Guarding against electrical malfunctions with preventive maintenance
WHY should health facilities professionals maintain their electrical power systems? Why should they change the oil in their cars? In both cases, the answer is the same--so that the equipment will continue to operate as reliably as it was designed to operate.
Many hospitals do not pay enough attention to electrical testing and maintenance because the electrical power systems do not have moving parts and, therefore, appear to be more benign than they really are. However, hospitals that do not regularly maintain their electrical systems are practicing a high-risk sort of maintenance often known as "run-to-failure" or "breakdown" maintenance.
The risk of hospital power system outages--internal blackouts that interfere with patient care--is high when this approach is taken. While preventive maintenance (PM) cannot absolutely eliminate all risk of failures, it substantially reduces the risk. In fact, the Institute of Electrical and Electronics Engineers (IEEE) has concluded that the failure rate of electrical components is three times higher in facilities that do not PM their electrical systems.
Most electrical equipment in hospitals operates 24/7. Needless to say, as with any other apparatus that operates continuously, failures will occur. The purpose of an electrical testing and maintenance program is to improve operational reliability by finding the incipient failure and correcting it before it occurs. What can go wrong in a hospital electrical power system?
The following list of instances is not all-encompassing, but it does provide an overview of the issues that create the need for regular electrical power equipment maintenance:
* The switches, circuit breakers, unit substations, switchboards, panels and motor control centers could have loose or corroded connections. Approximately 25 percent of all miscellaneous electrical equipment failures are caused by loose electrical connections. Loose connections might have been that way from installation or might have become loose because of thermal expansion and contraction caused by varying load demands.
This equipment can also have poor or misaligned contacts, unbalanced loads, overloading and overheating. Infrared thermography can find some of these conditions, but attention should also be paid to the loading itself independent of the thermographic inspections.
* Circuit breaker springs can break, or can lose their tension or pressure. Arc chutes can become deteriorated or dirty. The moving parts of operating mechanisms can exhibit excessive wear, binding, hanging up in their travel path, or can be delayed by impediments in the travel path.
* Insulators and conductor supports can be cracked, broken, or otherwise damaged or deteriorated. Conductor insulation can be cracked, flaking, overheated, wet or deteriorated in some other manner.
* Many electrical equipment rooms do not have filtered air supplies. As a result, dust and dirt will accumulate inside the equipment on the connections and on the insulators between energized components. If the electrical rooms become very humid--another common occurrence--the dust and dirt can become conductive, providing high resistance paths for future short circuits. This failure mechanism is estimated to account for approximately 30 percent of electrical failures.
Regular electrical room maintenance includes cleaning the rooms to minimize the amount of contaminates that find their way inside the electrical equipment. Where used, filters should be changed. Rooms and equipment also should be inspected for evidence of water, since water and electricity are a mixture that no hospital wants.
* Transformers can have loose or deteriorated connections, overheated bushings, poor tap changer contacts, overloading, unbalanced three-phase loads, blocked or restricted cooling tubes, and low cooling fluid levels. Liquid-filled transformers are most commonly used in unit substations and outdoor locations. Because their cooling oil can break down and cause early transformer failures, regular oil sampling and laboratory testing can result in more proactive management of the transformer's physical condition and longer transformer life.
* Medium voltage equipment can have unwanted electrical discharges such as corona, arcing and tracking. These discharges can grow into large faults (short circuits) if they are not discovered in time. Portable ultrasonic instrumentation can be used to locate these discharges.
* Motors and generators could have overheated bearings; unbalanced loads; shorted or open windings; heating of brushes, slip rings and commutators; overloads; overheating; and blocked cooling passages.
* Emergency generators and automatic transfer switches could have poor battery terminal connections, dead cells in batteries, defective or inoperative contactors, and defective transfer switch components.
Detection and prevention
Many of these problems can be detected through infrared thermography, which is a rapidly growing noncontact, nondestructive testing method that allows users to identify components that are experiencing excessive heating. This tool is important because it allows deteriorating components to be identified prior to catastrophic failure. This technology was actually one of the first instances of predictive maintenance (PdM) for electrical power systems.
Infrared thermography used for electrical equipment condition monitoring can reveal problematic situations when the current operating temperatures of components are compared with baseline operating temperatures.
The baselines are established when the electrical systems are operating under normal load and operating conditions. Facilities that have a power monitoring system installed can easily determine normal load and operating conditions.
