I HAVE AN UNSIZEABLE VALVE IN MY PROJECT

By Nibal Ata on Wednesday, 02 October 2019

Posted in Irrigation

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while sizing the laterals in my plan, i found one valve connected to a dripline area unsizeable.

i went through the documentation of this error, and specifically the cause of it that this vakve has an excessively high friction loss setting..

and did get the solution but my question is:

why does this valve have excessively high friction loss setting?

what cause this to happen?

is it something wrong i did while piping or maybe something else am not aware of?

Thanks in advance,

Nibal

Nibal,

Thank you for sending those.

As I suspected -- note that your Design Pressure is 1.38 bars, and your Pressure Variation is set 20%, which would be 0.27 bars. Yet you are generating 0.48 bars in friction loss. So the message is just notifying you that the Pressure Variation setting is unable to be used. There is nothing that unusual to 0.48 bars of friction loss -- I calculate that as being from about 63m long pipe.

So all the message is telling you, is that the Pressure Variation setting cannot be used on that valve. That instead, you are advised to leave the Pressure Variation set in the Off position, and manually adjust the Velocity to the best fit.

--J

Jeremiah Farmer

5 years ago

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#3278

Nibal,

Please watch this webinar I recently presented. There is one slide in particular (specifically at 5min 30sec into the video) that should help you understand why there might be so much pressure loss through your drip valve. If you still have questions let us know and we can try and help as needed.

Designing with Drip

Jake Lott

5 years ago

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#3245

Hi Jake,

i went through the webinar, and understood that the case of unsizeable valve happened due to pressure loss through the specific valve as a result of the difference between the design and required pressure..

but still not getting why there should be a difference,

I am using a valve of size 25 mm(1") with a flow of 52 l/m(13 gpm)

and how can i get rid of it?

I didn't the drip kit which was mentioned in the webinar..

it's just a solenoid valve Rain Bird PEB-PRS-D-NP-HAN witha pressure regulator.. and covers a small pits of shrubs area..

Thanks

Nibal

Nibal Ata

5 years ago

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#3273

Nibal,

This message is usually due to high friction loss, not loss through the valve. It would be helpful if you could include a screenshot of the Size Laterals dialog box.

My hunch is just that you have a low design pressure, which makes it very easy for friction loss to exceed any realistic pressure variation factor. All the message is doing is attempting to alert you to this. We probably should reword it, as it isn’t necessarily “unsizable”, it’s just a higher than nominal friction loss.

—J

Jeremiah Farmer

5 years ago

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#3274

Hi Jeremiah,

kindly check the attached file..

Nibal Ata

5 years ago

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#3275

Many thanks Jeremiah,

NIBAL

Nibal Ata

5 years ago

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#3280