Helix deltaT version 6.0.22 onwards has the capability to
design Pipe Conveyors. In a Pipe Conveyor, the belt is formed into a circular
tube which fully encloses the conveyed material. The conveyor belt is an open
trough under the loading chute and it is trained and formed into an enclosed tube for
the length of the conveyor until it is once again opened to a troughed shape at the discharge
pulley.
Download an example report of a Pipe Conveyor modeled in the Helix deltaT6 Conveyor Design Program:
Demo 22 Existing PipeConveyor PC01 Coal 1000tph 4km Helix delta T6 Design Report.pdf
In Helix deltaT6 a Pipe Conveyor is denoted by selecting or inputting 6 Roll Idlers and a 360 degree Troughing Angle.
A typical Pipe Conveyor crosssectional view. The belt is formed into a tubular shape by 6 idler rollers.
Summary of Pipe conveyor Advantages
 Conveyed Material is fully enclosed and weather protected
 Enclosing the conveyed material has environmental benefits with limited spillage
 Pipe Conveyors can generally navigate tighter (smaller radius) vertical and horizontal curves than conventional troughed conveyors
 Maximum lump size = 25% to 33% of Pipe Diameter (use lower % for high proportion of lumps)
 Maximum Loading = < 70% of load area for small lumps
 Maximum Loading = < 60% of load area for larger lumps
 Even / Constant Load Feed is required to prevent overloading
 Maximum Incline angle can be larger than for troughed conveyors, up to ~27 degrees for sluggish flowing material
 Maximum Recommended Idler rotation speed is 600  750 rpm
 Tube Fold Transition Length: Allow at least 25 to 40 x D for Folding and unfolding belt for Fabric belts (use larger value for large Pipe Dia)
 Tube Fold Transition Length: Allow at least 40 to 50 x D for Folding and unfolding belt for Steel belts (use larger value for large Pipe Dia)
Summary of Pipe conveyor Disadvantages
 Special Belt is required. The conveyor Belt must be designed for the Pipe Conveyor application and
have correct transverse stiffness for the application
 The belt must be stiff enough to be self supporting in tube form
 The belt edge sections must be flexible in the transverse direction to allow for the overlap folding
 Steel cord belts have transverse fabric layers to ensure sufficient self supporting stiffness
 Pipe Diameter (D) = Belt width / 4
 Maximum lump size = 25% to 33% of Pipe Diameter (use lower % for high proportion of lumps)
 Maximum Loading = < 70% of load area for small lumps
 Maximum Loading = < 60% of load area for larger lumps
 Material Surcharge Angle does not affect load capacity
 Even / Constant Load Feed is required to prevent overloading
 Belt Thickness affects the load area of the tube
 Maximum Incline angle can be larger than for troughed conveyors, up to ~27 degrees for sluggish flowing material
 Maximum Recommended Idler rotation speed is 600  750 rpm
 Tube Fold Transition Length: Allow at least 25 to 40 x D for Folding and unfolding belt for Fabric belts (use larger value for large Pipe Dia)
 Tube Fold Transition Length: Allow at least 40 to 50 x D for Folding and unfolding belt for Steel belts (use larger value for large Pipe Dia)
 Carry side belt resistance is normally higher than for a similar capacity troughed conveyor due to less load area availability and higher proportion
of belt mass to material conveyor material mass
 Return belt resistance is normally substantially higher than conventional troughed conveyors due to larger number of return belt rollers
(rim drag is increased)
Calculation Methods
Helix Troughed Conveyor Calculation Method
The Helix deltaT6 Program has three main methods of estimating the conveyor resistances, namely:
 ISO 5048 (DIN 22101) Method
 CEMA method

VISCO method  this method uses the rubber rheology properties to calculate the indentation resistance
of the rubber belt on the conveyor idler rollers and also calculates the material and belt flexure losses,
the idler rotation (rim drag) losses and the belt to idler scuffing losses.
These four components make up the total resistance to movement of the conveyor belt. This VISCO method is also used to
calculate conveyor resistance using Low Resistance Rubber (LRR).
The above methods have been successfully used to design many thousands of conventional troughed conveyors by Helix
users in more than 30 countries.
The VISCO method is considered to be the most flexible and most accurate method of estimating the conveyor resistance because
it allows the user to adjust multiple input values for different types of equipment which all affect the total conveyor resistance. For Example:
 The user can specify the belt top and bottom cover rubber properties.
 The user can specify the belt and material flexure factor.
 The user can specify the Idler Rotation Resistance.
 The user can specify the Idler Scuffing Resistance.
The above main resistances are all influenced by the load per m on the belt, the belt speed V, the idler spacing,
the number of rollers, the idler roll diameter, belt top and bottom cover rubber properties (indentation hysteresis losses),
the current belt tension which affects the amount of belt sag and resulting material and belt flexure losses, the accuracy of the
idler vertical and horizontal alignment.
In the Helix deltaT program, the user can adjust all of these parameters and see the effects on the conveyor.
A Sensitivity Analysis can be performed to arrive at an optimised conveyor design which will have the lowest total cost of
ownership i.e capital, maintenance and operating cost.
Helix Pipe Conveyor Calculation Method
The resistance of a Pipe Conveyor may also be broken down into four main categories, namely:
 Belt to Idler Indentation Resistance
 Material and Belt Flexure losses
 Idler Rotation (Rim Drag) Resistances
 Belt to Idler scuffing losses
1. Belt to Idler Indentation Resistance
In a Pipe Conveyor, the folded belt adds additional load on the idler rolls imparted by the stiffness of the belt.
There are also more idler rollers (normally 6 for Pipe Conveyor vs 3 for a Troughed Conveyor) and more idler face length
is in contact with the belt.
The gravitational force resulting from the mass of the material and belt is taken on the three lower idlers, as it is in a
conventional troughed belt.
The upper two wing rollers and the top centre roller also have indentation losses due to the
folding of the stiff belt into a tubular shape.
There is also a resultant force on the lower three rollers due to the belt tension in a Convex vertical curve.
In a Concave vertical curve, there is a resultant force applied to the three upper rollers due the belt tension.
In addition, the wing rollers (the two on each side of tube) must also take the
resultant force due to the tensioned belt being curved around Horizontal curves.
The belt to idler indentation forces in a Pipe Conveyor may be summarised as follows:
 Belt Folding force  on 4 side rollers and top roller
 Gravitational Forces due to belt and material mass  on bottom centre and lower wing rollers
 Convex Curve Belt Deviation Load  on bottom centre and lower wing rollers
 Concave Curve Belt Deviation Load  on top centre and upper wing rollers
 Horizontal Curve Belt Deviation Load  on lower wing and upper wing rollers on inside of curve
In the Helix deltaT6 program, when you perform a Pipe Conveyor calculation, all of these
individual indentation losses are calculated for each section of the conveyor and added to arrive
an equivalent friction factor f for indentation resistance.
The user can see the resulting proportion of conveyor resistance attributed to
Indentation, Flexure, Rolling Resistance and Belt Scuffing in the
Viscoelastic Friction Factor Report.
2. Material and Belt Flexure Resistance
In a Pipe Conveyor, as well as a Troughed Conveyor, the belt will tend to sag down to some extent
between supporting idlers under gravitational forces induced by the material and belt mass.
The pipe tube will also tend to bulge slightly between idler stations and there is a resulting
resistance loss due the flexure of the material and belt as it deforms in travelling from one
idler station to the next. The total material and belt flexure loss is a function of the belt tension,
the amount of belt sag, the resistance of the material moving / shearing (internal coefficient of
friction of the material) and amount of belt flexure resistance due to its stiffness. Estimating this
flexure loss is performed as described in the Belt and Material Flexure Calculation help topic in the Helix deltaT6 Program.
Adjusting the Material Flexure
To adjust the amount of resistance due to belt and material flexure you need to adjust the
Material Flexure Adjustment Factor input value on the Viscoelastic Belt Properties Input Form.
The default input value is set to 1.0 and this is the setting required for Iron Ore. You need to adjust this
input value to reflect the relative internal coefficient of friction of the material being transported.
For example, if it is say dry Wheat, use a factor of 0.8 or even 0.7, and if the material is very hard, sharp
angular ore or rock, use a value of say 1.1 or 1.2. The amount of flexure also depends on the amount of belt sag
and also the troughing angle of the Idlers, the sag is calculated automatically and adjusted for each section.
3. Idler Rotation Resistance
In a Pipe Conveyor, as well as a Troughed Conveyor, the idler rollers have a resistance to rotation. The amount
resistance depends on the manufacture of the idler, bearing and seal type. The actual value of the resistance can vary
considerably from idler to idler and for a pipe conveyor, due to the higher number of idler rollers, this resistance can
have a considerable effect on the total Pipe Conveyor resistance.
4. Idler Skew and Tilt Resistance
If the idler rolls are not aligned perpendicular to the belt travel direction, a scuffing resistance results.
The magnitude of this scuffing resistance depends on the amount of misalignment as well as the coefficient of
friction between the belt and idler roll. The coefficient of friction will in turn depend on whether the belt
surface is dry, wet or moist.
Pipe Conveyor Friction Factor
The conveyor resistances for each section of the conveyor are calculated using the methods shown in the Viscoelastic
calculation method as described above. The four main resistance components (Indentation, Flexure, Idler Rotation and
Skew and Tilt resistance) are then added to give a total resistance R for each section
of conveyor. This total section resistance in Newtons is then used to back calculate the Friction factor μ because
the masses and idler loads m are known.
Pipe Conveyor Friction Factor Report
The following report shows the values of each component of the conveyor resistances.
You can see from the above report that in the carry sections of the Pipe Conveyor, the total friction
factor varies in sections with no horizontal curves and increases in the curved sections.
(increases from 0.0247 in section 4 with no horizontal curve to 0.0322 in section 5 with 300m radius horizontal curve)
On the return belt sections from 26 onwards, the friction factor is higher than carry sections at about 0.045 to 0.056;
However, this does not mean the section resistance is higher in the return run because the mass is much lower as
there is no material being transported.
Resistance R is lower
on the return belt even though μ is higher because m is much lower.
Proportions of Indentation, Flexure, Idler Drag and Idler Skew (Scuffing) Losses
In the report shown above you can see the proportions of the resistances as a percentage of the total for
each section:
Carry side (Section 11)
 Indentation loss is about 53.9%
 Flexure loss is about 2.6%
 Idler Drag loss is about 38.1%
 Idler Skew loss is about 5.3%
 Total μ = 0.0345
Corresponding
Return side (Section 29)
 Indentation loss is about 35.0%
 Flexure loss is about 1.2%
 Idler Drag loss is about 60.2%
 Idler Skew loss is about 3.6%
 Total μ = 0.0513
It is clear that there is lower Flexure loss on the return run (no material) and the additional idlers
make the Idler drag losses proportionally higher on the return side than on the carry side.
Indentation losses are lower on the return run than the carry side due to no material mass.
The proportions of each resistance component can vary widely depending on the belt rubber properties, belt speed,
idler spacing and idler rim drag. The designer should explore different settings to get an optimal design.
Steps for Design of a Pipe Conveyor
In Helix deltaT6 a Pipe Conveyor
is denoted by selecting or inputting 6 Roll Idlers and a 360 degree Troughing Angle
 Build the model of the conveyor in the normal way as described in the Getting Started help topic in the Helix deltaT6 Program.
 In the Input, Input Carry Idlers form, select a suitable Pipe Conveyor Idler and ensure the Number of Rolls is set to Six (6)
 In the Input, Input Return Idlers form, select a suitable Pipe Conveyor Idler and ensure the Number of Rolls is set to Six (6)
 In the Input Belt Details form you need to select a Belt Width and the corresponding recommended Pipe Diameter of Belt Width / 4 will be displayed
 In the Idler Trough Angle dropdown, select the 360 degree option
 The belt and tube crosssection will be drawn and the percentage full etc. calculated for you
 Now you can go to the Input Carry Idlers form, press the Open Idler Database button and select a suitable idler from the
Helix Pipe Conveyor idlers category. Choose an idler for the Belt Width and Pipe Diameter you have input in Belt Details.
 The Pipe Conveyor Idlers which are in the Helix deltaT Idler Database are presented as a design
guide only. The Pipe Conveyor Idler database is derived from the Sandvik Carry idler data with the Idler Face width, Bearing Centres and
Support Centre dimensions adjusted to suit the selected Pipe Diameter. These specific idler dimensions are theorectical only,
designers must obtain real idler data from their own manufacturer for final design.
