Weighbridge used to measure bagasse flow on conveyor belt

[SA07]

Hi
Bagasse coming from the sugar mill passes over several conveyor belts before entering our 2 boilers to be burnt as fuel. The flow is controlled by a PLC and is measured by Precia Molen weighbridge installed on the conveyor using load cells.
Every Sunday when the sugar mill stops, a calibration of the weighbridges can be done. From Monday to Sunday morning, the plant operates 24/24 and no calibration can be done.
We notice that the weighbridge measurement drifts quickly after 1-2 days of calibration. Someone from Precia Molen came on site to check but problem still the same.
On the conveyor belts, there are belts on either side to prevent spillage of bagasse. When these side belts wear, the force they exert on the conveyor belt decreases and this affects the reading of the weighbridge.

Are there are technologies that can be used to measure flow of bagasse on conveyor belts accurately?

 

[3DDave]

What you show should not have side belts. Is there a picture showing where the side belts are?

 

[FacEngrPE]

All of the belts (side belts and main belt) must run at exactly the same speed or there could be slippage of load material. This would result in the average speed of material on the conveyor being different than the measured speed of the conveyor.

 

[SA07]

Plz see a picture of side belts on the conveyor to prevent spillage of bagasse. These are fixed and not moving.

 

[FacEngrPE]

The picture above shows what I would have considered these to be sideboards, rather than sidebelts, as they do not move with the belt.
I see lots of possibilities for force to develop between the conveyor and the sideboard. If you are attempting to get close to the published accuracy of the weigh bridge (class 2 of better) the interaction of the sideboards and the belt can be significant.
Not sure if this would fix the problem or make it worse. I would try setting the bottom of the sideboard so that it does not rest on the conveyor belt (a bit more clearance than 1 sheet of paper). Too much gap might create a problem with fibers getting stuck in the gap.

 

[danw2]

>The main problem is that a higher set point must be used for a chain conveyor. This have caused bagasse jam in chutes or conveyors, stoppage time.

What action does raising the setpoint activate? Does raising the setpoint increase the belt speed in order to deliver more product in a given time interval? If so, it appears that a step increase in setpoint/beltspeed causes the product jam in chutes or conveyors, correct? The higher delivery rate at the increased setpoint chokes the mechanics of the system, right?

Hence there is a maximum limit for the setpoint, otherwise the system chokes. Is setpoint limit known? Would it make it sense to determine that SP limit value and limit the setpoint range of the controller?

How much is the setpoint increased to make up for low delivery 1/2%, 1%? 5%? 10%? Is the operation ignored until lunch time and then an operator makes a guesswork setpoint bump to make up for low delivery?

It seems that the initial setpoint on day 2 and day 3 when the so-called drift is occurring that the system is not providing an adequate flowrate, right? Is it possible to increase the initial setpoint on day 2 or day 3 or day 4 by some minor amount to compensate for the drift? A minor increase in the initial setpoint might provide sufficient delivery over time as opposed to a large step change in delivery rate to try to make up for the shortage, which then chokes the system.

Has anyone documented what the maximum delivery rate is, with this product, that the system mechanics can tolerate before the system chokes?

Is there a flow totalizer that indicates the total product delivery mass over time?

 

[SA07]

All is controlled by a PLC.
Increasing set point on the chain conveyor increases its speed. It is controlled by a VSD.
Correction should be done within minutes else the boiler will lack bagasse as fuel. It cannot be increased gradually over a few days.
In the weighbridge there are totalizers also on the scada.

It seems the radiometric sensor may be a solution for us. As wear on the side belts will not affect it contrary to the load cells of the Precia Molen. We have requested quote and we will inform you of the outcome.

 

[RedSnake]

No bagasse is sticking to the drum or speed sensor

How about bagasse sticking on to the belt itself?

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein