Since the 1980s, on the basis of digesting and absorbing foreign advanced manufacturing technology, we have first developed a beer filling machine liquid gas control system with our own characteristics in China. It has been nearly 20 years since its development, and now it has developed to the fourth generation, basically in step with the development of the international filling machine liquid gas control technology.In this process, through the research on the physical process of beer filling, the communication and discussion with domestic and foreign equipment manufacturers, it is found that some problems need to be clarified, some problems need to be explained, and some other problems are worth further research and discussion.Before discussing the specific problems, firstly, the connotation of beer filling is analyzed scientifically.Beer is a kind of liquid food brewed by biochemical reaction. Its matrix is water. It should follow the basic principles of hydrodynamics, such as energy conservation, fluid continuity and force balance.Its main body is the metabolites of microbial and biochemical reactions as well as some inorganic substances.Among them, carbon dioxide and protein in microorganism and metabolite are the main factors that must be faced in the beer filling process, which is also the difficulty of beer filling different from other liquid food filling.For example, reduce the amount of oxygen to reduce the living space of microorganisms; follow Henry's law of gas solubility in physical chemistry, determine the back pressure according to the content of carbon dioxide and filling temperature; protein is easy to bubble under the action of carbon dioxide gas, and the bubble holding time is long, etc.Filling refers to the filling of commodities, which are to be traded in the market. Therefore, the volume, quality or liquid level under a certain container must be measured.It is impossible to improve the quality of any food packaging, and it will inevitably have an impact. The principle of packaging technology is to minimize the adverse impact.I. the core of beer filling technology is the filling valve. In the media and professional meetings in China, we can often see and hear some opinions. The increase in the number of filling valves is publicized as a technological progress, and manufacturers also use it as an advertisement. It seems that the more the filling head, the more advanced the filling technology, the faster the filling speed.In fact, no matter how many valves there are, as far as each filling valve is concerned, its working state and process are the same. The increase in the number of valves is only due to the large diameter of the cylinder, some changes in the required power and transmission, and no progress in the filling technology.The so-called high speed of high-speed filling refers to the increase of tangent speed of in and out bottles and the increase of the number of bottles filled in unit time.However, the angular speed of the filling machine is the same, that is, the time required for filling each bottle of beer does not change at all. For each filling valve, it is still a circle to complete the filling process.The real change is the conveying system, high-speed non pressure conveying and non blocking conveying system is the core technology of high-speed filling.As long as the filling valve has the same function and structure, its filling technical performance is the same. For each filling valve, excluding machining and assembly errors, it should be identical in theory.It is the filling valve itself, not the number of valves, that determines the filling quality and technical level.For example, Germany's KHS and Krones companies classify and form their own product series based on the function and structure of filling valve; while domestic enterprises, most of which do articles on the number of heads, have not yet formed a product series with valve as the core technology.At present, in China, as far as I know, only Nanqing external mechanical filling valve, whose performance is superior to other existing mechanical valves, is the only filling core technology with its own intellectual property rights.To this end, two years ago, I wrote and publicized this innovative achievement in relevant newspapers.After the 2000 China International Beer and beverage manufacturing technology and equipment exhibition, I have commented on the differences between foreign and domestic exhibits. Foreign exhibitors mainly display technology, while domestic exhibitors mainly display processing capacity and manufacturing level.It shows that Chinese enterprises have not really become the main body of technology development and innovation.The core of beer filling technology is the filling valve. Only when there is a valve can it be organic; the machine is divided according to the valve.The progress of filling technology is mainly reflected in the technical performance of valves, rather than the number of valves.The key to improve the level of filling technology is to carry out the research of single valve technology of filling valve.2、 The key to beer smooth filling is the equal pressure opening valve of the filling valve. In the 1980s, China imported two kinds of manufacturing technologies of mechanical valve filling machine from Germany, one is the external long tube machine of Sen company, the other is the internal short tube machine of H & K