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  • 1.  Effect of frequent starts on process equipment designed for continuous operation

    Posted 6 days ago

    Dear all, I'm currently investigating the effect of starts and stops for major process equipment that are used in process industry and mainly designed for continuous operation.  Frequent starts of centrifugal compressors, MV electrical motors, turbines (turbine-expanders), transformers will for sure have a negative impact on maintenance cost, expected remaining lifetime, MTBF, etc. Within our organization we have insufficient historical data to quantify this. Is there anyone that can help me with some advice or has a reference to literature regarding this subject? 



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    Ben Engels
    Reliability Mgr Europe
    Zwijndrecht
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  • 2.  RE: Effect of frequent starts on process equipment designed for continuous operation

    Posted 5 days ago
    Edited by Howard Penrose 5 days ago

    Ben,

    On the electrical side there are a number of resources at cigre.org, nema.org, IEEE and IEC.  This is an area that has been studied in the past but has, more recently (recently meaning starting in the 1990s), become a significant focus due to energy efficient/energy conservation approaches many companies are taking.  We don't really pay attention to the smaller (ie: lower integral horsepower) electric machines and smaller transformers due to their low costs.  However, in medium voltage (>1000 V, as defined by NEMA and IEEE) and high voltage (>6000 volts) the number of starts a machine will typically see is often called out in purchase specifications - the selection of materials, including rotor conductors (rotor bar materials) and transformer cores, has a direct impact.  Unfortunately, the data is not necessarily spelled out in the standards as the material mix in electric machinery (motors, generators and transformers) varies.  I'll look into additional guidance on the topic, but looking at your specifications, in particular on the electrical side, which includes asking the question about what the overall lifetime starts are specified (if not on your end the OEM should have it) and the number of start limits per period of time (ie: per hour or per day).  On larger machines, if they are specified as continuous then IMHO you will generally find the materials are less able to stand repetitive starts.

    Yeah, squishy answer, but, unfortunately, that's where the industry is at the moment.



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    Howard W Penrose, Ph.D., CMRP, CEM, CMVP
    Past SMRP Chair (2018), 2019-2022 Govt Relations Smart Grid, Infrastructure and Cybersecurity Working Group Chair,
    Chair Technical Standards wind, solar, energy storage, American Clean Power (formerly AWEA), and
    President
    MotorDoc LLC
    Lombard, Illinois
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    Original Message


  • 3.  RE: Effect of frequent starts on process equipment designed for continuous operation

    Posted 3 days ago

    Dear all,

    Thanks for the valuable information and guidance. Highly appreciated.



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    Khalid Al Habsi
    Improvement and Job Instructor Mechanical
    Oman Lng L.L.C
    SUR
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    Original Message