52185717-Troughed-Belt-Conveyors

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Troughed Belt 
Conveyors 
 
 
Jyoti Ranjan Nayak 
jyotiranjan541@yahoo.com 
Troughed Belt Conveyors 
 
The troughed belt conveyor is probably the most widely used and well known conveyor design of all 
types of belt conveyors. 
The troughed belt conveyor has proven to be a reliable and versatile conveyor in many applications 
and is probably more forgiving than most other types of conveyors when exposed to adverse 
operating conditions. 
Improved technology supporting the design of conveyor systems together with innovations in 
component design and a better understanding of the dynamics prevalent in conveyor belts during 
operation, have propelled troughed belt conveyors into broader applications and higher conveying 
capacities. 
 It is imperative that designers, users and learners are kept informed of the latest developments in 
the field of conveyors, and the associated technical and economic benefits which these technologies 
hold for the end-user. 
 
 
 
Functional Description 
 
 A troughed belt conveyor comprises an endless, rubberized flat belt (a) suspended between 
pulleys at either end and supported along its length by a number of rotating idler rollers (b). The belt 
is driven via one of the pulleys (usually the head pulley (c)) and the tension in the belt is maintained 
by using a sliding pulley (d) which is tied to a gravity take-up unit (e). 
 
 The material (f) is loaded onto the conveyor at the tail-end via a chute (g) and is transported along 
the carrying-side (h) to the head-end where it discharges into a discharge chute (i) which guides the 
product onto the downstream equipment. 
 Impact idlers (j) are located at the loading point to support the belt where the load impacts onto 
the belt as it is dropped down the loading chute. 
 Once the material has been discharged from the carrying belt, the return belt (k) is guided back to 
the tail pulley on return idlers (l). 
 The impact, carrying and return idlers are spaced at different intervals. On the carrying-side, the 
mass of the belt plus the load conveyed is greater than the mass to be supported on the return-side 
and thus, for the tension in the conveyor belt (by the take-up and induced by the drive unit), the 
idler spacing is selected accordingly. This 'sag' in the belt between the carrying and return idler sets 
must therefore be designed on the basis of the heaviest load that the conveyor is to transport. 
 Snub pulleys (m) are sometimes incorporated into the design of a conveyor in order to increase 
the angle of wrap (n) of the belt on the drive pulley. The greater wrap angle on the pulley allows 
more power to be introduced into the belt as is passes around the drive pulley without slip 
occurring. In this way, fewer drives are needed on longer conveyors or conveyors with high 
conveying loads. 
 For a detailed view of a troughed belt conveyor click here to be routed to the "anatomy" of a 
trough belt conveyor, or click the appropriate item on the contents bar to the left of your screen 
 
 Applications for Troughed Belt Conveyors 
 
 Troughed belt conveyors are used extensively throughout the bulk materials handling industry and 
examples of applications where this type of conveyor is commonly used are listed below (click 
thumbnail for images) :- 
 
 
 
 
 
 
 
 
 
 
Short plant conveyors - horizontal, 
inclined or declined 
Long overland conveyors - straight or 
curved. 
Reversible conveyor. 
Boom conveyors - stacker-mounted, 
slewable. 
Inclined mine shaft conveyors. Shiftable conveyors. 
Tripper conveyors. Elevated conveyors in gantries. Two-way conveyors. 
Material to be Conveyed 
 
Troughed belt conveyors are able to transport a wide variety of materials in bulk. Notwithstanding 
this, factors which affect the performance of a conveyor belt, its success or failure often depends on 
whether or not the designer completely understands the properties and characteristics of the 
material to be transported. 
Knowing how a particular material will behave when it is dropped down a loading chute onto a belt 
conveyor below and whether a material is dusty, abrasive, free-flowing or extremely wet, is helpful 
to the engineer and in the long run, ensures that the client receives a conveyor that meets his 
expectations. 
Material Class Description 
 
