Page 47 - Market Analysis Report of Optical Communications Field in China & Global market 2020

For the communication pipeline trench excavated
separately, it is easy to cause the pipeline laying to be wavy Air blowing lubrication differs from traditional cable
and serpentine in the section with high groundwater level lubrication. The traditional lubrication is to pass the cable
as the field environment is complex, thus affecting the air through a sponge container full of lubricant (using the
blowing distance. Although the large pipeline diameter traction technology). However, cables with lubricant will
can offset some micro-bending caused by uneven trench make the air blower’s driving wheel or belt slip. When
bottom, too large pipeline diameter will increase the cables enter the air blower’s pressure chamber, most of
cost, so high laying quality of pipeline is essential for the the lubricant will be wiped off or blown away. Although
construction of air blowing cable laying. sponge balls can be placed behind the lubricant to push
it through the pipe, only front pipes can be properly
3. Coefficient of Internal Friction of Pipeline lubricated. Moreover, excessive lubricant can cause viscous
The friction between pipeline and cable will affect the resistance in pipes due to the residual lubricant. Meanwhile,
air blowing laying, so adding lubricant to pipeline is also sponge balls are likely to get stuck in the pipe if they are
the key of air blowing laying. The air blowing effect of too large. It is extremely important to use sponge balls of
different lubricants is different, so it is very important to the correct size and material. Therefore, during pipe run-
select the proper lubricant. In most cases, lubricants are through, operators must first run through the pipe before
used to reduce friction between cable and pipeline. There air blowing. This marks the successful completion of early-
are two different friction values, namely fluid friction and stage work for the air blowing laying and lays a solid
boundary friction. foundation for the air blowing work that will start soon.
With the air blowing cable laying technology, we need
Fluid friction or “thick film friction” mainly acts to the to ensure the laying quality of pipelines in all respects,
low tension area of pipeline, which is consistent with air reasonably select pipes, and reduce the friction coefficient
blowing. Under these conditions, the cable actually floats of pipeline inner. This will greatly promote air blowing
on the thick film of lubricant. The viscosity of lubricant construction.
plays a vital role in fluid friction, so it is preferred to use
the lubricant of low viscosity and make the lubricating III. Construction Cases of Air Blowing Cable
layer as thin as possible. Another method to minimize Laying
friction is to increase the effective distance between cables 1. Project Overview
and/or pipelines by adding more slots to the pipelines Fujian primary trunk of China Telecom has adopted YOFC
and cables (excessive lubricant can be squeezed into such GYTS04-144B1.2 nylon-shielded 144-core cable with an
slots). The fluid friction grows as the cable laying speed outer diameter of 21.5 mm, and 211 reels of cables for a
increases. We can see that friction always plays a dominant total distance of 706 km have been produced under the
role at a very high laying speed. contract.

When the positive cable-pipe pressure is high, or when the 2. Onsite Conditions
“thick film friction” is sufficiently small, the friction effect 40/33 silicon core pipes allowing air blowing cables are
of the boundary or the “thin film” becomes important. already laid along the entire Beijing-Taipei Expressway
These factors are reflected in high tension areas and on across Fujian Province from the south of Pucheng
curved pipes. Under higher lateral pressure, the lubricating County to Longyan City, and five project teams from two
layer is destroyed and fails. For this reason, the lubricant construction companies were performing air blowing with
needs to be optimized to adapt to the two types of friction. Plumett equipment and domestic equipment.
When the air blowing technology is used, it is crucial to
keep the positive pressure at a sufficiently low level and Fig 2
minimize the fluid friction.

The lubricant needs not only the best initial friction
coefficient, but also to maintain its properties during cable
laying. It must remain valid as time elapses. As we demand,
the lubricant must maintain its properties for a long period
to allow future removal of cables from the pipeline or
meeting the “lubricating before cable laying” requirement.
First, the lubricant should be firmly absorbed on pipelines
and cables, instead of being easily wiped off. Second, the
lubricant can be easily applied and spread along pipelines
and/or cables. Finally, during air blowing, the lubricant
must not foam in pipelines. As mentioned above, we 3. Construction Process
can identify the quality of lubricants through some tests. The organization of construction personnel at the air
Lubricant reduces not only the friction coefficient between blowing site includes 1 manager responsible for the onsite
cables and pipelines but also the electrostatic charges in project (assigned by each engineering bureau), 1 supervisor
cables. continuing to page 45
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