1. The feeding system controlled by computer improves the batching accuracy and solves the problems of tedious manual batching, loss of materials and chemical hazards to operators.

2. Efficient pneumatic conveying system replaces the heavy labor of mass material handling process and improves the production efficiency.

3. The material handling process is carried out completely in the closed pipeline, avoiding the pollution of dust to the workshop environment and the hazards to the workers.

4. The process of material preparation and handling is more centralized and efficient, with higher output, which can fully meet the needs of mass production.

Positive pressure pneumatic conveying system

PVC batching equipment dosing process according to the different final products, usually need to add a variety of solid or liquid additives to the PVC resin, such as heat stabilizers, lubricants, plasticizers and colorants, etc., and at a certain temperature so that the components and the resin is fully mixed and absorbed, in order to obtain the proportion of accurate, well-mixed and absorbed materials, which is a prerequisite for the production of high-quality products. Obviously, the dosage process is a time-consuming, technically complex and demanding stage in the whole material preparation process. Therefore, in the modern dosage technology, all without exception, the use of computer-controlled multi-component automatic weighing and measuring system.

In fact, the dosage process is to deal with the proportion of each group of components, therefore, the measurement of the material is the core of the dosage. Generally, there are two kinds of metering methods: volume metering and weight metering. Among them, weight metering is more reliable and widely used because it adopts high-precision load cell to measure the material directly.

According to the different weighing principles, weight measurement can be divided into three types, namely, batch cumulative weighing, loss-in-weight weighing and continuous weighing of flow process materials. For PVC blending, batch weighing is the most suitable, as it is very harmonized with the batch mixing method of the mixer. The industrial weighing modules presented here have a static accuracy of more than 1/1000 and a dynamic accuracy of 3/1000 or even higher when actually used in a feeding system, and are therefore perfectly suited to meet the requirements of the PVC dosing process. However, it should be noted that in most formulations, due to the PVC resin and CaCO3 accounted for a large proportion of the other various additives accounted for a small proportion, so if the same weighing device is used, in the larger measuring module range, easy to decline in relative accuracy, resulting in the weighing of additives when the super poor. For this reason, the general practice is to use two weighing devices with different ranges to weigh separately. Before weighing starts, the valve below the weighing hopper 4 is closed, and the components A, B, C and D are added to the hopper 4 in turn under the action of the screw feeder. Of course, the amount to be added has been set in advance in the controller 6, so that when each component has been added to the amount, the controller stops the corresponding motor. The controller accumulates the weights of the components so that they meet the recipe requirements. When the weighing is complete, the controller 6 waits for an external control signal to open the valve below the hopper 4 in order to place the material into the downstream equipment. The function of the controller 6 is to reduce the electrical signal from the load cell to a weight value and display it in the computer display. At the same time, it provides logical control of the motors and valves etc. in this system as required. In addition, it also has a variety of input and output interfaces, which can accept control signals from other parts to realize the linkage, but also can send its own weighing data to the main control computer for processing in real time. Generally, the weighing controller is supplied together with the load cell by specialized manufacturers. In addition to the above * basic functions, some weighing controllers and load cells also have automatic temperature compensation, variable speed control of the charging motor, automatic correction of the suspension value of the charging and automatic calibration of the scale.

Mixing process is generally completed by the high-speed mixer and cooling mixer together, part of the production of soft products can also be used only high-speed mixer. With the different products, mixing time and mixing temperature are also different. In general, the mixing temperature between 80 ~ 130 ℃, hard products will be higher (110 ~ 130 ℃), soft products are relatively low (80 ~ 100 ℃). The mixing time for each batch of material is 8~10min. In the mixing of PVC and additives, usually high-speed mixer-based. Mixing process is not only the dispersion process of small particles of material, but also between the components at a certain temperature mutual penetration and absorption process. Therefore, the uniformity of temperature rise in the mixer is the key to ensure that a high quality mix is obtained. Here the reasonable design of the mixing pulp and the * best control of the mixing pulp end line speed is very important.

Generally high mixing speed is conducive to the dispersion of materials, but the speed is too high will also cause the mixer in the local area of overheating, resulting in uneven temperature rise of the material and affect the quality of the mixture. According to experience will be a high-speed mixer mixing pulp end of the line speed control in 35m / s or less. As in the mixing process will produce a large amount of water vapor, these water vapor condenses into water and will fall into the mixer, thus affecting the quality of the mixture, the design of a reasonable exhaust system for the mixer is also very necessary.

PVC mixer to test the quality of the mixture using the following methods:

1. Visual observation: good quality mixture of normal color, no impurities, no lumps.

2. Heap density measurement: the correct mixing process will increase the pile density of the material.

3. Material fluidity: Prepare a funnel and install a plug valve at the discharge end. Load a certain amount of dry mix samples into the funnel, open the valve, calculate the time used in the funnel to completely drain the material, the shorter the time means the better the fluidity.

4. Flowability test: a good mixture, its flowability is also better.

5. Color test: generally should be used to detect the color meter color (especially white), the test can be carried out in daylight, ultraviolet, fluorescent and white light, respectively. Simultaneous testing of samples and standards, you can measure whether the sample is qualified.

6. Extruded samples: dry mix samples in a small test extruder extruded into a specimen, and test: extrusion process of the specimen's dimensional stability; specimen surface and cross-section of the color; specimen surface quality; specimen impact resistance; extrusion flow rate (weight per unit of time of the extruder); specimen whether it contains impurities, foreign objects; specimen surface and cross-section of the air holes.