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Recent content by Petri

  1. Petri

    which cage to use

    I have had some bad experiences with Polyamide Cage bearings in the past as well. I have read that Polyamide cages are effected by EP additives ( Sulphur ) in lubricating oils ( Hypoid ), with combination of elevated temperatures greater that 150 deg C, leading to material softening and could...
  2. Petri

    Hydraulic hose deterioration due to oil compatibility

    I have observed a neoprene lined hydraulic hose apparently weep the oil out. This is most obvious around the outside bend radius of the hose. The fluid is Quintolubric 888. Has anyone else seen this ?
  3. Petri

    Universal Joint setup and vibration

    Shabba Thank you. Yes the vibration problem was solved. The root cause was due to a faulty feedback resolver on the main dive motor. The F/B signal was causing an unstable control condition at low speed and light load.
  4. Petri

    Bearing Fluting & Rotor Bonding

    Unfortunately with the gaining popularity of variable speed AC inverter drives and DC converter drives, the occurrence of EDM will become a significant issue in any industry. Most solutions offered do not address the root cause and only provide high maintenance band aid solutions. We have tried...
  5. Petri

    Vibrations an electrical problem in a motor.

    The Entek diagnostic wall chart that I have indicates that a loose connection on a motor supply lead will produce 1/3 line frequency sidebands around the 2Xline frequency vibration peak. In my experience I have never nailed one of these.
  6. Petri

    Universal Joint setup and vibration

    My last posting requires a correction. my statement about putting the yokes at 90 deg is incorrect. I had assumed incorrectly. ( when you ASSUME , you make a ASS out of U and ME ). I have looked into the phasing of yokes a bit more and found that subtle changes on the yoke phasing can be made...
  7. Petri

    Universal Joint setup and vibration

    Yes this makes sense to me. I should have mentioned also that the dive train consists of several sets of hypoid gears. Having said that, your comment about alignment is crucial. A summary of the drive train is; DC Motor - gear coupling - hypoid gear shaft continues through to next gearbox via...
  8. Petri

    Universal Joint setup and vibration

    When setting up universal ( Cardan ) joints on a large high speed shaft is there a preferred orientation of the yokes on either end of the shaft. Should they be in-phase or 90 deg out of phase. Does it make a difference? I have a problem in that I am experiencing a horrible 1X shaft speed knock...
  9. Petri

    Can DC Motor Bearings have Fluting from Shaft Current?

    Yes, this is commonly called "false brinelling" as opposed to "true brinelling" which is created by bearing shock or impact during operation. I have seen many cases of false brinelling even on machines that have been installed with good bearings ( bearing changed in site )...
  10. Petri

    Palm Pilot based vibration analyzer

    Have a look at an add on from IMV Corporation. www.imv.co.jp This is similar to the one posted about the SKF instrument. They have an instrument now on the market called a Cardvibro VM 2001. It uses a Visor as it's PDA. Looks OK with specs. takes overalls, time waveform and 1600 line FFTs. Worth...
  11. Petri

    Can DC Motor Bearings have Fluting from Shaft Current?

    Gday Yes EDM ( Electrical Discharge Machining ) is quite common on DC Motors as they are on AC variable frequency drive motors. Just today I inspected a bearing from a 85KW GE motor that was showing outer race vibration peaks. What was found on the bearing was a large fluted section on the...
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