Conveyor System 1

[Josh2008]

I'm looking to plot a system curve for a conveyor system (Torque vs RPM), similar to that of a pumping system (pressure vs. flowrate), so that I can send it off to verify that an electric motor can accelerate my system within my alotted time.

I have been using Belt Analyst software, as well as the CEMA Belt Conveyors for Bulk Materials as references, but I'm not sure how to get the torque vs rpm.

My system is a two speed setup, where it modulates between a slow and fast speed that is controlled by time. I have alotted a specific time to accelerate between the two speeds. The low speed first runs with no material on the belt. After a period of time the material begins loading onto the belt at the low speed. Soon after, the material loading stops and the belt accelerates to high speed operation. The belt transfers all of the material off of the belt and slows back down to the slow speed.

Ultimately I believe I need to calculate an equation for belt tensions (force) with respect to belt speed, as torque is a function of the effective belt tension and pulley diameter, and RPM is a function of belt speed and pulley diameter.

I'm lost when calculating belt tensions with respect to belt speed. Cema has a long formula to calculate effective belt tension at the head pulley but it is dependant on a lot of variables, which include belt speed and mass flow rate.

Any suggestions?

 

[micalbrch]

Josh, this forum is unfortunately not one of the most active ones. If you do not get enough replys within in the next two days, I'll recommend to re-post it in the "Mechanical engineering other topics" forum. That one is very active.

 

[PersonalProfile]

Typical belt conveyors are generally accepted as "constant torque" machines, unlike some pumps (though not all).

Though the situation you describe is not quite "typical".

You can break the "sequence" into suitable sub phases which can be readly analysed with the software you mentioned.
The results can be presented as a time plot (throughout the cycle) which will faciltiate drive selection etc.

A rough guide for the sub phases would be:
1. Starting empty from zero speed to slow speed. If we assume a constant rate of acceleration, the torque will be constant and the power will be linear. Your software will tell you what power you require from which you can calculate torque etc.
2. Running empty at slow speed. Your software will tell you what power you require from which you can calculate torque etc.
3. Loading at constant slow speed. Assuming you know the maximum payload prior to the next phase (accelerating to full speed) is initiated, using your software you can calculate power and hence torque etc. The change in torque / power between between 2 and 3 can generally be assumed to be linear.
4. Starting loading from zero speed to full speed. If we assume a constant rate of acceleration, and knowing the payload from 3, the torque will be constant and power will be linear. Your software will tell you what power you require from which you can calculate torque etc.
5. Running loaded at constant full speed. Assuming you know the maximum payload, using your software you can calculate power and hence torque etc.
6. Running empty at constant full speed. Your software will tell you what power you require from which you can calculate torque etc. The change between 5 and 6 can generally be assumed to be linear.

This is very similar to an application which I have sucesfully used the above analysis / presentation method.

Regards,
Lyle