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  1. mechanicaljw

    Can a dry ai screw compressor be used for compressing nitrogen?

    Hi All, I have searched the forum to see if i would get an answer to my question to no avail. I am therefore posting the question here: Would it be possible to use a dry screw compressor that compresses air from atmospheric to 3.5 bar(a) for compressing nitrogen and get the same compression...
  2. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    @BA: I forgot to add that the mounting points at the bottom with rubber are not directly located under the notched points at the top. It looks so from the sketch but that is not the case. Thanks! Jimmy
  3. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    @BA: What do you recommend we do if notching is not going to work? Thanks! Jimmy
  4. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Hi Kingnero, I forgot to add that in one case, the beams are not touching the floor. In that case, the beams are connected to 4 rubber mountings of height 35mm. In this case i guess you will not add any load at the bottom of the beams in the modeling? I agree that with the four bars, the...
  5. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Hi Kingnero, Thanks for your Input. Appreciated. I will try to answer your questions. The longitudinal beams are resting on the floor over their whole length as you suggested. They are fastened using a bolt and a nut (single at each point) and so four in total. I'm not sure about the next...
  6. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Hello everyone, Thanks for your input. @ Jrisebo: I intend doing the following. We have two parallel beams & two cross beams at the ends of the parallel beams. The parallel or longitudinal beams are U-shaped. I want to determine the total weight of the machine and divide by 2 to be the...
  7. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Hi Jrisebo, Thanks for the response. By load, do you mean the static load (weight) of the machine(s)? What about the capacity? Can you please throw more light on this, eg how is it computed? Thanks again for support. Jimmy
  8. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Hi hokie66 & Thaidavid40, Thanks for your response. Don't you know of any citation or literature that can be of some help to me? Thanks!
  9. mechanicaljw

    How to check whether a given structural support or frame can support a given machine

    Dear all, I wanted to find out if structurally, there is a rule for finding out if a given support or frame can support a given machine? We have a current frame that supports a single machine but we need to connect or build an additional machine on top of this first machine and to support it...
  10. mechanicaljw

    Two rotors screw compressors design

    I forgot to add that any good material for a beginner would do for me. Thanks!
  11. mechanicaljw

    Forced Torsional Vibration Analysis of Screw Compressor-Physical Meaning of Negative Torque

    Hello rob768, I am looking for a good reference on the design of two rotors screw compressors? Do you or any of your colleague have such information? Something for a beginner would be most welcome. Thanks! Jimmy
  12. mechanicaljw

    Two rotors screw compressors design

    Hello All, Anyone with experience on how to design two rotors screw compressors? I would be grateful for any citation on a good literature source (book, paper, etc) on how to go about this. Thanks! Jimmy
  13. mechanicaljw

    Forced Torsional Vibration Analysis of Screw Compressor-Physical Meaning of Negative Torque

    Hi Rob768, And thanks as usual. We do agree with your assessment. I do have follow up questions though. When we repeat the test using MAN truck as drive instead of the electric motor, we still have this 1X input speed torsional frequency, which is our 1st torsional mode. So there is torque peak...
  14. mechanicaljw

    Forced Torsional Vibration Analysis of Screw Compressor-Physical Meaning of Negative Torque

    Hello Greg, And thank you for the response. I am wondering whether the idea of the motor being driven by the rest of the system would lead to a situation where gears in our machine are forced to run in the reverse direction and hence lead to gear contact/meshing and to noise? Is this something...
  15. mechanicaljw

    Forced Torsional Vibration Analysis of Screw Compressor-Physical Meaning of Negative Torque

    ...and to 1st stage and synchronization gear meshing. While trying to curve fit the torque signal from measurment at 1229 rpm in the form Asin(Omega*t+alpha)+C, i realized that A is negative in one case (with the highest goodness of fit). The phase in this case is +pi/3. When i change phase...
  16. mechanicaljw

    Forced Torsional Vibration

    @Tmoose-The compressor is a screw compressor (with male and female rotors and drive through female rotor) that we run between 1000 to 1800 rpm. The critical element in the system has also be shown to be the connection between the drive (in this case the electric motor) and the compressor...
  17. mechanicaljw

    Forced Torsional Vibration

    Hello electricpete, I am developing torsional models and for the forcing or external torque we measured time series data of the torque and use curve fitting to get the forcing function. The electric motor is running with a VFD: The first mode frequency is the torsional frequency. The crtical...
  18. mechanicaljw

    Forced Torsional Vibration

    ...is exciting the compressor at its first mode. I have now been able to get a time series data of the motor torque that is of the form T(t)=asin(omega*t+beta)+T0, where a is the excitation amplitude, T0 the steady torque, and beta the phase shift determined by curve fitting the experimental...
  19. mechanicaljw

    Determination of pv diagram of lobe and screw compressors

    Hello All, I am relatively new to screw and lobe compressors and I am looking for good literature on how i can determine the pv plot of such compressors analytically. Any suggestions would be much appreciated. Thanks! Jimmy
  20. mechanicaljw

    Torsional analysis-Model Setup

    Hello Rob, And thanks for your last reply. I am still trying to do the forced torsional analysis and we have been able to obtain the time series signal of the motor torque and with this information it was possible for me to determine the forcing or excitation function using curve fitting. The...

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