Re: Determining Capacity Of Vacuum System
For a fixed conveying length the system capacity is depended on the available vacuum. e.g. If you have a exhauster capable of pulling 400 mbar vac. and your system current pressure drop is 200 at a given solid flow rate you can increase the solid rate until you are close to max available vac. limit of the exhauster. This will be your system max. capacity. Since you have a test rig I am sure it will be very easy for you to do this. From this data you can equate the influence of solid flow rate for a given length.
Measuring air velocity is not advisable it can easily be calculated. I am sure you know your volumetric flow rate of exhauster at given vac. and you also know pipe size from these you can calculate the exit velocity. Now convert this vol. flow rate to atmospheric conditions and that will be inlet air flow rate / air velocity. Air velocities within the system are calculated by measuring pressure / vacuum at the required point and doing the simple maths. But normally inlet and outlet velocities are enough to do the necessary sums unless you are after pressure gradients. ■
Re: Determining Capacity Of Vacuum System
Hi Mantoo, thanks for the answer.
The only problem is that I cannot change the solid rate, because I do not have a feeder installed. The material is sucked into the pipes. Does this mean that we already use all the available vacuum and we are at max capacity?
And how can I set a number (e.g. kg/s) on this?
Thanks in advance! I really appreciate your help!
Johan ■
Re: Determining Capacity Of Vacuum System
No this doesn’t mean you are at max. conveying limit. This means you are feeding the system are fast as you can. As I said before the system limit will be close to the max. vac. rating of your exhauster.
I don’t know the exact details of the rig so I cannot tell you how to control your solid flow rate. But gravity feed into the system is enough for your needs. You don’t need a fancy feeder on vacuum system a small mass flow hopper and different size orifice plates work very well to control solid rates.
As far as determining solid flow rate is concerned it is very simple put a know quantity of solids and determine the time taken to convey it, this will give you solid rate. I will strongly advice you to read some academic papers on the subject to get more understanding. ■
Determining capacity of vacuum system
Hi,
I'm an engineering student working on a project about vacuum conveying systems. I've already built a test installation (transporting various plastics) with a pipe lenghth over 150m. Now I would like to determine the capacity of the system (in function of the pump's power and total equivalent length). First question, is it correct to assume that if I measure the airspeed I have an indication of the capacity? Second question, where do I have to measure this speed because the airspeed is variable along the track?
Another problem is measuring this speed. I do already have a testo 445 (without any extras - See website)
Maybe a pitot tube could do the trick?
Another possibility is measuring the airspeed with pressure difference between 2 points and then using Bernouilli's equation. Or are there any other methods wich are more commonly used?
Thanks a lot for your help! I really appreciate it!
Johan Smeets ■