Re: Barley Powder Conveying System (Vacuum)
1. Variable solids flow rate is not a problem ; if you run the system at max solids rate this will give you the maximum pressure drop in the system. Then calculate all your system parameters at this condition. If your exhauster is capable of maintaining the required air flow rate at max. vacuum the system will be able to cope with lower solids rate.
2. In these type of cleaning systems stepped pipes are common as long as they are designed to maintain the air velocities in a reasonable range.
3. 20 pick up points are also common and if you know the air flow rate (ask the exhauster vendor for exhauster air flow performance curves) of your exhauster air velocities in all the different diameter can be calculated at inlet (atmospheric conditions) and exit ends (max vac.).
4. Air only pressure losses are normally calculated use Fanning or Darcy equations.
5. Last but not least if you want to calculate theoretical pressure drops the K factor is calculated from trials carried out on that specific material in a test rig as stated in the paper you have read. So if you don’t have a K value for barley solids I am afraid solid pressure losses cannot be calculated. ■
Re: Barley Powder Conveying System (Vacuum)
Dear Jose,
In addition to mr Mantoo’s reply the following:
Where you are indicating a vacuum cleaning system with as many as 20 intakes, I presume that, when you are using one intake, the others are closed.
In case the other inlets are open, they act as false inlets and destroy any vacuum.
The operating intake gets blocked and dead.
With one inlet operating and the others closed, you can calculate the barley powder carrying pipes as one pneumatic conveying system.
This can be repeated for all the other inlets as well.
success ■
Teus
Re: Barley Powder Conveying System (Vacuum)
I'm doing an evaluation of an already installed barley powder pneumatic conveying system ( vacuum ). This is used as a particle collecting system from equipment used in barley grain cleaning process; therefore it's like a secondary cleaning process.
From what I've read in Mr Agarwal's article, I'd need to know the solids to air ratio as well as K factor, solids mass flow, etc.
The system has several pick-up points (more than 20) as well as many diameter variations during its route (over 10).
I guess the first basic question is, is this method of calculation appropriate to calculate this kind of system? (Because of the several intakes and diameter changes)
YES, THE CALCULATION METHOD GIVEN IN THIS ARTICLE CAN BE USED FOR YOUR APPLICATION.
Also, being this a cleaning system (the quantity of solids entering the system are variable depending on the equipment where the intakes are, as well as the kind of barley used), with no volumetric flow or mass flow measurement equipment during its route, is there a way for me to incorporate the solids into the calculation? The only measurement available is the total of powder picked during the operation of the system. But as I said before that’s variable depending on the factors I already mentioned.
FOR SYSTEM DESIGN, USE THE MAXIMUM/MINIMUM SOLIDS CONVEYING RATES.
My porpoise with this evaluation is to guarantee the velocity at the pick-up points to be enough for the system due to the material used (barley powder), and also to verify the selection of the blowers for the system.
CALCULATION METHOD WILL GIVE YOU THIS DATA.
If there’s no way to incorporate the solids to the calculations in this case, what method would you recommend to calculate the system using air only? Maybe using a friction multiplier to the total of friction loss in the system?
YOU SHOULD DIVIDE THE CONVEYING LINE INTO 20 SECTIONS SO THAT YOU COVER EACH OF THE 20 FEED POINTS.
FOR AIR ONLY, SOLIDS FEED RATE WILL BE ZERO.
IF YOU CANNOT RUN CONVEYING TESTS, TRY GETTING QUOTATIONS FROM WELL KNOWN VENDORS. MOST OF THEM KEEP A DATA BANK FOR MATERIALS THEY HAVE TESTED.
SOLIDS TO AIR RATIO ALSO INCREASES THE FRICTION FACTOR.
I don’t know I’m really needing some help, any ideas?
Thanks to all, any questions let me know…
MY ANSWERS TO YOUR QUESTIONS ARE GIVEN ABOVE.
REGARDS,
AMRIT AGARWAL
CONSULTING ENGINEER
PNEUMATIC CONVEYING CONSULTING
EMAIL: POLYPCC@AOL.COM ■
Re: Barley Powder Conveying System (Vacuum)
First of all thanks to all for responding so quickly, I really appreciate it.
Ok, so I’ll reply to all of your answers:
To clarify first, the system is working as a vacuum pneumatic conveying system.
Mantoo:
1.The problem is I dont know the solids rate on each equipment alone, I just have the information of the total of solids conveyed, that by messuring the level of the vessel where the solids are deposited.
2.Yes the system has stepped pipes, although as the system is already installed I don’t know if by the time of instalation that calculation was done, I suppose it was, as I said, my work now is to verify the state of the system. I’ve the meassurements of the current air velocities in the system, but I need to compare them with the one that should theoreticaly be.
3.Regarding the blower, I just have one operation curve (Static Pressure vs Flow) and the data about Max Flow, and Max Pressure Drop, Impeller Diameter, RPM, and that’s about it.
4.But my point is, having as much as n intakes, how would I consider the pressure drop at the inlet of the blower? Would it be an addition of the n pressure losses from all the intakes? Should I consider only the most critical route?
5.I might be able to calculate K factor.
Teus:
Yes, the system has all of those inlets, one for each equipment, anyway, I’ll attach a copy of the system drawing, and I’m marking with red arrows the inlets of the system for the most critical operation. The other inlets you can see would be closed for that operation. Also, the system or I should say systems because there are two of them ar connected by a bypass in case one of the blowers gets damaged. In a normal operation that bypass is always closed.
Mr. Agarwal:
As I said earlier, I have no way of calculating each equipment’s solids conveying rate or addittion to the system, I can just get the information about the total of solids conveyed at the end of the operation. And that would be a total from all the equipments.
And also as I asked earlier, if I run my calculations with just air, how should the pressure losses should be considered? As an addittion of all inlets route to the blower? As the pressure loss from the most critical route?
Thank again to everyone for the help, I’m a student so therefore I’m new to the subject even when I’ve about 5 months studying the system.
PD: Remember all of you to check the drawing so you can have a better idea of the system.
Attachments
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Re: Barley Powder Conveying System (Vacuum)
ehm hi again guys, anyone had a chance to check my last post? I'm really needing your help to finish this task.
thanks again for the help ■
Barley Powder Conveying System (Vacuum)
Dear Sirs:
I'm doing an evaluation of an already installed barley powder pneumatic conveying system ( vacuum ). This is used as a particle collecting system from equipment used in barley grain cleaning process; therefore it's like a secondary cleaning process.
From what I've read in Mr Agarwal's article, I'd need to know the solids to air ratio as well as K factor, solids mass flow, etc.
The system has several pick-up points (more than 20) as well as many diameter variations during its route (over 10).
I guess the first basic question is, is this method of calculation appropriate to calculate this kind of system? (Because of the several intakes and diameter changes)
Also, being this a cleaning system (the quantity of solids entering the system are variable depending on the equipment where the intakes are, as well as the kind of barley used), with no volumetric flow or mass flow measurement equipment during its route, is there a way for me to incorporate the solids into the calculation? The only measurement available is the total of powder picked during the operation of the system. But as I said before that’s variable depending on the factors I already mentioned.
My porpoise with this evaluation is to guarantee the velocity at the pick-up points to be enough for the system due to the material used (barley powder), and also to verify the selection of the blowers for the system.
If there’s no way to incorporate the solids to the calculations in this case, what method would you recommend to calculate the system using air only? Maybe using a friction multiplier to the total of friction loss in the system?
I don’t know I’m really needing some help, any ideas?
Thanks to all, any questions let me know… ■