Package dyeing machine requirements and features

The pack dyeing machine has been invented for more than a century and is therefore used extensively in the yarn dyeing and knitting industries. S Short process flow and less pollution.

The functional range of the machine has been expanded in recent years with the development of related technologies such as fiber materials, dyes and electrical engineering. It not only meets the criteria of the dyeing process, but also takes into account variables such as efficiency, energy consumption, and environmental standards.

This study looks at these new features both theoretically and practically in order to fully understand them.

Basic requirements for packaging drying machines

The essential requirements for packaging dyeing machines are wide production application, high processing quality, economy and environmental protection.

Quality

Economical

The aim of companies investing in yarn dyeing equipment is to maximize profit by performing yarn dyeing operations, therefore low liquor ratio, low energy consumption, short dyeing time and a effective coloring essential elements loweringof manufacturing costs.

Environmentally friendly

High-quality yarn dyeing machines must be equipped with modern computer control systems to precisely regulate the dyeing process and tube operation and ensure dyeing repeatability to meet the above basic criteria.

Click hereto Learn more about the causes of reproducibility problems in yarn dyeing.

Main functions of pack drying machineFlow control of dye liquor circulation

The circulation pump completes the forced circulation of dye liquor. The goal is to ensure that all stained items receive the same temperature and exchange frequency of the same staining solution at the same time. In theory, the greater the exchange frequency of dye liquor and dyed object, the better the leveling effect; and the exchange frequency is related to the circulating flow of the dye liquor; the flow is set by the main circulation pump. Therefore, the fill level of the bobbin yarn is highly dependent on the flow rate of the main circulating pump. big or too little is not good for coloring.

How do I choose the flow?

There are no hard and fast rules for choosing a flow. Early pack drying machines were built on theDeveloped based on experience to meet minimum flow requirements and the idea There is no color difference between the inside and outside of the coil. Leakage of dye liquid inside and outside the circulation is high in early coil drying machines due to serious flaws in the sealing structure between the coils, and at least 30% of them produce a short circuit. To compensate for this part of the damage, the flow has to be increased.

At the same time, in real applications, the water intake is different. Using a constant flow rate has several disadvantages. Due to the difference in water absorption, the flow rate of colored pure cotton yarn is larger than that of colored polyester-cotton blended yarnumwolle is fulfilled; whereas the flow rate of pure cotton yarn may be satisfied, if the polyester-cotton blend yarn is satisfied, the packaging may deform or fray.

Synchronized drying control

The amount of circulating dye liquid not only affects the Drying quality, but also causes energy waste.

The dyes have different dye absorption rates in different temperature ranges during the dyeing process. In the temperature range with high dye absorption, attention should be paid to a higher cycle frequency; in the temperature range with low dye absorption, the cycle frequency of the dye liquid can be reduced. This increases the level of colored material while reducing energy consumption, which brings long-term economic benefits. Therefore, it is important to control the circulating flow of the staining liquid in Echt time to ensure adequate flow under all operating conditions, including yarn type change load, the latest so-called synchronous drying control.

Currently, the more advanced packet drying machines have this type of control. The control approach is to input the flow curve data of the main circulation pump under different speed conditions into the computer, and using the PLC logic control, input the required liquor circulation flow according to the specific process needs. At the same time, the feedback signal is the pressure is supplied to the PLC via the measurement of the pressure difference between the inside and outside of the package to correct the deviation between the actual flow and the programmed flow.

Differential pressure control

It is worth mentioning, that modern packagingLifting machines are marked \"differential pressure control\", which is wrong. The head of the main circulating pump is used to overcome the resistance of the entire circulating system (including the package). And the actual working point of the main circulating pump is determined by the intersection of the main pump flow rate and pipe network flow rate

In practice, when the identical main cylinder is loaded with a package, the pipe network characteristic curve is also determined. The pressure differential mainly refers to the pressure drop created as the dye liquid flows between the inner and outer layers of the package, however, it may change during the dyeing process but cannot be regulated. (Example: cThe change in the winding density of man-made fibers in contact with water leads to changes in the pressure drop.)

Method and structure of heat transfer

The heat exchanger completes the heating, heat storage and cooling of the dyeing liquor wthroughout the dyeing process. Heat exchangers come in a variety of configurations. At present, the bobbin dyeing machine uses indirect steam heating and cooling water cooling. Most classic bobbin dyeing machines use a bobbin heat exchanger positioned in the lower section of the main cylinder, which requires a certain amount of space in the main cylinder. At present, most of the most complex bobbin dyeing machines use tubular heat exchangers placed in the main circulation line.

According to the heat transfer principle, the tubular heat exchanger has higher heat exchange efficiency than the bobbin heat exchanger, and the placement of the tubular heat exchanger in the main circulation line can reduce the dye liquid better ensure fluidity. The homogeneity of temperature throughout the circulation system plays an important role in improving dye absorption rate and color fastnessend of the heating or heat preservation process.

