solids flowrate in gravity lines

[tonycpe]

Where can I find a good reference source for predicting/calculating gravity solids flowrate capacities in various line sizes?

Nothing in Perry's or any of my other design books, perhaps its a mechanical engineers gig?

Thanks
Tony

 

[MJCronin]

tony,

The "Piping Handbook" by Nayaar contains information about gravity drainage of piping versus the slope and material.

For quick, ballpark estimates, use 1.5-2 ft/second average velocity and calculate a line size.

Let us know waht you find out about the best source for this information....


MJC

 

[saxon]

tontcpe, For sewer designs, I've utilized the Handbook of Hydraulics, Horace King, McGraw-Hill Book Co. and the Clay Pipe Engineering Manual by the National Clay Pipe Institute. These two references will allow you to design any type of sewer for any application. Both will show you how to calculate req'd. velocity and line slope to move particulate matter.

Hope this helps.
saxon

 

[tonycpe]

Let me be more clear about the question... I was specifically looking for dry solids flow only, not slurry piping. For example, solids out of a dryer with a drop chute.

Thanks
Tony

 

[saxon]

tonycpe, Well, well! See two phase flow-gas solid mixtures and pneumatic conveying, Perry's. It will also give a Biblio. for other sources.

Hope this helps.
saxon

 

[CHD01]

Tonycpe: Its been awhile since I have done this, but you would be surprised how much pellet flow you can get through a small orifice from just gravity flow of pellets in a vertical line. I would contact a pneumatic conveying vendor and start by looking at their variable speed rotary valves (used to act as an airlock between the storage silo's for pellet blending and the conveying line); each rotary valve has a restrictive flow orifice inside it to prevent over-filling the vanes of the rotary valve; the orifice for flow is normally about 1-inch wide by maybe 4-6-inches long. One of these relatively small valves with maybe a 4-in diameter (?) inlet and outlet (again I can't quite recall what I use to use) will pass several M pph of pellets I think. The vendor should have flow curves.

For flood-feeding an extruder, I believe you just look at the volumetric capacity of the extruder screw flights; and provide a flood feed line sufficient in size to fill the screw at its maximum rate AND to cover the flights at the pellet feed inlet.

Also, it is a good idea, to require the supplier of your equipment to guarantee his equipment with demonstrated rate testing after installation.

If you find a good web site let me know.

Last, one thing you will need to know is the bulk density of the pellets in order to equate volumetric displacements to the actual mass flow in pph. Note this is not the same as the density of the material; bulk density reduces the density to allow for the void fraction.

The more you learn, the less you are certain of.