Re: Selection Of Bends For Pneumatic Conveying
Originally Posted by chavannilesh
For abrasive,fragile material is there special type of bends used? ■
Re: Selection Of Bends For Pneumatic Conveying
Dear chavannilesh ,
what are the parameters for selection of bends in pneumatic conveying?
A bend serves as a part of the conveying pipeline to change the direction of the material flow.
Accepting this task, you know that there are forces involved.
As the material tends to maintain its direction, it bounces against the outer wall of the bend and stays there until the acting forces can not withstand the gravity forces.
A bend acts as a centrifuge and the same formulas apply.
The involved parameters follow from this observation.
-Incoming material velocity
-Bend radius
-Bend friction
-Bend orientation
From the bend impact resistance and the material/wall friction, an assessment can be made in how far the material will wear and how far the outer wall of the bend will wear.
For abrasive, fragile material is there special type of bends used?
For an abrasive material, special bend liners are available, or an outer bend box is made, where the material is trapped, causing the material to wear on itself.
Using the above list of parameters, it is possible to find an optimum bend radius, whereby the impact wear in the bend and the material sliding wear along the bend is minimal.
A possible problem is that the material velocity along the bend becomes too low, due to friction plus gravity, and the bend gets choked.
In most cases a 1.5D to a 2.5D bend (with or without lining) is the optimum option. ■
Teus
Re: Selection Of Bends For Pneumatic Conveying
Originally Posted by Teus TuinenburgA bend serves as a part of the conveying pipeline to change the direction of the material flow.
Accepting this task, you know that there are forces involved.
As the material tends to maintain its direction, it bounces against the outer wall of the bend and stays there until the acting forces can not withstand the gravity forces.
A bend acts as a centrifuge and the same formulas apply.
The involved parameters follow from this observation.
-Incoming material velocity
-Bend radius
-Bend friction
-Bend orientation
From the bend impact resistance and the material/wall friction, an assessment can be made in how far the material will wear and how far the outer wall of the bend will wear.
For an abrasive material, special bend liners are available, or an outer bend box is made, where the material is trapped, causing the material to wear on itself.
Using the above list of parameters, it is possible to find an optimum bend radius, whereby the impact wear in the bend and the material sliding wear along the bend is minimal.
A possible problem is that the material velocity along the bend becomes too low, due to friction plus gravity, and the bend gets choked.
In most cases a 1.5D to a 2.5D bend (with or without lining) is the optimum option.
thank you sir. can we use bend after bend in series? is it suitable for conveying line? How we calculate pressure drop in bend? ■
Re: Selection Of Bends For Pneumatic Conveying
Dear chavannilesh,
can we use bend after bend in series?
If you can or can not is up to you.
If you look at the involved parameters, mentioned before, you are already in a position to answer this question.
The incoming material velocity brings the material through the bend at the cost of it’s impulse.
Before entering the next bend, that velocity impulse must be restored again and that can only in a straight pipe section, where the segregation is no longer existing.
If the impulse is exhausted in the bend, the bend will choke, or the material gets blown through the bend as a destroyed plug at the cost of a significant pressure drop.
is it suitable for conveying line?
NO
How we calculate pressure drop in bend?
The only pressure drop, you can calculate in a bend, is the air pressure drop.
Keep in mind that the free cross section is decreasing, because of the reducing material velocity.
For the rest, there is a material velocity drop, due to friction velocity loss.
The velocity loss is compensated by acceleration after the bend. ■
Teus
Selection of bends for pneumatic conveying
what are the parameters for selection of bends in pneumatic conveying? ■