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Joined: Apr 1999
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Dear Jack,

We have some questions about the SAE J444 and AMS 2430. The SAE Staff
Representative (Gjysta Kqiraj) requested us to direct any questions
about the J444 to you.


Last year we bought a new Ro-tap sieving machine (DuraTap). However,
when running our yearly calibration we found that the machine did not
completely comply with the J444 and AMS 2430 requirements. An short
investigation led to the conclusion that this is due to differences
between the American 60 Hz AC system and the European 50 Hz AC system.
We got the impression that machines operating at 60 Hz AC do comply, but
on the European 50 Hz AC are non-compliant.
However when we compared several manufactorer specifications with the
standards, the problem got even worse. In the attached Excel sheet
you'll find the specifications of our current DuraTap machine and of an
alternative model of Haver-Boecker (which is actualy the original
Ro-Tap(r) Test Sieve from WS Tyler). As you can see, when the tolerances
specified by the manufactorers are included, neither model does comply
with the SAE J444 and/or AMS 2430 requirements. At the moment we have
not found manufacturers that do comply to SAE J444 and/or AMS 2430.

Because of this situation we have the following questions:
1) On what basis were the requirements for shaking speed and taps per
minute determined (in both the SAE J444 and the AMS 2430)?
2) Why would the characteristics of the machines from Duratap and
Haver-Boecker not give a good sieving result?
3) Is it possible to use less stringent tolerances for rotation and
tapping speed?
4) Can you help us in finding a manufacturer that does comply to SAE
J444 and/or AMS 2430?
5) SAE J444 and AMS 2430 do not specify characteristics like amplitude
or tapping force. We feel that such kinds of characteristics can be
relevant too for the sieving result. Is the committee planning to
implement additional requirements for sieving machines?

We would appreciate a response to these questions as we are in a
situation that we have to purchase a new sieving machine compliant to
J444 and/or AMS 2430. In addition you will understand that we want to
prevent that in the (near) future, due to revised criteria of SAE J444,
this new machine will become non-compliant as well.

We look forward to your response.

Best regards,
(Name witheld)

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Code:
Additional information:
                        Shaking speed (rpm)     Taps per minute 
Current Duratap machine 
model DT258 (50 Hz)           250                     160 
      
Haver-Boecker machine 
model RX29 (50 Hz)            278 +/- 10            150 +/- 5 
   
SAE J444 requirement          275-295              145-160 

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What are your actual results and how are you obtaining the information?

We have a brand new Tyler RO-Tap RX-94 115V 60z and it is running at 281 RPM with 150 taps per minute.

I found that a simple solution is to mount two thumb operated hand counters in position so that the hammer / sieve frame will activate the thumb button. Use a calibrated stop watch and run the sieve stack for 60 seconds. Then simply check the number displayed on the counter.

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Our reply:
We used an calibrated pulse counter to count the number of rotations and taps per minute. The actual results are 265 rpm and 147 taps per minute.

Haver&Boekcer has let us know that, although their specs have a +/-10 rpm tolerance, in practice the device has an exact rpm rate of 278. Their device isn't actually their own design, but simply the WS Tyler Ro-Tap 8'' RX-29. They also sell the exact model you have with the same specs.
Your test results show that the remark of Haver&Boecker is actually not correct: you have measured 281 rpm, an deviation of plus 3 rpm from the specified 278 rpm. Would this be minus 4 rpm, your machine would not have met the SAE J444 specs, although it would still be within the manufacturer specs.

The whole point of our questions is that the SAE J444 (and AMS 2430) specs for sieve shaker do not seem to reflect *any* product on the market. Even the tolerances of the original WS Tyler Ro-Tap do not comply with the J444. There seems to be no rationale which clarifies on what basis these J444 requirements were determined.

Do you feel that your test results would be different when the J444 requirements would be less stringent, say 250-300 rpm and 140-160 taps per minute?

And what is your opinion about the significance of characteristics like tapping force or oscillation amplitude?
(name withheld)

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I’ve tried to determine where the specifications for ro-taps listed in J-444 and AMS 2430 originated. I can add the following. MIL-S-851C which was revised from the B revision in May of 1972 had the same wording as the current J-444.

We currently have four WS Tyler RX 29 models which meet these requirements and WS Tyler published specifications are 278 oscillations and 150 taps per minute. The four are running around 280 – 285 oscillations per minute which meet the SAE J-444 and AMS 2430.

