In mechanical engineering, cleaning mechanical parts has become an indispensable step in the manufacturing process. Different cleaning methods can be used according to the dirty degree and the geometric shape of the parts. The choice of cleaning method has no effect on the subsequent drying process. In addition to convective drying or air drying by recycling hot air in the hot heating cleaning process of parts themselves, vacuum drying is an effective and fast method in the drying process. Through this article to learn about vacuum drying and vacuum pumps for vacuum drying.
Industrial parts are usually cleaned after processing or grinding, or after heat treatment. Cleaning methods can be basically divided into two categories: water solution cleaning and solvent cleaning. Of course, there are also some special processes. The final choice of cleaning method depends on a variety of factors. The most suitable cleaning methods must be selected according to the material of the parts, the type of the dirt (different types of oil, grease, emulsion, dust, etc.) or the geometry of the parts (surface structure, holes, undercuts, etc.). Consideration must also be given to the purity level required for components.
Subsequent drying of cleaned parts is essential. In the case of water medium, even the smallest residual moisture can cause corrosion damage to the product, which leads to high follow-up costs. Undried solvents can cause the workpiece to be decomposed. Convection drying is the simplest drying method. During the cleaning process, the components are heated to between 70 and 80 degrees Celsius to evaporate the attached water. Circulating air drying is the flow of hot air over the workpiece, resulting in water evaporation. Both methods are suitable for parts with simple geometry. Vacuum drying is very reliable and effective, it can even ensure the rapid drying of parts with complex geometry, and can be used for cleaning methods involving aqueous solutions and solvents.
Vacuum drying is based on the boiling temperature of droplets under vacuum conditions, i.e. the physical properties of liquids that evaporate even at low temperatures. For example, in the pocket position, the liquid still exists after cleaning, and it is difficult to remove it by other methods, while vacuum drying can make it evaporate as quickly as the residual liquid on the surface of the workpiece.
Functional description of water solution cleaning system
Once the working chamber is occupied and sealed by the parts to be cleaned, a vacuum pump is needed to vacuum at a pressure of about 100 mbar. The cleaning medium is pumped into the working chamber through a water pump. The vacuum chamber ensures that the cleaning fluid penetrates into the smallest chamber. For example, because of the air gap, the jack can not be ignored. There are various steps in the subsequent cleaning process. Usually it includes the process of soaking and spray cleaning. Ultrasound cleaning is sometimes used, which is usually followed by one or more cleaning cycles. When the cleaning liquid is pumped away, the actual vacuum drying process takes place. In this process, the pressure in the working chamber is further reduced after being pumped by a vacuum pump. The steam generated at this time is sucked out by the vacuum pump and transferred to the exhaust pipe.
Functional description of solvent cleaning system
In principle, the solvent cleaning process is similar to the water solution cleaning process. However, vacuum pumps generally need to do additional work. First of all, it is crucial to meet the explosion-proof requirements. There are two different solutions. Either a vacuum pump with explosion-proof standard design can be used, or a cleaning system without explosion-proof operation can be operated under a pressure-driven system with a constant value of less than 100 mbar. The pressure of the system can be generated by any kind of vacuum pump, although the second type of smaller vacuum pump is usually used to complete the work. Secondly, the solvent evaporated during drying can be volatilized in a vacuum distiller (a device in which the solvent can be distilled from contaminated media). The solvent distillate is returned to the cleaning process through the pool, while the oil/dirt is concentrated in the barrel.
Use of Vacuum Generator
Oil-lubricated rotary vane vacuum pump
Oil lubricated rotary vane vacuum pump is widely used in cleaning system. Experience shows that this type of vacuum pump is very suitable for this kind of application requirements, and it has become the standard pump in the drying process of cleaning system. Rotary vane vacuum pump is a powerful vacuum generator with long service life and high vacuum level. However, when it comes to the cleaning process with high steam generation probability, the rotary vane vacuum pump can not always prevent the condensation of steam during the suction and removal process of the vacuum pump. At the same time, condensate oil emulsifies vacuum pump oil. This may lead to insufficient lubrication of rolling bearings and rotating blades, resulting in wear and tear of other parts of the vacuum pump, suction performance and expected vacuum may also be affected. These effects can lead to increased maintenance and overall operating costs through more frequent destruction of vacuum pump oil and filters.
Dry screw vacuum pump
The dry rotary screw vacuum pump manufactured by Dr. K. Busch GmbH has a long and successful history in a wide range of vacuum technology processes. Vacuum pumps have successfully met various specific application requirements. Since 2005, they have been successfully applied in the field of industrial cleaning and drying technology, and have been widely disseminated as a new standard of vacuum technology in this field.
Busch COBRA screw vacuum pump does not need oil as working fluid. In the drying process, it has the advantage of forming non-contact oil by condensation in the compression process, thus eliminating the possibility of problems related to oil-lubricated rotary vane vacuum pump.
In COBRA screw vacuum pump, the twin-screw rotors rotate in the opposite direction in the cylinder and do not contact each other or with the inner wall of the cylinder. Similarly, seals are sealed in a non-contact manner, so that no wear and tear occurs. If the steam condenses in the COBRA screw vacuum pump during the compression process, it will still be pushed to the exhaust side of the compression chamber by the airflow to exclude. Therefore, several liters of liquid volume per hour can pass through the pump body without any problems. Designing the drainage outlet in this way, even when the vacuum pump is in a standstill state, condensate can be easily discharged.
Unlike rotary vane vacuum pumps, screw vacuum pumps are water-cooled. The well-designed cooling principle ensures that an absolutely uniform and stable temperature passes through the whole pump body. The amount of coolant can be adjusted by the average value of constant temperature, which allows the vacuum pump to have an ideal temperature control in the process and avoids unnecessary waste of water resources. In addition, a vacuum pump (heat exchanger) with a sealed cooling system can also be installed in a device where there is no coolant available.
Comparison of Vacuum Pumps
It is difficult to say which is the better choice for cleaning system, oil lubricated rotary vane vacuum pump or dry screw vacuum pump. In terms of technology, the principle of both pumps is possible. For cleaning systems with relatively low condensation risk, rotary vane vacuum pumps are a more sensible choice in view of reducing procurement costs. However, if the effect of condensation leads to an increase in service and maintenance costs, screw vacuum pumps can save overall operating costs faster and more profitably. It is important to consult vacuum specialists before making purchase decisions for vacuum pumps.