Coal Development Executive Roundtable

September 2009 • www.power-eng.comSpecial Report:Coal DevelopmentExecutive Roundtable

A Wireless VibrationMonitoring SystemA 1,050 MW power plant adds a state of the art monitoring system.By Gregg W. Rebenstorf, P.E. Southern California EdisonIn December 2008, the Southern California Edison Co.completed installing a state-of-the art wireless vibrationmonitoring system at its Mountainview Generating Stationin Redlands, CA.The system was installed on all 4.16 kV critical pumps,compressors and motor drivers as well as critical 480V watertreatment equipment as part of a predictive maintenanceprogram to both maintain and improve station reliability. In addition,difficult to reach gas turbine enclosure blowers were added to thewireless monitoring list.The 1,050 MW combined cycle power plant facility is comprised oftwo blocks of 2-on-1 combined cycle units using GE 7FA gas turbinesas the prime movers. Each of the two blocks is rated at 525 MW netoutput and each contains a GE D11 condensing steam turbine. GEPower Island equipment is vibration monitored by the GE BentleyNevada system; however, the balance of plant (BOP) equipment hadlittle or no vibration monitoring. Critical BOP equipment such as thenatural gas rotary screw compressors have a local alarm panel with acommon trouble alarm signal sent to the control room DCS system.The gas compressors, boiler feedwater pumps and circulating waterpumps currently only have thermocouples in the pump and motorbearing caps, which are monitored and trended in the DCS.Proof-of-Concept PhaseThe project began in June 2008 when engineering selected 10 piecesof equipment as part of the project’s proof-of-concept phase alongthe north side of the station. The north side was selected to checkfor potential interference from nearby San Bernardino InternationalAirport (formerly Norton AFB). Using the northern-most part of thestation potentially addressed signal strength as well as interferenceissues from large steel structures such as heat recovery steamgenerators, concrete turbine decks and other objects obstructingline-of-sight communication. Since cell phone communication ispoor throughout the plant, it was first necessary to demonstrate thatthe wireless system could communicate continuously and at sufficientsignal strength for the project to move forward.By late August 2008, the ITT ProSmart wireless system hadprovided sufficient evidence of its capability and the project movedto build-out phase. The station’s technical manager, Steve Johnson,placed the order for the build-out. The goal was to use an October2008 outage to install vibration sensors on critical equipment thatcould not be shut down, while less critical equipment could be shutdown when the station returned to service from the outage. ITT andthe station contractor completed the installation and commissioningof wireless equipment and sensors by the first week of December.The Data MonitorsThe wireless system consists of powered data modules (or DMs)that collect tri-axial vibration data, temperature, shaft speed andother analog data for 68 pieces of BOP equipment. In general,each piece of equipment requires one DM to transmit data up to acommunication module, or CM.The gas turbine enclosure fans had only one sensor installed onthe lower motor bearing. Those DMs shared multiple services andreduced the total number of DMs required. In all there were 52ProSmart DM22x’s installed for this project. The recently redesignedReprinted with revisions to format, from the September 2009 edition of POWER ENGINEERINGCopyright 2009 by PennWell Corporation

DM22x is approved for Class 1, Div. 2Group ABCD hazardous areas. The datamodule communicates at 2.4 GHz frequencyhopping spread spectrum up to 3,000 metersin a point-to-point communication range.ITT is developing software to allow datamodules to communicate in a self-healingmesh arrangement that will allow up to9,000-meter-long transmissions. These newDMs include an integral junction box forconnecting up to three 4-20 mA signals,two digital inputs, a single form C relay anda power supply termination block. On theoutside of the case are diagnostic LED’s forpower supply, as well as vibration warningand alarm functions. Operators making theirrounds can