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Cut grain cut “crooked”? Follow these 4 + 6 to a pair of change a change!

August 04,2022

In actual production, by the production conditions, the external environment, personnel and other factors, polyester cut pellets product appearance quality abnormalities occur, which has a negative impact on production stability and product quality, and even make enterprises lose some fixed customers, resulting in product stagnation, resulting in damage to the economic benefits of enterprises.

Then how can the cut grains be so “ugly”? How to solve this problem?

Everyone follow the table below to pair up.

Analysis of the causes of abnormal appearance quality of cut pellets

01 Operators

Job operators are not strong sense of responsibility, operation is not standardized, quality awareness is weak, not timely detection of problems, or find the problem can not be dealt with in a timely manner, these are the reasons for the appearance of abnormal quality of cut pellets. In addition, the DCS post and the field cutting pellet post operators do not cooperate tacitly (especially when abnormalities occur), will also lead to cutting pellet products appear abnormal cutting pellets.

02 Granulator cutter

Cutting clearance actually refers to the clearance between the moving and fixed knives, and the size of the cutting clearance has a serious impact on the cutting force. Within a certain range, the cutting gap is inversely proportional to the required cutting force. If the cutting gap is not adjusted properly, it will not only accelerate the tool wear and affect the service life of the cutting knife, but also have an obvious impact on the slicing quality, which is easy to appear burrs, even grains and other heterogeneous cutting grains.

The lead gap is the radial distance between the outer diameter of the front and rear lead rolls. When producing a certain specification of cut pellets, the thickness of the cast strip should be the same. When the lead gap increases, the friction between the cast strip and the two lead rollers decreases, and the corresponding pulling force of the moving knife on the cast strip decreases, the cast strip enters the moving knife slower and abnormal pellet cutting occurs; when the lead gap increases further, the cast strip will not be introduced between the front and rear lead rollers, and the melt will accumulate on the raw head plate, causing photoelectric fault alarm and resulting in melt discharge; conversely, if the lead gap is too small, the On the contrary, if the lead gap is too small, the cut particles will be flat.

03 Production load adjustment

In the process of device lifting, lowering production or transferring production between pellet cutters, due to changes in the output of the pellet cutter, the knife speed needs to be adjusted in time. If the knife speed of pelletizing is raised too fast, it will produce small pelletizing; if the knife speed is adjusted too slowly, it will cause oversized pelletizing and cause the sticking of pelletizing, which will seriously block the dryer and vibrating screen and cause abnormal stopping of the pelletizer. Therefore, during the change of load of the pelletizer, strictly control the quality of 100 pellets in (3.20 ± 0.15) g, timely adjustment of the pelletizing knife speed and quality to match, to avoid the pellet weight of the pelletizer exceeds the standard.

04 Process regulation

The main process parameters that affect the quality of cutting pellets are overflow water flow, spray water flow, cutting knife speed, desalination water temperature, etc.. The control of water flow and water temperature varies from person to person, and the cutting knife speed is basically controlled by the operator according to the production load. Especially when the device output fluctuations, the cutter load changes, the water flow is not timely adjustment to the best point, and load changes do not match the lack of the best process parameters with the melt cast strip instability, easy to stick to each other to produce sticky particles, and particles and other heterogeneous cut particles.

05 Desalinated water

The demineralized water of the polyester pelletizing system is divided into three parts: overflow water, spray water and conveying water, which plays the role of cooling and conveying in thepelletizing production processand has a greater impact on the appearance quality of the pelletizing. Desalinated water also has a certain impact on the use of cutting knife, desalinated water can take away the heat generated in the cutting process in time, slow down the knife wear speed, there is a certain role of lubrication, but the purity of desalinated water directly affects the service life of cutting knife.

In the operation of the granulator, due to the overflow water, spray water, transport water flow and granulator output load match improperly, so that the water flow is too large, beyond the dryer work load, the water separation effect decreases, the dryer failed to make the water and cut grain completely separated, so that part of the water brought into the slices, resulting in the cut grain water content exceeds the standard. When the water temperature of the granule desalination water is too low, it will lead to excessive cooling of the granule, so that when the granule enters the dryer there is not enough heat to evaporate the water on the surface of the granule, which is also an important factor leading to the excessive water content of the granule.

After the cast strip is cut and shaped, if the temperature of the cut and desalted water is too high or the water volume of the cut and desalted water is too small and fails to cool the cut particles completely, the internal temperature of the cut particles will still be high, and then after drying and removing water, the internal heat transfer in the subsequent vibrating screen screening and slicing storage tank will soften the appearance of the cut particles, resulting in two particles or more particles bonded to each other, forming sticky particles, and in serious cases, a large number of cut particles bonded The particles will become lumps and block the conveying pipeline.

Measures to improve the appearance quality of polyester cut pellets

01 Improve the skill level of operators

(1) Training in operational skills through targeted live simulations.

(2) Strengthening job training and organizing work group labor competitions to mobilize the enthusiasm and autonomy of workers.

(3) Strengthen the training and assessment of pelletizing positions, and standardize the operating standard rules and precautions for pelletizing positions.

(4) Strengthen the team consciousness building of the team and improve the tacit understanding between DCS personnel and field personnel.

02 Timely adjustment of production load

With the change of the cutter load timely adjustment of the knife speed; adjust the knife speed amplitude to be uniform and slow, to avoid too small or too large cut grain; debug knife speed with visual inspection method to adjust the knife speed, the end of the timely weighing calibration grain weight, control 100 grain quality for (3.20 ± 0.15) g.

03 Process parameter adjustment

The performance of each pelletizer is evaluated and the parameters are optimized according to the load to find the corresponding cutter speed, spray water and overflow water to ensure the long and full operation of the pelletizer; the corresponding optimal parameters are matched under different production conditions.

04 Optimized adjustment of clearance

Cutting gap, lead gap is the core of the cutting knife adjustment of the granulator. The standard requirement of cutting clearance is high, should be controlled at 0.03~0.04mm, because the cutting clearance is too large, too small or uneven, will have an impact on the life of the knife, and the adjustment of the clearance needs to be carried out according to certain procedures, tightening sequence and torque are also required. The adjustment of the lead gap is to ensure proper and uniform, and the suitable lead gap is 1.7~1.8mm.

05 Optimization of adjustment of cutting water parameters

The adjustment of pelletizing water parameters is mainly flow rate and temperature. Operators have to adjust the granulating water flow and temperature to match the conditions under different working conditions. The temperature is generally controlled at 29~34℃, while the flow rate of conveying water is generally 10~15t/h. In order to ensure the cleanliness of the granulating water, optimization measures are taken: increase the frequency of water filter cleaning, timely update the water filter cloth, regularly clean the demineralized water tank, strengthen the granulating predictive maintenance, use steam to clean the overflow water, spray water, foreign objects in the conveying water line and thoroughly clean the demineralized water system.

06 Optimization of the fixed knife of the granulator

Device fixed knife is divided into two materials: alloy and ceramic, the use of the process, alloy knife life is shorter, not conducive to product quality and stability, ceramic material stability is higher.

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