Kosti Koivisto
CONVEYOR ENGINEERING
Kosti Koivisto
CONVEYOR ENGINEERING
English translation by
Juhani Kuusilehto and Keith O'Hiobhaird
www.kostikoivisto.com
© Kosti Koivisto 2018
Publisher: BoD – Books on Demand, Helsinki, Finland
Manufacturer: BoD – Books on Demand, Norderstedt, Germany
ISBN: 978-952-801-298-6
CONTENTS
PREFACE 7
CHAIN (SCRAPER) CONVEYOR
Common qualities 9
Main components 11
Chain conveyor design 22
Examples and drawings 33
SCREW CONVEYOR 62
Common qualities 62
Main components 65
Screw conveyor design 70
Examples and drawings 82
ELEVATOR 106
Common qualities 106
Main components 107
Elevator design 115
Examples and drawings 125
BELT CONVEYOR 148
Common qualities 148
Main components 150
Belt conveyor design 156
Examples and drawings 171
LOCKER CONVEYOR 192
Common qualities 192
Main components 192
Locker conveyor design 199
Examples and drawings 206
7
PREFACE
Solid material conveyors have always had a very signi›cant role in industry. In pow-
er plants, conveyors are needed to transport solid fuel to warehouses and further from
warehouses to boilers. In the feed industry, corn is re›ned into animal feed, our, malt
and so on by transporting raw material from one re›nery to another. In the mining in-
dustry, long and effective conveyors are needed for the transport of ore. In the process
industry, the re›ning of solid materials into ready-made products is predominantly car-
ried out with the help of conveyors.
Even though the role of conveyors in industry is signi›cant, there is not enough com-
prehensive literature with clear design instructions on this topic. When I was study-
ing engineering, the syllabus included only very limited instruction in conveyor design.
When later I became lecturer of engineering in Technical College, the situation was al-
most the same. Later, I established a company which designed and manufactured con-
veyors, and I was a designer there. At the same time, I lectured at the University of Ap-
plied Sciences.
Now, with 20 years’ experience as a lecturer and 25 years’ experience as a designer, I
have written this book. The book covers the following conveyor types: chain conveyors,
screw conveyors, elevators, belt conveyors and locker belt conveyors. The book exam-
ines the utilization of solid material conveyors, their construction and operation with a
focus on design, including dimensioning instructions. Additionally, it includes practical
examples for every conveyor. These examples further deal with conventional capacity
and power calculations as well as strength analysis and dimensioning of axles, bear-
ings, belts, chains and chain wheels. Assembly- and detail drawings are also present-
ed for several of the examples.
The book is intended primarily for engineer level designers, as quite a few engineers
work at conveyor design jobs.
My hope is also that conveyor design would be more broadly included in the curriculum
of engineering students. This would be of great relief to employers, who nowadays, al-
most without exception, are forced to train young novice engineers in this area.
Lahti, Finland May 21st, 2018
Kosti Koivisto
8
9
CHAIN CONVEYOR
COMMON QUALITIES
Chain conveyors are mainly used for the movement of bulk materials, e.g. powder and
granular materials. In the fertilizer and malt industry, chain conveyors are widely used.
Similarly, in the food industry, such as in mills, chain conveyors are useful. They are
suitable also for the transport of materials of relatively small grain size like wood chips,
sand and ash in power plants and for transport of various materials in the chemical pro-
cess industry. The chain conveyor is not suitable for the movement of sticky, adhesive
or clumpy materials.
A chain conveyor is used for medium distance material movement. Transport distanc-
es are from a few meters to several tens of meters. Conveyor elevation angle can be,
depending on material uidity, as high as 30–40 degrees. For elevation angles over 40
degrees, special scraper constructions are needed. The conveyor is also known as a
scraper conveyor or simply chain conveyor.
A chain conveyor’s best feature, compared to, for instance, a belt conveyor, is its tight
construction, which is a signi›cant advantage in the transport of dusty materials. Trans-
port of materials takes place by dragging with a chain and scrapers attached to it.
Thus, friction between construction parts has great signi›cance in choosing the mate-
rials rubbing each other and in dimensioning dynamic parts and especially when cal-
culating need of power.
The need of power is signi›cantly higher than belt conveyors, because in belt convey-
ors, the belt transporting material runs on rolls equipped with effective bearings. The
sliding friction of the chain conveyor is many times higher than the rolling friction of
bearings.
