Production practice has proved, if we strictly control the air in the forming area of wire drawing, it is beneficial to the stabilization of tank furnace’s operation, especially to make the G – 75, E – 225 and D – 450 electronic strands. Because the instability of airflow in the forming area will give rise to the difference of light monofilament’s diameter, cause the broken wire and flying wire during the process of wire drawing, even stop to operate. The air condition affects the whole process of rapid cooling that glass is formed as a solid wire from the state of liquid. In the drawing forming zone, dynamic change of airflow, makes the change of root temperature of liquid glass silk, even the leakage board temperature changes of different level, which leads to the diameter unevenness of electronic yarn of monofilament, then causes the change of the former serial number of electronic yarn, namely inner unevenness of premier serial number of electronic yarn we produced.
The principle of air flow control
Electronic monofilament heat was passed on to the surrounding gas medium by convection heat transfer in forming process, and as for the intensity of convection heat transfer, to such an extent, it depends on the gas medium temperature and speed.
Electronic monofilament’s forming speed and the rate and flow velocity of airflow must be controlled within the scope of the technical requirements under the condition of normal production. As it is greater than the specified technical requirements, the heat transfer to the surrounding medium of liquid glass silk will be stronger. This makes the viscosity of liquid glass wire transcend the scope of viscosity that technique have required, therefore, the electrons monofilament appears excessive tension among production. When the tension is greater than the electronic monofilament fracture stress, it will appear phenomenon of beheaded and flying wire, then temporarily be forced to stop drawing operations.
Similarly, while the air flow rate and flow velocity is less than the prescribed technical requirements, the heat transfer of liquid glass wire on the surrounding medium will be reduced. Due to insufficient cooling degree of liquid glass, makes the liquid glass viscosity less than the scope of specified requirements, so that electronic monofilament is unable to be up to required tension, also causes excessive beheaded and flying silk to suspend drawing operations.
When rushing into the direction of wire drawing machine with a great acceleration in drawing process, then nearby gas is driven with a rapid downward movement, later, there is a positive pressure zone in sector face of wire drawing. The positive pressure of air flow spreads around from the sector or lateral, or becomes backflow to negative pressure area near leak board. It will form some random turbulence and vortex in hundreds of monofilament on sector face of flying wire.
In addition, airflow, added to the forming area around from the adjacent edges and wire drawing machine and from rotating upward directional airflow that is winding by the machine, all bring with a large number of glass monofilament hairiness, the splash infiltration of micro particles and floating impurities in the air. Once these things approach electronic monofilament that is formed through high-speed operation, it will be a huge impact in an instant, and break off the monofilament bundle. It seems that one bird in the sky, will hit the high-speed plane and resultant a hole.
It must be pointed out that the electronic monofilament is formed at high linear velocity, so the surrounding gas medium must have tremendous friction force on it .The size of the frictional resistance behaves through the tension attached to the monofilament.
Conducted by glass fiber science and technology literature, when being in high speed wire drawing, prior silk’s tension will increase about 40% because the fierce friction between monofilament bundle and nearby air , fulfill instant flying silk, and force to interrupt wire drawing operation. If allowed to artificially control the air flow of drawing forming area in the drawing operations, it can make air flow around float at the same air velocity and airflow direction, similar to the air flow near electronic monofilament, to greatly reduce frictional resistance between monofilament and the surrounding air, thereby, significantly reducing the total tension of monofilament to push the beheaded flying silk phenomenon away.
And it must be noted that, tank furnace commonly apply to porous plate, in order to greatly improve production. But the density of discharge spout of big porous plate leakage is much larger than normal leakage board, so there is not sufficient area among the spacing of discharge spout installing the cooling .Though it is possible to install a small number of cooling fins, cooling area is too small to cater for cooling requirements of wire, also the cause of huge glass liquid flow and the capability of heat transfer of air cooling.
Parameters control of airflow
In order to strictly control the air flow, to ensure the normal production of electronic yarn, two adjacent leakage boards are usually separated by stainless steel plate in workshop of tank furnace, making each plate leakage become an independent working area. On the fixed position of each leakage board, there exists a device that introduces air.
Sending two kinds of air flows into the wire drawing forming area. The first approaches monofilament lying between the sprayer and leakage board. The second keeps contact with monofilament standing between the sprayer and buncher. The distance, from the bottom of leakage board to the sprayer, generally is in 304. 8 to 609. 6 mm, most of them is about 457 mm; besides, the distance from the bottom of the board to the buncher is commonly 711. 2 ~ 1066 8 mm, mostly is around 914 mm. The amount of air to leakage board, changing in a certain range, mainly depends on the drawing speed of board and other technical requirements.
Generally speaking, there are not serious requirements for the air flow to be air curtain, it is enough to form the air curtain. However, strict requirements should be made for the air flow to drawing forming area.
According to the relevant patent report, the first airflow, namely approaching the monofilament to be sent into the area of leak board and sprayer, its flow rate shall not be less than 5, 66 to 16. 99 m3 / min (200 ~ 600 ft3 / min), usually at 11. 33 m3 / min (400 ft3 / min), which is about two-thirds of airflow that was sent into the drawing forming. The second, keeping contact with monofilament of sprayer and buncher, the flow rate shall not be less than a half of the first airflow for 2. 83-8. 49 m3 / min (100 ~ 300 ft3 / min), usually for 5. 66 m3 / min (200 ft3 / min) that is about a third of the drawing forming. Both of the flow rate can’t be too much, otherwise, the mixture of them will form some random turbulence and vortex in the drawing forming zone, interfering with the normal drawing operations.
Air, transported by airflow, should be clean after being filtered, Air pressure is for 27. 6 ~ 276 pa (0. 004 ~ 0. 04 p/In2 (gauge pressure), the air temperature is 18. 3 ~ 23. 9 ℃ (65 ~ 75 ℉), relative humidity is 65% ~ 75%.In addition, the input angle of airflow to the drawing forming zone, also has certain requirements. The angle between the first airflow and the horizontal plane is for 15 to 30 °, and the angle between the second airflow and the horizontal plane is 45 ~ 90 °.The direction of two kinds of airflows, can be adjusted freely within the scope of the above according to the need of the wire drawing operation. Strictly controlling the airflow, provides the essential acknowledgement for high quality of electronic raw silk. But this is merely the first step for production of high quality of electronic cloth.