Other types of failures, and their methods of avoidance and detection, include the following:
* Generator sets. Generator maintenance programs include regular inspections, oil changes, filter changes, coolant testing and regular replacement of batteries, belts, hoses and coolants. They also include monthly load transfer testing, periodic fuel tank cleaning and even load bank testing when indicated.
The National Fire Protection Association (NFPA) 110, Standard for Emergency and Standby Power Systems provides criteria for testing and maintenance of emergency power systems and associated components.
The most common cause of emergency power supply system failure is lack of maintenance and testing of the batteries, battery cables and other components of the starting system.
The next most common cause of diesel generator failure is associated with the diesel engine's fuel oil system. Fuel oil that is too hot, or contaminated with water or impurities, can result in an engine failing to meet its performance criteria.
Fuel oil contamination can result from many causes, including natural fuel degradation from aging, day tank corrosion, clogged or fouled fuel oil filter, excessive fuel oil filter replacement interval, workmanship during fuel oil system renovation, fuel oil truck operator error, day tank microorganism contamination, inconsistent fuel oil quality from the supplier, incorrect biocide usage and even inadequate sampling techniques.
Hospitals need to ensure that their fuel oil is fresh and clean, and following their engine manufacturers' PM recommendations along with regular fuel oil testing programs and fuel oil tank cleaning programs will enable them to meet that challenge.
Regular load transfer testing is a requirement in hospitals. It is important because it tests the complete emergency power supply system (EPSS). However, it does not fully load test the generator set since generator sets are usually not fully loaded when the tests are conducted. Load bank testing can be used to operate the generator set at full load, which is necessary to fully evaluate some of the diesel engine's systems according to some manufacturers.
* Electrical protective devices. Electrical protective devices are the fuses, circuit breakers and relays in a power system. They must operate as designed in order to mitigate the impact (damage) caused by short circuits. The circuit breakers need to be maintained regularly or they could fail to open when needed. When circuit breakers fail to open or trip when they should, the overload or short circuit that is occurring will intensify and adversely affect a much larger part of the hospital.
The settings for adjustable circuit breakers and protective relays, and fuse types and sizes, are determined by the electrical protective coordination study, which is done in conjunction with the power system short circuit study. Both studies must use the actual power system configuration, and this information will come from accurate up-to-date electrical one-line and riser diagrams.
These diagrams are also required for the electrical system maintenance process to be managed proactively and safely. Circuit breakers and protective relays must be tested regularly to ensure that they will still operate within the fault clearing times required by the protective coordination study.
* Arc flash hazards. Maintenance personnel safety is always very important, and code changes have introduced new criteria that require action by hospitals and other facilities. The 2002 National Electrical Code (NEC) introduced a new Section 110.16, "Flash Protection," in response to the issue of electrical arc flash hazards.
This requirement mandated field marking of switchboards, panelboards, industrial control panels and motor control centers that are likely to require examination, adjustment, servicing or maintenance while energized. Even hospitals that conduct electrical shutdowns for maintenance--a highly recommended approach--will still conduct periodic examinations and perhaps adjustments of circuit breaker trip settings in response to updated coordination studies. Therefore, all such equipment should now be field-marked.
The 2004 edition of NFPA 70E, in Article 130.3, requires a flash hazard analysis to be done in order to determine the "flash protection boundary" and the personal protective equipment that people within that flash protection boundary must wear.
Those who must perform the flash hazard analysis can obtain help from IEEE Standard 1584-2002, Guide for Performing Arc-Flash Hazard Calculations, as well as from NFPA 70E.
Electrical equipment maintenance is a combination of common sense and highly technical activities around and inside high-energy equipment with the downside potential for disastrous results.
Industry standards have been developed for this purpose and are highly recommended. The resources list on page 24 includes some sources that maintenance personnel and managers should be aware of, but readers are cautioned that there are other sources that should also be consulted.
Most electrical equipment manufacturers publish recommended maintenance activities and intervals for their equipment. The manufacturers' recommendations should be factored into the overall maintenance program.
The hospital's insurance company may also have specific maintenance criteria to be followed. Some insurance companies also publish their own maintenance recommendations on the Internet, while others have them available for their own customers.
Managing the risk
Electrical system faults are among the most disrupting and even dangerous occurrences that could happen in the health care setting, but proper detection and maintenance methods can help health facilities professionals successfully manage this risk.
David L. Stymiest, P.E., CHFM, SASHE, is a senior consultant at Smith Seckman Reid, New Orleans, a firm specializing in building and infrastructure design, and compliance and facility management. He can be reached at DStymiest@SSR-INC.com.
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