The angle of repose of a material is that angle to the horizontal assumed by the stir-face of a freely 
formed pile, The angle of surcharge is that angle to the horizontal assumed by the surface of a 
material at rest on a moving conveyor belt. The surcharge angle may be anything up to 20 less than 
the angle of repose. The flowability chart on sheet 2 shows the general relationship between the 
angles of repose and surcharge. 
C.E.M.A. Handbook UNIROYAL Conveyor Belt Selection Guide PROK Handbook 
The classification table are based upon nvrm4e conditions and typical materials. The determination 
of angles of repose and surcharge and maximum recommended conveyor inclination must be 
considered with due regard to such properties as size and shape of fine particles and lumps, 
roughness of the surface of the particles, proportion of fines and lumps present, moisture content, 
dustiness, stickiness, abrasiveness, corrosive action, etc. Materials or characteristics omitted from 
the tables may be roughly appraised by comparison with similar listed materials. 
 
Material Angle of Repose and Surcharge Angle 
 
 
 If details about the material to be conveyed are known and fall within the experience of the 
designer, the engineer is able to cater for the specific features necessary on the conveyor which will 
ensure that the material can be loaded, conveyed and discharged in accordance with the users 
specification. This will in turn lead to a more reliable and efficient troughed belt conveyor operation. 
 From the above it is obvious that the conveyor designer must have a firm grasp on the properties 
of the material which is to be transported along the conveyor in addition to a fundamental 
understanding and appreciation of belt conveyor design. 
 
 Conveyor Selection Criteria 
 
 For the novice, a brief outline of the basic considerations and limitations of the troughed belt 
conveyor are given below. Reference is also made to alternative types of belt conveyors which may 
be more suitable than troughed belt conveyors in some instances. 
 As can be seen below, it is incumbent on the engineer to establish the most cost-effective and 
practical conveyor system in each application. Where necessary visitors should consult the 
appropriate sections dealing with these alternative types of conveyors by clicking on the title bar at 
the top of your screen. 
 Note that detailed design by a competent engineer is required to establish the specific layout 
parameters for each conveyor. The information provided below serves merely as a guide. 
Layout 
 
For 'short' troughed belt conveyors 
(whose length is less than 
approximately 500 m) and troughed 
belt conveyors installed in factories or 
plants should be straight in plan view. 
These conveyors may be inclined, 
horizontal or declined in elevation, or 
parts of a conveyor may be inclined, 
horizontal and declined. 
 
 For 'long' troughed belt conveyors 
(where the conveyors' length is in 
excess of 500 m) and where the 
conveyor is an overland-type conveyor 
following ground line, horizontal 
curves of radius greater than 1000 m 
can be considered. 
As above, these conveyors may 
include inclined sections, horizontal 
sections and declined portions 
between the loading and discharge 
points. 
 
 
 Profiles of Troughed Belt Conveyors 
 
The possible profiles which a troughed belt conveyor can follow are almost unlimited. In the process 
of determining whether a troughed belt conveyor is the correct type of conveyor for anygiven 
application, the layout of the conveyor plays a significant role. 
One aspect of the layout of a conveying system is the profile which the conveyor must follow. To a 
large degree the vertical profile is limited by the character of the material being conveyed e.g. 
whether the material will roll back along the belt while being transported up an inclined section of a 
conveyor. To ensure that this does not occur, the designer must consider the material properties 
and must tailor the profile of the conveyor accordingly. 
Assuming that the material properties, physical obstacles on the Plant and the process requirements 
are taken into consideration, the profile which a troughed belt conveyor can follow is almost 
unlimited. 
Some examples of troughed belt conveyor profiles commonly seen are provided below :- 
 
