By Dan Steiner, PE, President; CEM, CDSM, CEA, CMVP
Editor’s note—This article is the second in a four-part series on the subject of electrical power systems reliability.
In part one of this series, I cited reliability expert Joseph Patton’s definition of reliability: “the probability that an item will perform its intended function without failure for a specified time period under specified conditions” (from his book Maintainability & Maintenance Management). I then used this definition as my basis for saying a reliable electrical system is one that works as designed without fail all of the time (i.e., 100% reliability). I also made the case that not only is a reliable electrical system possible, it is really the only alternative for a company wanting to guarantee its longterm competitive position.
In this article, I’ll discuss the relationship between electrical reliability and electrical maintenance—specifically electrical preventive maintenance.
A basic principle of electrical reliability is this: the degree of reliability in an electrical system is directly tied to the maintenance policy used for its “care and feeding.” The main approaches to electrical system maintenance are:
- Corrective—Perform maintenance functions when something breaks.
- Time-based—Perform maintenance functions and system upgrades according to a preset schedule (a.k.a., improvement maintenance).
- Preventive-based—Use past and predictive system data to perform only necessary maintenance functions and only at the time when these should be completed in order to keep the system running at its optimum level (think of this as “justin-time” maintenance).
Corrective maintenance is false economy because of the unexpected and unnecessary expenses it can create (injured employees, lost production, damaged equipment). Time-based maintenance often ends up repairing or replacing components that don’t need to be—and can introduce maintenance issues that wouldn’t have even been issues otherwise.
Preventive-based (a.k.a., reliabilitybased) maintenance, on the other hand, increases employee/equipment safety and operating equipment efficiency (OEE), while lowering system maintenance costs. A program of electrical preventive maintenance, then, is the best pathway to a truly reliable electrical system.
What Is Electrical Predictive Preventive Maintenance?
Electrical predictive/preventive maintenance (EPPM) is an electrical maintenance system that attempts to maximize the service life of electrical equipment through regular inspections and well-planned and executed maintenance operations. Deeper in scope than time-based maintenance, it doesn’t repair/replace components “whether they need it or not.” It also doesn’t wait for failures like corrective maintenance does. Instead, EPPM uses a range of data to track system performance and help predict component failure points in order to accomplish an important two-part goal: (1) keep the electrical system from failing and (2) keep it running at its best. Both aspects are fundamental to electrical system reliability.
EPPM is an intelligent, proactive approach offering multiple benefits to companies that practice it.
Economic—According to NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, as soon as it begins operation, an electrical system starts deteriorating (§4.1). EPPM slows this process for a longer overall system service life. In between, it helps identify and head off potential equipment failures before they turn into actual ones, leading to unscheduled shutdowns, lost production, and damage to other components and systems as a result. And because it relies on “informed anticipation,” EPPM helps avoid replacing components that that are still useable, it simplifies maintenance scheduling, and it promotes better management of the maintenance parts inventory.
Safety—”An effective electrical preventive maintenance (EPM) program should enhance safety” (NFPA 70B §5.1). Even more important than the economics, EPPM increases worksite safety. A properly maintained electrical system is appreciably safer than a poorly maintained one—and to avoid equipment failures is to avoid unsafe situations. NFPA 70E Standard for Electrical Safety in the Workplace mandates: “Electrical equipment shall be maintained in accordance with manufacturers’ instructions or industry consensus standards to reduce the risk of failure and the subsequent exposure of employees to electrical hazards” (§205.3; emphasis added). Unless time-based maintenance is manufacturer specified, EPPM promotes better system maintenance and greater system safety.
Intangible—Increased safety from EPPM leads to improved morale and performance as workers see management’s commitment to a safe workplace. More productivity from a reliable electrical system—minus bad publicity due to electrical accidents fosters the public’s perception of a company as a well-run organization.
EPPM and System Startup
An EPPM program can benefit an electrical system at any point, but the best time to implement EPPM-based reliability is during system startup and acceptance testing. This is when it is easiest to identify installation errors (e.g., loose connections) that can cause major failures on startup or later, after loads increase. Maintaining critical component data records that are accurate and complete is also easier when these records are established at system startup.
The InterNational Electrical Testing Association (NETA) publishes Acceptance Testing Standards (ATS) that support the EPPM concept.
EPPM Program Development
Planning and developing an effective EPPM program involves four steps:
Step 1, list electrical equipment and systems—This consists of listing all components to be tested regularly, typically those above 480V. “Listing” includes data collection, locating all documents/resources needed to support these functions: assembly, wiring, installation, programming, operation, maintenance, troubleshooting.
Step 2, decide which equipment/systems are critical—Equipment is critical when its failure to operate normally poses a danger to people, the product, or other equipment nearby. This includes equipment vital to the process (e.g., melting furnaces), as well as protective equipment (circuit breakers, protective relays, etc.) and monitoring/alert systems.
Step 3, create a system for staying up-to-date with maintenance needs—EPPM program success is based on information and its proper use. A complete data record of each critical component or system should be built and maintained. This record should include a description of its operating environment, its history (nameplate data, location, use, installation date, maintenance inspection/test details), its inspection/test interval, its inspection/test/maintenance procedures and schedule, and the results of all maintenance procedures.
Step 4, find the people qualified to do the work—NFPA 70E describes a qualified person as “one who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved” (Article 100). Only qualified employees or contractors should be tasked with performing EPPM!
NFPA 70B contains a more detailed explanations of these four steps. The main point to remember is that each step must be an ongoing process, not a one-time event, if EPPM is to be effective—and the electrical system is to be more reliable.
In my next article, I’ll discuss reliability and the technical review (system studies).