The typical method to ensure smooth implementation of dyeing temperature control is to increase the heating rate by increasing the heat exchange area, but it takes up too much space and the coil is too long. As steam passes through the end of the coil, condensation occurs, usually after the steam has released latent amounts of heat in the front area, which not only does not give off heat, but also absorbs heat, reducing the overall efficiency of heat exchange. Therefore, an effort must be made to improve the heat transfer coefficient by modifying the shape and structure of the heat exchanger. An example is the use of an external tube heat exchanger.

Reversing device and control Method of reversing the circulating dye liquor

There are two ways, the circulating color to reverse fluid: one uses a main circulation pump with axialem flow, the other uses centrifugal pump or mixed flow pump.

Axial flow main circulation pump

The forward and reverse rotation of the main pump allows the dyeing liquid to inward and flow outside. The structure is simple and the piping occupies very little area, which helps to reduce the liquor ratio. Secondly, since the conversion of the dye liquid in this arrangement is done by the forward and reverse rotation of the motor and the switching frequency is high, the influence is minimal, if the motor life is affected.

Centrifugal pump or mixed flow pump

The internal and external circulation of the dye liquor is realized by the reversing device.

With increasing yarn volume, the stroke of the axial pump is difficult to meet the requirements can, most package drying machines today use a centrifugal pump or other mixed flow pump with reverser.

The shape of the reverser

There are different types of reversers, the most common are: gooseneck, right angle elbow and valve plate.

The gooseneck type reverser (also called \"X\" type known) has a superior streamlined flow channel, so the resistance is small, but it takes up a lot of space and is expensive to manufacture. This design is primarily intended for reverse double suction centrifugal pump. Right-angle elbow type reversing device, the existing right-angle junction has been changed to an elbow junction, the local resistance of the flow channel is small, the manufacture is simple, and the rotating shaft is also arranged horizontally instead of vertically. The valve plate reverser is the most basic type of reverser. She has the following characteristics: smooth commof the dye liquor, no shocks and good water flow properties. When the main cylinder is filled with yarn, there may be problems that water can enter the inside and outside of the yarn at the same time (especially fast water entry), which ensures that the inside and outside of the yarn absorb water evenly and the yarn is not washed .

The reversing mechanism of the new coil drying machine is mostly of the right angle and valve plate types, and its performance and reliability are excellent.

Commutation control is mainly concerned with controlling the internal and external cycle times. Different yarn types, yarn shapes and winding densities have different control times. After the process test is successfully completed, the successful parameters must be entered into the computer, and the computer and PLC control system will be completed automatically.

Dosing system

The degree of the feeding system The control program has a significant impact on the dyeing quality. The previous method of simple linear feed is not sufficient for the new dyeing process. For example, with light colored yarns, the linear feed of dye uptake cannot be controlled and non-linear dosing must be used to ensure adequate dye uptake. This type of control can be based on the different hues of different dyes, and the dyes or auxiliaries can be released more precisely in different temperature ranges so that the dyed object gets an optimal drying result and color fastness. This is particularly important for reactive drying techniques.

Overflow Salt Device

Reactive drying processes require the use of large amounts of salt. Controlling the level of salt in the dyebaths can affect the absorption rate and speed of the dyechange ffs. Different amounts and rates of salt addition must be used to dye with different depths of color. Therefore, the way salt is applied should be carefully considered.

The typical method of adding salt is to return a significant amount of dye liquor from the main tank to the feed barrel (some auxiliary tanks) to add the salt to dissolve, and then to inject it into the main tank. The downside of this approach is that the main tank must hold a large volume of dye liquor to ensure that after the liquor required for the brine has been drawn out, the top yarn in the tank is not exposed to the liquor surface, resulting in an unnecessary liquor ratio that is actually increased .

If an overflow type salt adding device is used, the dissolved salt and salt injection can be carried out at the same time, and there is no excessive flowLiquid return required to keep main tank liquid ratio as low as feasible. At the same time, the concentration of the salt solution can be constantly changed during the salt injection process.

Proportional control of temperature rise

It is important to proportionally control the heating rate and the degree of fixation are proportional to the heating speed during the staining process. The frequency of opening and closing the shut-off valve controls the conventional heating rate. Such a heating curve is truly stepped and controlled. Achieving a moderate heating rate presents a challenge. When proportional control is used, the heating rate curve becomes continuous and smooth, temperature fluctuations are eliminated, and the heating rate can be adjusted within a relatively narrow range. This has a nice leveling effect on some colors yarns that are temperature sensitive.

With the constantWith the development of new dyeing processes, the functions of dyeing machines are becoming more and more demanding. The features of modern dyeing machines include controlled dyeing, simultaneous dyeing and fast dyeing. You, as a device manufacturer and user, should study carefully to develop or improve the functionality of the devices.

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