Energy chains or motor cable drums?

Whenever design engineers have to guide hoses and power and data cables
in moving applications with long travels (more than 100 metres), the question
arises about which energy supply system is the most efficient, especially
considering such factors as reliability, maintainability, and future security. Would
it be a motor cable drum or an energy chain?

The advantages and disadvantages of the two systems are explained below:

The motor cable drum

A proven energy supply that has been in use for decades in applications
such as cranes, transfer carriages, and the bulk material industry, the motor
cable drum is – in its simplest form – like a garden hose reel. When a gantry
crane, for example, moves back and forth on its four supports, the cable is
deposited on a prepared surface on the ground and is rolled back up on a drum
mounted on one of the supports.

There are several variants for retracting the cable. In addition to
motorised drums, there are designs for shorter travels that work with spring
force: the rolling action is normally either cylindrical or spiral rolling. In
the cylindrical form, also called broad rolling, the cable first rolls up from
left to right along the drum body. Then it rolls up vertically, layer by layer.
Spiral rolling works differently. The cable is stacked immediately after the
first rotation.

The market for cable drums is growing. A key region is North America,
and one reason is because the demand for cranes in the northern United States
is rising. Another booming region is the Asia-Pacific, especially China and
Japan. Among the reasons for this are urbanisation and a flourishing
construction industry. According to the Persistence Market Research institute, the
global market volume will be more than $3.4 billion in 2026.

The energy chain

An alternative for guiding cables on cranes, handling portals, or
stackers/reclaimers, the energy chain is a mobile protective cage. It consists
of parallel side links that are connected with crossbars along the top and
bottom of the carrier. When the system moves, the chain folds, and the upper
run glides on the lower run. No motor is required; the chain is attached to the
crane’s boom, for example, and moves with the movement of the crane.

Like the cable reel, the energy chain has been well-tried. Inventor
Gilbert Waninger launched the chain in 1953. At the time, it was entirely made
of steel, but today’s manufacturers are more flexible. Since 1969, companies
have developed high-performance plastics that can be used under a wide variety
of environmental conditions – constant contact with salt water and heat in
metal works, for example.

Energy chain Vs motor cable drum

Round 1: Installation space and
weight

Energy chains generally have weight advantages for long travels. If the
chain folds, the upper and lower run reach a height of around 800mm, depending
on filling and chain series. This makes them compact. Motorised cable drums
operate differently. They do not require guide troughs, saving space on the
user’s travel path. But in many applications, their drums have diameters of
6,000mm or more. If this space is not available, the cable drum cannot be used
as a solution. Another disadvantage of drums is that they are relatively heavy.
This makes systems heavier and lowers their energy efficiency. The crane’s
structure must also be designed for this additional load. Sample calculation:
for a travel of 400 metres in length and a cable weight of 10 kg/m, the
additional weight of the rolled-up cable is about 4 t. Then there is the
weight of the drum, the steel structure, and the drive technology. Energy
chains made of high-performance polymers, on the other hand, are much lighter
and contribute to energy savings. No additional load must be calculated on the
crane.

Round 2: Assembly

Motor cable drums may have an advantage in this round, since their
functionality is very simple. It is just as easy and fast to assemble the
drums. Energy chains are also relatively quick to assemble, especially when
users order the system with cables and plug-in connectors so that it is ready
to connect. However, only qualified technicians should carry out the assembly.
For long travels, a guide trough is obligatory for gliding applications (when
the upper run lies on the lower run), and an energy chain riser guard or an
enclosure that protects the system from weather may be recommended as
necessary. This allows safe operation under any weather conditions.

Round 3: Cable protection

The task of motor cable drums and energy chains is to protect moving
cables and hoses from mechanical loads. The chain comes out ahead here, since
it guides cables and hoses safely through the interior separation and relieves
strain at the fixed and moving ends. They are subjected to neither tensile
forces nor high mechanical loads during movement. Moreover, some
high-performance polymers have vibration-damping properties. The cables and
hoses are protected from wear along their entire length. Motorised cable drums
operate differently. There is a constant tensile force during rolling and
unrolling so that the cable experiences a greater load, reducing its service
life.

Round 4: Wear and maintenance

Motor cable drum manufacturers now have corrosion largely under control.
But in extreme environments, such as offshore facilities, rust can force
operators to intensively maintain or replace their motorised drums over the
course of the years. Bearings and the slip ring body are the elements that are
especially affected by corrosion and wear. At worst, this can cause long,
expensive system downtime. Then there is occasional maintenance work for guide
elements, clamp connections, and motor and switch deflectors. This means that
operating motor cable drums involves time and expenditure. Energy chains operate
differently. High-performance polymer variants are resistant to chemicals, salt
water, and UV radiation. The result is that, in some applications, energy
chains can be operated for almost ten years with hardly any maintenance.

Round 5: Combinability and extendibility

Transmitting energy and data via motor cable drums requires either
different drums or expensive special cables. If additional fibre optic cables
or hoses for supplying air, water, or oil must be moved, additional drums and
components are indispensable. Energy chains, on the other hand, accommodate the
use of a wide variety of cables and hoses in a single system from the very
beginning. In order to react flexibly to technological trends, they allow easy
addition of other cables if reserve space is set aside from the beginning of
operation. This is not true of motor cable drums: it is very difficult to add
hoses or cables later on. To do so, the operator needs either a special design
or additional drums.

Round 6: Compatibility with
Industry 4.0

In the Industry 4.0 era, more and more users are integrating machines
and systems into the Internet of Things in order to digitise processes. This
enables systems to autonomously call attention to a problem. Energy chains come
out ahead here. Manufacturers have begun equipping energy chains with break
detection systems and push/pull force systems. Anomalies in set parameters,
such as those caused by breakage in a chain link or blockage in the energy
chain run, can activate emergency stop systems or trigger maintenance missions
in good time – before expensive system failure.

Round 7: Operation and speed

Today, industry everywhere requires faster turnaround times, which
necessitates faster and faster travel speeds for moving equipment. A system
with motor cable drums can achieve average travel speeds of up to 120 m/min (up
to 300 m/min with limitations). An energy chain system with integrated rollers
in the chain link can reach travel speeds of 600 m/min – constant across
the entire distance. Systems with motor cable drums must brake when they reach
or pass infeed points so that the cable can be properly rolled up or deflected.

Conclusion

So which energy supply system comes out ahead? Energy chain or motor
cable drum? There is no blanket answer because, in the industrial world, no two
applications have exactly the same conditions. Different elements are weighted
differently. Some points favour the motor cable drum – among these are its
simple assembly. Others, such as cable protection, largely maintenance-free
operation, and the extendibility, favour the energy chain.

Treotham offers a large range of lubrication-free igus energy chains for
a variety of applications and industries.

For more information, please visit the Treotham Automation website www.treotham.com.au or call 1300 65 75
64.

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