determine if the equipment is inalarm when the red alarm light is on.DMs are mounted four feet from thegrade in an upright position with theantenna pointing up. The antenna needsto be clear of obstruction 10 inches aroundit and should be three feet or more apartto avoid the DM signal cancelling. Asidefrom that, anything goes. What surprisedeveryone was when four of the DMs werelocated inside the west end of the warehousebuilding adjacent to the firewater pumps. Itwas thought the corrugated steel buildingwould trap the signals. However, theytransmitted to the communication moduleon the control building several hundredfeet away, with a strong signal even with therollup door closed.Communication ModulesThe CM receives data from the DMs andprovides a secure connection to the ProNetplatform via LAN, DSL, cell or 802.11wireless routers. Mountainview has twoCMs on each of the steam turbine decksand one on the control building roof. Thecontrol building CM communicates to theProNet platform through a DSL line, whilethe four CMs on the turbine deck have cellphone connections to the internet.Shown in Figure 1 are two power blocksin a slide along arrangement of 2-on-1combined cycle units. The steam turbine deckfor each block is shown to the north abovethe two CTG-HRSG trains. There are fiveCM-DM circuits shown in the plant generalarrangement with each circuit represented bya different color. The colored dots representthe DMs; the CMs are represented bystars. To improve communication strength,temporary cell phone CMs were added onthe north side of each steam turbine deck,which are shown in white and red stars.When the mesh network software is installedlater in 2009 these two temporary CMs areexpected to be eliminated. Locating theCMs at a high point in the plant allows someequipment DMs to communicate via line-ofsight.Since the signal emitted from an antennais cone-shaped and 360 degrees around, thehigher elevation prevents the bottom of thecone from being cut off if it hits the ground.This also allows for greater signal bouncefrom adjoining structures.During the proof-of-concept phase of theproject equipment was powered from the110V GIFF receptacle with plug in cords,which proved to be problematic. The GIFFcircuits typically will trip from heavy moistureFigure 1 sensor overviewor after a rainstorm. During the build-outphase the 24 VAC power supplies for theDMs and CMs were hard wired through atransformer/power supply from the 110Vlighting panels. Power supplies, includingfuse blocks, were attached to a D-rail insidea stainless steel NEMA 4X enclosure. Thehard-wired power supply has improved thesystem’s reliability.Vibration SensorAt the heart of the vibration monitoringsystem is a tri-axial accelerometer probethat also incorporates a temperature sensor.Four sensors are required on horizontalequipment to monitor inboard and outboardmotor, pump, compressor and fan bearings.On vertical equipment, three sensors areused for monitoring the motor and theupper pump bearing. On vertical enclosurefans the utility’s senior vibration analyst,Costa Yiannakakis, felt that the lower motorbearing was sufficient to determine if thefan-motor assembly was failing. These fansvibrate at 0.35 ips under normal conditionsand increase to 0.6 ips as they begin to fail,so the high level of vibration is transmitted tothe shutdown standby blower unit as well.Tachometer SensorOne of the project’s more challengingaspects was installing the tachometer sensors.The original concept (and least intrusiveapproach) was to strap a piece of key-stockon the shaft. The sensor gap was adjustedto 5 mm or less to detect changes in theshaft’s magnetic profile, which acts as a pulsetrigger. Keeping the key-stock on the shaftproved difficult and our installation shiftedto using either the keyway or shaft key itself.On some equipment neither was long enoughso the keyways were elongated or a separateLast weekthis was just atiny vibration.Think about itt.ITT ProSmart ® provides affordable,state-of-the-art predictivecondition monitoring to any pieceof rotating equipment. It checksand analyzes up to 22 criticalconditions every five seconds.So you’ll lower maintenancecosts, extend equipment life—and avoid catastrophic failures.Find out more. Visit www.ittmc.com,or call 1-800-734-7867.

