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will also change as the building ages
The maintenance mix is one of the criteria used to measure the quality of maintenance and the robustness of the overall maintenance program.
The purpose of a maintenance mix is:
Maintenance Mix Option #1
The first method establishes the maintenance mix based on the relative ratio of the following two classes of maintenance:
Maintenance Mix Option #2
Maintenance Mix Option 3
The third method establishes the maintenance mix on the basis of the different parties that are performing the maintenance tasks.
The appropriate ratio of contracted-to-non-contracted maintenance will depend on several factors, including:
Listed below are the key steps in determining the appropriate maintenance mix for the assets;
For proper alignment, maintenance strategies for each asset should be selected based on risk analysis (criticality analysis).
Maintenance Mix Relative to Each System
Listed below is an outline summary of the ratios of time-based and condition-based maintenance relative to each of the primary physical systems:
Finding the optimal balance in the triad of Preventative Maintenance (PM), Corrective Maintenance (CM/RTF) and Predictive Maintenance (PdM) requires a tremendous amount of skill and mountains of data.
Many organizations do not have sufficient structured and quantitive data to prepare a compelling business case to support the appropriate Maintenance Mix - that is, the balance of RTF-PM-PdM. In the absence of this data, most of us rely on criticality assessments to ensure that all maintenance-worthy assets are subject to PM-PdM and RTF is reserved for a particular class of assets where the risks (read, consequences of failure) are deemed acceptable.
Reliability-centred Maintenance (RcM) is a fourth class of maintenance that seeks the optimal maintenance mix that is aligned to each asset across the asset register and then periodically revisited and recalibrated as the assets age and approach potential failure (P) and functional failure (F).
Fig. Alignment of the four different types of maintenance strategies across the asset portfolio on decisions that are risk-based and consider the whole-life of assets will result in a maintenance mix that is in conformity with ISO 55001 standards.
Fig. Alignment between Maintenance, Repairs and Renewals will help the organization find the optimal MRR ratio.
Fig. Comparing the Maintenance-Repair-Renewal (MRR) trade-offs at different organizations.
Fig. The resource mix should reflect the organization's competencies, which will evolve over time with education, training, mentoring and experience of the team.
Fig. The changing ratio of the maintenance mix over time.
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Fig. The risk spectrum extending along the P-F interval indicating the relationship between time-based maintenance (TbM) and condition-based maintenance (CbM).
Fig. Variable interval events mapped onto the P-F curve to illustrate the relationship between time and condition.
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Fig. The maintenance mix for a building based on the ratio of contracted maintenance to non-contracted maintenance.
Fig. Generator service is a form of routine maintenance.
Fig. "I. Care" takes us through the challenges of interpreting the maintenance manual find the right blend for the maintenance mix.
Fig. Different types of maintenance tasks distributed across the four seasons of an annual maintenance program.
Exterior painting Sealant review
Fig. Window washing is an examples of preventive maintenance carried out on fixed time intervals.
Fig. I. Care is trying to blend the optimal maintenance mix for the assets in his portfolio.
Fig. Pool tank cleaning is an example of major maintenance.
Fig. The correlation between the maintenance costs and repair costs associated with the three different maintenance strategies.While Predictive Maintenance (PdM) generally has the highest maintenance cost, it will result in the lowest repair costs. CM, on the other hand, has the lowest maintenance cost but the highest corresponding costs associated with asset repairs.
Fig. Thermography is an example of level-3 maintenance since it requires specialized skills and equipment.
Fig. Different types of maintenance activities at various life stages of an asset.
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