 Repeat the pipe conveyor Idler Selection process described above for the Return Idlers
 The Number of Idler Rolls must be six (6) for a Pipe Conveyor
 Now return to the to Belt Input Details form and the Belt Crosssection will be redrawn with the selected Idlers and Belt Width
 The crosssection above shows the percentage full and belt overlap length as well as the chosen idlers.
Note the idler rolls overlap each other slightly in this diagram, these are staggered idler panels with Offset idlers
 Ensure the conveyor material low and high bulk density are correct, adjust if necessary
 Adjust the belt speed to yield a pipe percentage full of less than 70% for fine material or less than
say 60% full for material with large lumps.
 The Maximum Belt speed will depend on the Idler Load and Bearing life and should be adjusted to give an idler rotation
speed of less than 600 rpm.
 There are no known published maximum belt speed limits for Pipe Conveyors, but as for Troughed conveyors,
a speed higher than about 5.0m/s is considered an upper limit, especially with 152mm diameter rollers.
Belt Speeds exceeding 5.0m/s may result in resonance problems, material shifting
in the pipe tube which can cause material bunching and force the belt to open and spill material. There are many factors which
can affect the Belt Resonance / Material Bunching phenomenon such as belt tension, belt sag, idler spacing, idler roll diameter,
idler rotation speed (belt seed) and caution should be exercised in selecting a reasonable belt speed which is not too high.
Details and videos of Belt Resonance and Material bunching are shown in the new Helix website at Helix Web: Belt Resonance
 Complete all Input Values in all the other forms in the main form Input Menu including
the Takeup, Drive and Motor Inputs etc.
 You also need to complete all the Viscoelastic Belt Input Details and the Viscoelastic Idler Input Details.
 Once all Input values have been completed, you can do the conveyor calculation using the VISCO method.
Pipe Conveyor calculations must be performed using the VISCO method. The ISO and CEMA methods will not yield correct
belt tensions and power for a Pipe Conveyor, but are included for comparison purposes only.
 Once you have completed all inputs and the VISCO calculation method, you can view all the results by using the Reports menu
 The next step for Pipe Conveyors is to check the suitability of the Vertical and Horizontal curve radii.
Use the Horizontal Curve Calculations help topic in the Helix deltaT6 Program for further explanation.
Summary of Design Guidelines for Pipe Conveyors
Pipe Conveyors have some additional features compared to conventional troughed conveyors, i.e the belt has to
be formed into a tube after the loading point and it also has to
be opened from tube to flat at the discharge pulley. These sections of the belt are called transitions;
they are similar to the Trough Transition in a conventional Troughed belt conveyor, except that the edge length
(hypotenuse) is longer as the belt goes from flat at the pulley to more than 360 degrees of closure.
 Conveyor Belt must be designed for the Pipe Conveyor application and have correct transverse stiffness for the application
 Belts can be Fabric or Steel cord reinforced
 The belt must be stiff enough to be self supporting in tube form
 The belt edge sections must be flexible in the transverse direction to allow for the overlap folding
 Steel cord belts have transverse fabric layers to ensure sufficient self supporting stiffness
 Pipe Diameter (D) = Belt width / 4
 A Larger Pipe Diameter requires an increased belt transverse stiffness to maintain the tubular shape
 A Smaller Pipe Diameter requires less belt transverse stiffness to maintain the tubular shape than a larger diameter pipe
 Maximum lump size = 25% to 33% of Pipe Diameter (use lower % for high proportion of lumps)
 Maximum Loading = < 70% of load area for small lumps
 Maximum Loading = < 60% of load area for larger lumps
 Material Surcharge Angle does not affect load capacity
 Belt Thickness affects the load area of the tube
 Even / Constant Load Feed is required to prevent overloading
 Idler Trough Angle must be set to 360 degrees for Pipe Conveyor
 The No. of Idler Rolls must be six (6) for a Pipe Conveyor
 Maximum Incline angle can be larger than for troughed conveyors, up to ~27 degrees for sluggish flowing material
 Maximum Recommended Idler rotation speed is 600  750 rpm
 Tube Fold Transition Length: Allow at least 25 to 40 x D for Folding and unfolding belt for Fabric belts (use larger value for large Pipe Dia)
 Tube Fold Transition Length: Allow at least 40 to 50 x D for Folding and unfolding belt for Steel belts (use larger value for large Pipe Dia)
 Carry side belt resistance is normally higher than for a similar capacity troughed conveyor due to less load area availability and higher proportion of belt mass to material conveyor material mass
 Return belt resistance is normally substantially higher than conventional troughed conveyors due to larger number of return belt rollers (rim drag is increased)
 The VISCO calculation method must be used Pipe Conveyors
 Check the minimum Curve Radius required for a each curve in Pipe Conveyor.
