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  1. JJPellin

    Anti reverse rotation arrangement

    These mechanisms are common and necessary on some big, vertical well pumps and fire water pumps. Depending on the length of the pump, it will spin in reverse on shutdown even if the check valve holds. We had deep well pumps with 400 feet of line shaft. The vacuum developed at the check valve...
  2. JJPellin

    reworking fretted/undersize coupling seat on motor shaft

    I have seen Chrome plating crack or delaminate. Welding stresses can result in runout or cracks (depending on the shaft material). I agree with Artisi. I would clean up the shaft and make a new hub. Do you know the reason for the fretting? Poor alignment. Excess runout. Frequent start/stop...
  3. JJPellin

    Troubleshooting High Vibrations in API 610 Multistage Pump Operating with Saltwater

    I guarantee there is a balance line. The seal system could not function otherwise. I don't believe you have made any statements about the vibration characteristics. What is the primary frequency? What is the maximum amplitude? Where is the vibration highest? In which direction?
  4. JJPellin

    Troubleshooting High Vibrations in API 610 Multistage Pump Operating with Saltwater

    If this balance line plugged off, it would have little or no affect on thrust load. It would only result in increased pressure on the outboard seal, potentially resulting in premature seal failure.
  5. JJPellin

    Troubleshooting High Vibrations in API 610 Multistage Pump Operating with Saltwater

    The balance line would be external. It would connect the first stage suction to an annulus between the fourth stage suction and the non -drive end seal. Since this line is only for pressurure balance and not thrust balance, it is probably a very small line.
  6. JJPellin

    Troubleshooting High Vibrations in API 610 Multistage Pump Operating with Saltwater

    This pump uses opposed impellers (3 facing each direction) to balance thrust forces. It still has a balance line to reduce the pressure on the non-drive end mechanical seal. It probably uses two volutes to feed the flow into the long crossover channels from the third stage discharge to the...
  7. JJPellin

    Two holes in oil groove in journal bearing

    Having oil present in the bearing at startup is certainly beneficial for long term reliability. But I would not classify the delivery of pressurized oil to that groove as hydro-static lubrication. At most, I might call it pre-lubrication.
  8. JJPellin

    Literature for vertical shaft journal bearings

    I do not have access to any papers on the subject. Vertical shaft journal bearings are prone to oil whirl. A tri-lobe bearing with three axial grooves and three tapered lands is commonly used to stabilize a vertical shaft and avoid oil whirl. Do an internet search for "tri-lobe bearing"...
  9. JJPellin

    Two holes in oil groove in journal bearing

    Tug, The axial grooves serve the purpose of breaking up whirl and whip which can pound bearings to pieces. The small hole would have have sprayed oil on a thermometer. The fact that there is now an embedded RTD does not change that. It costs money to change a design. Even if that change...
  10. JJPellin

    Request for Sharing Maintenance Experience of a Similar Type of Pump

    The A dimension would be measured with the springs removed or fully compressed. Cutting the nose of the cover to less than A allows the springs to be loaded, but not bottomed out.
  11. JJPellin

    Two holes in oil groove in journal bearing

    Your pump could be purchased with or without pressure fed bearings. If it had a pressure fed oil to the bearings, the larger hole would have been the oil supply to the bearing. The smaller hole would have directed a small amount of oil to a temperature probe. There is probably a threaded port...
  12. JJPellin

    Balancing Line in Centrifugal Compressor

    It is usually a single line for both. I have seen one compressor (1955 Clark) that had separate lines for thrust balance and seal chamber pressure control.
  13. JJPellin

    Is ASME U stamp required for buffer/barrier fluid reservoir

    Yes. If it is 6 inches in diameter or greater, it is a pressure vessel. Johnny Pellin
  14. JJPellin

    Balancing Line in Centrifugal Compressor

    Yes. The balance line is also needed to lower the pressure on one of the compressor shaft seals. Johnny Pellin
  15. JJPellin

    Twin Lobe Blower taking Extra Amp Problem

    Bearing failure or bearing wear causing internal rubs on end wall. Fouling caused by inlet filter failure. Johnny Pellin
  16. JJPellin

    Tilting pad journal bearing design

    There are many options for the pivot on the back of the pad. The most common would be a button design with the button being a much smaller curvature than the bore it rests on. This is essentially a point contact which allows the pad to pivot in any direction. That point contact will tend to...
  17. JJPellin

    Steam turbine speed sensor spikes while at 3 rpm.

    There is a setting within the governor / tachometer / OST system for the probes that are looking at that toothed wheel. I think it might be called gain. We changed this setting and altered the probe air gap to solve a buggy speed indication problem on a large steam turbine. All square toothed...
  18. JJPellin

    Steam turbine speed sensor spikes while at 3 rpm.

    What is the tooth profile. In my experience, turbine manufacturers make toothed wheels with a square tooth design. The manufacturers of the governors and overspeed trip systems expect a gear tooth profile. This makes the system extremely sensitive to air gap. Johnny Pellin
  19. JJPellin

    In steam turbine we sealing steam w

    On condensing steam turbines, it is common to use the leakage from the high pressure packing to supply the sealing steam to the low pressure packing. If the leakage is not sufficient to maintain about 3 psi, a regulator will introduce low pressure steam. If the leakage from the high pressure...
  20. JJPellin

    Motor's high vibrations on vertical pump unit

    I agree that resonance is the most likely cause. We have successfully mitigated this type of vibration on vertical motors driving vertical pumps by adding a tuned mass damper. Basically, we clamped a piece a steel bar stock to the motor and tuned it by changing the length and adding weights to...

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