I would suggest we look at couple of things before we make any changes in these specifications and please keep in mind that there are other private company peening specifications that also list this type information.

1. Round Robin testing of samples to see if any differences cased by oscillations differences exist. The problem with this is, test sieves openings will vary enough to make this small oscillations difference undetectable if any. The only way you could determine is to have the same test sieves and samples sent within this round robin. I would suggest this to be impracticable.
2. Request the manufactures tells us what the standard is. They are designing these machines, what standards are they designing too? Can we then assume that any difference in design will create insignificant differences in results? Maybe they would like to determine if any differences are created between the different machine oscillations.

My personnel opinion is there is no difference between 250 and 280 oscillations. This is what I would suggest. If I had a Ro-Tap that ran at 250 oscillations (opm) I would increase the 10 minute time to 11 minutes meeting the requirement of 2750 opm in ten minutes. The intent of this specification is not opms but to assure the material is screened with a mechanical machine and certain work is completed. In this case the work is defined as minimum Taps, Oscillations, in a given time. If an auditor will not accept that then you have a much bigger problem.

ASTM STP 447 Guidelines for Establishing Sieve Analysis Procedures discuss satisfactory sieving end points. It defines ultimate accuracy as not more than .5 percent change when increasing the time by 5 minutes.

You will find much more variation using two different test sieves then you will ever in two Ro-Taps.

Dennis Scharer
Technical Services Manager
Ervin Amasteel

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I have just a little more information to share on Ro-taps. ASTM B 214 “Standard Test Method for Sieve Analysis of Granular Metal Powders” describes the sieve shaker as follows. “The number of rotations per minute shall be 270-300. The number of taps per minute 140-160.”

I suggest J-444 and others including AMS 2430 and AMS 2431 revise their specifications to recommend these ASTM Ro-tap requirements. ASTM seems to have done extensive work on this method and I know the two other groups have but maybe not to the extent of ASTM.

The problem is; AMS 2430 and AMS 2431 just finished being published and will not be re-opened for 5 years or else there is a major problem, which I’m not sure if this qualifies.

One other note, we sell a test machine world wide and when we sell to 50 hz customers we have to fit the machine with a different sheave to produce acceptable RPM range. Could this be an option instead of asking to re-open these specifications before the five year reviews?

Dennis Scharer
Ervin Amasteel
Technical Services Manager

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Code:
  [additional comments]
Adding Retsch to the list of known shaker manufacturers now 3 known companies:
-------------------------------------------------------------------------------------------------------                                       
                               Shaking speed (rpm)    Taps per minute    Website
AdvanTech Duratap                    250                  160         [URL=http://www.advantechmfg.com/]Advance Tech[/URL] 
WS Tyler (or Haver-Boecker)          278 +/- 10           150 +/- 5   [URL=http://www.wstyler.com/rotap_test_sieve_shakers.html]WS Tyler RoTap[/URL] 
Retsch                               280                  150         [URL=http://www.retsch.com/377897.0.html?&L=7]Retsch[/URL] 
-------------------------------------------------------------------------------------------------------
 
 
The comment on the Retsch website also gives some insight in on what basis the shaking and tapping speed have been determined: 
"This combination of sieving motions simulates hand sieving." Combined with the comment in the ASTM D1214 this gives the impression 
that the shaking and tapping speed requirements in the SAE J444 and ASTM B214 may be based on the simulation of hand sieving. 
However still this does not give any information why exactly these tapping and shaking speed requirements are specified in the J444. 
I can only assume that somebody at some point in time must have done some research to determine this.
 

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W.S Tyler ROTAP SPECIFICATIONS


The Ro-Tap has specifications of 280 rpm +/- 10 sieve rotations and there are 150 taps/minute +/- 5 taps. The most common used sprocket has 14 teeth and the timing belt pulley has 87 teeth. By taking the actual rmp of the motor and multiplying by 14/87, you should get the actual rpm of the Ro-Tap.

I.E.! 1750 x 14/87 = 281.6 = 282 rpm

There are 29 teeth on the timing belt pulley hub and 54 teeth on the cam gear.

282 x 29/54 = 151 taps per minute

R-30015 timing belt pulley w/hub

R-20039 cam gear

R-10070 14-tooth sprocket


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