Water entry method and liquid level control of airflow dyeing

1. Water inlet and liquid level control before the fabric is put into the tank

During airflow dyeing, before the fabric enters the tank, the water inlet valve is first opened through the control system to enter the water. The amount of water entering is automatically controlled by the electrical control system through the pre-set liquid level. When the amount of water entering reaches the set liquid level , the water inlet valve automatically closes and stops the water inlet. This liquid volume is actually the liquid volume required to meet the main pump and pipeline circulation and dissolve the dyeing material, that is, the first part of the dyeing liquid.

Because the airflow dyeing machine adopts the differential pressure transmitter analog precise liquid level control, the analog value is displayed on the control computer, not the actual liquid value. In the actual application process, the equipment is in the initial installation and debugging. At the time, the actual liquid volume corresponding to each liquid level can be obtained through calculation and water level adjustment. At present, the current airflow dyeing machine and equipment manufacturers generally provide the corresponding table between the simulated liquid level and the actual liquid volume. Therefore, through the computer display the simulated liquid level, you can know the actual liquid volume value of the incoming water. For the same cylinder type, the water input is the same, that is, the liquid level set by the control system is constant. In fact, it is the protection liquid level that satisfies the normal operation of the dye liquor circulation system of the airflow dyeing machine. Once set, generally Circumstances do not need to change arbitrarily.

It should be noted that the setting of this liquid level cannot be higher than the PTFE pipe at the lowest position of the cloth storage tank in the cylinder. This part of the liquid volume of the airflow dyeing machine is generally stored in the filter at the bottom. , the liquid level is lower than the PTFE pipe at the lowest position of the storage tank, the reason is:

First, if the water level is above the polytetrafluoroethylene pipe, the fabric in the cloth storage tank will be partially immersed in the dye solution during airflow dyeing, which increases the running resistance of the fabric, and the fabric does not run smoothly in the cloth storage tank. It is easy to cause the cloth to be entangled and press the cloth, and at the same time, the water carrying capacity of the cloth is increased, and the resistance of the cloth is increased, thereby increasing the tension of the fabric. Therefore, the airflow dyeing machine should not add the required amount of water for the dyeing bath ratio into the tank at one time before the fabric is put into the tank. Instead, when the fabric is put into the tank, the water is automatically replenished twice, because the dyeing bath is reached. Compared with the water volume, the liquid level has exceeded the PTFE pipe at the lowest point of the storage tank.

Second, the exchange of air-dyed fabrics and dye liquor is completed in the nozzle system. If in the cloth storage tank, the part of the fabric deposited below is immersed in the dye liquor, while the part of the fabric deposited on the top is not soaked in the dye. In the liquid, the probability of contact between each section of the fabric and the dye liquid will be inconsistent. At the same time, because this part of the dye liquid and the dye liquid exchanged with the fabric in the nozzle system, there is a certain temperature difference and dyeing material concentration difference, so it is very important It is easy to cause dyeing quality problems such as dyeing and dyeing step difference.

Third, this water level is too high, which actually increases the dyeing bath ratio and increases the cost of dyeing production. On the premise that the bath ratio can meet the dyeing conditions, it is completely unnecessary to artificially increase the bath ratio.

2. Water inlet and liquid level control when fabric enters the tank

After the first water supply reaches the set liquid level, the rope-like fabric can enter the tank. At the same time as the fabric enters the tank, through the dye liquor circulation, the fabric gradually absorbs moisture and swells in the nozzle system, which will consume a part of the dye liquor. The liquid level will decrease, and at this time, the water inlet valve is opened by the control system for automatic water replenishment. The water replenishment process of the fabric entering the tank is a dynamic process, which is completely controlled by the automatic control system. When the dye liquor is lower than the set liquid level, it will automatically replenish water, and after the water replenishment reaches the set liquid level, it will Automatically stop water replenishment. When the fabric is completely in the tank and the liquid level is stable at the set liquid level, the process of filling the fabric into the tank and replenishing water is completed.

The water replenishment amount when the fabric is put into the tank is basically the amount of liquid required for the fabric in the tank to absorb moisture and swell, that is, the sum of the second part and the third part of the dye liquor mentioned above. The liquid volume value of this part can be obtained by the following two methods:

The first method is calculated by the weight of the dyed fabric in the dye vat. Because the amount of water required for the hygroscopic swelling of the dyed fabric per unit weight is known, the weight of the dyed fabric is multiplied by the hygroscopic swelling of the fabric per unit weight. The amount of water required is the liquid value of this part.

The second method is that, for the airflow dyeing machine equipped with a water inlet flowmeter, this liquid volume value can also be directly obtained through the measurement of the inlet water flowmeter. It is worth noting that when calculating the bath ratio, if the moisture content of the fabric before entering the tub is high, and this moisture content has a certain influence on the bath ratio, if the measured value of this flowmeter is used as the fabric moisture absorption and swelling If the required liquid volume value is used to calculate the liquor ratio, the moisture content of the fabric before it is put into the tank should also be included. The reason is that under the same environmental conditions, the amount of liquid required for the moisture absorption and swelling of the same variety of fabrics per unit weight is constant, and it will not be different because of the different moisture content of the fabrics before entering the cylinder. In the process of airflow dyeing, the total amount of liquid required for the fabric in the tank to absorb moisture and swell is actually the sum of the moisture content of the fabric itself before entering the tank, plus the water replenishment amount when the fabric enters the tank.