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3 main factors affecting the air blowing cable length

Information Source:Henan Huadong Cable Co., Ltd Release date:2014-06-03

The quality of the pipe

We know that the gas blowing pipe of a method is called HDPE silicon core pipe, HDPE is high density polyethylene material, can withstand high-pressure air blowing of gas. If the wall will be having a low coefficient of friction of solid silicon added in the HDPE pipe, forming the low friction coefficient can be used for pipeline gas blowing cable of long distance. Mentioned above, in the pipeline not by pushing or pulling machinery for long distance laying, but formed on the fiber surface airflow through the high-speed flow drag force pushing cable forward. That is to say, the friction between the pipe and cable is small, the drag force airflow can be cable laying farther. Because the pressure is gradually decreased with the length of the pipeline, the drag force is also decreases with increasing pressure drop. So the gas blowing, on one hand the pipeline can bear high pressure pipeline is inferior, often can not bear high pressure, especially at high temperature under the action of the airflow, low pressure will make the pipeline along the longitudinal cracking. The coefficient of friction on the other hand, pipe wall with smaller, drag the thrust produced by the friction between the cable and pipeline can be overcome, the advancement of the optical cable. At present we inclined pipe plate measuring friction coefficient, minimum value can reach 0.065; the maximum value can reach 0.28, the ratio of 4.3 times the difference. This explains why the same pipelines, gas blowing effect is indeed very different. We have done a test, we first laid in a non silicon core pipe lubricating layer within the cable, blowing a length of about 650 meters, and then we apply the lubricant in the pipeline gas blowing, blowing length of 1500 meters. This shows that in the pipeline laying quality good, if the friction resistance of high pipe, it can in a short distance over flow drag force on the surface of the fiber optic cable, velocity caused by the cable end head descends, the spiral section of cable from the beginning to shorten, the friction resistance is new, finally caused enough cable failure.

Pipeline laying quality

If we only focus on the choice of pipeline, and ignore the weight of pipe laying, also won't get cable gas good blowing effect. In general we require smooth pipe ditch, trench line straight, turning radius must satisfy the pipeline laying requirements (generally 20 times the pipe diameter), field installation, the turning radius can try to enlarge the pipeline, elevation changes, should be gradual to prevent pipe length, flight. But in actual construction, due to the use of human construction, pipe trench standard and quality is difficult to meet the above requirements. Especially in the laying in one ditch, a pipeline water or marshland conditions within the trench, very easy to cause the pipeline in the groove of undulating waves, a lot of micro bend. When the high-speed airflow through the micro bend, will produce great flow attenuation. Under normal circumstances, we export pipeline in good quality can hear air whistle, but if the quality of pipe laying is very poor, we export in the pipeline 1 kilometers, almost feel the flow of air. Air attenuation will directly affect the role in the cable on the surface of the drag force, also will cause bad effects of cable. The worst blowing effect will not be more than 100 meters. In addition to the pipeline from the disc release, due to the existence of the winding disk memory pipeline will have a certain degree of bending, the pipeline can be placed first relaxation on the ground for a period of time, the memory wipe and then into the ditch.

Cable blowing index

In the cable in the choose and buy, people tend to focus on the optical fiber loss and other technical indicators, while ignoring the cable blowing index, we refer here to blow indicators include cable hardness, non circularity and pipe diameter, diameter ratio and optical fiber cable. If the cable is too soft, the friction between the resistance will be increased because of pipes and cables, cable soft more easily bent, increases the contact surface of cable and pipe. Fiber optic cable is too hard, the formation of a greater friction in turn will pipe. If a smaller turning radius pipe, cable easy card at the corner. Because the bending the friction drag force over the air on the cable force or the thrust has been unable to end cable with pipeline and change. Non circularity will cable caused by airflow in the seal leakage within the warehouse, increase resistance cable propulsion. At the same time, big airflow leakage will reduce the pressure inside the pipeline. The best gas cable outer diameter and the inner diameter of the pipe blowing ratio is 2-2.3 times of cable pipe, if the ratio is too high, the cable bend easily. If the ratio is too small, the flow resistance will cause the air rise. The people in the purchase cable, think GYTA is lighter than the GYTS, so the GYTA blowing effect is better than GYTS. But if in a pipeline 40/33mm gas blowing a 10mm diameter GYTA or GYTS cable, blowing effect is greatly different. We have been in the project, Sinopec Sichuan East gas transmission, cable on the 9 cable factory GYTA and GYTS made 1.5 km pipeline gas blowing performance test, the air blowing test field is composed of a circle every 100 meters 5 ring rectangular pipe and each lap 50 meters a total of 20 8 words. The result is GYTS blowing performance is better than GYTA, the ratio is the main reason for the pipe diameter, diameter and fiber optic cable is too large, the GYTA form more easily than GYTS bending in the pipeline, if the weather is hot, high temperature pipe, cable is more likely to become soft and the formation of spiral coil.

Effect of temperature on the length of cable

When the temperature is above 25 ° C, recommend the use of cooler, because out of air compressor in air than in high external temperature 30-40 ° C, and when the ambient temperature is above 50 ° C, high gas pipeline will lead to inner wall of pipeline optical cable outer sheath and become soft, the friction resistance between the pipe and cable rise, but also make the pipeline in the gas blowing process from softening, expansion to the likelihood of rupture. In addition the heat flow in pipe is easy to form water droplets, appear siphon phenomenon, increase the flow resistance caused by air. Air attenuation increase. In addition no flow of water will greatly increase the frictional resistance between the cable and pipeline, through the test of friction coefficient, we find that when the droplets appear cable, the friction coefficient will increase from 0.12 to 0.22, then the blowing effect will be influenced greatly.

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