|
| Particulars | Decision matrix | Weighted mean normalized sum | Relative significance/weight | % contribution | Criticality rank |
| Key process input | Potential failure mode | Potential causes | Potential failure effects | Current controls | C | D | M | SP | ES | EC |
| What is the process input? | In what ways can the process input fail? | What causes the key input to go wrong? | What is the impact on the key output variables once it fails (customer or internal requirements)? | What are the existing controls and procedures that prevent either the cause or the failure mode? | Chance of failure | Detection probability of failure | Maintainability criteria | Spare parts criteria | Economic safety criteria | Economic cost criteria |
| | | | | | | | | | | | | | | | | | | MCI | | Rank |
|
| Bearing failure | Bearing high temperature | Improper lubrication & defective sealing | Bearing gets jammed/bearing housing jammed | Lubricating the parts when occurred | 8 | 9 | 7 | 8 | 1 | 2 | 2 | 3 | 3 | 4 | 3 | 4 | 0.1297 | 0.1297 | 60 | 9 |
| Bearing corrosion | Higher speed than specified | Increase in vibration & noise | Proper coolant | 8 | 9 | 5 | 6 | 1 | 2 | 2 | 3 | 3 | 4 | 4 | 5 | 0.1244 | 0.1244 | 58 | 10 |
| Bearing fatigue | Design defects & bearing dimension not as per specification | Life reduction | Bearing replacement | 9 | 10 | 7 | 8 | 6 | 8 | 3 | 5 | 9 | 10 | 9 | 10 | 0.2156 | 0.2156 | 100 | 1 |
| Roller balls wear-out | Foreign matters/particles | Sudden rise in thrust | Regular cleaning of parts | 7 | 9 | 6 | 7 | 4 | 5 | 3 | 5 | 7 | 8 | 5 | 6 | 0.1662 | 0.1662 | 77 | 4 |
| Bearing misalignment & improper mounting | Sudden impact on the rolls | Shaft damage & impact damage on other parts | Routine check-up | 8 | 10 | 5 | 6 | 6 | 7 | 5 | 7 | 9 | 10 | 9 | 10 | 0.2079 | 0.2079 | 96 | 2 |
| Electrical damage | Loss of power | Operation interrupted | Electrical wiring check-up | 7 | 9 | 1 | 2 | 1 | 2 | 3 | 4 | 5 | 6 | 2 | 3 | 0.1062 | 0.1062 | 49 | 12 |
|
| Rolling mill gearing failure | Gear teeth wear-out | Inadequate lubrication-dirt, viscosity issues | Rough operation & considerable noise | Routine check-up of lubrication | 7 | 8 | 2 | 3 | 5 | 6 | 3 | 4 | 7 | 8 | 4 | 5 | 0.1401 | 0.1401 | 65 | 8 |
| Gear teeth surface fatigue (pitting) | Improper meshing, case depth & high residual stresses | Gear life reduction | Preventive maintenance | 8 | 9 | 4 | 5 | 5 | 6 | 3 | 4 | 4 | 5 | 5 | 6 | 0.1444 | 0.1444 | 67 | 7 |
| Gear teeth scoring | Overheating at gear mesh | Interference & backlash phenomenon | Lubricating when needed | 4 | 5 | 3 | 4 | 2 | 3 | 2 | 3 | 2 | 3 | 3 | 4 | 0.0863 | 0.0863 | 40 | 14 |
| Gear teeth fracture | Excessive overload & cyclic stresses | Sudden stoppage of process plant | Breakdown maintenance | 9 | 10 | 2 | 4 | 6 | 7 | 3 | 4 | 7 | 8 | 7 | 8 | 0.1700 | 0.1700 | 79 | 3 |
| Gear teeth surface cold/plastic flow | High contact stresses due to rolling & sliding action of mesh | Slippage & power lose | Gear replacement when needed | 3 | 4 | 6 | 7 | 3 | 4 | 3 | 4 | 2 | 3 | 3 | 4 | 0.1022 | 0.1022 | 47 | 13 |
|
| Rolling mill shaft (primary & secondary) failure | Shaft fretting | Vibratory dynamic load from bearing | Leads to sudden failure | Breakdown maintenance | 5 | 6 | 4 | 5 | 3 | 5 | 3 | 4 | 3 | 4 | 3 | 4 | 0.1096 | 0.1096 | 51 | 11 |
| Shaft misalignment | Uneven bearing load | Vibration & fatigue | Preventive maintenance | 8 | 9 | 4 | 5 | 5 | 6 | 4 | 5 | 4 | 5 | 5 | 6 | 0.1477 | 0.1477 | 68 | 6 |
| Shaft fracture (fatigue) | Reverse & repeated cyclic loading | Sudden stoppage of process | Preventive maintenance | 9 | 10 | 2 | 3 | 6 | 7 | 3 | 4 | 5 | 6 | 6 | 7 | 0.1526 | 0.1526 | 71 | 5 |
|
| | | | | | 100 | 117 | 58 | 73 | 54 | 70 | 42 | 59 | 70 | 84 | 68 | 82 | | | | |
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