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fburgos

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Reply with quote  #1 
I would like to know how you guys would setup a compressor with a built in gearbox.

We have some atlas copco and aerzen compressors where the input speed is multiplied inside, I have 3 different shaft and speeds, each shaft with their own set of bearings

Input (equal to motor/pulley)
Male screw
Female screw.

Attached a sketch of the ac and the actual gears on the aerzen

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png Screenshot_20180512-074730.png (91.03 KB, 19 views)
png Screenshot_20180512-075227~01.png (1.54 MB, 21 views)

Noknroll

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Reply with quote  #2 
Simply calculate the rpm for each shaft, add the bearing fault frequencies for each position/end of the 3 shafts, add the male female screw frequencies & gear mesh frequencies at the appropriate locations as N x rpm, each measurement position may need 2 or 3 ap sets to effectively monitor bearings, gears and screw frequencies. Hz frequency analysis is an effective method as screw frequncies will transmit and appear as non-synchronous frequencies on your input shaft. I also use velocity, peakvue, and a 10khz acceleration measurement at each location, did that answer your question or completely miss the point?
fburgos

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Reply with quote  #3 
Un sorry I'm not following how to do it on the rmbwizard, my first time using using mhm, literally first day using it

You speak as "manual" input of points, I'm using graphic draging wizard thing, where is the other way?

Vibe-Rater

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Reply with quote  #4 
Largely as per Nok but the 2 screw shafts are invisible so only input speed can be measured.  And input could be fixed speed. Either way I would accurately measure input speed which can usually be done.  If variable speed then you need to measure input speed every time.  in any case the 6 / 4 rotor ratio sounds correct.  You should always build the ratios into your database which is definitely possible given you have the tooth numbers.  Work in orders since transmitted frequencies can be built into a CSI database (yes Nok, same as that abnormal bearing frequency you once had).  And when looking at male you will see dominant 4x and female a strong 6x.  Once you have located those you go looking for your geartooth frequencies which will be synchronous.  But there is something wrong here.33 / 44 = 0.75 and 4 lobes / 6 lobes = 0.6666.  And the tooth counts don't match in drawing and photo.  Tooth counts are correct iin photo because we can count them but they give a ration of 33/44 which cant be possible if 4 and 6 mating lobes with both lobes meshing.  Atlas Copco is famous for their non contact lobes and oil free requiring so much precision to hold pressure without any oil in the lobes.  the clearances are literally small enough to hold pressure.  150x 3200 line spectra is good and can be easily viewed in both acceleration and velocity.  Hope that helps.  You need to explain the difference between drawing details and the photo.

I'm suspecting the drawing is from a compressor where the male lob drives the female without them both having gears on them  In which case set them up and as per you drawing tooth numbers. Go and take some data - look at it and yes you guessed it Nok - in orders. find the dominant set of harmonics and you have your 4x. If it is not 4x, correct to be 4x and you can see your new running speed. Multiply by 4/6 to get your female running speed and there you have it.  You should then be able to see if the 49x is your gearmesh or if it is a different number.

Now - I honestly did not fully read you IP, particularly the sentence immediately above the images.  They now make a bit more sense to me. AC is famous for that design, not sure if that is patented.  Methods above hold though.  I would be curious of the arzen to see how many lobes / screws it has.  Can't be 4/6, probably 8/6 or 4/3. you'll be able to work that out because you have accurate tooth numbers.  Better still the machine is apart so just count them.  rgds
fburgos

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Reply with quote  #5 
Sorry for not been clear this are two similar cases I have.

They operate at fixed speed, only the atlas copco has a variable in take/discharge but they rarely work on different regime.


we have more lobe blowers and screw compressors driven directly from the motor or pulley where I don't find trouble using graphical rmbwizard to setup measurements.

This are two different compressors,

1) Atlas copco has an input shaft (60hz) with 49 tooth's, male has 62 thoots with 4 lobes diving a 6 female shaft, male and female have an oil bath male drives directly the female

2) Aerzen has a 72 tooth input shaft (121Hz) and a sync stage 44/33 tooths for the 4/3 lobes screw, the screws are oil free, never touch each other but still there's a strong vibration for the 4/3 lobes compressing air
Vibe-Rater

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Reply with quote  #6 
Quote:
Originally Posted by fburgos
Un sorry I'm not following how to do it on the rmbwizard, my first time using using mhm, literally first day using it You speak as "manual" input of points, I'm using graphic draging wizard thing, where is the other way?


I would recommend against using the Wizard and set up manually in the Database Setup module.  you can then build the machine from scratch and really learn how it works. Unfortunately I do agree that CSI is complicated in this way but you have full control whereas the wizard does stuff under the bonnet that could catch you out down the track.  Others might enlighten us all on that aspect of the wizard. rgds

see attached. the just New are, new machine, new points. You also have to set up a new analyss set and a few other things.  But that is a good start.

I don't have time to re write the manual but CSI is really good like that.  It knows where you are, just click on help and it takes you right to the place where you need to be in the manual. Save maybe a few page ups or down.  You can then figure it all out.