Refer to the Horizontal Curve Calculations help topic for an explanation.
The required minimum length of the transition is governed by limiting the edge tension rise and also
limiting the center tension drop which results for the edges being stretched.
Pipe Conveyors  Horizontal and Vertical Curve Calculations
Pipe Conveyor Curves
In a Pipe Conveyor curve, the portion of the belt furthest away from the centre of the curve is stretched while
the portion or half of the belt on the inside of the curve is compressed into a shorter length.
The belt is under tension and the change in tension Δ delta T is added to the outside portion of the belt and a corresponding
reduction in tension is applied to inside portion of the belt because the average tension across the belt width remains a constant.
We need to ensure that the rise in tension does not exceed the working tension of the belt and also ensure that the reduction in
tension on the inside does not force the belt into compression because it will buckle.
The Pipe Conveyor Curve Calculations must be performed for each Vertical and Horizontal curve in the pipe conveyor.
Design of curves for a Pipe Conveyor
One the main advantages of Pipe Conveyors is that they can negotiate relatively small radius Horizontal
curves when compared to conventional Troughed conveyors. Each vertical and horizontal curve in a Pipe Conveyor needs to be checked for:
 Belt Tube Outside belt tension rise  too high a tension will overstress the belt
 Belt Tube Inside belt tension fall  too low a tension will make the belt go into compression and cause tube and belt buckling
 Concave Vertical curves must have sufficient radius to ensure that the belt does not tend to lift off the lower idlers and
cause the tube to be compressed against the upper idler rollers. The belt lift is caused by the belt tension resultant force from
the change in vertical angle. This calculation is the same as for a Troughed conveyor.
 Concave and Convex vertical curves have a Belt Tube Outside (upper half) belt tension rise  too high a tension will overstress the belt
 Concave and Convex vertical curves have a Belt Tube Inside (lower half) belt tension fall  too low a tension will make the belt go into
compression and cause tube and belt buckling
The required minimum concave curve radius for belt lift off for Item no. 3 above is calculated as it is for Troughed conveyors
and is shown in the Vertical Curves Report.
For each Concave and Convex vertical curve and each Horizontal Curve in a Pipe a Conveyor, the Calculate Pipe Conveyor Curve calculation
under the main form Calcs menu must be used to check for high and low tensions in the curve. Refer to the Calcs menu shown below.
 Enter the input values for the curve under consideration. You can enter a Curve Description which
shows the location of each curve so that this description can be used to identify which curve
has been calculated.
 Enter the Belt Width and Pipe Diameter in mm
 Enter the Belt Modulus, Curve Radius and Idler Spacing
 Enter the Trough Angle. It must be 360 degrees for a pipe conveyor
 Enter the Belt Rated Working Tension in kN/m width
 Enter the Minimum Tension as a percentage of Rated Tension. Default value is 5% minimum belt tension,
less than this may result in belt buckling due to the belt going into compression
 Press the Calculate Tube Tensions button
 The program will calculate the rise in tension in the outer half of the belt.
The belt is stretched through a further distance in the outside of the curve and travels through a shorter
distance in the inside of the curve.
 Curve radius plan view here
Pipe Conveyor Curve Calculation Report  Tension too low
After doing the Pipe Conveyor Curve Calculation as described above,
you can View and Print a report for each curve in the Pipe Conveyor
Tension at inside of curve is below the minimum required tension of 15% of belt rated tension. (The 15% value is a design input value,
a minimum of at least 5% is recommended)
Pipe Conveyor Curve Calculation Form  Tension too high
Tension at outside of curve is above the rated tension of the belt.