Hello Nicki,

Would you elaborate on your request?

Conveyor speeds vary depending on a number of factors, but primarily on the process requirements (i.e. what the receiving equipment needs or can handle).

Generally, conveyors with fixed speeds require a motor or motors at a set RPM, a gear reducer(s) with a set reduction ratio, sheaves or sprockets at a set ratio, and a specific drive pulley diameter. Change any of these, and you change the speed.

Conveyors with adjustable speeds normally use electrical (VFD) or mechanical means to change the speeds during operation.

If you simply need a range of speed possibilities - conveyors in the industries you mentioned run anywhere from just a few feet per minute (some belt feeders) to well over 1000 fpm. You can contact belt manufacturers, system designers, motor manufacturers, and pulley manufacturers to determine what is possible.

Regards, ■

Nicky,

A. Belt speed is usually dictated by a number of factors such as:

1) cross-sectional capacity of the most cost effective belt that is usually the narrowest belt that the belt speed limits

2) dust control along belt length

3) belt flap on return strand

4) chute design that can properly handle the range of belt speeds

5) belt incline/decline stable loading asssociate w/ lump size/shape

6) overland or short in-plant where wear life and down time are factors

There are conveyors running up to 10 m/s and tested up to 15 m/s in coal, 7.5 m/s in bauxite, 6 m/s for large (300 mm) hard rock, 2 m/s for fine cement ( except for pipe conveyors). often it depends on the operators comfort zone.

Typical values are less. For ROM coal, 6 m/s is practiced for overlands, depending on moisture level, where less the 2% moisture might be held to <4 m/s, and > 6% moisture can operate faster than 6 m/s. In plant conveyors migh range from 2.5 to 4 m/s. Short < 50 m length might be limited to 1.5 m/s for life or tramp metal inspection.

Primary and secondary crushed hard and quarry rock do run > 4 m/s and can run > 7 m/s. As th conveyor speed is increased beyond published norms, you should seek assistance form engineers with experience and know the troubles of high speed.

Reference the CEMA manual, DIN 22101, or belt manufacturers data base as Mr. Miller suggests.

B. Pulley diameters are normally selected for the belt construction. Number of fabric plies and carcass construction dictate the minimum diameter. For steel cord belt the minimum pulley diameter is dictated by the steel cord wire strand size, cord construction, belt tension and belt safety factor.

Counterpoint to this is the desire to shed fugitive muck. The smallest diameter will enhance belt cleaning. The outer surface is stretched to expell embedded particles along with the higher centrifical force. Also ther is a desire to minimize the transfer height for ore flow control and structural assembly.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Nicki,

Yes. Select the minimum pulley diameter from the belt manufacturers suggested table.

Competent belt suppliers:

1. Goodyear Tire & Rubber Co. - USA, Canada, Brazil, Australia, South Africa:

http://www.goodyearindustrialproduct...conveyorbelts/

2. Bridgestone Corporation - Japan & Spain

http://www.bridgestone.co.jp/english.../conveyorbelt/

3. Phoenix AG - Germany

http://www.mining-technology.com/con...rials/phoenix/

4. ContiTech - Germany

http://www.contitech.de/ct/contitech...baendere.html

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Belt conveyor speed depends upon various factors and considerations as stated in earlier replies. The belt speed also depends upon quality of design and quality of conveyor components. Fundamental considerations are as below :

1) The selected belt speed should result into technically workable equipment, in context of the applicable aspects.

2) Higher speed tends to reduce initial cost.

3) Higher speed tends to increase wear and consequently more replacement. Thus, it can lead to higher operating costs.

Published literature belt speeds are for overall economy (i.e. minimum total of initial cost + operational cost) and workable solution; based on longtime experience in industry.

If one wishes to opt for higher speed, the same should be done in consultation with the experts in conveyor design. It is a complex and subjective decision.

Regarding pulley diameter, it depends upon belt carcass and tension in the belt. Thicker carcass will need comparatively bigger diameter of pulley (for same material of carcass).

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

Nicky,

ROM coal is Run-of-Mine coal. That is coal from the mine before it is passed through meshes to form stream coal.

I will let Mr. Nordell elaborate.

If you want to explore different coal terms, do an Internet search on "coal", "ROM coal", "PRB coal", etc. (PRB = Powder River Basin). ■

Nicky / David / Ishwar,

I thank David for taking the initiative to answer on ROM. As he knows, ROM is unsized coal from the mine verses plant sized by screening, orother separating method, coal that may be require to:

a) meet a power plant specification for its burners/boilers/fluidized bed combustion chambers,

b) separate out tramp rock such as in a rotary breaker,

c) into and out of a wash plant that may have a specification to eliminate fines,

d) and so on.

High speed does require better control of tolerances such as idler TIR when running the rollers beyond 600 rpm and sometimes below this value when manufacturing is not to industrial norms.

There are many other issues that need proper advanced engineering when designing for beyond 5 m/s. This requires a dissertation of its own.

I contend that high speed does not necessarily translate to high wear. A proper transfer chute design can place the mineral onto the receiving belt at close to its axial speed.

I am sure David can offer more detail, if he is so inclined.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

David,

My applology on implying you to further the topic of speed. You may do so, however, I was inviting you to discuss the ROM definition which I may not have covered.

LKN ■

Nicky,

As Lawrence has pointed out, a high conveyor speed does not create wear of components (belt, idlers, pulleys, etc.). However, a high speed acts as a time magnifier of conveyor design, installation, and maintenance faults. That is, the problems that are in the operation will show up sooner on a high-speed conveyor than on a low speed one of the same basic design. However, in terms of wear per tonnage conveyed, the high-speed conveyors will normally exhibit the same, or lower, wear characteristics than slow speed lines. Whatever the speed, the conveyor design must take into account the design speed to optimize performance.

As far as ROM coal is concerned, I believe the explanation given is sufficient for your needs. As it is very mine specific, detailed information should come from individual mines.

To get back to your original question –

[1] The speed of a conveyor should be decided on the basis of production needs. That is, how many tons per hour need to be delivered by the unit. Once this is established, the choices begin.

[2] Next, the belt is chosen. A wide belt can deliver more tons per hour than a narrow belt at a given speed, or can deliver the same tonnage at a lower speed. However, wider belts are more expensive on a cost per foot basis and they require more expensive idlers, pulleys, frames, etc. Also, wider conveyors take up more space, which can be a consideration if the conveyor is in a plant. Finally, it is always safer to talk to the belt manufacturer when contemplating unusual speeds – they may have a special compound that will extend the life of the belt.

[3] Next the idlers, pulleys, chutes, skirting, motors, reducers, etc. are chosen or designed. Generally, larger idlers should be used for high-speed belts – this reduces the idler rpm requirement. The motor(s), reducers, sprockets, and pulley diameter (include lagging thickness) all work together to give the conveyor speed. The chutes (load and discharge) must be designed to accommodate the material flow without doing damage to the belt or to the receiving item; to prevent blockages; and to control dust.

[4] After the belt, speed, and components are selected, a cost-benefit analysis should be done. This will confirm that you have made the right choices, or not.

Finally, each conveyor is part of an overall transportation and/or processing system. Because of this, the conveyor parameters (speed, width, elevation, path, chutes, etc.) must be considered as part of the system and be designed to prevent unfortunate side effects on other equipment.

Hope this helps. ■