FOCUS on POWER
Preventative maintenance for the UPS
Eaton Corporation outlines the importance of preventative maintenance for the uninterruptible power supply (UPS) and offers some tips for devising your own plan
Because companies rely on an uninterruptible power supply (UPS) to deliver continuous power without any disruption to their business, a maintenance plan is a critical component to ensuring a UPS minimizes the risks of downtime and performs as expected. Eaton recently analyzed data collected from its service organization, and numerous findings on downtime compiled by industry experts to help end users understand the prevalence and consequences of downtime.
No matter how you assess it, downtime carries an enormous price tag. The Electric Power Research Institute (EPRI) estimates the national cost of power interruptions at approximately US$80bn per year to US electrical customers, with momentary interruptions accounting for two-thirds of the total cost at $52bn.
The US economy loses between $104bn and $164bn to outages each year, and another $15bn to $24bn to power quality issues, according to the EPRI. Furthermore, the annual downtime average for the utility grid in the US is currently eight hours and 45 minutes. However, with on-site generation equipment and UPS solutions, this downtime can be reduced to the equivalent of five minutes and 15 seconds per year.
Other studies concur that the cost of network downtime can be crippling to a corporation, with financial implications starting at about $10,000 an hour for smaller companies and extending to $1m per hour for those that rely heavily on measures such as e-commerce.
WHAT ARE THE ROOT CAUSES OF DOWNTIME?
It may come as a surprise that more than two-thirds of downtime events stem from preventable causes, according to the 2007 Study of Root Causes of Load Losses compiled by Eaton. Studies have also shown that about 4% of UPS failures are the result of components wearing out due to age, while up to 20% fail due to bad batteries. Studies into the causes of downtime reveal the following:
Causes of preventable downtime (67%) • Human error • Lack of process • Incorrect procedures • Poor design • Inadequate redundancy • Insufficient maintenance
Causes of non-preventable downtime (33%) • Equipment failure (despite proper maintenance and testing)
• Supply chain/service chain failure • Cyber terrorism
Of the 67% of reported load losses identified by Eaton during analysis of its own service data on Powerware UPS products, failures resulting from preventable human error and site design problems were attributed to: • Site operations error • Site design error • Service technician error • Batteries • Product design • Defective parts • End of life/product wear out • Factory quality
THE MOST COMMON CAUSES OF UPS FAILURES There are numerous reasons why a UPS fails. The most common causes are:
1. Batteries – The heart of any UPS, batteries require inspection and maintenance, regardless of age or warranty status. Studies show that up to 20% of UPS failures can be attributed to bad batteries, with temperature and cumulative discharges cited as the primary culprits. During a preventive maintenance visit, data is obtained from thorough testing procedures, during which impedance or conductance measurements trace the battery performance and identify any batteries with internal potential failures.
2. Fans – Some fans fail because of their own electrical or mechanical limitations, or when their ball bearings become dried out. Fans may perform well for more than 10 years of continuous use, while others run for only short periods before locking up for mechanical reasons.
3. DC caps – See the explanation below to understand more about capacitors.
4. Transient spikes – Damage may be caused to the input side of the UPS (filter/rectifier) when a transient spike occurs. During a preventive maintenance call, these parts are checked for any impairment.
Other factors that lead to UPS failure: • Lightning – A common misconception is that a UPS constantly protects the equipment load from lightning, but it primarily depends on the amount of energy in the transient. Preventive maintenance inspections can readily identify lightning damage and any appropriate repairs.
• UPS internal connections – These may be affected by vibrations from the building or machinery close to the UPS. It is recommended that the UPS be scanned every three months to check for hot spots, as well as checked annually with a
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