It would depend on what sort of starting regime you are using.

eg

fluid coupling 1.4x

DOL up to 3x

It will also depend on what sort of take up you are using and other factors.

I don't recommend using such generic formulas as every situation and conveyor is different.

For what purpose do you wish to know the value?

I would use 3.5x as a safe limiting value but could be very conservative depending on the design. Such a number maybe useful for head frame design or similar.

Best Regards,

Gareth Blakey

blakeyg@conwag.com ■

Typically, many points should be included in the important features of the conveyor's design that quantify the starting multiple of the motors nameplate rating:

1. terrain geometry,

2. belt safety factor,

3. belt type (fabric or steel),

4. vertical and/or horizontal curves,

5. trade-off with civil structural costs

6. temperature range and belt rubber properties

7. take-up type

8. starting method/acceleration curve configuration such as linear or higher order polynomial of dv/dt

There are other factors, but this becomes very pedantic. ■

You question is too vague, requires substaitial discussion on the general equations, and requires many caveates to be useful.

I suggest you read a text on conveyor design such as the CEMA 5th or 6th edition, Goodyear design handbook, ContiTech design manual, German DIN 22101 calculation method of ISO equivalent.

You will need to know details on the wound rotor starting resistor impedance for each step, and their timings, the load distribution on the belt where there will be maximum resistance to starting.

The WR impedance of each resistor needs to be converted to torque vs RPM.

You will need to know the motor nameplate characteristics and the conveyor demand power for all governing cases.

In all likelyhood the torque spike will exceed 1.6 x the demand power/torque and may go much higher. This is a guess without knowing much detail of the conveyor geometry and the above. The explicit answer requires engineering, which is not the purpose of this forum. ■

Starting tension of the conveyor will depend on conveyor geometry, material load, take-up values, acceleration time of conveyor, various resistances, motor starting characteristics etc. Maximum starting tension will be different for DOL drive motor than variable voltage variable frequency drive motor due to different motor starting torque.

Can get the tensions value at different points along the conveyor by using "Beltstat" conveyor software analysis. But ensure, correct profile input and other input parameters. ■

Dear Mr. Dharma Raj H,

The calculations of belt tensions during steady state, starting, stoppage, etc. is a complex exercise. Possibly, you are dealing with application engineering (involving money). So, i suggest you to refer to appropriate literature explaining the method for such calculation. There are many points but few noteworthy points are as below :

- You will be required to calculate belt tensions at different points (terminal, take-up, concave curvature, convex curvature). If this is a cross-country conveyor then such points will be very large in number.

- Above tensions to be calculate for no-load, part-load, full load, etc.

- The steady running tensions depend upon the characteristics of load.

- The starting tensions depends upon starting torque / force etc. (drive characteristics).

- The stoppage tension depends upon braking torque / force.

- All the aforesaid tension depends upon the take-up type and its setting.

- You have mentioned some regenerative situation. This adds further complexities of analysis for variation in conveying friction coefficients (this means entire exercise to be done 2 to 3 times considering the probable differing values of conveying friction coefficient).

The designer strives to choose the right kind of features among the multitude of variants, so that conveyor performs satisfactorily with the best of economy.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■