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  • Users: fredt
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  1. fredt

    Lay person question about gongs

    Best to hang them on a chain to minimise damping effects.
  2. fredt

    Speed necessary for move ring in a Sleeve Bearings

    Sleeve bearings require the shaft to be rotating at a certain minimum speed in order to create a hydrodynamic oil film. If rotational speed is too low there will be metal to metal contact. Having said that - 100RPM should be enough to create that film in most cases. Fredt
  3. fredt

    T-1 equivilent to ASTM A514?

    The main characteristic of T1 is that it is a quench and tempered steel. It gets its properties from heat treatment rather than alloying. There are a large number of international equivalents from Europe, Scandanavia, Japan and here in Australia. The steel is readily weldable and can be post...
  4. fredt

    Positive or Negative Pressure Filtration

    I would generally favour a negative pressure system mainly because of potential fan erosion with a pressurised system where the fan is upstream. It isn't always essential to have a cyclone pre-collector with a fabric filter unless dust loadings are extremely high. Because the greatest plate...
  5. fredt

    Absolute roughness for textile ( fabric ) duct material

    Don't forget permeability. It has a significant effect on fan rating.
  6. fredt

    Power Factor

    There isn't anything special about the motor, it is a conventional induction type, my reference was about the voltage which is a bit unusual. No VFD it is DOL start. It is a delta connection. I am some distance from the plant so I cannot readily check all the details at present and the meter...
  7. fredt

    Power Factor

    Thanks for all your responses. The motor is 2pole, 50Hz, 1000V (special application voltage). I do have theoretical PF and efficiency curves for the motor although just manufacturers data - not tests on that particular machine. Question arose because we did have a rented power meter but it...
  8. fredt

    Power Factor

    I'm a mechanical engineer trying to measure power input to a 150kW motor. The power factor of the plant to which the motor is also connected is known to be low at present (without the motor running). The motor is probably a major proportion of plant load when operating. The nameplate PF for...
  9. fredt

    4-Run Method of Balancing

    As a PS to MachEng comments. Be careful about removing all balance weight as this could result in dangerous out-of-balance when you try to run the fan. Large balance weights are often applied by the manufacturer to correct fabrication asymmetry which is not unusual on big fans. Therefore...
  10. fredt

    4-Run Method of Balancing

    Having balanced many large fans it always surprises me that many engineers consider that it was all black magic when it really was just following the theory. However, there are many pitfalls. You do need an analyser but it is vital that you understand the vector method or things can go awry if...
  11. fredt

    motors sharing common load

    As a mechanical engineer I have always assumed that it was not a simple matter to split load equally between two motors coupled to the same machine. Small differences in slip in the motors could result in one being overloaded and the other taking much less load. Perhaps fluid couplings could...
  12. fredt

    Estimating fan RPM

    A fan engineer with access to appropriate data can reverse engineer it from the pressure, flow and diameter to determine its original speed. Blade stress or blade attachment probably will be the limiting factor but calculating it accurately is not that simple.
  13. fredt

    Duct/fan sizing over long distance

    This is a more complex problem than it appears. The issue of suitable fan(s) is not the major problem as other respondents have stated fan suppliers will provide a suitable machine to suit the specific requirements but fan suppliers do not design systems like this - it is a specialist business...
  14. fredt

    Static Pressure in air blowers

    It is a convention which is probably related to "useful" pressure as somewhere along the line you are likely to lose velocity pressure when the air is discharged. However, I do understand the confusion and it is incorrect to specify "Fan Static Pressure" (which is a defined term in the Fan...
  15. fredt

    air flow past a flat plate at some inclined angle

    This sounds like a damper blade application. One thing to note is that the centre of pressure isn't necessarily at the centre of the plate depending on the angle of attack. It is difficult to find airfoil data when the damper is near closed and empirically torque is greatest at around 80 deg...
  16. fredt

    Fans in series and interlocks

    remp I think that you are on the right track and I can't think of any problems. If the axial fan had been fixed speed there would have been an issue with stall but not if you regulate speed to maintain a low positive pressure in the plenum. You probably won't need the 50Pa shut down (it may...
  17. fredt

    Corrosion Protection

    Thanks for responses. The blade tips are moving at around 100m/s so any particulate potentially will cause erosion. There will be a small amount of small particulate that carries over from the scrubber and some water droplets. Although erosion is not severe it probably is the trigger to...
  18. fredt

    Centrifugal fan for hot air transportation

    1. The fan has to be correctly selected for the air density at temperature which is much less than the ambient density. Fans are volumetric devices which means that compared to handling cold air in simple terms the volume will be about the same, the pressure and power will be reduced by the...
  19. fredt

    Corrosion Protection

    Hi I am looking for ideas to improve corrosion/erosion protection of an ID fan impeller following a wet scrubber on a sugar mill boiler (there is some erosion as well as corrosion). The flue gases are saturated at around 50C. I am looking for a paint or coating system. The impeller is made...
  20. fredt

    A typical pressure drop for large silencers... ?

    A typical ID fan silencer system would have a pressure drop of the order 1.5-2" WG. The silencer face area will generally be much larger than the duct cross-section. This means that losses in the transitions can be almost as high as the silencer. The above is a broad generalisation. As...

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