Knowthe flow.Skipthe meter.Think about ITT.You probably knowthat PumpSmart ®prevents failures,improves pumpreliability and greatlyreduces energy andmaintenance costs.But did you knowthat it also providessensorless flowmeasurement forthousands of dollars less than aflow meter? One more reasonsmart plant managers arechoosing PumpSmart—theintelligent pumping solution.View our Sensorless Flow videoat www.ittmc.com, or call1-800-734-7867.PumpSmartslot was cut into the shaft. The slot had to besufficiently long to allow for shaft movementdue to motor magnetic center.The first iteration resulted in strangedroops on the revolutions-per-minute trendsas the shaft moved from the deep part ofthe keyway to the tapered area. The seconditeration centered the sensor over the deeppart of the keyway so the result was a nicesharp rpm trend. The learning curve waspainful as each iteration required repeatedequipment clearances. All sensor bracketswere custom made for each equipment typefrom sufficiently thick bar-stock to avoidalarm condition. It appears that the warningalarm prompted operations to shutdown theequipment until it could be determined ifthis was real vibration or not. It was thenrestarted and continued to trend into thepre-alarm area. The scale on the left side ofthe trend is in inches per second (ips).Software Setup and ConfigurationSetting up the software pre-alarm, alarm,alarm delay times, sampling rates and filtersvaried slightly from one equipment type toanother and required a good deal of effortto avoid nuisance alarms. Each of the fourITT ProSmart wireless system hadprovided sufficient evidence of itscapability and the project moved tobuild-out phase.vibration movement of the sensor.Originally, equipment speed was to beused for performance trending, but thisdata also proved useful in vibration trendsto determine when the equipment wasrunning.The Wireless SystemThe ProSmart platform provides theability to view, analyze and store data in asecure environment at the ITT facility inSeneca Falls, N.Y. Station personnel andvibration specialists may access their datafrom any internet connection with properusername and password. The system canbe set up to send text messages or emails topre-designated personnel should an alarmcondition prevail. Once connected to theProSmart platform, the vibration analystselects the generating asset from any numberof facilities. Listed under a generating asset isthe status of each piece of equipment beingmonitored. Shown on the status overviewbelow with a yellow dot is a boiler feedwaterpump in a pre-alarm condition. Should thevibration or temperature condition worsenthe yellow dot will change to red indicatingthe equipment is now in alarm. The analystcan drill-down by opening up the equipmentto determine exactly which sensor is in alarm.All other equipment shown with green dotsare in good condition.This dashboard arrangement focuses thevibration analyst on the problem areas andprovides drill-down to the problem sensorin a few seconds. A vibration analyst canquickly focus his or her attention to theproblem areas over several generating assets,which could reside in different parts of thecountry.The dashboard also allows for trending,as is shown below when the vibration leveltrends into the yellow pre-alarm condition.It can also be seen by the droop in vibrationlevel that the equipment was shutoff andthen restarted a short time later. The scalealthough difficult to view in its reduced size,shows the vibration level trending up over aseveral day period until it reached the pre-sensors on a horizontal equipment has anx, y and z component that can have fromone to 10 times running speed band alarmssetup. To some extent, some data could becopied from one sensor to the other but eachrunning speed needed to be checked forcorrectness. SCE’s senior vibration analystworked with ITT software engineers tocome up with a consistent configurationset that characterized each equipment type.Concurrent with this effort were ITT’s ownsoftware upgrades which added featuresand fixed bugs that presented an evengreater challenge. It wasn’t always clear ifthe problem was a configuration issue or asoftware problem. The debugging went onfor a better part of two months.Station operations and maintenance staffwere introduced to the vibration system inseveral training sessions provided by bothITT as well as by SCE’s vibration expert.There were introduction classes to explainoverall how the hardware worked and carein removal and reinstallation of sensorsduring overhauls. A software class providedinstruction on the basics of logging in anddetermining equipment status. More recentclasses dealt with the analysis of the alarmand vibration training.The SCE vibration expert and the plantengineer, Bruce Liu attended a configurationclass to learn the details of configuring theITT ProSmart software.As described earlier, the software isundergoing upgrades to add new featuresincluding a self-healing mesh network.Currently under development is a morerobust sensor, which will separate thesensor from the cable and facilitate removaland replacement of the sensor duringmaintenance.Author: Gregg W. Rebenstorf, P.E. is aplant performance engineer with SouthernCalifornia Edison. He is a degreed ChemicalEngineer, a licensed Mechanical Engineer inCalifornia and has 35 years experience in therefining, chemicals and power industies.