1. Determine the type of force applied by the nature of the material and then find the type of crushing equipment.
Before selecting the crushing equipment, the method of crushing the force should be clarified. People can adopt the corresponding force application method according to the material properties, particle size and the requirements of the crushed product [1] , and then the crushing equipment type.
(1) The hard material with larger or medium grain size is crushed and impacted, and the teeth have different shapes on the pulverizing tool;
(2) The smaller size of the hard material is crushed, impacted, milled, and the surface of the pulverizing tool has no teeth and is smooth;
(3) Powdered or muddy materials are ground, impacted, crushed;
(4) Materials with weak abrasiveness are impacted, struck, and ground, and sharp teeth are provided on the pulverizing tool;
(5) The abrasive material is mainly crushed, and the surface of the crushing tool is smooth;
(6) The tough material is sheared or quickly struck;
(7) Multi-component materials can be crushed by selection under impact, or multiple force fields can be combined.
2. Requirements for selecting the material of the crushing machine
In addition to airflow pulverization, most dry pulverization will rely on the high-speed rotating rotor. The granules between the rotor and the fixed stator are pulverized by the shearing force, or the grinding between the rotating parts and the fixing parts is frequent. The direct contact parts are seriously worn, so that insoluble impurities and metal particles are easily generated during the pulverization process.
According to GMP, pharmaceutical equipment has corrosion resistance requirements for materials that are in direct contact with materials. Generally, austenitic stainless steel is used for this material, and the hardness of austenitic stainless steel surface is relatively low for multimetals. When austenitic stainless steel is used as the material of the pulverizer, metal particles are easily generated. However, an important way to reduce wear particles is to increase the hardness of the material of the pulverizer. The lower the carbon content in the material, the lower the hardness, and the high carbon material is very easy to rust. Therefore, the choice of the material of the pulverizing machine in the pulverizing equipment should pay attention to the contradiction between the corrosion resistance and the hardness of the material.
To deal with the above contradictions, it is necessary to analyze the main points of the contradiction. The wear resistance of the crushing machine is the main body, and the corrosion resistance must be ensured under the premise of ensuring wear resistance. For dry pulverizing equipment, the dry matter of the material generally does not precipitate chloride ions, that is, the probability of intergranular corrosion in the material is extremely low, that is, the material of the pulverizing machine must be similar to the lower hardness. 316L ultra low carbon stainless steel. Therefore, the author suggests that the material of the crushing machine can be selected from three aspects:
(1) High alloy nickel-chromium steel [2] ;
(2) Austenitic stainless steel is specially treated, such as stainless steel hardening treatment like medical surgical equipment. It is reported that domestic pharmaceutical machinery manufacturers have successfully applied this example;
(3) Hard ceramics.
3. Other selection principles to be considered
3.1, bearing and sealing at the rotor, in addition to the selection of high-precision bearings, the bearing should be multiple seals. While ensuring that the lubricant in the bearing does not leak, it is also necessary to ensure that the material powder does not penetrate into the bearing (that is, no dust is allowed to remain). These two points are necessary to prevent cross-contamination.
3.2. In the dust removal section, a large amount of dust will escape from the powder outlet, so most of the crushing equipment (especially the classification and combination equipment) have dust removal devices. When selecting dust removal, the dust removal material should be required. The dust removal material should be determined according to the product variety and safety level.
3.3. Washability, in addition to the direct contact with the material, there is no cleaning blind zone, pay attention to the following points:
(1) For equipment that is manually cleaned, the part in direct contact with the material shall be completely disassembled;
(2) For equipment with CIP or WIP, the cleaning problem at the bearing should be considered. In the PHARMAPLEX bearing system of the Hosokawa Micron company in Japan, the treatment method is that any particles eroded from the bearing seal can be taken out through a cleaning passage to ensure that the product chamber is not contaminated [4] .
3.4. In terms of online particle size analysis, this is a consideration for selecting advanced crushing equipment. Features of the online particle size analysis system:
(1) Control product quality and adjust grading during production;
(2) Continuous quality control at maximum measurement frequency, stable product quality, automatic recording of all parameters, no manual sampling, offline operation.
4. Comprehensive selection of pharmaceutical crushing equipment
The pharmaceutical crushing equipment can be comprehensively analyzed and considered according to the original conditions of the required crushed materials, the crushing requirements and the production process requirements.