With the vigorous development of modern aquaculture and feed industry, the requirements for feed quality are becoming higher and higher. For pellet feed produced by feed pellet mills, pellet length is a very important quality assessment indicator. Neat and consistent pellets not only meet the sales needs of feed manufacturers, but also the actual breeding needs of users. Pellet feeds that are too long, too short, or uneven are not conducive to animal feeding.
Factors Affecting the Length of Granulator
In actual production,a particle produced by a granulator，length is generally required to be 2~3 times of particle diameter. If you produce pellets with a diameter of ф3mm, the length is generally 6-9mm. Of course, depending on the needs of the actual user and different feed varieties, the length requirements may not be within this range.
Let the output of the pelletizer be Q (kg / h), the inner diameter of the ring die is D (mm), the effective width of the ring die is W (mm), the linear speed of the ring die is V (m / s), and the speed of the ring die is n (r / min), ring die diameter is d (mm), ring die opening ratio is ψ, the number of openings is N (number), the length of the produced particles when not cut is L (mm), particle density Is ρ (kg / m3), then the length of the pellets without cutting can be calculated as:
Factors Affecting Particle Length
For the above formula, it is not difficult for us to analyze the factors affecting the particle length L of the pellet machine:
As can be seen from the formula, the particle length L is directly proportional to the yield Q. With other parameters unchanged, the higher the yield, the longer the particles, otherwise, the particles are shorter. Therefore, in order to meet specific particle length requirements, adjusting the output of the granulator is a possible selection method. In actual feed production, feed manufacturers do the same, sometimes even sacrificing a lot of output to meet the particle length requirements.
As can be seen from the formula, both the particle length L and the ring mode linear speed V or the ring mode speed n are inversely proportional. Under the condition that the feeding speed, that is, the output Q is unchanged, the faster the ring die speed, the shorter the instantaneous extruded particles, and vice versa. For granulators of different sizes, the rotation speeds of ring molds are very different. Generally, small granulators have high rotation speeds and large granulators have low rotation speeds. 6m / s ~ 9m / s to meet the needs of granulation. When the line speed of the ring die is small, the quality of the produced particles is high, but the particles produced may be longer than required, and too low line speed will affect the output; when the line speed of the ring die is high, it is beneficial to the output. However, the granules produced may be shorter than required, and the quality of the granules will deteriorate. This requires feed manufacturers to choose their own ring mold line speed according to different feed varieties. The method can be adopted Change the transmission ratio of the pellet mill drive system to achieve.
Effect of ring die aperture and aperture ratio
Ring die hole diameter d does not directly affect the particle length L. It and the opening number N together have an effect on the length L, that is, the ring die opening rate ψ. The larger the opening rate of the ring mold, the shorter the particles made, otherwise， the longer the particles. The opening ratio of the ring mold is different when it corresponds to different ring mold apertures. For example, the ring mold with a ring mold diameter of ф1.8mm has an opening ratio of about 25%, and the ring mold with a ring mold diameter of ф5mm has an opening ratio. It is about 38%. Generally, the larger the pore size, the higher the opening rate. In actual production, especially in the production of small diameter pellets, such as the production of shrimp ф1.8mm, some users will complain that the pellets produced are too long, because the corresponding ring mold opening rate is lower at small apertures. Caused. The solution: First, it can be achieved by sacrificing a part of the output; secondly, it can be achieved by increasing the linear speed of the ring die; the other method is to adjust the cutter.
For a granulator, the ring die inner diameter D and ring die effective width W are relatively fixed parameters, which generally do not change, and are not easy for users to change. The density of the granules is related to the raw materials for granulation, and it is also related to the compression ratio of the ring die. The larger the compression ratio, the stronger the granules and the higher the density. However, for general products, the density of the particles does not differ much, so the density of the particles is not a major influence parameter, so it will not be discussed too much here. In short, for the same granulation raw material, the greater the density of the particles produced, the shorter the particle length.
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