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Anonymous Poster #1

Stroke Time Calculations

06/11/2014 12:28 AM

Hi all,

Anyone plz help me to calculate the stroke time calculations for Pneumatic Cylinder actuator. Wheneva i have been asked to calculate the stroke time calculation for valves, am struggling with that.
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lyn
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#1

Re: Stroke time calculations

06/11/2014 12:53 AM

Check the data sheet.
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IdeaSmith
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#2

Re: Stroke time calculations

06/11/2014 1:11 AM

Whats your input?

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Anonymous Poster #1
#3
In reply to #2

Re: Stroke time calculations

06/11/2014 1:14 AM

My inputs are Stoke lenght of actuator, CV of positioner, Volume booster, Cylinder volume, Piston dia, stem dia, spring thrust
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IdeaSmith
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#4
In reply to #3

Re: Stroke time calculations

06/11/2014 1:34 AM

Complete stroke or only outward?

Which formula are you currently using?

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Anonymous Poster #1
#5
In reply to #4

Re: Stroke time calculations

06/11/2014 1:56 AM

For both Open & close timing of actuator
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IdeaSmith
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#6
In reply to #5

Re: Stroke time calculations

06/11/2014 3:21 AM

So you missing the formula?

Anything that you need should be in here?

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Kilowatt0
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#9
In reply to #6

Re: Stroke time calculations

06/11/2014 10:05 AM

Thanks for the link!

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Needanser.com
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#7
In reply to #5

Re: Stroke time calculations

06/11/2014 4:13 AM

I have tried [Q = (Volume*Cv)/time] for both actions

But am not sure, whether the answer i get is correct
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IdeaSmith
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#8
In reply to #7

Re: Stroke time calculations

06/11/2014 5:03 AM

Then measure it and compare!

How do you account for the load that's possible on the actuator?

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#10

Re: Stroke Time Calculations

06/11/2014 10:21 AM

A pneumatic actuator is much more difficult to analyse than a hydraulic due to the air (or gas if air is not the fluid used) compressibility.

Several parameters are involved:

- source pressure AND cylinder pressure

- valve flow depending on valve opening AND pressure difference

- piston area

- mass to be moved and total opposed resistance to movement!

In fact it is a force balance which gives the accelerations and speed every moment.

It is difficult because depending on speed and resistance the pressure drop at the valve changes and also the MASS flow through the valve. To give an example if at start the cylinder was empty the pressure drop can be so high that the valve chokes but if the cylinder is not moving very fast the pressure increases and the pressure drop decreases and accordingly the flow. Most of equations you find in the litterature for stroke time estimations are based on a constant resistance and on constant line and cylider pressures so that their value is only INFORMATIVE.

The computing by hand is quite complicated better use a soft for dynamic simulation as "open modelica" or simmilar.

If you can it is good to write the equations in order to understand the results.
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#11
In reply to #10

Re: Stroke Time Calculations

06/11/2014 10:26 AM

Is it possible to calculate stroke time, if we know the cpmressibility factor of air.
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IdeaSmith
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#12
In reply to #11

Re: Stroke Time Calculations

06/11/2014 9:55 PM

The answer for you is: No.

And this is because the compressibilty factor of air is known and you did ask how to calculate the stroke time.

But it certainly will have to be part of the equation. Whats preventing you from measuring it?

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Hilton
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#13

Re: Stroke Time Calculations

06/12/2014 3:39 AM

The cylinder manufacturers name should appear somewhere on the unit, so the full design criteria should be known by them.

On the other hand, these designs may be standardised to a large degree.

Two manufacturers that may be able to assist you directly are Norgren and Martonair .
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horace40
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#14

Re: Stroke Time Calculations

06/12/2014 9:26 AM

There are so many factors to take into account that the result of your calculation is likely to be no better than the accuracy of the assumptions you make about the parameters.

In practice you will probably find you will need to slow things down to the speed you want by tweaking the cylinder exhaust valve.

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PWSlack
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#15

Re: Stroke Time Calculations

04/05/2023 7:13 AM

If it's fed from 500m of 6mm Ø piping then it will take longer, under the same conditions elsewhere, than if it were mounted 50mm from the outlet connection of the instrument air reservoir.

So just measure it; it is a worthless calculation otherwise.

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SolarEagle
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#16

Re: Stroke Time Calculations

04/05/2023 8:10 AM

I suspect somebody's having a joke with you as there are too many variables involved to get a generic answer....

You might try this...

https://virtualengineer.parker.com/myprojects/Sizing/Sizing?WFID=8cd2daff-680a-ec11-981f-0003ffd9db3e

https://ca01.smcworld.com/catalog/BEST-Guide-en/pdf/1-m30-45_en.pdf

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Anonymous Poster (2); Hilton (1); horace40 (1); IdeaSmith (5); Kilowatt0 (1); lyn (1); Needanser.com (2); nick name (1); PWSlack (1); SolarEagle (1)

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