The resources of underground pipe holes are tight, and the air blowing micro cable is not fragrant?

1   Preface

Micro cable is a kind of ordinary pipeline optical cable with cable diameter less than the same capacity （ hereinafter referred to as “ Common cable ”）1/2 Special optical cables . Because the cable diameter is relatively fine 、 Mechanical properties a Bad , Micro cables cannot be laid manually , It can only be placed in a microtubule with an outer diameter slightly larger than the micro cable by air blowing .

At present , Whether it is trunk line or metropolitan area network , Underground pipe hole resources are very tight . Compared with ordinary cable , Use air blowing Micro cable , It can save the resources of the pipe hole near 50%. that , Is the air blown micro cable technology worth popularizing ？

2   Brief introduction of air blown micro cable technology

2.1 Micro cable

The common structures of micro cables are central tube type and layer twisted type . The central tube micro cable has good temperature characteristics , But the maximum number of cores is only 24 core , The common type is GYCFXTY.

  The maximum number of cores of layer twisted micro cable can reach 576 core , Its temperature characteristics are poor , When blowing for a long distance , A certain length shall be reserved at the beginning and end of each air blowing section to adapt to the change of cable length caused by temperature . The sheath of layer twisted micro cable is thin , If filling structure is adopted , The micro cable is stored for a long time , The ointment may leak out and affect the air blowing effect ; therefore , Layer stranded micro cables usually adopt dry or semi dry structure , The type is GCYFY.

Micro cable and common cable with common core number （ With GYTA Take optical cable as an example ） The ratio of outer diameter to cross-sectional area of is shown in the following table .

  The allowable stretching force of optical cable is generally proportional to the cross-sectional area of optical cable , so , There is a large gap between the allowable stretching force of micro cable and the ratio of common cable . Long term of micro cable / The short-term allowable flattening force is 150N/450N, Not enough common cable （ long-term / The short-term allowable flattening force is 300N/1000N） Half of .

2.2 tiny tube

Microtubules are round , The maximum outer diameter is not greater than 16mm, Soft plastic pipe . Microtubules are made of silicon plastic composites , The tube is usually of a striking color . The outer wall of microtubules is generally High density polyethylene (HDPE), The inner wall is a permanent solid lubrication layer （ Silicon core ）, The inner wall can be equipped with a diversion groove .

  According to different laying methods , Microtubules are divided into ordinary type and reinforced type . The wall of common microtubules is thin , It is mainly used for air blowing in the existing silicon core pipe , It can also be manually placed in the tube hole without optical cable .

  The wall thickness of reinforced microtubules is thicker , It is suitable for occasions with high requirements for resistance to tension or pressure , Such as ： Lay in the tube hole of the existing optical cable , Or protect the micro cable in the handhole .

  The applicable microtubule specifications for micro cables with different outer diameters are shown in the table below .

Optical cable type and number of cores		Outside diameter mm	Applicable microtubule specifications
			Ordinary type	Reinforced
Central tube	6、12	2.3	5/3.5	7/3.5
	24	2.6
Layer stranding	12、24、36	4.5	8/6	12/10
	72	5.4	10/8
	96	6.1
	144～216	7.9	12/10	14/10

The newly-built microtubule pipeline generally adopts cluster pipe , Cluster tube is also known as “ Pipe cable ”, Generally, it contains one or more Root microtubules of the same specification and different colors . The outer sheath of the bundle tube is generally HDPE texture of material , The whole body is a certain solid color .

  At present , Cluster pipes are widely used in communication pipelines along some domestic highways , Commonly used cluster tubes contain 7 root 12/9 microtubule .

2.3 Air blowing micro cable

The air blown micro cable uses mechanical thrusters to push the micro cable into the microtubule , At the same time, the air compressor sends a strong air flow into the microtubule , The high-speed flowing gas in the microtubule forms a forward thrust on the surface of the optical cable , Push the optical cable forward , The maximum section length of one-time air blowing can reach 1000 Meters above . The same is true for air blowing microtubules in silicon core tubes .

3 Blow The influence of micro cable on the capacity of pipe hole

3.1 Main line

The main pipeline usually adopts 40/33 Silicon core tube , Each silicon core tube Blown with air Way to lay a common cable . If micro cable is used , Can be in 40/33 Blow into the silicon core tube first 4 root 12/10 or 5 root 12/8 microtubule , Each microtubule can be air blown 1 Micro cable . Even after it has been laid 1 In the silicon core tube of a common cable , You can also blow air into at least 1 Root microtubule . Using micro cable technology can make the trunk The capacity of the pipe （ Number of optical cables ） increase 1 More than times .