Physical properties, like particle size, density, uidity and stickiness of the transport-
ed material has essential signi›cance in designing the conveyor. To minimize noise
and friction, materials of low friction are used in moving parts. In the same way, clean-
ing scrapers can be made from plastic, especially in the food industry. PE-plastic pan-
els can be used to cover the whole bottom part. Wear rails and plates are attached by
screws, so that they are easily replaceable.
A chain conveyor is suitable for middle distance transport, for several tens of meters, nor-
mally for horizontal transportation or elevation angles < 40 degrees. It is best for powdery
and granular material like grain, our, malt, woodchips, sawdust and splints etc.
10
Picture 1. Dimensioning drawing of basic chain conveyor.
11
In picture 1 there is a dimensioned drawing for a simple basic mono chain conveyor,
which easily shows the conveyor’s construction and operation. The dimensioned draw-
ing can be used in offer/tender calculations and in the beginning of the actual design.
When transported material and needed capacity is known, by using the table in pic 1,
can choose the basic dimensions for the conveyor and start designing.
MAIN COMPONENTS OF CONVEYOR
FRAME
The frame consists of the axle housing in drive end and housings in the middle and
folding end housing. The frame has a panel construction and is airtight. The aim is to
make it partly self-supporting. Support brackets are nevertheless needed, especially
for long conveyors, so compromises must be made with self-supporting.
Picture 2. Jam detector in conveyor’s driving end.
12
The material for housing constructions is usually structural steels S235 and S355.
Often, in the food industry, stainless steel or acid-proof steels like Aisi304 or Aisi316
are used.
It is worth it to dimension the conveyor housings and especially housings in the middle
so that standard sizes of plates can be used. For instance, 3 m plate length is optimum
for design and handling of the housings.
DRIVE MECHANISM
The driving mechanism is installed in the drive end. A combination of AC motor and
gearing is normally chosen as driving mechanism. Here, the electric motor is compact-
ly attached to the gearbox with a ange mounting. Most often, an alternating current
motor is used where a bush ring axle is the secondary axle. This type of gear motor is
easy to mount to the driving axle of the chain conveyor. In addition, it is easy to ser-
vice. otation speed can be controlled with a recti›er if needed. In the gearbox, there
is a so called torque ›tting, from which the gearbox is supported to the corresponding
torque ›tting in the conveyor. The torque ›tting must hold the forces caused by the ax-
ial torque forces from the gearbox.
On both sides of the gearbox torque ›ttings, rubber cushions are mounted, to absorb
jerks or shocks, especially in connection to the start up of the conveyor. Also, during
running, there are small jerks because of the polygon shape of the chain gear.
Torque ›tting in the frame must be designed carefully to avoid possible bending and
deformation. The forces caused by torque from the gearbox are directed to frame con-
structions through the torque ›tting. One should not minimize material thickness.
A separate electric motor and gearbox can also be used with a v-belt or chain drive. On
the other hand this combination requires more service and a v-belt drive has its own
risks. Not recommended.
When choosing the electric motor, one must consider the protective system against ›re
if the transported material is very dusty.
ubber absorbers for torque ›ttings and robust plate construction of torque ›ttings can
be seen in the drive end housing. In addition, it is useful to take the whole support of
the axle housing in the drive end into consideration already in the design phase (pic 3).
The drive end housing must be designed so no shelves are formed at the front end
of the housing, where transported material could accumulate. An ample-sized hole is
made in the bottom plate for outlet.
From a manhole attached with protective netting, one can inspect the running of the
material and carry out service measures. Protective netting must be installed so that
it cannot be opened without extra tools. A jam guard is installed in the front wall of the
housing.
13
Picture 3. Driving end, outlet opening, gear motor and moment support with rubber cushions.
Picture 4. Folding end housing, trimming plate, trimmings screw and collar step bearing.
14
In the folding end housing for controlling the tightness of the chain, trimming plates and
screws and bearing units are attached to trimming plates, axle and chain wheel. The
manhole with protective netting should be installed at the folding end cover.
CHAIN WHEELS AND CHAINS
Chain wheel(s) in the drive end are best fastened to the axle with a shaft key. Light and
short chain conveyors are made as mono chain and demanding and long conveyors
with double chains, depending mostly on capacity and on properties of the transport-
ed material.
In the drive end, a gear wheel is used as chain wheel, which converts torque from the
drive axle to the chain as the force which transports material further.
In design, it is recommended to consider a few aspects affecting choice of chain wheel.
