Customer Success Story

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Here is an interesting case study regarding reciprocating compressors of a major US refinery. Check out this case study to know, how condition monitoring reduced the need for “just in case” inspections, lengthy outages, and improved machine reliability.

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Customer Success Story

  1. 1. GE Energy Oil & Gas – Petroleum RefiningCustomer Success Story Bently Nevada* Asset Condition MonitoringUsing PV Curves to Diagnose a Recip Valve ProblemThe single most important measurement for condition monitoring ofreciprocating compressors is cylinder pressure. Armed with accuratecylinder pressure at each point in the piston’s stroke, a Pressure-Volume(PV) curve can be constructed, which provides indispensable informationon the machine’s health.ProblemThree reciprocating compressors provide compressed hydrogen for the catalytic cracker ina major US refinery. In order for the unit to run at full output, all three compressors must runsimultaneously. The loss of one machine results in a 20% loss in plant production.SolutionA 3500 Series monitoring system provides alarms on high vibration and transmits allparameters to System 1* Condition Monitoring and Diagnostics Software for storage anddisplay. Parameters monitored include cylinder pressure (displayed as pressure vs. volume, System 1* Softwareor PV), cylinder valve temperature, main bearing temperature, suction and dischargetemperatures, frame velocity, crosshead acceleration, piston rod vibration, and rod position.Important parameters derived from these measurements include rod load (compressionand tension), degrees of reversal, peak cylinder pressure, discharge pressure, minimumcylinder pressure, suction pressure, and compression ratio.PaybackAn increase in vibration in the crosshead vibration on the low-purity, third-stage cylinder 3500 Seriestriggered an alarm in the 3500 monitor which alerted the plant’s rotating equipment Monitoring Systemengineering group. Through cylinder pressure information provided online by System 1,engineering was able to assess the stresses that the malfunction induced upon the recipro-cating compressor and, based upon these stresses, decide when to shut down the machineso that further damage did not occur. This resulted in a shorter outage, lower maintenancecost, and the prevention of a major failure. As a 20% reduction in production results fromhaving one machine down for maintenance, a large part of the savings can be attributed tothe decrease in unscheduled maintenance downtime.Benefits• Reduced need for “just in case” inspections through accurate, real time machinery information that shows actual mechanical stresses and conditions.• S horter, more efficient outages by knowing what needs attention and what doesn’t along with what parts and skills are needed.• Improved machinery reliability through the ability to correlate process conditions with mechanical conditions and make necessary operating adjustments to prolong asset life. As seen in Learn more by reading the feature-length case study article in ORBIT magazine Vol. 24, No. 1, 2004 at © 2008 General Electric Company, all rights reserved. www.orbit-magazine.com * Trademarks of Bently Nevada, LLC, a wholly owned subsidiary of the General Electric Company. www.ge-energy.com/ocsuccess GEA17072 (08/08)

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