 

3.2 Metropolitan Area The Conduit

The inner diameter of the pipe hole of the metropolitan pipeline is 32mm Of Seven hole plum blossom tube （ hereinafter referred to as “ Plum blossom tube ”） And the inner diameter is 100mm Of Single hole Plastic pipe （ hereinafter referred to as “ Single hole pipe ”）. Common cables with different cable diameters can be arranged in a sub hole of the plum blossom tube 1～3 root , Each plum blossom tube can be used to lay ordinary cables with various outer diameters 10 More than .

  Through different specifications Combination of microtubules , Multiple microtubules can be manually arranged in a sub hole of the plum blossom tube . Due to the large number of cores of optical fiber ribbon cable is not suitable for micro cable structure , therefore , The plum blossom tube needs to be left with part of the tube hole cloth to enlarge the number of cores of the optical fiber belt and optical cable . Taken together , When mainly laying micro cables , Each plum blossom tube can be used to lay micro cables and general cables 20 strip above .

  Single hole pipe Put it on the cloth optical cable The sub pipes should be laid before , If the sub pipe adopts 40/33 Silicon core tube , be 1 root The single hole tube can be used to lay about 10 strip , Or lay micro cables and general cables for about 20 strip .

  In practical engineering , In order to increase the number of ordinary cables laid in a single hole pipe , Single hole Inside the tube Go to Lay the common cable directly without laying the sub pipe , such , A single hole tube The number of ordinary cables laid inside can be reach 20 More than . But in this case , Because many common cables are intertwined in the pipe hole , It is easy to cause damage to the sheath of the general cable when laying , And it is not convenient to replace the common cable , It is not comparable with air blown micro cable .

so , In comparable cases , In the city Micro tubes are manually arranged in the pipeline , Blow the micro cable through the microtubule , The capacity of the pipe hole can be increased by nearly 1 times .

4  Micro cable And The cost of common cable is relatively

4.1  The main pipeline is laid

Main line stay When the pipe hole resources are insufficient , If air blowing microtubule is not used for capacity expansion , You need to re select the route and build the pipeline . The construction cost of trunk pipeline is as high as 7 Ten thousand yuan ～10 Ten thousand yuan / km （3 Silicon core tube ）, And the expansion cost of using air blown microtubule Technology （ The cost of air blown microtubule and micro cable minus the cost of common cable with the same number of cores ） Not enough 2000 element / km . therefore , Using air blown micro cables to expand the capacity of trunk pipelines has remarkable Of advantage .

4.2 Metropolitan Area Lay in the pipe

The cost of micro cable and general cable mainly considers the occupation cost of pipe hole and the construction cost of optical cable . In many cities , Communication tube holes are obtained by purchasing , The purchase price of each plum blossom tube is about 4 ten thousand element / km ～10 Ten thousand yuan / km , If each plum blossom tube can be laid at most 10 Calculation of optical cables , Then the pipe hole occupation cost of each optical cable is ：4000 element / A kilometer ～10000 element / A kilometer . Put with cloth 48 Take core optical cable as an example , See the following table for the unit cost of laying micro cables and ordinary cables in Metro pipelines （ The cost of optical cable construction is based on a province in the East 2020 Pipeline engineering build Price standard estimation ）.

Type of optical cable	Micro cable	Common cable
Company	element / A kilometer
Pipe hole occupation cost	2000～5000	4000～10000
Optical cable construction cost	9450	7500
Subtotal of cost	11450～13450	11500～17500

Because it is not included in centralized procurement , The unit price of micro cable is higher than that of ordinary cable , And before laying the micro cable, the micro tube should be laid , This leads to the construction cost of micro cable is higher than that of ordinary cable . After comprehensively considering the occupation cost of pipe holes , The cost of micro cable is generally lower than that of ordinary cable , Especially in some metro networks with high pipeline construction or purchase cost , The cost advantage of micro cable is more obvious .

5 At the end

In terms of cost , Air blown micro cables have great advantages in trunk lines . In some highway supporting pipelines, due to the use of cluster pipes , Micro cable has also become an inevitable choice .

Although in the Metro pipeline, micro cable also has a certain cost advantage over conventional cable , However, the construction unit is required to have cable blowing equipment ; in addition , Due to the poor mechanical properties of micro cables , Its safety is tested in the handhole ; This also leads to the current air blown micro cable in Metropolitan Area The utilization rate in the pipeline is low . However, the use of air blown micro cables can be reduced several times , Multiply the capacity of the pipe hole , As labor costs rise 、 Pipe hole resources More and more The more scarce , Air blowing micro cable Of The advantages are becoming more and more obvious .

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chart / writing ： Old Ding tou ;      Review ： Shu Yongji     

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