PSI - Issue 70

Rajesh Dube et al. / Procedia Structural Integrity 70 (2025) 365–371

368

Final failure approach allows the operator to prioritize and optimize the maintenance activities & allocate the current cycle repair budget to other production or safety critical structural equipment/ component. 2.2. Progressive Failure approach In the progressive failure approach, the intermediate damage stages are predominantly considered, and probability & consequence of failure is based on next stage failure of the structural member. This approach is typically applied to secondary and tertiary structural access members, such as grating, deck plates, deck drain, handrails, ladders, stairs etc. Owing to their design, exposed location and personnel usage, these members degrade at a faster rate compared to load carrying primary structural members. Also, these members typically do not have any redundancy & any failure of these members will directly lead to personnel safety hazard resulting in loss time injury or in some cases fatality. Safety incidents are taken very seriously by regulators and company management; hence all the access structure members are closely monitored to observe their progressive degradation in subsequent inspection cycles. At any stage of progressive degradation, if an access structure observed to be moving towards a risk level, which can potentially cause an injury hazard, a temporary mitigation is performed, and permanent repairs/replacement are planned. The probability of next stage failure of access structure members is typically on the higher side of risk matrix. However, the consequence is low as the risk has not yet reached a level which can cause potential injury hazard or financial impact. For example, grating load bars undergoing progressive metal loss reached a stage where significant thinning of load bars occurred but still have adequate strength against collapse under person weight. At this stage, flexing of load bars may lead to a trip/ fall but it will be a very low consequence (minor or no injury to person). Since the cost associated with repairs of access structure is very low compared to primary structure, hence a lower financial impact. Progressive failure approach helps the user to maintain the risk at an acceptable level by implementing some low cost solutions and deferring the major repairs to an appropriate time. Figure 4 below shows the typical risk scatter on risk matrix of access structural member anomalies selected under progressive failure approach.

Fig. 4 Typical risk scatter of access member anomalies selected under progressive failure approach