How to predict electrical equipment failures

Electrical engineers can provide many services to help facility managers predict electrical equipment or power distribution system failures.

08/22/2017


Learning objectives

  • Identify the top electrical and power equipment in a facility that needs an overhaul or replacement.
  • Explain how to calculate the reliability of an electrical system.
  • Evaluate infrastructure, budget, and other needs to provide facility managers with appropriate electrical and power systems.

Problem: Facility managers with aging power distribution systems often lack comprehensive data to effectively communicate to managers responsible for budgets and allied stakeholders the need for equipment overhaul or replacement. The gap in communication prohibits facility managers’ ability to influence budgeting in a timely manner when significant failures are avoidable.

Main point: Consulting engineers can provide a variety of services to assist facility managers in predicting equipment failures and communicating the impacts of the failures to other stakeholders (see Figure 1). Consulting teams also can help develop emergency operating procedures in the event of equipment failures and long-term equipment-replacement plans, both of which lead to better budgeting with fewer surprises.


Figure 1: Facility managers can engage engineers as consultants to assist in predicting equipment failures and communicating potential impacts of failures. All graphics courtesy: Page, Dror Baldinger PhotographyThere are many tools on the market that calculate the reliability of a system. However, it is important to understand their limitations. Most of the tools only calculate reliability for single-source systems, thus additional calculations are required for the assessment of multiple-source systems. Another challenge with the tools is that information such as mean time to repair (MTTR) is based on IEEE 493-2007: IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems, which in turn is based on a survey that covers a wide range of industries. Often, companies employing these standard tools find that MTTR actually takes longer than the time listed in the IEEE reference due to requirements such as root-cause analysis and safety reviews. The use of the IEEE reference will result in higher reliability values, possibly affecting the equipment-replacement decision process. Establishing detailed procedures to remove equipment for repairs or maintenance can significantly reduce MTTR and increase system reliability.

Reliability-centered maintenance

Reliability-centered maintenance (RCM) refocuses analysis of a maintenance and replacement program to overall impact on operations, as opposed to the more traditional approach that focuses on equipment individually (see Figure 2).

Basically, an RCM program asks whether a given maintenance activity will introduce more risk than it mitigates. There always is an opportunity for failure in the process of performing maintenance or equipment replacement: A bolt may not get retorqued, a wrench might be left inside the switchgear, or a firmware update may have a bug in it. In addition, there often are business costs associated with maintenance, even if it goes perfectly—this is especially true for systems with a single power distribution pathway.

RCM programs are common in industries with extreme consequences in case of failure, such as aircraft maintenance. They are less common in power distribution systems for buildings and campuses. But RCM programs are arguably appropriate for all facilities that have far-reaching impacts on the communities or organizations they serve.

Figure 2: Reliability-centered maintenance is a comprehensive analysis of an equipment maintenance and replacement program’s overall impact on operations.To create an RCM program, a consultant typically starts by developing standard maintenance procedures for each component of the power distribution system. The next step is to calculate the system reliability based on current procedures. This analysis helps quantify the implementation of the existing procedures. The consultant then develops a failure modes and effects analysis (FMEA) for the power distribution system. The analysis determines the possible failures that could occur, the likelihood of their occurrence, and the impact each specific failure would have on the overall facility. If enough stakeholders participate within the facility owner's organization, the analysis can expand to include impacts to the broader organization beyond the individual facility under consideration. Typically, the people involved in the FMEA are the people executing the work, and they generally focus on failures that relate only to their systems. However, when multiple stakeholders, such as information technology equipment owners or managers, are engaged in the process, the evaluation becomes more comprehensive and more effective in helping to identify the possible impacts of failures. This communication enables the creation of broader mitigation efforts and project management.

After the FMEA is complete, the consultant can provide guidance regarding which maintenance activities bring value and which ones don’t. The results are often counter-intuitive to facility managers with many years of experience—especially within organizations that treat individual equipment failures with the same level of fear that they would a complete system outage.

Thus, it is very important that the consultant asks for buy-in from the facility manager at each step of the FMEA. Often, the FMEA demonstrates that it is better to run a particular piece of equipment to failure rather than proactively maintain or replace it. The results vary dramatically based on system configuration, the business impact of the facility, and the reliability of the maintenance program.

After an RCM system study is complete, a facility manager can create an RCM-based maintenance program. A comprehensive program provides written standard operating procedures, maintenance procedures, and emergency operating procedures. It also outlines a development plan for training maintenance staff and a 10-year maintenance and equipment-replacement plan including projected budgets. Finally, it identifies a plan for future system improvements where desired to increase system reliability.

It is critical that the consultant clearly documents all underlying assumptions used in an RCM system analysis. For example, a primary struggle with equipment replacement is how to deal with outages. This is particularly difficult in health care where outages require relocation of patient care. Temporary power costs can equal or exceed the cost to replace the equipment. Replacement projects also will require design professionals for sealed drawings that the local health department or fire marshal can review, which also increases the cost of replacement as an entire project cost. Projects that require competitive bidding for construction work also will undergo a design process and have associated engineering fees.

Executives often choose not to participate in the process of creating an RCM program. They also may not accept the results if the study recommends a higher-than-expected expenditure on maintenance.

Reliability studies depend heavily on the assumptions made about the future reliability of equipment and maintenance activities, and it is easy for those who do not participate in the assessment of these numbers to disagree with the results. A technique for eliminating possible disagreements is to analyze the sensitivity of each assumption and identify how much change would be required to each assumed value before it would affect the outcome of the study. This additional analysis work can then focus subsequent conversations on the assumptions that have the most impact on the study.


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