Revamps 2024 Issue

frequency. A sample risk matrix is shown in Figure 2 , where 5 is the highest frequency, and 5 is the highest consequence:  Step one of a PMO is the determination of equipment criticality, typically in a workshop format. The workshop can be made more efficient if some prework is conducted beforehand. This consists of a review of site data and pre-assignment of criticalities to selected equipment. Instrumentation equipment lends itself to pre-assignment as it can typically be categorised based on specific criticalities. For example, emergency shutdown systems can be designated as safety-critical. Safety-critical equipment refers to equipment that serves as a barrier to prevent, detect, control, mitigate, or recover from a major incident such as fire or explosion. Participants in the workshop should include: • Operations: Primary input for consequence of equipment failure. Secondary input for frequency of failure. • Engineering/reliability: Primary input for validation of pre- work assumptions, frequency of failure, and failure modes. • Crafts: Secondary input on equipment failure mode and frequency of failure. Once the equipment criticality is determined, some key checks should be done when reviewing the distribution of equipment on the risk matrix: • Safety-critical and business-critical equipment should be identified in the highest criticality on the risk matrix. • There should be a cluster of equipment considered very low criticality. • The distribution should be consistent with industry bench- marks on criticality. Based on benchmarking in the petro- chemical industry, a typical breakdown of equipment is:  Step two of a PMO is to use the equipment criticality to determine which tool to utilise for each criticality. FMEA considers the known failure modes for the equipment and results in the most comprehensive mitigation strategies for the equipment. Equipment with a high criticality should utilise this approach to determine the mitigation strategies. Examples of high-criticality equipment include equipment that is considered business-critical or safety-critical equipment. Non-essential equipment will be identified based on very low criticality. On the risk matrix, equipment failure scenarios appear as a low frequency and a low severity. A run-to-fail- ure (RTF) approach or a FRACAS approach can be used with this equipment. The PM Library can be developed quickly compared to conducting FMEA. Approaches for PM Library development include using corporate subject matter experts (SMEs) or independent third parties to develop maintenance activities and performing FMEA on generic equipment (see Figure 3 ).  Step three of a PMO is to use the recommended mitiga- tion strategies to modify the existing PM programme. The capabilities of a computerised maintenance management system (CMMS) are often not fully utilised due to a lack of ■ 10-15% of equipment is safety-critical. ■ 10-15% of equipment is business critical. ■ 30-60% of equipment is essential. ■ 20-30% of equipment is non-essential.

3 5 4 2 1

L L L L 1 L

M M

H M L L 3 M

H H

L L 2 L

M L 4 M

M M 5 H

Consequence

Figure 2 Example risk matrix

to identify the root cause of failure. In step 3, a corrective action is implemented and tracked. The FMEA approach is the most proactive of the three approaches and requires the most resources to implement. It considers all failure modes and results in the highest equip- ment availability. However, this approach does not account for the fact that considering all failure modes provides reduced benefits for lower criticality equipment. The bulk of the effort in the PM Library comes from estab- lishing the database of recommended PM. This can be done at a corporate level with only some effort at the site level to localise the activities. This approach reflects either corporate or industry-accepted practices. Without considering failure modes, the mitigation strategy can be too conservative as they occur more often than required for the risk or do not address a failure mode and are, therefore, unnecessary. It is also possible that a hidden defect is not addressed, as its failure mode was never considered. The FRACAS approach is the most reactive and the slow- est of the three as you wait for failures to occur before taking steps to mitigate future failures. PMO using equipment criticality Using only reliability-centred maintenance (RCM) or FMEA in a PMO implementation for all equipment has proven to be highly resource-intensive. Even streamlined approaches that only look at dominant failure modes have not proven to significantly reduce the resource effort. There is a need for an approach that reduces the resource effort while maintaining the overall benefit. The following approach uses equipment criticality to differentiate the specific approaches used for equipment. Equipment criticality is a consequence-based ranking pro- cess that considers the safety and business consequences of failure for individual equipment items. It is based on both the frequency and consequence of failure. If a piece of equip- ment in a low criticality process fails, it will have a lower consequence compared to an identical piece of equipment in higher criticality process. As an example, the interior lights in your car failing to operate has a lower potential consequence than your headlights or brake lights failing to operate. In a downstream refining environment, equipment down - time has varied consequences depending upon the product stream and configuration of the refinery. Therefore, it is rec - ommended that a risk matrix is utilised to determine equip- ment criticality. Risk is a combination of consequence and

Revamps 2024