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• Comments on model selection
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• Related issues in GMP applications

​♦  GMP application-related issues
In accordance with the requirements of the GMP specification, relevant requirements for the machine have been proposed. But the requirements are given for all pharmaceutical machinery, including some ancillary facilities used in the pharmaceutical workshop. To digest the "norms" to truly meet the requirements, pharmaceutical machinery manufacturers and pharmaceutical manufacturers need to work together. In fact, the application occasions, process, and the physical and chemical properties of different media bring different requirements on the centrifuge of pharmaceutical manufacturers, such as: anti-corrosion requirements, explosion-proof requirements, medium temperature, workshop purification level and so on.
​♦  Compliance with sealing requirements
High environmental requirements are proposed for the production process of pharmaceutical centrifuges, whether for non-sterile drugs or sterile drugs, pharmaceutical intermediates or finished drugs. Under such high environmental requirements, such as in GMP 10,000 and 100,000 class purification workshops, good sealing performance can maintain an effective isolation between the external and internal of the machine. The solid, liquid, gas phase in the cavity of centrifuge should not cause pollution to the workshop environment. In turn, the operator, and the external environment should not produce pollution to the material. Therefore, the equipment procurement department, when making an order, should inform the centrifuge manufacturer of the sealing requirements. Manufacturers conduct special design on the centrifuge’s sealing performance, which is fully embodied in the manufacturing. Generally the following parts are considered:
Sealing of cover: For easy cleaning, the cover is generally designed as a quick-opening type, and the joint surface with the housing should have reliable sealing measures. If the seal structure or anti-corrosion measures fail, it may cause liquid and gas leakage, leading to environmental and personal damage. The anti-corrosion properties, sealing performance and reliability of the sealing groove structure and sealing strip should be fully taken into account in the design and selection. 
For the installation interfaces of the feed pipe, washing pipe, observation mirror and other devices, there should be reliable sealing measures.
Sealing of spindle: For the spindle nuts and bearing seat, the sealing measures of traditional models are relatively simple, and can only achieve relative effect. For example, seal ring is generally not set on the joint surface between the spindle nut and the drum. In the process of the centrifuge operation, infiltration of liquid and gas phases corrodes the spindle cone, and infiltration is even made into the bearing, which causes damage to the bearing, thus affecting the normal use of the machine. The upper bearing cap is generally provided with a skeleton-type seal, but the part between the bearing cap and the drum cone is exposed, and the gas phase in the inner chamber of the centrifuge may corrode the exposed surface of the spindle. For the centrifuges used in the pharmaceutical industry, most of the materials to separate contain solvents and other organic solvents, or acid and other media. So when ordering, the sealing requirements of these parts should be taken into full account. Dynamic seal or static seal structure should be set to meet the sealing requirements.
Sealing of conveyor working area: Traditional centrifuge’s conveyor is of open type, mainly designed from the security point of view. Only a protective cover is set on the motor side to improve its use safety. But environment pollution generated by friction dust is not under control, so it is not feasible to use it in a clean area. Therefore, it is necessary to seal the conveyor working area to prevent the leakage of dust.
For other parts (outlet pipe, feed pipe, hopper and other interface parts):For the centrifuge’s external pipes, such as feed pipe, washing pipe, and cleaning pipe, under normal circumstances, flange installation should be used to ensure the sealing performance of the interfaces. For some applications with high cleanliness requirements, hygiene grade quick-opening interface devices should be selected for easy cleaning.
​♦  Compliance with online cleaning requirements
Set a cleaning device in the centrifuge chamber, so that the centrifuge’s internal surface can be cleaned without opening the lid or during the operation. Under some process conditions, solid phase is separated because the main product has high requirements on its solid content. Even the entry of the liquid phase dripped from the online cleaning pipe hole into the solid phase is not allowed, so the online cleaning pipe should be designed with appropriate measures to clean the tube.
​♦  Corrosion requirements and surface treatment
Selection of material is the key to achieve the anti-corrosion performance and meet the cleanliness requirements. The pharmaceutical industry should generally use stainless steel structure. Some external parts should not be in direct contact with the material. But still, stainless steel is preferred, which facilitates the cleaning of the surface and the plant environment.
Select the appropriate material according to the corrosion data (chemical properties, temperature, concentration, etc.) of the separated materials. To meet the GMP requirements, select ultra-low carbon stainless steel, titanium, Hastelloy and other materials. Alternatively, the surface that contacts the materials can be lined with plastic, rubber, or coated with a halar coating.
Hygiene grade pipes and quick clamps should be used in order to eliminate the pollution of the pipes.
For some structural parts that are not in direct contact with the material or are only for support, they may also be lined with stainless steel.
The structural design should be as smooth as possible. Flat surface should be ensured. Hygienic dead ends such as water and material dead ends.
All stainless steel surfaces should be polished smoothly. The roughness of the surface in contact with the material should not be lower than Ra0.4.
​♦  Gas source
The pneumatic components equipped with the centrifuge, such as pneumatic scraper, pneumatic bag cylinder, gas-assisted scraper, and gas recoil device, use gas as the power source (compressed air or compressed nitrogen). The gas source should be purified to ensure that drugs are not contaminated by impurities in the gas.
When the gas enters into the centrifuge, the user should set up an oil-water separator, and often check it, especially when the air humidity is high. The oil-water separator in the centrifuge’s air distributing device should also be regularly checked to avoid the air moisture entering the cylinder and the control valve. The oil fog generator in the air distributing device should always be filled with lubricating oil, which can reduce the wear and resistance of the pneumatic system 

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