Views: 2000 Author: Site Editor Publish Time: 2022-09-13 Origin: Site
The quality and condition of microduct
We know that due to the bending stress of Blow Micro-cable itself, when it is released from the cable reel, the Blow Micro-cable is not straight, so when we blow the Blow Micro-cable into the microduct, the Blow Micro-cable is in the microduct actually moves forward in a spiral shape, so the high-quality microduct with a small friction coefficient actually reduces the frictional resistance of the Blow Micro-cable. We once did an experiment. First, we laid Blow Micro-cable in a microduct without a silicon core lubricating layer, and the air blowing length was about 650 meters. Later, we sprayed Cablejeting Lubricant into the microduct, and the air blowing length reached 1500 meters. A long air blowing cable was successfully completed. This means that if the microduct is laid with good quality, if the frictional resistance of the microduct is high, it can exceed the drag force of the airflow acting on the surface of the Blow Micro-cable in a short distance, causing the end of the Blow Micro-cable to move slowly or Stop, the helical pitch of the cable begins to shorten, and new resistance is generated, causing the cable to fail.
Similarly, if the quality of our microduct is good, but the quality of pipe laying is poor, especially when the microduct is laid in a trench with water, it is easy to cause the microduct to undulate in the trench and form many micro-bends. When the high-speed airflow passes through the microduct, it will cause very Large airflow loss. Under normal circumstances, we can hear the whistle of the airflow at the outlet of the microduct with good quality, but if the quality of the microduct is poor, we cannot hear the whistle at the outlet of the microduct. The loss of airflow will directly affect the drag force acting on the surface of the Blow Micro-cable, which will also cause the cable to fail.
Effect of temperature on blowing cable length
When the outside temperature exceeds 30°C, it is recommended to use a cooler, because the air from the air compressor is 25-30°C higher than the outside temperature, and when the airflow temperature exceeds 50°C, Blow Micro-cable's polyethylene outer protection The sleeve and the microduct begin to soften, so that the frictional resistance of the microduct and the Blow Micro-cable begins to rise.
At the same time, the hot air flow is easy to form water droplets in the microduct, and a siphon phenomenon occurs, which increases the flow resistance of the air flow and easily leads to the failure of cable laying. Generally speaking, the cooler allows air flow of up to 14 cubic meters per minute, and the temperature of the air passing through the cooler does not exceed 10 °C compared to the outside temperature. At the same time, the cooler can also remove moisture from the air.
Quality of Blow Micro-cable
The quality of the Blow Micro-cable mainly refers to the stiffness of the Blow Micro-cable, the out-of-roundness and whether the ratio of the inner diameter of the microduct to the outer diameter of the Blow Micro-cable is appropriate. If the Blow Micro-cable is too soft, the frictional resistance between the microduct and the Blow Micro-cable will increase. In this case, we can use a bullet specially used for air blowing, which is a semi-open design, on the one hand, it can ensure the high-speed flow of the air in the microduct, and on the other hand, it can give a pull to the Blow Micro-cable. Stretching, increasing the stiffness of the Blow Micro-cable.
FIG3-Bullet for blowing
The out-of-roundness of the Blow Micro-cable will cause air leakage in the airtight chamber, increasing the propulsion resistance of the Blow Micro-cable. As above, we believe that if the inner diameter of the microduct is 2~2.2 times the outer diameter of the Blow Micro-cable, it is more conducive to air blowing the cable.
FCST's CablejetingLubricant is specially designed to lubricate microducts and is a white emulsion. It has strong adhesion with the inner wall of the microduct and a very small coefficient of friction. During the cable laying process, this lubricating effect will not be destroyed by the dry Blow Micro-cable in the front section. At the same time, it is non-toxic and non-flammable. -cable does not corrode.
FIG5-FCST's Cablejeting Lubricant
Before air-blowing the cable, it is first necessary to determine whether the microduct has passed the air-tightness and penetration inspection, because the air leakage of the microduct, the falling off of the joint and the deformation or blockage of the microduct will affect the length of the air-blowing cable. If the microduct is found to be faulty, you can use the Telecom Duct Detector to find the specific location of the obstacle, or use the microduct segmented search method.
FIG6-Sponge ball Penetrates
Choice of air blowing method
Usually we choose the air blowing method and air blowing point according to the on-site construction situation.
First of all, we must understand the line and pipe laying situation, and then we can help us choose the air blowing point according to the construction experience. For the specific selection method, refer to the article "Microduct Fiber Optic Cable Installation"
FIG7-Cable Jetting Schematic Showing Placement Without Intermediate Assist