Use method and failure analysis of feed extruder
Release time: 2021-09-02
Use method and failure analysis of feed extruder
   Due to the process arrangement and operation technology of the extruder, the output fails to meet the expected design requirements, and the surface of the particles is not smooth, uneven, easy to over-expand, spraying, etc. The editor now analyzes the main reasons that affect the production efficiency of the extruder during the granulation process as follows:

  一. Raw material factors

  The raw material factors directly affect the granulation effect. The materials with higher starch content are easy to be gelatinized. These raw materials are easy to form a new state after being extruded by the extruder at high temperature and high pressure, which is conducive to the molding of expanded granules. For raw materials with high crude fiber content, adding a certain amount of grease can reduce the friction between the material and the barrel/screw during granulation, which is conducive to the passage of the material through the barrel, and reduces the excessive heat generated by friction and causes blockage. At the same time, it is appropriate Add some starch-containing materials, so that the appearance of the granules after puffing and forming is smooth. The general addition amount is about 1%. If the addition amount is too high, it is easy to cause spraying. If you need to add more grease, you can consider spraying after granulation, which is especially suitable for the production of high-energy feed. The particle size of the crushed raw materials determines the surface area of ​​the feed composition. The finer the particle size, the larger the surface area. The material is easier to pre-gelatinize and expand in the barrel after high temperature and high pressure. From the perspective of granulation, the crushing is fine, the extrusion molding strength is high, and the materials are also prone to qualitative changes. The resulting granular structure is more dense, but it is easy to block the machine if you don’t pay attention to it, and the raw materials are crushed too finely. The crushing power consumption is too high. Too coarse particle size will increase the abrasion of the barrel and screw, and if there are larger particles, it is easy to cause mold blockage, especially small diameter molds are more difficult to mold, resulting in high material consumption, low output, and coarse particles. Therefore, in the production of livestock and poultry feed, the crushed corn should be crushed to 60-80 mesh, which can avoid the disadvantage of too fine particle size and ensure the particle size required for sufficient conditioning of the feed. In addition, attention should be paid to the uniformity of mixing before pelleting, because the composition of the feed formula is complex and the proportion of various raw materials varies greatly. For different formulas and varieties, different mixing times are used to make the coefficient of variation of mixing uniformity reach about 5%.

  二. Feeding volume control

  In order to make the extruder work at full load in a balanced manner without stopping, the material flow into the extruder must meet the granulation needs, and the feeder speed must be adjusted according to the main engine speed to adapt to the main engine's operation. Take the DSE120-Ⅲ extruder as an example, the material flow rate should not be less than 2T/H. In addition, it is necessary to adjust the speed of the feeder to match the main engine in actual production. Many feed factories are just busy when the extruder production efficiency is abnormal. The extruder itself looks for the reason, but ignores the incoming material factor. In fact, many times the production efficiency decline is caused by the insufficient incoming material flow. Generally speaking, when the extruder is running smoothly and normally, it is best to increase the feed rate of the feeder until the main motor current reaches about 80% of the rated current value. If the main motor current is low, it means that the incoming material flow is insufficient. At this time, the cause should be found out and the symptoms should be treated.

   3. Production operation

   Correctly adjust the gap between the two screws until it is balanced. If the gap between the screws is unbalanced, the two screws are likely to collide and cause wear or damage during the production process, and the noise is loud; if there is no gap, the screw will be seized and the screw and barrel will be damaged if there is no gap. It can be measured with a feeler gauge during adjustment, or visual inspection without a feeler gauge. Taking the new screw as an example, visually observe that the occlusal parts of the two screws are evenly divided and the gaps between the two screws are the same. After that, check whether each part of the extruder has reached the production standard, whether the oil tank is filled with lubricating oil, whether the feeder's feed teeth can be moved normally, whether the mold and die seat are placed in place, whether the rotary cutting motor can operate normally, and whether the blade Whether the gap between the mold and the mold is too large or not, it should be adjusted until it is slightly close to the mold. Install the peeling protective cover after zui. When everything is ready, turn on the extruder to preheat, and prepare the raw materials before production during the period (preparing the raw materials according to the recipe). When the extruder is preheated to the predetermined temperature required by the formula, turn on the oil pump motor, wait for the oil pump motor to run for about 2 minutes, turn on the main motor of the extruder to 800 rpm (26Hz), and evenly add about 500ml of water to the feed inlet to facilitate the discharge , At the same time, start the feeding motor and adjust the frequency converter from slow to fast. If the discharge is normal, the main motor speed will gradually increase to 1100 revolutions (36Hz) at the same time. The feeding amount is required to meet the requirements of the host, and no material accumulation is required. , And do not empty the material. After adding the material, you should always pay attention to the indication of the main motor ammeter, and the current should be controlled at about 80% of the rated current. When the material is extruded normally from the die (no foreign matter, good puffing), check again whether the rotary cutter is suitable (rotate the rotary cutting belt manually), start the rotary cutting motor when it is suitable, and then close the rotary cutting machine cover baffle. Adjust the rotation speed of the rotary cutting motor until the desired length and shape are cut.

  Before shutting down, add 1~1.5kg of raw materials with relatively high water content to clean and protect the host. When shutting down, stop feeding first. After about 3 minutes, the die will stop discharging. Stop the host. After unloading the die, turn on the main motor and add the puffed waste from the inlet until there is no sticky material at the outlet. , It can be shut down, the die head is cleaned, and edible oil is applied, and it is loaded into the main engine to prepare for the next start-up.

  ☆When a shutdown occurs under high current conditions, such as a material blocking that causes a protective action of the motor, or a power failure during normal operation, the main motor should not be restarted immediately, otherwise the gearbox, screw, and barrel will be damaged. If the shutdown occurs due to the above failures, the die head should be removed, the reducer pulley should be manually turned, and the residual material should be squeezed out until the resistance is small before starting the main motor (low-speed start).

  4. Extruder mould

   Whether the material can be squeezed through the die during the granulation process depends on the pressure produced by the screw in the barrel and the barrel and die. This is related to the friction coefficient, moisture content, raw material size, temperature, plasticity and compressibility of the material between the barrel and screw, as well as the screw speed and the amount of feed. These characteristics are closely related to the number and diameter of the mold hole. Relevant (the process of material discharging is equivalent to pressure relief). Generally speaking, to achieve the ideal production capacity of the equipment is to find a balance point between pressurization and depressurization. Adjust the speed of the screw (main motor), the feed amount of the feeder, and the diameter and quantity of the opening of the mold according to the mastered mature formula. If the formula is immature, it should be mainly adapted to the extruder, and adjust the proportion of each material and the moisture of the formula on the basis of meeting the necessary nutrients for the product. 
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