Chain pitch affects considerably on weight. The longer the pitch, the lighter is the
chain, and this in turn reduces power required from the motor. One should notice that
the number of teeth in the chain wheel affects the size of the chain wheel ›rst and sec-
ondly the height of the frame housing. On the other hand, the lower the number of
teeth, the more uneven is the running of the chain because the chain wheel is polygo-
nal.The chain does not follow the reference circle but runs at an angle.
The chain wheel can be manufactured as one piece or be divided into two pieces. A di-
vided chain wheel is more expensive to manufacture but replacing it is easier, because
you don’t have to dismantle the axle. It is enough to open the cover from the end hous-
ing and loosen the bolts that hold the chain wheel halves together.
The chain wheel can also be made as a so-called half-tooth, when for instance, a chain
wheel with 6,5 teeth has 13 teeth spaces. There is always one tooth space between
every chain bushing.
Because the number of teeth spaces is uneven, the chain bushing touches teeth spac-
es only on every second round. Thus, wear on the chain wheel is less severe and op-
erating life can even double.
The chain wheel in the drive end is connected to an axle, either with an axle key or
with an adapter sleeve. In the key joint fastening axle, key piece and polar is checked
according to surface pressure and key piece still according to cutting. When using an
adapter sleeve, pay attention that movement of torque is based on friction.
The chain wheel in the folding end does not necessarily need a gear, because its func-
tion is only to guide the running of the chain. A so-called disk wheel is enough to guide
the running of the chain.
The chain is tightened via trimming tabs/screws, fastened to the folding end.
15
INTERMEDIATE BOTTOM, LOADING- AND UNLOADING HOPPERS
Mostly material is transported from point A to point B. In these cases, a feeding hop-
per is placed at the folding end in front of the chain wheel, where material is dropped
through the return chain to the bottom and from here, the chain below moves materi-
al to the outlet hopper, which is of course placed at the driving end. In these cases, an
intermediate oor is not needed.
If material is fed to the conveyor from several points and out from several points, an
intermediate oor is needed, along which an upper chain moves material towards the
folding end. In this type of case, the lower chain transfers material to outlet hoppers.
Depending on the process ow, there can be several outlet hoppers.
When there are several inlet and outlet hoppers, so that materials are fed and removed
from the conveyor in several places, but because of process ow factors, not always
from the same places, openings can be installed with electric or pneumatic closing
devices.
AXLES, BEARINGS AND SEALS
The drive end axle must withstand torque from the driving motor and bending moment
caused by the chain force transporting the load.
A collar step bearing unit is normally used as the bearing, or, in more demanding plac-
es a pedestal bearing and ball bearing or cylinder bearing. Normally, material is trans-
ported only on the bottom plate, thus the lower chain transports material and the upper
chain works as an empty return chain. There is no torque in the folding end axle, only
friction force caused by the returning chain, so there are hardly any forces affecting the
axle, so bearings can be considerably smaller than in the driving end.
If there are several inlet and outlet openings, an intermediate oor is needed, on which
the upper chain transports material to the folding end and drops it before the folding
wheel on the bottom plate. In this case, bending force caused by drag force from the
upper chain affects the axle in the folding end and it can be considerable.
When considering sealing the axle inlet, the harmful properties of dusty material must
be considered. Seals are normally tape seals, which are easy to service. Circular radi-
al seals are dif›cult to change, because it requires considerable dismantling measures.
16
Picture 5. Hub types of single and two-parts chain wheels and their marking principle.
17
Picture 6. Chain wheel’s reference diameters by teeth count and hub lengths.
18
Picture 7. Basic chain types and measurements table.
Although use of conveyors in industry is signi›cant, good and comprehensive literature
from the topic is not available.
Now based on 20 years of teaching experience and 25 years of conveyor designer ex-
perience I have written the book. In the book following conveyors are covered: chain
conveyor, screw conveyor, elevator, belt conveyor and locker belt conveyor. In the
book is explained use of bulk material conveyors, structures, operation, and as main
topic design with calculation guidelines and in addition there is practical examples from
every conveyor. In design and examples are included in addition to normal capacity
and power calculations also structural design and dimensioning of axles and bearings
and belts, chains, chain wheels and so on. From some of the examples also assembly
drawings and technical drawings are made.
The book is written primarily to engineer level designers and in general to conveyor
manufacturing companies. The book is also suitable for mechanical engineer students.