At loading points, the 
maximum inclination of the 
belt should not be greater 
than approximately 5 
degrees to the horizontal. 
This maximum inclination is 
dependent on the belt 
speed, the material 
characteristics and to a 
lesser degree the layout of 
the feed point. Inclining the 
loading point to a greater 
angle may result in spillage 
at the loading chute. 
 A further consideration at loading points is the height required above the conveyor belt for the 
loading chute work. It is important that material is loaded onto the center of the conveyor belt to 
ensure that the belt runs centrally along the conveyor structure. To achieve this the loading/feed 
chute must be wide enough at the top of the chute to collect all material being fed into it, while the 
bottom of the chute must be no wider than 2/3 of the width of the conveyor belt. 
The side walls of the chute must 
be steep enough to prevent 
material accumulating on the 
side walls and corners of the 
chute, which could lead to 
blockages. Typically side walls of 
chutes range between 45 
degrees and 70 degrees 
depending on the material to be 
conveyed. 
 It can be seen in the sketch 
therefore that careful consideration must be given to the layout of the tail station. The height 
required above the new conveyor belt for the feeding system and chute work must not be 
overlooked. 
 The discharge of material from a troughed belt conveyor is usually via a chute onto another 
conveyor, into a silo, etc. As with the feed chute, the discharge chute must be carefully laid out in 
order to establish the required elevation of the head / discharge pulley to ensure that the discharge 
chute does not block under full load conditions. 
 It has been explained above that troughed belt conveyors are generally designed as straight 
conveyors (plan view), certainly in the case of short belt conveyors. When a designer is considering 
the layout of a conveyor in a factory for example, the desired route which the conveyor is to follow 
may not in fact be possible due to physical obstacles located between the feed point and the desired 
discharge point. 
In such a case the designer 
is presented with a number 
of options which should be 
investigated prior to 
finalising the design of the 
belt conveyor system to be 
used. 
 A first option may be to use two a troughed belt conveyors with a transfer point between the two 
conveyors, as can be seen in this sketch. 
 A second option may be to use a different type of belt conveyor for example the pipe conveyor or 
Sicon conveyor which offer the ability to negotiate corners without the need of transfer points. Each 
of these alternative types of belt conveyors has their own layout constrains, advantages and 
disadvantages, which the designer must take into consideration as part of the investigation. 
 The inclination of a belt conveyor is also a factor which must be considered by the engineer, when 
selecting the type of belt conveyor to be used. The maximum inclination or decline of a conveyor 
generally depends on the characteristics of the material to be transported. To assist the learner in 
determining which type of conveyor should be used for a particular application, a graph may be 
viewed by clicking here. 
Conveyor Duty & Material Specification 
 
 It is important that the duty which the conveyor is expected to fulfill is clearly established at the 
commencement of the design phase, as this will impact on numerous items in the detailed design of 
the conveyor and component selection. 
 The capacity of the conveyor (in tons per hour or cubic meters per hour) as well as the average 
operating hours per day or per year are important design criteria. Details pertaining to the material 
to be conveyed must also be specified. 
 Having established the duty that the conveyor is expected to fulfill and obtained the material 
specifications the designer is in a better position to determine the most cost-effective conveying 
method to be employed. 
Environmental Considerations 
 
 The need to improve the local environment at factories and plants is gaining support throughout 
the world and is often driven by legislation. As such the type, layout, design and correct operation of 
belt conveyors and their associated equipment is becoming more important. 
 Environmental considerations cover an extremely wide scope of issues ranging from the degree of 
pollutants generated by the working conveyor to the visual impact of a conveyor on the local 
community. The designer cannot therefore neglect to include the environmental considerations into 
the assessment of the most appropriate type of conveyor. 
 Environmental legislation differs from country to country and from factory to factory and it is 
therefore important that the specific environmental legislation and rules be established and 
introduced into the overall conveyor feasibility and design procedure. 
 For the purposes of list Beginners Guide, some of the most obvious environmental-related issues 
are itemised below to provide the learner with an holistic approach to conveyor design. 
 Products which are dusty or which tend to generate dust at transfer points for example 
powder cement and dry fly ash, may be conveyed in enclosed conveyors. Examples of 
enclosed conveyors include pipe conveyors, Sicon conveyors, bucket elevators, screw 
conveyors and pneumatic transportation systems. 
 
 In considering the layout of the conveying system, the number of transfer points between 
conveyors should be minimised to reduce the number of dust and spillage generating points 
in a conveying system, thereby minimising the impact of the system on the local 
environment. 
 
