Tubular Cable & Chain Drag Conveyors - Powder and Bulk ... · Tubular Cable & Chain Drag Conveyors . Function, Performance &Benefits . ... A conveyor inlet is created by removing

Original Release 08-2010, Updated 09-2013

1609 Airport Road Monroe NC 28110 | 704.246.0900 | spiroflowsystems.com Page | 1

Tubular Cable & Chain Drag Conveyors Function, Performance & Benefits Robert Sutton Global Product Specialist Tubular Chain/Cable Drag Conveyors Spiroflow Systems Inc.

Numerous health, safety and hygiene standards for the chemical, food and general processing industries, in

North America and Europe in particular, mandate the need for enclosed conveying systems for dry bulk solids,

additives and ingredients in whatever form – powders, granules, flakes, pellets and many others. When

considering equipment to transport finely divided, flowable bulk materials, the mechanical tubular chain/cable

drag conveyor should always be considered. This is truly a “problem solver in a pipeline” and is a concept that,

while often overlooked and by the food industry in particular, has been serving a wide range of industries for well

over 50 years.

In addition to the food and chemical industries, it has also found application in the waste water treatment,

minerals, brick-making, cement and glass industries. Design and construction can vary enormously to reflect the

demands of the duty to be performed.

Fig. 1 Section of conveyor showing chain & disc assembly



Fig. 2 Casing bends with welded steel flanges at each end allows the conveyor path to change directions

HOW IT WORKS

The tubular chain/cable drag chain conveyor is comprised of a stationary outer housing, usually round in shape,

through which a chain/cable is pulled by a sprocket. See Figs 1 and 3. Round conveying flights of a diameter

slightly smaller than the inside diameter of the casing are attached to this chain/cable assembly at fixed intervals.

As this endless chain/cable assembly is pulled through the casing by a sprocket bulk material is pushed from the

feed sources to the discharge points by the conveying flights. This process is all mechanical. No compressed

air, blower or filter system is required.

The conveying rate is established by varying the casing diameter and/or the chain/cable velocity. Conveying

capacities with this type of equipment can reach as high as 20ft3/min, which will satisfy the needs of most

processing equipment as well as the needs of general industry.

The conveyor casing (stationary outer housing) is made from carbon steel or stainless steel pipe and typically

available in 3”, 4”, 6”, 8” and 10” sizes. The casing sections are furnished in lengths up to 20 feet, as dictated by

the required conveying path, and are

supplied complete with welded steel

flanges at both ends or pipe couplings

- according to conveyor type and duty.

To allow the conveyor path to change

directions the conveyor casing is

formed into a sweep radius elbow, at

whatever angle is required, and steel

flanges are welded to each end. The

straight casing sections as well as the

casing bends can then be combine

with gaskets and bolted together in the

field to form rigid, dust tight joints.

TOTALLY ENCLOSED & DUST TIGHT The single most significant feature of this conveyor style is the enclosed construction. This conveyor operates

within the confines of a pipeline and is inherently dust tight. This design effectively contains the material being

conveyed, along with its dust, to protect the atmosphere and personnel from any adverse effects from dusting. It

also protects the bulk material from contamination from the outside atmosphere and moisture. If required, this



Fig. 3 The drive sprocket engages directly with the conveyor chain for positive movement.

equipment can be operated under a light vacuum, positive pressure or product can be conveyed under a blanket

of inert gas, such as nitrogen.

Although predominantly designed for dry materials, Tubular Chain/Cable Drag Conveyors are equally adept at

conveying moist and wet materials too. Running along the bottom of a settling tank this style of conveyor can

collect fines as they precipitate from the fluid in a tank and elevate them above the fluid level to a waiting vessel

or piece of process equipment. In the process of elevating the fines there is a natural de-watering effect, via

gravity, which could enhance the process at hand. The enclosed construction serves well in containing odors and

free moisture that may be present with some sludge and slurries.

THE CHAIN & CABLE ASSEMBLY At the heart of every tubular chain/cable drag conveyor is the chain/cable assembly, which is the single most

critical component in the system.

A chain assembly is made of a series of

links and pins. A quick examination will

indicate that the chain will readily flex with

the direction of the chain pin but this is only

partially true. A tolerance designed into

the pin and link connection points allow the

chain to rotate out of plane in any direction.

For heavy-duty applications (minerals and

cement etc), a chain assembly of the pin

and link style is the preferred mechanism

to move the flights for several reasons:

First, the sprocket meshes directly with the

chain to provide positive movement.

Friction type drives are unpredictable and

they may slip if the infeed rate surges or if

the conveyor take-up is out of adjustment. Sprockets that drive to the flights instead of the chain could develop

problems if the lug or hub of a flight shifts, thereby destroying the continuity of flight pitch and resulting in

component damage and system failure. The flights do not have adequate long-term durability to withstand the

forces normally required to operate this type of conveyor on heavy applications. It is therefore very important that

the sprocket engages directly with the chain assembly.



Fig. 4 Thousands of circuit layouts are possible

Pin and link style conveyor chains are less prone to fatigue, wear and stretch than steel ropes or ball-and-socket

style chains. As wear occurs or if an individual component is somehow damaged in a pin and link style chain

assembly, each individual part can be replaced.

Conveying flights can be made of a wide range of materials from the latest grades of UHMW polyethylene, nylon,

polyurethane or even cast iron, steel, stainless steel or aluminum. The particulars of every application will

determine the appropriate flight material.

CONVEYOR CONFIGURATIONS A virtually unlimited variation

of conveyor circuits is

possible, by virtue of the

flexible chain design, custom

casing lengths and casing

bends. These conveyors are

manufactured in modular

form with bolted flange

connections for easy erection

in the field. Figure 4 shows a

few common configurations

and there are thousands of

other variations possible.

This type of conveyor can be

installed in existing facilities

by-passing obstacles that

would interfere with the paths

of other types of conveyors.

Most commonly this type of

conveyor is used to transfer

material less than 100 ft and

involve only one or two

directional changes.

However, transfer distances

of several hundred feet are

well within the capabilities of

this conveyor style.



INLETS A conveyor inlet is created by removing a short upper half of the conveyor casing and flaring out with sheet metal

to make a hopper. Numerous inlet points can be incorporated in a single conveyor. As a general rule, material

can be flood or surge fed at these inlet points. The conveyor chain/cable assembly will fill with product as it

passes below the inlet opening. There are a few very difficult materials that will not self-feed with this style of

conveyor. In those few cases, a flow assist in the form of a vibrator, mechanical agitator or an air pad will resolve

the flow problem.

OUTLETS Free-flowing materials

A conveyor discharge is substantially identical to an inlet hopper except that its position is inverted. When the

chain and bulk material reach an opening in the casing the bulk material will flow from the chain through the

opening. Multiple discharge points can be built into a single conveyor. In such cases, if control of the discharge

point cannot be left to a simple open style discharge, then gate or butterfly valves can be used to select from

which outlet material is to be discharged. Discharge from the open bottom of the conveyor drive box housing or

idler box is not at all uncommon. The action of the conveyor chain changing direction as it runs around the drive

or the idler sprocket has a beneficial flow promotion effect.



Difficult Products

Many free flowing materials will readily flow from the conveyor casing and chain/cable assembly at a discharge

point. If it is imperative to your process that you get a complete discharge of material, if the product has sluggish

flow characteristics or is sticky, a special chain vibrator is used. This mechanism is comprised of a fractional

kilowatt/horsepower electric motor driving through a v-belt to a shaft with adjustable eccentric weights, which is

mounted on a spring plate, external of the conveyor. From this spring plate two shafts then penetrate the

conveyor housing through sealed openings to connect to a flat bar that will in turn impart a controlled, low

frequency vibration directly to the conveyor flights as they pass over a discharge to effectively induce the product

to flow from the conveyor. This mechanism is extremely effective on even the most stubborn materials.

Fig. 7 Chain Vibrator. Imparting low frequency vibration directly to the conveyors flights this motorized chain vibrator causes even the most stubborn material to

discharge from the chain assembly.



BENEFITS 1. No Segregation of Mixtures

The positive displacement action of this conveyor makes it ideal for handling blended materials without separation.

2. Gentle Conveying Action

The slow moving chain assures gentle product handling with an absolute minimal of attrition.

3. Reliable & Long Service Life

The slow moving chain, with its robust construction assures long service life, low maintenance and a very high degree of reliability.

4. Low Noise

The equipment operates at a minimal noise level. In most applications it is difficult to hear the conveyor operating.

5. Wide Temperature Range

With cast iron flights and chains, tubular chain/cable drag conveyors will not only handle materials up to 450oF, they can be used to deliver materials to furnaces and the like.

6. Low Energy Consumption

Energy consumption should be a key factor in equipment selection as the ever-rising cost of energy is a key component in the overall cost of purchasing and operating the equipment. Due to the slow-moving nature of the tubular chain/cable drag conveyor, the power requirement is very low. In many applications, when compared to less energy efficient conveyor types, this equipment can pay for itself in a short period of time based on energy savings alone. A typical tubular drag chain conveyor is operated by a single low horsepower drive motor, usually in the 1 to 5 HP range. This fact makes it one of the most energy efficient conveyors available.

Fig. 8 Three tubular chain drag units, in an outdoor setting, are shown receiving material to the top of a storage silo. The conveyor not only contains the product and its dust but at the same time it protects the material from contamination from the elements.

Fig. 9 Two tubular chain drag conveyors (in blue) traveling in a path around existing machinery & structures, a feat that cannot be accomplished by some other conveyors.



No Dust Filtration System

The tubular chain/cable drag conveyor is all mechanical and does not require the addition of any air -

compressed or otherwise. It is ideal for handling hygroscopic materials either with or without dry air or an inert

gas blanket. And because there is no air added to the system there is no need for product/air separation

equipment at the discharge points. More significantly, there is no need for an expensive bag house filtration

system and no loss of valuable or toxic material in the form of collected dust.

CUSTOM DESIGNS

As a custom design and build piece of equipment, special features can be added to the system to enhance the

operation. Examples would be water jackets to cool or heat the casing, cooling fins, pipe insulation, drains or

purge connections.

SELECTING THE CORRECT CONVEYOR

In selecting the type of conveyor best suited to your application you should consider:

• The various characteristics or qualities of the product to be conveyed.

• The performance and functional features required by the process.

• Operating features desired.

• The projected duration of the process or operation the equipment is to serve.

• The long-term energy requirements of the equipment.

Tables 1, 2 and 3 show a general comparison of different types of bulk handling conveyors. These charts are

intended to help you in your evaluation process. As with all generalizations, there are exceptions to the rules and,

accordingly, these charts are for guidance only. The final choice of conveyor must be made in conjunction with

your chosen supplier.



Table 1: Operating Features

CONVEYOR OPERATING FEATURES

Tubu

lar D

rag

Con

veyo

r

Flex

ible

Scr

ew C

onve

yor

Con

vent

iona

l Scr

ew C

onve

yor

Trou

ghed

Bel

t con

veyo

r

Cle

ated

Bel

t Con

veyo

r

En M

ass

Con

veyo

r

Buck

et E

leva

tor

Vibr

atin

g C

onve

yor

Pneu

mat

ic C

onve

yor

Aero

Mec

hani

cal C

onve

yor

Volume - High Volume - Medium Volume - Low

Variable Conveying Rate

Low Maintenance Facilities - New Facilities - Old Installation Costs - Low Installation Costs - High

