ASME PCC-3:2017 pdf free download

ASME PCC-3:2017 pdf free download.Inspection Planning Using Risk-Based Methods.
(g) determine the risk, including a sensitivity analysis, and review risk analysis results for consistency/ reasonableness (see section 9)
(h) develop an inspection plan and, if necessar other mitigation actions, and evaluate the residual risk (see sections 10 and II)
lithe risk is not acceptable. consider mitigation. For example, lIthe damage mode is general metal loss, a mitigation plan could consist of onstream wall thickness measurements, with a requirenwnt to shut down or to repair onstream if the wall thickness mcasurenwnts do not rot-el predetermined values or fitness-for-service acceptance criteria.
2.3 Inspection Optimization
When the risk associated with individual equipment items is determined and the relative effectiveness of different inspection techniques in reducing risk is estimated or quantified, adequate information is available for developing an optimization tool fur planning and implementing an RBI program. Inspection affects perceived risk; physical actions such as mitigation activities perfonned as a result of an inspcctitm affect actual risk.
inspections may affect the calculated risk by reducing uncertaint) When there is uncertaintV about the risk associated with operating equipment items, the default action should be to make reasonably adverse (conservative) or even “worst-case” assumptions resulting in relatively high calculated risk. For example, during an initial analysis one assumption may be that the only credible damage mechanism for a component is general corrosion (i.e., general metal loss). If examination reveals that no measurable metal loss has actually occurred, then the probability of failure may be reassessed to a lower level with a corresponding reducticm in the calculated risk
Figure 2.3 presents styhzed curves showing the reduction in risk that should be expected when the degree and frequency of inspection are increased. The upper curve in Fig. 2.3 represents a typical inspection program. Where there is no inspection, there may be a higher level of risk, as indicated on the It-axis. With an initial investment in inspection activities, risk generally is significantly reduced. A point is reached where additional inspection activity begins to show a diminishing return and, eventually, may produce very little additional perceived risk reduction. Any inspection activity beyond this point may actually increase the level of risk. This is because invasive inspections in certain cases may cause additional damage (e.g., introduction of oxygen into boiler feedwater, water contamination in equipment with polythionic acid, damage to protective coatings or glass-lined vessels, or improper reclosing of inspection openings that may result in leakage of harmful fluids). This situation is represented by the dotted line at the end of the upper curve.