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Ten Tips for Commercial ChillerMaintenance Mar 1, 2010 RICHARD GRENZ | Contracting Business
Chillers often represent a plant's single largestelectric load. But factor in fouled tubes, leaking refrigerant, or myriad otherfactors, and operating costs can quickly escalate by eight to 10%. Operatingchillers at their peak performance will save energy and maintenance costs. Chiller maintenance has advancedsignificantly, due to new developments in centrifugal chillers with magneticbearing chillers, and new remote monitoringtechnologies. As a result of remote monitoring, the industry hasbeen moving toward demand maintenance programs and away from pre-determinedschedule maintenance. Whichever program you use, here are10 maintenance tips that apply to most centrifugal chillers, to help maintain high efficiency: 1. Keep a daily log
The daily log is still the first step toward maintaining an efficiently-runchiller plant. The log allows you to build a history of operating conditionsincluding temperatures, pressures, fluid levels, and flow rates. Remotemonitoring technologies allow you to inspect machines continually rather thanmonthly or every other month. And, it allows you to easily generate trendreports that help to identify maintenance needs before they become an issue. 2. Keep tubes clean forefficient heat transfer Heat transfer efficiency has the greatest single effect on chiller performance,so clean heat transfer is fundamental to maintaining high efficiency.Contaminants such as minerals, scale, mud, algae and other impurities increasethermal resistance and reduce overall performance. Approach temperatures are agood indicator of heat transfer efficiency. Higher approach temperatures are prime indicators that heat transfer efficiency is decreasing. Condenser tubes should be brush cleaned at least annually, or per your demand maintenance schedule to keep them free of contaminants. 3. Treat condenser water to preventscale, corrosion
All condenser water loops using open cooling sources (such as atmospheric cooling towers) require water treatment of somesort to eliminate scale, corrosion and biological growth. All lead to foulingin the condensers and impede heat transfer and can decrease tube and pipingeffectiveness. Inspect chilled water loops once a year or regularly with remotemonitoring for general water quality and evidence of corrosion. 4. Lower entering water temperature
Lowering the temperature of the entering condenser water will improve thechiller's efficiency. On some building systems, the operator will lower thechilled water set point to overcome air handler deficiencies such as dirtycoils. This cures the symptom but not the problem, and makes the chiller workharder for the same net cooling effect. 5. Keep chilled water flow rate between3 to 12-ft per second
Changing the chilled water flow rate affects a chiller's performance. Too low aflow rate lowers the chiller efficiency and ultimately leads to laminar flow. The minimum flow rate is typically around 3-ft. per second (FPS). Too higha flow rate leads to vibration, noise, and tube erosion. The maximum recommendedflow rate is typically around 12 FPS. 6. Maintain adequate refrigerant charge
The actual amount of cooling a chiller provides depends on how much refrigerantit moves through the compressor. It is important to maintain theproper level of refrigerant for the conditions desired. Refrigerant leaks, aswell as air and moisture introduced into the system, will decrease efficiencyand the reliability of the system. A low refrigerant charge will cause thecompressor to work harder for less cooling effect. 7. Prevent inefficiencies caused bynon-condensables Non-condensables such as air andmoisture leak into low pressure chillers because their evaporators operate in avacuum. Non-condensables can lower the real efficiency of the chiller from therated performance by as much as 4% at 60% load and 7% at 100% load. Purge unitsminimize the effect of non-condensables. 8. Analyze compressor oil
Send a sample of the lubrication oil to a laboratory for a “spectrometric”chemical analysis once a year. Like any hermetically sealed refrigerationsystem, the oil should only be replaced if the analysis indicates it's needed.High moisture can indicate a problem with the purge unit. Sample low pressurechillers more frequently, based on purge run hours. Check oil filters for pressuredrop and replace them if the oil charge is replaced. New, magnetic bearing frictionless chillers require distinctlydifferent maintenance and operations from traditional centrifugal chillers. Oil has been eliminated in the design of these chiller systems, furtherreducing maintenance costs. 9. Check operation of starters andmotors
For efficient operation of starters and motors, check the safety and sensorcalibrations on microprocessor controls (consult manufacturer's guidelines).Then, check electrical connections, wiring, and switchgear related to thechiller for hot spots and worn contacts. To prevent insulation faults, testelectrical motor windings for insulation resistance to ground andwinding-to-winding. Check the shaft seal ofopen drive motors for possible refrigerant leaks, and clean motor cooling airvents to ensure maximum cooling effect. 10. Install variable speed drives
The chiller motor is typically the largest single electrical load in abuilding. With the right operating conditions, variable speed drives (VSD) canoffer significant energy savings. Varying motor speed matches motor efficiencyto load and wastes less energy. Variable speed drives also act as asoft starter to lower the inrush current for the motor to almost that of thefull load running amps. This is an important factor for chillers operating onemergency power generators. VSDs reduce the mechanical shock ofstarting large horsepower motors, increasing chiller reliability, and life. Richard Grenz is national service sales manager for McQuay International's, FieldService Division.
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发表于 2016-9-22 15:53:54
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好文章！待我找出我珍藏10多年的牛津大辞典再慢慢品读！
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