1. The role and characteristics of dryer fabric
The main function of drying fabrics:
The first is to pass the paper through the dryer section;
The second is to press the paper sheet on the drying cylinder, which can enhance the contact between the paper and the cylinder surface, which not only improves the heat transfer efficiency, but also improves the surface performance of the paper sheet to avoid wrinkles and wrinkles during the drying process;
The third is that it drives the drying cylinder and each roller.
Production requires drying fabrics with good durability, dimensional stability, air permeability, water absorption, smoothness, softness and stain resistance.
The durability includes heat resistance, abrasion resistance, tortuosity resistance and corrosion resistance.
Dimensional stability means that no or little elongation of the warp and shrinkage of the weft occurs.
Air permeability and water absorption are important conditions for improving drying efficiency.
And the smoothness and softness are good, not only can the paper sheet not be pressed out of the carpet mark, but also can tightly press the wet paper on the surface of the dryer, improving the heat transfer efficiency.
As for the antifouling property, the dry cloth can not be easily stained by resin, fine fibers, etc., so as to ensure its air permeability.
2. Types of fabrics and their characteristics and selection
There are three types of drying fabrics: wool woven blanket, cotton canvas and plastic drying net
⑴. The woolen blankets are relatively finely structured. The weight is between 3 and 3.5kg/m2, which is unprovoked. It is rarely used now and is mostly replaced by needle-punched blankets.
The basis weight of needle-punched dry blanket is between 1.3～2.0 kg/m2. Because it is a synthetic fiber, reinforced cotton yarn is used as the base cloth, which has high strength and low elongation. It is also layered with 30% nylon and 70% wool to make it wear-resistant, high-temperature resistant, stable in operation, and free of cracks, so it has a service life long.
However, the air permeability is similar to that of ordinary dry blankets and is still very low.
⑵. The weaving method of cotton canvas mostly uses plain weaving, but the number of layers is single-layer, double-layer and three-layer, and the flat-weave double-layer and three-layer with a basis weight of 2.0～2.4kg/m2 are more used. Due to poor air permeability and acid resistance, it is gradually being replaced by polyester dry mesh.
⑶. The dry net is woven with plastic monofilament or multifilament and finished by heat setting treatment. It has high air permeability, heat resistance and dimensional stability.
The outstanding feature of the dry net is that it has a particularly large air permeability (up to 3000-32000cm3/cm2.min), which is generally 8-12% larger than canvas, and its service life is 1.5-2 times that of canvas, followed by dimensional stability and durability. Good performance, no water absorption, light weight.
At present, foreign countries have developed flat wire dry nets and anti-sticking dry nets for special purposes. The flat wire dryer has good flatness and is very suitable for the use of a dry group. It hardly leaves a screen print on the paper during use. The flat wire anti-sticking dry net is suitable for surface sizing or coating and the first drying dry net.
3. The use and maintenance of fabrics
Dry nets must be inspected and maintained during use to ensure their service life. Therefore, the tension of the dryer fabric should be properly controlled. Normally, the operating tension is 1 to 3 kg/m. If the tension is too high, it may break the roller or cause the joint to open. If the tension is too small, it will affect the drying efficiency or paper quality.
If the dry net is wrinkled or damaged during use, it can be repaired by:
⑴. If the edge of the mesh is damaged, you can use scissors to cut the damaged area flat and cut it, and then heat it;
⑵. If the inside of the net is cracked, it can be sewn with a polyester suture, and then coated with adhesive. For small cracks, it is enough to apply adhesive;
⑶. The joints are raised, and zigzag sutures are made with polyester sutures to prevent the weft from pulling apart;
⑷. Slight wrinkles, can be ironed on the roller, when the wrinkled part is worn, you can apply adhesive.
There are large holes on the dryer screen, which are easily clogged and soiled by paper dust, dust, and oil. After normal use, if dirt is found, the washing should be strengthened.
The washing method is as follows:
⑴. Washing on the machine, generally can use the pressure of 400～500KPa compressed air, or variable pressure washing, also can be washed with dioxane detergent, and then washed with water;
⑵. Wash under the machine, generally in 50-60℃ hot water, soak in neutral detergent for 24h, then scrub with soft nylon brush, and finally rinse with high-pressure water.
Post time: Sep-23-2020