Rotor sealing system of the hottest internal mixer

The rotor sealing system of internal mixer

nowadays, the production of compound containing multiple components is mainly carried out by internal mixer. The compound includes polymers, fine and easily dispersed powdered fillers, carbon black, calcium carbonate, a small amount of chemicals such as vulcanizing agents, accelerators or processing aids, and liquid components such as plasticized oil. These liquid and fine powder components are controlled by the rotor sealing system of the internal mixer to limit their entry into the external environment

at first, people treated these fine and easily dispersed ingredients through oil film adhesion, which is called bonding. Due to the high pressure in the internal mixing chamber, these pastes will be slowly extruded along the shaft of the rotor. In order to limit the outflow of these pastes, sealing rings are added at both ends of the rotor shaft

the seal ring itself consists of two rings, usually with a hard surface layer in the sliding area. One is fixed on the rotor shaft and the other is installed on the frame. The essential difference of each rotor seal system lies in the different surface pressure applied, which is divided into automatic rotor seal (SSA), spring-loaded rotor seal (GA) and hydraulic rotor seal (WYH)

dust proof design

ssa sealing principle is based on the use of pressure in the mixing chamber. If the pressure in the mixing chamber increases, the pressure will be transmitted to the sliding sealing ring, so the locking force of the sealing ring will be increased. In order to apply the minimum surface pressure, the disc spring assembly is used to press the inner sliding ring onto the outer fixed ring. Nowadays, new internal mixer is equipped with GA and WYH rotor sealing system

in the spring loaded rotor seal (GA) system, the seal ring is located outside the mixing room. Here, the inner ring is fixed to the frame, and the outer rotating ring is assembled on the rotor shaft. The surface pressure is applied by several disk spring assemblies arranged around the rotating ring, and the spring is preloaded by the nut. The lubricating plasticizer is injected into the annular gap of the sealing ring to bond some fine and easily dispersed rubber components. The deeper lubrication hole is located in the fixed sliding ring to lubricate the sliding surface

in the case of hydraulic rotor seal (WYH), the seal position is closer to the rotor and is located inside the end of the frame of the mixing chamber. The inner rotating sliding ring is fixed on the rotor shaft. The outer fixing ring is compressed with it through the yoke sleeve. The contact pressure is generated by the hydraulic cylinder and disc spring assembly, and the pressure is transmitted to the pressure ring of the outer sliding ring through the yoke sleeve. The lubrication method is similar to GA rotor sealing system. In fact, the cross-sectional direction of the sealing system will shift to the mixing chamber, and fine materials will bond here in the shaft gap between the rotor and the wear-resistant disc

comparing the two systems (GA and WYH sealing system), it is obvious that the sealing position is the factor that distinguishes them. Because WYH sealing system is close to the rotor, only a small dead corner may accumulate materials. On the other hand, the moving packing with wear effect is easy to enter the sliding surface directly, which will adversely affect the wear of the equipment. GA sealing system has a relatively long annular gap. Because the powder stays in the annular gap for a long time, it can be bonded better by oil. Therefore, the sliding surface can be better protected and the force of seal loading can be minimized. However, at the same time, the danger of some materials accumulating in the annular gap increases, and the sealing oil is particularly important here

lubrication system

sealing system is divided into two separate parts. Lubrication of sliding seal ring and material bonding. As a conventional lubrication system, the lubrication of sliding seal ring has the following functions: to compensate the speed difference of the surface by generating shear in the liquid; Take away the heat generated by friction; It plays a protective role in case of material bonding failure; Cooling parts; Take away the particles worn down from the contact surface; Foreign particles are allowed to enter and take away, such as various components of the compound and corrosion protection

the task of the material bonding part cannot be explained as clearly as the lubrication of the sliding seal ring. Its main task, like its name, is to bond various components of fine dispersion. The use of high viscosity operating oil ensures the bonding effect. This function is very important in hydraulic seal system. As the sealing system is closer to the mixing chamber, the packing with wear effect is easier to enter the sliding surface directly, and the freely moving packing is easier to enter the outside world. The above basic configuration is about 30000 yuan. In addition, the material bonding part can flush the gap between the end of the frame and the rotor shaft, so no material will accumulate here or produce sulfur. Because the GA sealing system has a long annular gap, this cleaning effect becomes very important in this system. At the same time, the addition of operating oil reduces the viscosity between the rubber, the rotor shaft and the end of the frame, and in this way also reduces the transmission of materials along the rotor axial sealing system. Therefore, it is very necessary to add bonding oil

problems in the rotor sealing system

regardless of the wear of the sliding seal ring, the material bonding and the oil required for the lubrication of the sliding seal ring will also lead to some substantive problems. Realizing the above functions requires a large amount of oil, resulting in high oil procurement costs. Moreover, these oils, which contain various components of the compound, such as polymers and fillers, also need to be treated after coming out of the mixing chamber through the rotor sealing system, which is also quite expensive. As we all know, more than 80% of the oil used flows into the mixing chamber, which may cause major quality problems. As mentioned earlier, if the amount of lubricating oil in the bonded part of the material is too small, part of the compound will accumulate in the annular gap and start to sulfur, which may cause the next truck of material to be contaminated. Secondly, too little lubricating oil in the sliding seal ring will lead to rapid wear of the seal ring

