11/25/2014 9:24 PM  
Joined: 8/16/2010 Last visit: 7/25/2024 Posts: 636 Rating: (12) 
Hi all. Is there possibility to measure the flow in kg/h if we know the current weight (read from load cell) and screw conveyor speed. Flow=WeightxSpeed is that right? 
12/2/2014 11:47 AM  
Joined: 4/11/2011 Last visit: 7/16/2024 Posts: 132 Rating: (7) 
Yes, but "weight" is material weight per meter (kg/m). flow (kg/min) = weight (kg/m) * speed (m/min) Are you measuring weight of screw conveyor?

I'm just a human. Mistakes are allowed. 

12/2/2014 12:59 PM  
Joined: 8/16/2010 Last visit: 7/25/2024 Posts: 636 Rating: (12) 
Yes, I would like to know how to measure flow with screw conveyor? Also I see system where screw conveyor throws material on "slant trough" equiped with load cell which measures the flow...How it works? Best regards, Miloš 
12/3/2014 1:38 AM  
Joined: 4/11/2011 Last visit: 7/16/2024 Posts: 132 Rating: (7) 
Load cell do not measure flowIt measures weight only. Flow rate is result of calculation.  To get material speed (m/min) you must convert motor speed (rpm, frequency etc) to linear speed of conveyor (depends on motor speed, gearbox ratio, pitch of screw).  to calculate weight per meter you must know lenght of the screw (where material is present). weight per meter = total weight of material / screw lenght Calculation is easy part of this case. In dynamic weighing more important are mechanical factors:  if conveyor (deadweight of system) is much more heavyer than material on it, then you loose accuracy in weight measurement  motor/gearbox vibration  screw speed deviation (fixed speed or encoder for speed feedback)  mechanical construction of weighing system (how many load cells; whole conveyor is on load cells or just one side is measured etc) 
I'm just a human. Mistakes are allowed. 

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8/31/2021 2:00 PM  
Joined: 10/29/2018 Last visit: 7/20/2024 Posts: 9 Rating: (0) 
Hello Milosh, Were you able to calculate mass flow? Right now I am having same problems and I was hoping to find an answer to your question. Could anyone atleast show me the correct way to figure out how to calculate mass flow in "t/h" and total mass in "tonnes". What I have is an analog input signal 010v from belt conveyor load cells and pulses from an encoder. I understood from your discussion above that: 1) analog input from load cell is instantaneous mass 2) By using pulses from encoder and measuring time from conveyor start I calculate distance traveled by material and speed of the conveyor what is my next move? 1. Do I divide instantaneous mass from load cell by travelled distance and multiply it by speed? > massFlow = m/L*speed OR 2. Sample measurement from load cell every 80cm (for example) and sum it up, then divide by quantity of samples. Ex: Lets say belt travel distance is 800 cm. So I have 10 samples of load cell measurements. Sum them all up. lets say it equals 500 kg. Then divide by 10 = 50 kg per 80cm. then use this "average" to calculate flow? Like: (50kg per 80cm) * (80 cm per sec) = 50 kg per sec = 3600*50 kg per hour = 180 t/h. I am totally lost now. Need any help. Actually I am trying to calculate total mass. But I do not know whether there is a way to find it. I was thinking to calculate mass flow first. And then by using mass flow calculate total mass by sampling mass flow each 100ms. Any help is appreciated.

9/1/2021 12:12 AM  
Joined: 7/7/2010 Last visit: 8/7/2024 Posts: 15068 Rating: (2404) 
You need to know the unloaded mass (calibrated load cell reading when belt conveyor is empty. You need to know on average how much mass flows on the belt which will include slippage or imperfect conveyance. One way to find this out is to run the belt conveyor with a nominal flow rate, using the pulse train to integrate the mass on the conveyor (mass reading less the unloaded running conveyor mass reading). Dump the conveyor for 1.0 minutes into a container you know what it weighs empty. Weigh it after a full minute. That's average mass flow rate in kg/min. If you counted up the encoder pulses, you know the 'average' mass flow rate per pulse over the entire minute. Then you can use the mass difference between empty conveyor and actual measured mass to get moving mass every encoder pulse. Then you can average it out and extrapolate to 1 minute. Now you know the relationship, accounting for slippage or imperfect conveyance, and actual mass moved in one minute, and you know how many pulses from the encoder you received. That allows you to establish some estimation values for mass flow rate while the conveyor is running. If you want more accurate values, you need to account for mass that leaves the conveyor along the way (falls off).

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