company. For various reasons, if China's glass bottle manufacturing is not standardized, most of the breweries in China adopt themWith the short tube machine, this paper takes the short tube machine as an example to discuss the stable filling of beer.Beer foam is a characteristic of beer flavor. It is one of the main indexes to evaluate beer quality. Beer should be filled with foam beer.However, this feature of beer brings a lot of trouble to the filling, and the anti bubble phenomenon can often be seen in the filling site of the brewery.The causes of beer anti bubble may be as follows: bottle positioning and alignment are not in place, bottle mouth defect is not sealed tightly and sealing ring is aging to form unequal pressure filling; carbon dioxide content is too high or back pressure is too low to make carbon dioxide overflow from liquor; flow speed is too fast or flow along the inner wall of the bottle is not formed to cause excessive disturbance to beer, etc.Once the foam is formed, it will take a certain time to disappear. Once the foam floating on the liquid surface of the beer reaches the bottom of the return pipe, it will affect the normal return gas velocity, resulting in uneven liquid level.The mechanical valve is opened under the force of spring force. Theoretically, the valve should be opened when the inflation pressure in the bottle is equal to the back pressure in the cylinder. The spring force is only used to overcome the static pressure difference between the liquid level in the cylinder and the valve port, but in fact, it needs to overcome the friction force when the valve is opened, and there must be room, that is, the valve is opened when the inflation pressure is lower than the back pressure.Therefore, for all the filling by opening the valve with spring, when opening the valve, the force to push the fluid flow increases the differential pressure between the back pressure and the pressure in the bottle, which is the differential pressure opening valve.After the valve is opened, due to the back pressure communication between the air return pipe and the cylinder, the additional force disappears when the valve is opened, forming equal pressure filling.However, when the differential pressure opens the valve, the foam produced by the larger force will not disappear. It will affect the whole filling process, and the spring strength is inconsistent. The disturbance intensity caused by the unequal additional force is different. The uneven level is the inevitable result.This is the main reason for the poor consistency of filling liquid level of domestic mechanical valve spool machine, which is related to the material and technology of spring, the manufacturing technology level and quality management of filling valve.It is observed that the mechanical valve filling machine of German KHS and KRONES company can see the filling process when opening the backfill plate of the filling machine under normal running condition. It can see that there is a high and low liquid level on the diagonal line, and there is not much difference in the number of bubbles floating on the liquid surface, and the consistency of liquid height is better after filling.The reason is that the consistency of valve opening is better, and the consistency of spring force and static friction force to be overcome is better.The way to solve the problem is to improve the manufacturing process of the valve to the level of KHS and Krones, but this still does not eliminate the additional force when opening the valve.Another method is to open the valve actively without spring at all, just like the electronic filling valve when it is under constant pressure, so as to eliminate the additional force when opening the valve from the source and realize the filling with equal pressure opening the valve. This is the core principle of the external filling valve of Nanjing Light machinery.In fact, the reason is very simple, that is, the filling speed of beer should follow the slow fast slow rule.The slow start is to prevent a lot of froth, and the end is to reduce the flow inertia and make the liquid level accurate.However, the fast in the middle is not as fast as possible. The limit should be non foaming. Moreover, the flow rate is restricted by the outer diameter of the air return pipe and the inner diameter of the bottle mouth.In the traditional mechanical valve, because the spring valve is a differential pressure valve, it can't start slowly. When the beer opens the valve, the bubble is inevitable, so the liquid level can't be very accurate.In addition, when the spring differential pressure valve is inflated after the first evacuation, the inflation time must be adjusted shorter to avoid the wine valve mistakenly opening, which virtually damages the evacuation effect.Therefore, the electronic filling valve that can overcome this defect appears. The external mechanical filling valve of Nanjing Light Machinery Co., Ltd. can also achieve this goal.To sum up, the key to beer smooth filling is to open the valve at the same pressure of the filling valve, or the key is to avoid beer foaming as much as possible when opening the valve.3、 At present, the overspeed operation of beer filling machine is basically based on the following technological process: bottle feeding → vacuumizing → carbon dioxide filling → vacuumizing → carbon dioxide filling → filling → standing → pressure relief → mechanical