Attached Images
jpeg 3TreeStructureMenu.jpg (16.96 KB, 3 views)
jpeg 2DBSetupMenu.jpg (28.37 KB, 3 views)
jpeg 1DBSetupIcon.jpg (10.20 KB, 3 views)

Vibe-Rater

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Reply with quote  #7 
Quote:
Originally Posted by fburgos
Sorry for not been clear this are two similar cases I have. They operate at fixed speed, only the atlas copco has a variable in take/discharge but they rarely work on different regime. we have more lobe blowers and screw compressors driven directly from the motor or pulley where I don't find trouble using graphical rmbwizard to setup measurements. This are two different compressors, 1) Atlas copco has an input shaft (60hz) with 49 tooth's, male has 62 thoots with 4 lobes diving a 6 female shaft, male and female have an oil bath male drives directly the female 2) Aerzen has a 72 tooth input shaft (121Hz) and a sync stage 44/33 tooths for the 4/3 lobes screw, the screws are oil free, never touch each other but still there's a strong


I did not read properly.
fburgos

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Reply with quote  #8 
Quote:
Originally Posted by Vibe-Rater


I would recommend against using the Wizard and set up manually in the Database Setup module.  you can then build the machine from scratch and really learn how it works. Unfortunately I do agree that CSI is complicated in this way but you have full control whereas the wizard does stuff under the bonnet that could catch you out down the track.  Others might enlighten us all on that aspect of the wizard. rgds

see attached. the just New are, new machine, new points. You also have to set up a new analyss set and a few other things.  But that is a good start.

I don't have time to re write the manual but CSI is really good like that.  It knows where you are, just click on help and it takes you right to the place where you need to be in the manual. Save maybe a few page ups or down.  You can then figure it all out.



thanks I'll check on monday, I'm just following the install instructions, I think I'll do the pumps/fans with the wizard for starting
Noknroll

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Reply with quote  #9 
Your Aerzen compressor will also likely have integral 6 vane oil pump mounted on the 3rd or female shaft,(top shaft at DE in attachment) one of my clients has a bank of VML 60's and VML 35's
Are you sure the gear arrangement in you "actual gear" photo aren't the other way round Male 33 and female 44 ? Most screw compressors I see (Sullair, Champion Aerzen etc) the female is stepped down in speed
Aerzen VML 60.png 

fburgos

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Reply with quote  #10 
hi Nok, I have a drawing for the VML25 with the tooth count corrected by me, and a picture I took counting the vanes (see the dust inside, its all over the place even on the "breathing holes" of the oil reservoir),

I think the arrangement is right, how to tell male/female i just called the first shaft male.


we have 4 of these vml60 do you think you can share with me your AP configuration.


Quote:
Originally Posted by Noknroll
Your Aerzen compressor will also likely have integral 6 vane oil pump mounted on the 3rd or female shaft,(top shaft at DE in attachment) one of my clients has a bank of VML 60's and VML 35's
Are you sure the gear arrangement in you "actual gear" photo aren't the other way round Male 33 and female 44 ? Most screw compressors I see (Sullair, Champion Aerzen etc) the female is stepped down in speed
Aerzen VML 60.png 



Attached Images
png AERZEN VML25.png (189.88 KB, 16 views)
png AERZEN VML25-armado.png (967.86 KB, 16 views)

Noknroll

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Reply with quote  #11 
Hi fburgos
I just used text book AP sets 
for gears = (3.5 X Number of gear teeth X (rpm in Hz))/ 12,800 lines, (80t input shaft, 2 pole motor)
for bearings = (80 X (rpm in Hz)) / 6400 Lines. for >5000 rpm
                  = (80 X (rpm in Hz)) / 1600 Lines. for < 500 rpm
                  = (80 X (rpm in Hz)) / 3200 Lines. for general purpose

Others may use something different but these suit me for most applications
Vibe-Rater

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Reply with quote  #12 
Gr4eat effort Nok. rgds
Danny Harvey

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Reply with quote  #13 
Regarding RBMWizard Viberater is correct in saying that it doesn't get everything right.  But it does do a really fine job of setting up all your shafts, gears and bearings.

Unless they have changed it since V 5.42, the trick has always been to understand that the AP and AL sets that RBMWizard assigns might not be ideal.  For that reason, I have always (for almost 20 years now) used the Wizard to configure machines, then reassign all the AP and AL sets to ones that I created. I have standard sets that I copy to each database with numbers starting at 100 so that I can just use the Modify Points utility in Dbase to change them. It takes less than a minute per machine to change and I can be sure that my AP sets will be getting me good data. Of course, there will be fine tuning to do but that never seems to stop.
fburgos

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Reply with quote  #14 

Im doing what danny said using the wizard to generate the machine structure.

suprisingly i got the atlas copco to use the correct rmp for each shaft, using Compressor - Rotary, Dry Screw 1 stage.

but it generates 4 measurement points in the compressor... since im using triax and is "faster" i'll measure each side of the compressor.

thanks all for your inputs.

Attached Images
png AC G162 - RMWIZARD.png (26.93 KB, 11 views)
png AC G162 - RMWIZARD -SPEED.png (19.21 KB, 11 views)

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