more decisive parameters of seal ring wear also include the variety and hardness of packing, the geometry of rotor, the installation position and the adjustment of surface pressure. Taking wear and flushing treatment as a function of surface pressure, two opposite trends can be observed. If the pressure influence factors are considered independently, it can be determined to use a lower contact pressure to reduce the wear rate. On the contrary, increasing the contact pressure can cause the seal ring to wear faster

principle analysis of annular gap process

the following research investigated the influence of material transmission from the mixing chamber to the sealing ring, especially the influence of bonding oil

the mixing test was carried out in a laboratory mixer with a tangent rotor with a capacity of 7 liters. In order to achieve the test purpose, the sealing rings at two sealing positions were removed. Natural rubber (RSS 1100phr) was used as the raw material for the test, which was tested without lubrication and with bonded oil (BP enerpar 16) added in the external area of the mixing room

the objective of this group of research tests is to investigate the weight difference of rubber when the internal mixer is not sealed. The difference is defined as the ratio of the initial rubber weight Mo to the leaked rubber weight mexit. To achieve this, collect the leaked rubber from each position separately. When adding bonded oil, separate and collect the rubber from the leaked oil

all tests were conducted after adding polymer and mixing for 15 minutes. The top bolt pressure is selected as 50n/cm2 as the typical value. The rotor speed is 30 and 50rpm, and the filling factor varies from 50% to 80%, or from 40% to 70%. After discharging, test the temperature of the batch by hand

each rubber difference curve shows that the weight of leaking rubber continues to increase. The washing treatment can be divided into two parts. At first, it can be detected that the treatment quantity slowly increases. When the temperature range reaches about 130 ℃, the rubber difference of each curve increases with almost the same slope. When the rotor speed rises to 50rpm, the rubber leakage is doubled due to the increase of shear rate. In this case, rubber leakage will also occur when the mixing chamber is filled with low volume. The assumption leading to this result is that the material transmission is caused by the ibenberg effect, which is the core technology of we country. At high filling coefficient, this effect superimposes the effect of pressure rise in the mixing chamber. Considering the actual mixing process, the result is that the material transmission increases the pressure on the rotor sealing system. Especially natural rubber - based on high temperature formula

based on the weibenberg effect, the trend of material sliding with the sidewall increases with the decrease of shear force. The decrease of adhesion leads to the decrease of shear force, which will lead to the decrease of the weight of leaking rubber. This reduction is equivalent to stopping the leakage of materials, which can be obtained by adding bonding oil

in order to compare the weight difference of natural rubber under non lubricated and lubricated conditions, the amount of oil changes according to two levels. The total amount of specified oil includes two unsealed rotor sealing parts. By wetting the rotor shaft, the overflow of rubber can be prevented by a considerable amount. At the maximum flow rate of 1016ml/h, there is no material coming out of the mixing chamber within the range of the studied filling coefficient. When the flow rate is reduced to 440ml/h, the maximum difference of rubber is 0.7%, and the rubber overflow begins when the filling coefficient exceeds 65%. With the rise of temperature, the oil absorption capacity of rubber increases. Friction again exceeds adhesion. In this way, adding bonding oil has a new and deeper significance. First, the fine fillers must be bonded. With the improvement of mixing temperature and uniformity, the materials moving outward along the rotor sealing system can reduce and enhance the green and safe development of new materials in the whole life cycle by reducing the viscosity between the compound and the rotor shaft. Therefore, it is strongly recommended to use bonding oil

analysis of process parameters

the parameters related to seal ring wear and flushing treatment are the adjustment and application of contact pressure. As an important condition to ensure reliable sealing function, it is necessary to prevent the seal ring from opening, which means that the surface pressure of the seal ring must exceed the pressure generated at the front end of the rotor sealing system

on the one hand, reliable sealing must be ensured; on the other hand, the surface pressure should be minimized to reduce the wear of the sealing ring. For this reason, we must know how much pressure is generated at the front end of the sealing ring

in order to obtain these data, a pressure sensor is installed on the fixed ring of GA rotor sealing system, which can provide information about the pressure generated in the mixing chamber during the mixing process

the mixing process parameters of EPDM formula under conventional mode were recorded in the test. First, the polymer and carbon black are added into the internal mixer together and mixed for 45 seconds. At this time, the filling coefficient is calculated as 47%. The first peak power occurs after the upper top bolt is lowered. In the low filled mixing chamber, no or only slight pressure generation can be detected. Add other packing and operating oil after the second lifting of the top bolt. The filling factor is now 87%, and then the pressure rises suddenly after the top bolt is lowered. Here, the maximum and minimum values of pressure in a sequence cycle can be observed

a detailed investigation of the maximum and minimum pressure can be observed during the second lowering of the top bolt. Pressure generation includes two parts, one part is caused by the rise of pressure in the mixing chamber; Another part