SolutionsPredictive Maintenance SavesMoney Improves Plant Reliability ,A predictive maintenance program started Built in 1996, the Cargill Vitamin E Plant diagnostic data generated by these devicesat the Cargill Vitamin E Plant in Eddyville, has nearly 1500 HART technology smart are captured by the AMS Suite: IntelligentIowa, has yielded hundreds of thousands of field devices connected to its distributed Device Manager software installed nearlydollars in documented savings since 2001 control system. In addition, digital valve three years ago. The information obtainedthrough improved maintenance resulting in controllers, or smart positioners, are is integrated into a single database, organ-decreased process variability and greater installed on about 350 control valves ized, processed, and presented on a PCreliability. Estimated savings through cost throughout the facility. Massive amounts of monitor, all without interfering with controlavoidance are even greater. For example,costly plant shutdowns have probably beenprevented by daily monitoring of 1500instruments and control valves, and thenscheduling maintenance based on criticali-ty of devices. This is in line with a stated goal of find-ing cost savings through asset optimizationand predictive maintenance, which werenot previously practiced at the instrumentlevel in this plant. Prior to 2000, schedule-based preventive maintenance was sup-ported by reactive maintenance. We fol-lowed manufacturers’ recommendations incaring for their products, and we reacted toproblems as they arose. As long as thingsran smoothly, nothing was done to seek outpotential problems and prevent them frombecoming actual. Predictive maintenance is the term givento the practice of identifying productionequipment needing maintenance attentionbefore its performance gets to the point thatproduct quality is reduced or an unplannedshutdown occurs. Information about the con-dition of equipment is the key to successful-ly predicting maintenance requirements inorder to take timely corrective action. The information we rely upon principallycomes from smart, microprocessor-basedfield instruments that evaluate their owncondition and that of associated equip-ment in addition to reporting the basictemperature, pressure, and flow data need-ed to control production processes. Evenwith these advanced devices in place, tech-nicians formerly had to go into the plant,locate an instrument, and attach a hand-held communicator to extract the informa-tion. The evolution of communications pro-tocols, such as HART and FOUNDATIONFieldbus, and asset management softwaremade it possible for engineers and techni-cians to communicate with smart fieldinstruments from one central location. Cargills Eddyville, Iowa facility.
tation used for process control as well as Documentation Benefits the intelligent device management soft- NIST-traceable calibration certificates must ware. This resource is too valuable to be be provided as a part of the regulatory doc- ignored, which could happen if a specific umentation in the Vitamin E facility. With person does not have this as a full time our system, a calibration certificate on any responsibility with authority to take whatev- instrument on the control network can be er action is necessary to protect the integri- printed out showing that instrument’s cali- ty of the processing system. bration history, accuracy, date last tested, condition “as found”, condition “as left”, etc. Predictive Maintenance To calibrate a transmitter, all the data Emerson’s Intelligent Device Manager soft- required is downloaded from the Intelligent ware makes predictive maintenance possi- Device Manager database to a documenting ble. Once the process control system is calibrator, which is taken to where the actu- optimized and all the loops are running as al calibration is done. At the end of the day, well as they can possibly run, monitoring of the results are uploaded to the PC and the field instrumentation helps sustain that archived in the database. Some instrumentsWade Howarth, Automation Manager at the Cargill level of efficiency. We now catch potential do not have to be calibrated periodically asVitamin E plant in Eddyville, Iowa, has helped his problems before they can impact quality or long as we can verify that their calibrationcompany achieve "hundreds of thousands of dollars in productivity. A case in point is a recent trav- parameters are within design specifications.documented savings" over the last three years by apply- el deviation alert on a control valve that The documentation within the instrumenting a predictive maintenance strategy based on asset caused technicians to check out the valve, database serves as a reliable source for thatmanagement software. which seemed from the control room to be verification, making these historiessystem inputs and outputs. Using this tool, operating properly. They found a plastic air extremely valuable.technicians are able to look deeply into the supply line that was too close to a steamprocess in a way never before possible. line had melted and collapsed, restricting ConclusionFrom the safety and comfort of the mainte- the passage of air to the valve actuator. As a It is difficult to quantify the actual value ofnance shop, they’re able to perform all the result, the valve was responding very slowly predictive maintenance in dollars. Savingsfunctions generally associated with the to control signals and introducing a lot of in some cases, such as preventing the losshandheld communicator - instrument com- variability into the process, but the opera- of nitrogen, are easily computed. If variabil-missioning, configuration, and trou- tors didn’t know anything was wrong. ity on a steam loop is decreased, the energybleshooting of potential problems. Status In another instance, technicians checking saving can be calculated, but how can youAlerts inform them if the performance of out the report of a “non-responding” instru- put a value on decreasing loop variability?specific instruments begins to slip. In addi- ment found that it had been disconnected Similarly, it is impossible to assign a dollartion, all maintenance activities are automat- at the termination panel. This “fail-open” amount to time saved by technicians - oftenically documented. valve was allowing the loss of nitrogen, because no data is available for compari- which went unnoticed by operators for six son. We are satisfied to say that enough hasAsset Management months. While the process was not affected, been saved to pay for the software.To ensure that this software is fully utilized, fixing the problem prevented the further A word of caution; do not expect immedi-we employ an asset manager, whose job it is loss of nitrogen and reduced the loading on ate results! It is important for the individu-to monitor the instrumentation, keep all a scrubber by about 20 percent. als working with the software to understandconfigurations and calibrations current, and Many potential problems are simply it and learn how to recognize potentialmaintain the database. Based on informa- avoided because the asset manager system- problem areas. A tool is valuable only if it istion received from the field instrumenta- atically checks every instrument on the net- used properly. If a predictive maintenancetion, the asset manager determines mainte- work, looking for the warning signs that program is implemented, an asset managernance needs and generates work orders as indicate an impending failure. When he put in charge, and work practices changedappropriate. He helped establish the pre- catches a transmitter before it gets too far as needed, savings should become appar-dictive maintenance system and trains out of calibration or expires, he is helping to ent within 12 to 24 months.other maintenance personnel to use it. maintain the reliability of the production Our work practices have certainly He is also responsible for continuously system. If early action by the asset manager changed. We have been able to shift ourmonitoring the health and status of the 30 avoids a plant shutdown, the savings could focus to prevent from correct, and the docu-Critical Control Points identified as essen- be substantial. mented savings are significant. We intend totial to the safety and quality of our product. Since the predictive maintenance pro- keep exploiting the predictive maintenanceMonitoring these critical points for baseline gram began functioning, the reduction in environment and avoiding unexpectedand calibration certification using NIST- work orders has been noteworthy, with stoppages. The more we can plan andtraceable procedures allowed changing the maintenance following a more orderly plan schedule our work, the more efficient we willquality control procedure from fully analyti- and schedule. Previously, a great deal of be, and that is our ultimate goal.cal to a process instrumentation-based sys- time was spent reacting when somethingtem. The reduction of in-process testing has broke. We’re still doing reactive mainte-saved us enormous amounts of analytical nance, but now we’re reacting to predictionstesting time and dollars. based on field-based information and not It is essential in any processing plant that breakdowns. Instead of smoke coming out — By Wade Howarthone individual be designated as asset man- of a motor housing, we react to an indica- Automation Managerager. That person must be very knowledge- tion that there will be smoke unless some- Cargill Vitamin E Plantable about the process and the instrumen- thing is done to prevent it. Eddyville, Iowa Reprinted with permission from Pharmaceutical Processing May 2004