Using a pipe conveyor which incorporates a gradual 90 degree curve can eliminate one 
transfer point in an equivalent troughed belt conveyor system, where two troughed 
conveyors would otherwise be necessary. 
Alternatively, a Sicon 
conveyor may be a better 
solution due to its superior 
cornering ability and 
increased flexibility. Should 
a troughed belt conveyor be 
used however, the conveyor 
can be installed into an 
enclosed gantry or tunnel to 
reduce the possibility of 
material being blown off of the carrying side. Covers can also be installed over the carrying 
belt to reduce the risk of material blowing off of the conveyor and / or contain the dust. 
 
 The environment in which the belt conveyor is to operate may be subject to extreme 
variations in weather 
conditions. A conveyor 
located on a jetty for 
example, may be subject to 
high and low temperatures, 
strong wind conditions and 
an extremely corrosive 
environment. In such a case 
issues such as whether or not 
the conveyor is to be 
enclosed becomes extremely 
important. In addition, the 
materials of construction of 
the structure may be 
different to an equivalent conveyor located in a dry, noncorrosive environment. The 
corrosion protection specification applicable to the conveyor structure and components 
wouldtypically demand a far greater degree of control over the application and 
maintenance of the coating. 
 
 The material to be conveyed may inherently be a commodity of high value where the client 
wishes to limit access to the product and the opportunity for spillage. The transportation of 
diamond-bearing Kimberlite to and from a process plant is an example of such an 
environment. In such a case Sicon conveyors are employed for their ability to negotiate 
difficult conveying routes without the need for transfer points as well as the fact that they 
enclose the material. 
 
 The 'environment' in which a conveyor is 
to be installed may dictate that the 
space available for a conveyor is 
extremely limited. Transporting material 
from ground level to the top of a bin or 
silo may require the conveyor to be 
installed vertically up the side of the silo. 
In this case the equipment to be used 
would typically be a bucket elevator or a 
pocket belt or a sandwich type 
conveyor, all of which are able to 
transport material vertically. 
 
 The location of the 
site where the 
conveyor is to be 
installed may be in a 
cold, mountainous 
area. In this case 
(assuming ambient 
temperatures drop to 
well below freezing), 
special consideration 
must be given to the 
selection of the 
conveyor belt as well 
as to items such as the 
mechanical components (bearings) and the lubricant proposed. Starting belt conveyors in 
extremely cold conditions requires among other things additional power to overcome the 
friction imposed by cold lubricants and a stiffer belt. 
 
 In addition to the temperature aspect, it may 
be necessary to route the conveyor down the 
side of a mountain and the conveyor route 
must negotiate the natural contours of the 
terrain thereby forcing the designer to 
incorporate vertical and horizontal curves into 
the conveyor layout. Where the environment 
imposes extremely arduous 
parameters/limitations on the design of the 
conveying system, it may be necessary to 
reconsider whether in fact a belt conveyor is 
appropriate for the application. 
 
 
 
Cost 
 Like any other equipment, there are costs associated with belt conveyors and these costs must be 
determined to a reasonable degree of accuracy in order for a commercial evaluation to be 
developed which will accompany the technical evaluation. 
 It is generally accepted practice for the 'costs' of a conveyor to be presented in two categories 
namely; the initial capital outlay or capital expenditure for the system i.e. CAPEX and an ongoing 
operating and maintenance expense i.e. OPEX which the client will incur for the remaining life of the 
conveyor system. 
 CAPEX should take into consideration costs such as :- 
 the cost of the mechanical, electrical, civil, structural and instrumentation equipment 
purchased and installed on site as part of the conveyor. 
 the project management fee which a contractor / supplier will charge the user for executing 
the project. 
 the cost of any modifications to existing equipment which may be required on site to 
incorporate the new conveyor into the factory. 
 the cost to install, commission and test the conveyor system on site. 
 OPEX should take into consideration the following costs :- 
 the cost of spare parts which the user will have to procure over the operational life of the 
conveyor. This cost is based on a projection of the life of components within the conveyor 
and the cost of each of those components, based on the duty of the conveyor. 
 the cost of personnel required to operate the conveyor. 
 the costs of personnel and equipment required to maintain the conveyor. 
 the cost of electrical power to drive the conveyor. 
 Depending on the layout of the conveyor system and possibly the type of conveyor system to be 
used, the CAPEX and OPEX costs will differ. It is important therefore that the calculation of the costs 
for each option is performed according to the same basic parameters for example, similar costs for 
man hours and for electric power. 
 It is possible for the total life cycle costs (CAPEX and OPEX) for any given option to be represented 
in a number of ways. Examples include; all capital and operational costs may be shown as a present 
value cost, escalation and/or discount factors may be included or excluded from the financial 
analysis, etc. 
 
