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  1. tgmcg

    Problem with venturi flow meter

    Engdoibetter, It's a 12" Fluidic Techniques HHR-F venturi tube, with beta=0.70.
  2. tgmcg

    Problem with venturi flow meter

    rodym, I'm measuring raw DP and then calculating the flow. There's no square root extractor.
  3. tgmcg

    Problem with venturi flow meter

    Each of the three FT's is equipped with its own 3-valve manifold. I too thought that maybe one of the FT's might be leaking and pulling down the DP for the other FTs. But that would take a large leak, unless one of the root valves at the FE is barely open.
  4. tgmcg

    Problem with venturi flow meter

    thread698-332862 I am analyzing the performance of a centrifugal gas compressor equipped with a venturi flow element in the compressor discharge line. Gas MW = 11 (H2 + CO2). Flowing pressure = 650 psig. Flowing T = 340ºF. The venturi is about 30 years old. The compressor is connected in series...
  5. tgmcg

    Unexplained torque output from large VFDs

    Sibeen, I'm an "old and bold" myself. ;) TNF was accurately interpreted as torsional natural frequency. This appears to be one of those cross-discipline issues where there's actually not a whole lot of overlap between the electrical specialists and the mechanical specialists. Traditionally...
  6. tgmcg

    Unexplained torque output from large VFDs

    jraef, The original manufacturer is out of business. Parts and technical support are no longer available. There's actually been a number of recent failures attributable to subsynchronous torsional ineraction (SSTI)and even white noise from PWM-type VFDs. This has been a fairly hot topic at...
  7. tgmcg

    Unexplained torque output from large VFDs

    12-pulse
  8. tgmcg

    Unexplained torque output from large VFDs

    The acronyms are widely used industry terms and have been accurately clarified above. The OP deals with noise and unexpected torque pulsations. This is actually a very serious issue with large VFDs, can cause catastrophic failure of drive train components, and loss of millions of $$ in lost...
  9. tgmcg

    Unexplained torque output from large VFDs

    Hi Guys, Do you mind if we steer the discssion back to my question regarding noise, SSTI and unexpected torque fluctuations? [bigsmile] Does anyone have 1st hand experience with this, especially if it resulted in mechanical failures?
  10. tgmcg

    Unexplained torque output from large VFDs

    Sibeen...you are correct. LCI = load commutated inverter. mike kilroy...because it's not actually a water pump. It's a turbomachine with low torsional damping. Operating on a need-to-know basis.
  11. tgmcg

    Unexplained torque output from large VFDs

    Gunnar, It's possible we'll end up with a PWM design...I'm for the design producing the lowest amount of torque ripple. But even with PWM, there will still be a concern with SSTI and white noise excitation.
  12. tgmcg

    Unexplained torque output from large VFDs

    jraef, As mentioned in the OP, the existing VFD is a 12-pulse LCI drive. As a mechanical engineer, I lean towards using a VFD with the lowest achievable torque ripple and have done a torsional analysis for a large PWM driven compressor in the past. However, others on the team lean towards...
  13. tgmcg

    Unexplained torque output from large VFDs

    The observed unexpected torqe spikes and fluctuations are definitely not fluid-related. They were observed during a back-to-back VFD/motor test at the motor vendors factory back in the early 1990's. Numerous failures have been reported in the literature attributable to SSTI or white noise from...
  14. tgmcg

    Unexplained torque output from large VFDs

    I'm working on a project where we are planning to replace an older, non-supported VFD with a new VFD of similar 12-pulse LCI-type archtecture. The motor and driven equipment (centrifugal pump...>10,000 HP) remain unchanged. Reading through the original test report for the motor and VFD issued by...
  15. tgmcg

    Natural Gas Compressor Selection

    Competitively bid the job, e.g. the GE LM2500 driving a GE pipeline compressor In another couple of years the Solar Titan 250 may be proven enough for critical application.
  16. tgmcg

    Vibration Monitoring

    You need to get a spectrum analyzer on there. If the seemingly flow-dependent vibration occurs at a specific frequency or across a range of frequencies in the lower frequency range, then it may be cavitation. I would also suggest taking a close look at NPSHA vs NPSHR. Better to have a...
  17. tgmcg

    Best location of Anti-Surge Valve

    Throttling across a control valve is an isenthalpic process. If on 100% recycle, the enthalpy rise from compression will accumulate around the recycle loop if no cooler is provided to remove that heat. This can result in excessive compressor discharge temperatures. For most applications, it is...
  18. tgmcg

    Volume Ratio Effect

    Are you familiar with velocity triangles? Volume reduction ratio affects the velocity component in the flow direction tangent to each blade, which is then vectorially added to the velocity component tangent to the impeller OD. As the volume ratio increases (discharge volume reduces), the...
  19. tgmcg

    Output signal from Bently Nevada monitors

    TPL, The IOTECH looks like a great piece of kit. It certainly fits the bill in terms of functionality, but the analyzer costs $10k plus another $4k for the software. I'm an independent contractor and 14 smackers is more than I want to spend. If a cheaper system leads to a significant amount of...
  20. tgmcg

    Output signal from Bently Nevada monitors

    Prices for small, compact portable 2-4 channel PC-based analyzers are all over the map. From $4,500 to $20,000 for close to the same functionality. The ADRE system is commonly used for the job I need to do, but it is too bulky for my purposes and too expensive compared to the competing...

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