Energy Consumption - Low Energy Consumption - High

Length 0 – 20 meters Length 20 – 30 meters

Length 30 – 120 meters

Length Over 120 meters



Table 2: Functional Features

CONVEYOR FUNCTIONAL FEATURES

Tubu

lar D

rag

Con

veyo

r

Flex

ible

Scr

ew C

onve

yor

Con

vent

iona

l Scr

ew C

onve

yor

Trou

ghed

Bel

t con

veyo

r

Cle

ated

Bel

t Con

veyo

r

En M

ass

Con

veyo

r

Buck

et E

leva

tor

Vibr

atin

g C

onve

yor

Pneu

mat

ic C

onve

yor

Aero

Mec

hani

cal C

onve

yor

Totally Enclosed Construction Multiple Inlets Multiple Outlets Multi-plane Path

Elevate Variable Conveying Rate

Self-cleaning Dust Tight Gentle Action (non-degrading) Pressure Tight

Self-feeding

Requires Dust Filtration System



Table 3: Bulk Material Properties

BULK MATERIAL PROPERTIES

Tubu

lar D

rag

Con

veyo

r

Flex

ible

Scr

ew C

onve

yor

Con

vent

iona

l Scr

ew C

onve

yor

Trou

ghed

Bel

t con

veyo

r

Cle

ated

Bel

t Con

veyo

r

En M

ass

Con

veyo

r

Buck

et E

leva

tor

Vibr

atin

g C

onve

yor

Pneu

mat

ic C

onve

yor

Aero

Mec

hani

cal C

onve

yor

Sludge

Slurry

Moist

Dry Hot

Cold Hygroscopic

Maintains blends

SELECTING THE SUPPLIER There is always a danger in working with companies who only offer one type of conveyor. Unless your application

is a real ‘no, no’, there is always the tendency that they will make ‘one size fit all’ and, although the conveyor may

actually perform on the application for which it was specified, it may not be the lowest cost, operationally efficient

and lowest operating cost unit that you could have purchased. So, always look for a supplier offering a wide

choice of conveyors, one with a proven track record, one that can supply references, one that has a test facility

and, above all, one that will offer a process guarantee.

CONCLUSION The totally enclosed, mechanical tubular chain/cable drag conveyor will satisfy the demands of a wide range of

bulk material handling applications. Low energy cost, low maintenance cost, easy installation, elimination of the

loss of expensive product through dusting, combine to make this conveyor economical to own and operate over

the life of the process being served. With its features and benefits this style of conveyor should be considered for

every bulk transfer project. Proper equipment selection, with due consideration to the initial costs plus the long

term operating costs, will save time and money by improving the efficiency of your operation.



ABOUT THE AUTHOR Robert Sutton has a total of 42 years in the design, manufacture, marketing and application of tubular drag

conveyors. In 1980 he started his own business Dynamet Inc based in Kalamazoo, Michigan, USA. Spiroflow

Systems Inc of Monroe, North Carolina purchased the business in 2010 as part of its strategic goal to expand its

range of conveyors for dry bulk solids. Accordingly, Spiroflow Systems offers one of the widest choices of

conveyor in the business including Flexible Screw, Aero Mechanical, Vacuum and Tubular Drag types. Robert

Sutton has been retained by Spiroflow as their Global Product Specialist for Tubular Chain/Cable Drag

Conveyors.

ABOUT SPIROFLOW SYSTEMS, INC.

Spiroflow Systems is a worldwide supplier of a wide range of both standard and custom powder handling

equipment, specializing in Bulk Bag Dischargers and Fillers, a range of Aero Mechanical, Tubular Drag, Flexible

Screw and Pneumatic Conveyors, a range of 50 lb Bag Packing and Unloading equipment and the Pacepacker

range of Automatic Packing, Pick and Place and Palletizing solutions. The company offers a wide range of

innovative designs and design options.

An in-house test facility offers a free on-site and on-line service to customers to analyze and demonstrate

material flow properties under actual operating conditions. This, in turn, sets the parameters for selecting the

most suitable handling method for your process and ensures equipment is installed properly. Any system tested

in our test facility is guaranteed.

For more information about this article, contact Spiroflow Systems, Inc. at 704-246-0900 or e-mail

[email protected]. Spiroflow can also be found on the web at: www.spiroflowsystems.com.

mailto:[email protected]

http://www.spiroflowsystems.com/

Documents

Tubular Cable & Chain Drag Conveyors - Powder and Bulk ... · Tubular Cable & Chain Drag Conveyors . Function, Performance &Benefits . ... A conveyor inlet is created by removing