Standardisation 
 
If a belt conveyor is to be installed on either a new plant or existing facility, the choice of type of 
conveyor to be used may depend to a large extent on the need to standardise on the type of 
equipment used. 
 In the case of a new factory for example where a number of troughed belt conveyors are to be 
used throughout the facility then, in the interests of standardising and minimizing on spares to be 
held by the client and the training of personnel to operate and maintain the conveyors, the type of 
conveyor to be used should as far as reasonably possible be kept the same. 
 Notwithstanding the need to investigate the optimum layout and cost for a particular conveyor, 
practicality dictates that standardisation of equipment is very often in the long-term interest of the 
end-user of the equipment and the engineer should bear this in mind in his assessment. 
 Examples of Troughed Belt Conveyors 
 Having understood some of the basic considerations relating to the choice and feasibility of 
troughed belt conveyors, it is important that the learner is left with an indication of the capabilities 
of this type of conveyor. 
 The longest single-flight troughed belt conveyor in the world 
is installed in Zimbabwe, Southern Africa, by Bateman 
Engineered Technologies. The conveyor length measured from 
tail pulley to head pulley is 15.6 km (belt length = 31,372 km) 
and transports iron ore at a rate of 500 tons per hour. The belt 
is 750 mm wide, travels at a speed of 4,7 m/s and the installed 
drive power is 1000 kW. The troughing and return idlers are 
spaced at intervals of 4.5 m and 9.0 m respectively and the 80 
ton counter weight has a travel of 50 m. 
 The longest multiple-flight troughed belt conveying system is 
installed in the Sahara desert and transports phosphate rock at 
a rate of 1000 tph over a distance of 110 km. The conveying 
system comprises 11 individual conveyors. This system was 
designed and installed by Krupp. 
Among the highest capacity troughed belt conveyors in the 
world are mounted on mobile bucket wheel reclaimers in 
Europe. While these conveyors are relatively short 
(approximately 100 m pulley centre distance) the belts measure 
up to 3.0 m wide and travel at 8 m/s. The peak design capacity 
of these conveyors is up to 25 000 m3/hour and material lump 
size ranges up to 1.0 m particle diameter. 
 
Conveyor Selection Guide 
 
Choosing the correct 
type of the conveyor 
for any given 
application depends 
on a number of 
factors including 
material 
characteristics, 
conveyor system 
layout, duty, 
environment, etc. 
 
The following graph 
has been developed 
to assist learners with 
the selection of the 
correct type of belt 
conveyor system. This 
graph is intended for 
use as a guide only 
and Users would be 
well advised to 
approach suppliers of 
these conveyor 
systems in order to 
confirm whether the 
preferred type of 
conveyor is 
appropriate. 
 
 
 
Anatomy of a Troughed Belt Conveyor 
 
There are many possible variations in the design of a troughed belt conveyor depending on the 
purpose and duty for which the conveyor is being designed. Similarly the choice of individual 
components, features and accessories found on a conveyor should be selected on the basis of the 
functions which have to be performed by the conveyor. 
At this point in the Beginners Guide the learner is introduced to the different components and basic 
arrangement andfeatures which are found on the majority of troughed belt conveyors throughout 
the world. 
In this section a graphic image of a typical troughed belt conveyor is provided together with detailed 
images and photographs of specific components. The learner should also study the nomenclature 
and terms used by engineers and designers when describing troughed belt conveyors.