling & analysis to the next level. Summarize what is known about task in one place. Prepare for FMEA, detailed requirements development. Method (HMSEM) Apply to most primitive processes/activities in IDEF0 model i.e., ones with no child diagrams Fill in one row in [Summary] sheet in HMSEM workbook Task Analysis columns (R - W) Detail important task characteristics (Purpose, Location, etc.) Other Approaches Hierarchical Task Analysis

HTA of Cesarean Delivery Process ≈IDEF0 Nodelist

Example: Pre-Reflow Inspection Station (PRIS) Task Analysis

PRIS Hierarchical Task Analysis (Process/Task Hierarchy) A0: Assemble Electronics Components A1: Set Up Oven & Dispenser (Initial) A2: Program & Set Up SMT A3: Dispense Solder On Board A4: Place Component A5: Perform Pre-Reflow Inspection & Place Manual Components A51: Prepare & Review Documents A52: Program Reflow Oven A53: Inspect Board A531: Compare Board Match A5311: Study iView Diagram A5312: Study Individual Component / Group A532: Check Components (Loose, Misaligned, Skewed) A5321: Study iView for Check Components A5322: Assess Individual Component / Group (for Check Components) A5323: Adjust Parts (When needed) A533: Check Component Population (1st Board Only) A5331: Study iView Component Population A5332: Assess PCB Population A534: Check Component Orientation/Direction (1st Board Only) A5341: Study iView and OPIE A5342: Visually Assess Placement of the Component A54: Install Manual Components A6: Reflow

PRIS Task Analysis in HMSEM Workbook

Task Analysis Fields Purpose / Value Added why the task is necessary what value is added by performing the task Location where the task is performed Frequency & Timing Environmental Conditions illumination, lighting (lux, fc) temperature (deg) humidity (%) vibration, acceleration other Information Requirements information needed to perform the task Sensory / Cognitive / Motor Action sensing, memory, actions required to perform task

Some Sensory / Cognitive / Motor Action Verbs Attend to Detect Distinguish between Feel Hear Read View Remember Calculate Count Decide among Estimate Evaluate Generate Predict Process Configure Disengage Engage Grasp Manipulate Move Open Pick up Position Press Reach to Release Transfer Turn Wait for Walk to

Failure Modes and Effects Analysis (FMEA) Purpose Systematically, prospectively, identify ways in which a process (system) can fail: Failure Modes. Identify factors potentially contributing to failures. Estimate risk of failure Identify countermeasures Develop requirements Method (HMSEM) Select task on which to perform FMEA (TA should have been completed on it) Prepare task FMEA worksheet from [template] worksheet copy [template] worksheet rename new task FMEA worksheet to task's A-number copy task row from [Summary] worksheet to row 6 of new task FMEA worksheet (optionally) hide non-FMEA columns (A-Z) Perform FMEA

PRIS FMEA in HMSEM Workbook

FMEA Fields Contributing Factors Circumstances, conditions, events, factors, ... anything that might make a failure mode more likely. Potential Failure Mode A way in which the process/system can fail. Potential Effects of Failure Mode Consequences of the failure. Severity Numeric rating of the estimated severity of consequences, of the failure, e.g., negligible minor moderate major catastrophic

FMEA Fields (2) Probability Numeric rating of the estimated probability that the failure will occur, e.g., Remote Unlikely Occasional Common Frequent

FMEA Fields (3) Nondetectability Numeric rating of the difficulty of detecting the failure in time to prevent or mitigate its consequences, e.g., Should the failure occur, there is a virtual certainty that the existing controls will detect it. Very high Should the failure occur there is a high probability that the existing controls will detect it. Moderately high Existing controls have difficulty detecting the failure Low Controls are weak. Detection could depend on a lucky catch. Remote Very remote No controls for this failure mode exist RPN: Risk Priority Number RPN = Probability x Severity x Nondetectability

FMEA Fields (4) Potential Remediations Design strategies that could reduce the likelihood of the failure mode. Design Requirements Abbreviated requirements statements for remediations. Requirement numbers ([Requirements] worksheet).