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Basic formula to calculate pressure drop 5

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salmon2

salmon2

Materials
Feb 1, 2008
360
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Hi Experts,

Just got a task to do some calculation about our hydraulic control system. I have enough education to understand the dynamics, etc but almost never worked on such real problems.

Spent tody online and already got some ideas about how to calculate pressure drop in pipes. But need to know more cause our system got a lot of components such 90 or 45 deg elblows, branch and running tees, enlarger/reducer without approach lines (abrupt change on diameter) etc. Wondering if anyone can point me at here I can find the formula to calculate those. I don't mind seting up my own spreadsheet or matchcad or matlab, whatever :D, but available spreadsheet is certainly welcome.

Also a basic question, is there a max limit for flow rate in a pipe given a internal diameter? What is limiting factor if any? How to calculate it?

Thanks a lot in advance.

salmon2

 
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The conditions you describe made me think of Crane #410 manual. It is available from Amazon.com for around $90. If you're going to do this sort of math, that book is a must have.

There was a recent thread (I believe it was in this forum on eng-tip.com, but I'm not certain) on this subject that discusses limitations of the various techniques, but it would be a lot easier to follow if you had a Crane #410 in your hands while going through it.

David
 
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Latexman, how much has changed in the new version? Is it worth updating our libraries?

Thanks
katmar
 
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katmar,

I had it shipped to a new engineer at one of our plants. I didn't even see it.

Good luck,
Latexman
 
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The new one is cheeper because it doesn't have the wire binding. Other than that I've just seen the adds in Amazon.

David
 
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Thanks all for the feedback on Crane 410. Hopefully we can get a report from someone who knew the old version as well. The reviews on Amazon are all from years ago, and there is no mention that they are for a previous version. It's a real pity that they have done away with the spiral binding. I'm sure Art Montemayor mentioned that he still has a copy from the 1960's. I doubt that the paperbacks will still be around in 50 years.
 
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Thanks a lot for your sharing, everyone. Really appreciate it. Study them hard right now.

But seems like no formula available to calculate either f or K for valves or fittings, which is what I really need.
 
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Salmon2, my apologies for hijacking your thread to ask questions about the new version of Crane 410. While Crane 410 remains one of the best all-round references there are many others, and many freely available on the internet.

Just recently in thread407-292861 a very similar question was asked, and several links and tables were included there. If you Google for the specific pressure loss in which you are interested - e.g. "pressure loss in elbows" I'm sure you will find more than you will ever be able to read.

There is also a completely free, but fairly simple calculator available from There are others online as well if you don't like SI units.

Katmar Software
Engineering & Risk Analysis Software
 
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Katmar it is not what I felt. I actually felt all your discussions are quite
Informative. I didnot know crane 410 at all before. I usually don't buy
Books any more given Internet resoures. Also when you got the
Book you will never read it again.
 
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I've got a wall of books that rarely if ever get opened. Crane 410 and Cameron Hydraulics get used several times every week. The 25th time you've done a Google search for "Darcy-Weisbach" (and spelled it 26 different ways), you really start appreciating having a little book with the equation both findable and in a verified format (not always true on the Interwebz).

David
 
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Regarding the local loss coefficients, I recommend that you search specifically for the cases that you need, e.g miter, bend, globe valve. etc. Crane TP410 has one of the most extensive gathering of such coefficients (as pointed above) but it could still not cover what you're looking for.
Please take a look here for a some basic understandings and values (credted to IUPUI university):
local losses

Two good links to start looking for some k values on Internet:
Local Coeff 01

Local Coeff 02

I'm sure you'll find more by googling.

And here's a free Excel sheet:
[link h]Friction Excel[/url]

Finally, I recommend to download Epanet (it's free) and model your system easily with this software. you can have user-defined elements to assign your desired K values to them.

About your last question: Do you have a gravity line or pumped one? With gravity, the available static head dictates your pipe diameter. you can not make the pipe smaller cause there will be more head loss and less flow. so you should tale a diameter that passes your desired flow. on the other hand you don't want unnecessary large pipe to pay extra money for larger pipe.

if it's a pumped pipeline then there's no limitation! unless you want to restrain your flow velocity due to:
- high friction loss (more speed-->more friction loss-->bigger pump, higher pipe pressure class, more energy cost)
- your pipe lining can not tolerate the erosion

In water sector, normal water velocity range is between 0.5 to 3 m/s. economic diameter could be around 1.5 to 2 meter depending on where in the world you are located.

Hope this would help.
 
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Thank you so much waterpipe, your post has been extremely helpful. What you have shared is the best of what I can find online. But can you please double check the link for the Excel sheet? Seems not working on you.
 
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Ditto the suggestion on Crane TP410 - fantastic reference. I have the 2009 version and it is spiral bound. I don't remember what I paid for it. I also don't have experience with previous versions to say if it's worth updating.

Here's what is supposed to be updated (the forward goes into a bit more detail, but basically says the same thing)...

New in the 2009 Edition:
For the 2009 edition, additional valves and their resistance coefficients were added based on tests performed within the Crane Engineering Laboratories. Industry research was gathered on the latest calculation methods for hydraulic resistance and in resistance values for wyes and tees. Chapters on pumps, control valves, and flow meters were included and over thirty-five new sources have been added to the book.
 
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@djv - do "the latest calculation methods for hydraulic resistance" included in the 2009 version cover the Hooper 2K and Darby 3K methods?

Katmar Software
Engineering & Risk Analysis Software
 
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@ salmon2: I'm sorry for the delayed reply. Work has got me again.
@CarlB: Thanks for the cover! I don't know what went wrong with the link.
 
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