valve and electronic valve of bottle discharging, which are the same in technological process.In terms of time distribution, mechanical valves are generally distributed in the form of rotation angle, because the sliders or paddles controlling vacuum pumping, inflation, opening and closing wine valves (traditional mechanical valves only have closed valves) and pressure relief actions are all placed on the control ring according to the size of rotation angle, which is actually determined by time and the corresponding rotation angle shown under normal operation speed,The technical data given by the manufacturer is still time.When the speed is lower than the normal operation speed, the time for the whole process to be completed will increase, otherwise, the time for overspeed operation will be shortened.Therefore, the over speed operation of the mechanical valve may affect the quality of beer filling, such as the increase of oxygen content and the uneven liquid level, and even the phenomenon of anti bubble.Because in the overspeed operation, the control of all valves is completed by the slider or paddle on the control ring, the time between the slider or paddle of wine valve will inevitably reduce, which will affect the filling quality of the whole filling process.Electronic filling valve control is to control in time and sequence, and the time to complete each process of filling process remains unchanged when the speed changes.If there is no speed limit in the procedure, the overspeed will only affect the pressure relief time, that is to say, it will affect the last procedure, and will not affect the previous procedure, such as evacuation, filling, etc.In a word, when the filling valve is determined, the time to complete each section of the filling process is also determined. Unless there is a large margin in each section when designing or giving technical data, it will inevitably have a negative impact on the filling quality.Therefore, if we want to improve the production efficiency, we should start from improving the efficiency of the whole line and the operation reliability, rather than by increasing the speed of the filling machine.
4、 At the end of 1980s, we developed the liquid gas control system of the first beer filling machine in China for the 20000 bottles / hour filling machine produced by Guangzhou Light Industry Co., Ltd., which was put into trial operation in the third packaging workshop of Yanjing.In debugging, sometimes there are empty and full cylinder phenomenon. After analysis, it is determined that the phenomenon is caused by the fluctuation of back pressure in the cylinder.When measures are taken to stabilize the back pressure, the liquid level in the wine tank is stable at a certain position during normal operation, except for the fluctuation during startup and shutdown. However, the operator still needs to observe the liquid level at any time, adjust the adjustment of the flow of carbon dioxide air replenishment, which is essentially to fine tune the back pressure.The control scheme of the liquid level in the wine tank comes from H & K Company of Germany. At that time, it used the pneumatic instrument of Taylor company to control the liquid level in the wine tank by measuring the static pressure at the liquor inlet pipe.At the beginning, we did not make in-depth analysis of this control scheme and followed this method. We only changed the pneumatic instrument to the electrical instrument, while the actuator still used the pneumatic valve.When we meet the above problems in the debugging site, we use the basic principles of hydrodynamics to analyze and find that this control scheme does have defects.Because the static pressure at the liquor inlet pipe is not only affected by the liquid level in the wine tank, but also by the back pressure in the wine tank.Generally speaking, the pressure change measured by the pressure sensor cannot be distinguished from the source. The regulator only knows to open the regulating valve when the pressure is lower than the set value, and close the regulating valve when the pressure is lower than the set value.If the pressure changes due to the change of liquid level, the control is normal.If the liquid level is not changed but caused by the change of back pressure, the regulator still indicates that the inlet regulating valve is opened and closed small, resulting in the liquid level out of control. If the bottle is broken and the air supply is insufficient, the full cylinder may appear soon.It is difficult to achieve synchronous consistency in the control of this correlation, and the accuracy and stability of the control are not very good.In the early 1990s, we put forward the control scheme of independent control of back pressure and liquid level, and developed a sensor for controlling liquid level.In 1995, the second packaging workshop of Yanjing carried out the productive test on the improved Guangqing 60 head short pipe machine, which was welcomed and affirmed by operators and manufacturers.At that time, we only installed a liquid level sensor on the wine tank. It was found that when there was wine in the tank without filling the bottle or idling, the liquid level display value changed by three to four words and had nothing to do with the rotation speed.It is analyzed that this is caused by the impossibility of absolute parallel between the rotating surface of the wine tank and the natural horizontal plane, that is, the track of a circle at a certain point on the liquid level sensor can not fall on the natural horizontal plane, but has an included angle with the horizontal plane.If viewed from the vertical plane passing through the rotation center, the included angle is zero at the intersection of the rotation plane and the horizontal plane, and continues to rotate from the intersection, the included angle gradually increases, and reaches the maximum when turning to 90 degrees, that is, the included angle between the rotation plane and the horizontal plane.Then continue to reduce the rotation angle. When the angle reaches the intersection line at 180 degrees, the angle returns to zero.And then continue to rotate in the same direction, the included angle will become negative and increase. When it reaches 270 degrees, it will reach the maximum negative value, then decrease. When it reaches 360 degrees, it will return to its original position, and the included angle will return to zero again.According to the mathematical law, the vertical distance from a point on the sensor to the natural horizontal plane should be the product of the radius of rotation and the sine function of the included angle.Its value changes with the rotation angle, and the law of its change is exactly the same as that of the included angle. It changes according to the law of sine function.Therefore, in order to eliminate this error, it can be automatically eliminated by installing the same sensor at the same rotation radius phase difference of 180 degrees, that is, at the place symmetrical with the rotation center.At present, this control scheme is used in the filling machine of our country, especially in the filling machine with larger cylinder diameter.The filling machines of KHS and Krones in Germany are equipped with four sensors in the same radius. From a mathematical point of view, it is not necessary at all, and its effect is exactly the same as that of the two.Theoretically, as long as in the same radius, in the 360 degree range, according to the angle uniform distribution, such as every 120 degrees one is three, every 90 degrees one is four.The measured liquid level height is the sum of the measured values of all sensors divided by the number of sensors. Two are divided by 2, three are divided by 3 and four are divided by 4.From the point of view of physics, the speed of the filling machine is very low, the angular speed is very small, and the filling flow of each filling valve is very small, so it is impossible to have a significant impact on the state of the horizontal plane.Therefore, I think it is unnecessary to use four sensors. Only two sensors need to be installed symmetrically on the same circumference.The control of liquor level in the filling cylinder has a great influence on beer filling. The fluctuation of liquor level will affect the fluctuation of filling velocity, not only the filling time, but also the filling stability.Of course, as long as there is wine in the tank, the small fluctuation of the liquid level is irrelevant.However, if the liquid level and back pressure are not controlled independently, it will inevitably increase the number of stoppage of the filling machine, increase the operation intensity of the workers, and it is difficult to achieve full automation. Moreover, from the perspective of control theory, the control of this related quantity is also inappropriate.5、 In order to become a commodity after beer brewing, the non pasteurized beer must be packaged. Which packaging technology and packaging materials are adopted depends on the market operation and management.The packaging process here includes the terminal treatment of beer. The purpose of any terminal treatment method is to extend the shelf life of commodities, which is obtained at the cost of losing beer flavor. The longer the shelf life is extended, the greater the flavor loss is, and vice versa.The beer with the best taste is the turbid beer with more yeast unfiltered, followed by the fresh beer with most yeast filtered out.In Europe, especially in Germany, except for a few beers exported to a distant place, other beers are filled without pasteurization.The prerequisite for the realization of this beer packaging technology is pure purification brewing, which includes the effective control and management of microorganisms.For beer filling, it is mainly to prevent secondary pollution and effective microbial control.Beer is a food or an injection. It's ok if it's a little harmless. Besides, all oxygen consuming bacteria can't survive in beer at all.The most important two points in beer filling: one is cleaning and sterilization, the other is the operation reliability of the filling machine.The most important one is reliability, which is just the weakness of domestic equipment, which is one of the main reasons why most of the domestic filling machines for draft beer use imported equipment.The consistency of the filling valve and the reliability of the operation of the filling machine are the most obvious differences between the domestic equipment and the imported equipment, and also the most noteworthy aspects.At the beginning of this year, in the article of "pure draft" beer published in this journal, there was a special discussion. There is no more repetition here. After the technical level reaches a certain level, the reliability will rise to the first place.
