The current situation of continuous mixing batching system measurement method

1, the traditional use of continuous measurement methods

In such as building materials, grain and oil, mining and other bulk material measurement or online control of batching, there are a variety of methods. More typical are: belt scale class, punch plate flowmeter class, nuclear scale class, disk feeding scale class. These forms of measurement have their own characteristics, but the limitations are very large, affected by changes in the dosage machinery, accuracy is not high, installation and adjustment is cumbersome, maintenance is large. Belt scale process introduction, process: belt scale will be subjected to the unit area (weighing section) on the load signal and the change speed (belt speed) signal for the integral arithmetic derived from the flow value, as a controllable object.

Note: By controlling the speed of the drag type belt, change the amount of material dragged out, the material is shaped by the outlet of the feeding chute, its thickness is stable and uniform, regardless of the speed of the belt machine, the load on the belt is constant. Compared with other feeding methods, this method has better measuring and control accuracy.

Note: feeding and weighing functions are realized on two belts respectively

2、Continuous metering method in continuous mixing feeding system on the use of the current situation of continuous mixing, including: steel-plastic batching, PVC continuous mixing batching, plastic continuous mixing batching. In terms of metering accuracy, at present, these ingredients can not be compared with the intermittent type. Therefore, continuous mixing method is not favored by the majority of users, and is one of the reasons. Scientific analysis can show that the two measurement methods determine the mixing process have their applicable occasions, can not be due to temporary technical limitations and affect the application of continuous mixing.

At present, continuous mixing batching are used in the volumetric method or belt scales / spiral scales to measure the two types of measurement methods used in Europe can be made to high precision, such as the German Shenk's belt batching, dynamic batching accuracy of 2%. In China, but not, because of the constraints of China's machinery manufacturing and materials and other basic industries. At present, China's belt scales used in the highway industry measurement accuracy can only reach 5% or so, with the volumetric measurement of the difference, long-term stability is poor.

The revolution of continuous weighing

Automatic dosage systems are gradually replacing belt scales, spiral scales, and even totalizing scales, as a new measurement method, gradually applied to more and more material handling.

Basic principle: the weighing hopper and feeding mechanism as the whole scale, through the instrument or the host computer non-stop weight signal sampling on the scale, calculate the weight per unit of time as the ratio of the instantaneous flow rate, and then through a variety of hardware and software filtering technology, resulting in the control object can be used as the "actual flow". The acquisition of this flow is very important, is the dosage system can be accurate measurement of the basis. The figure presents a classic method:

Then FC through the PID feedback algorithm, approximate the target flow control operation, the output regulation signal to control the frequency converter and other feeder controllers.

Differential reduction scale (dosing system) in practice: from the principle can be seen it is not subject to mechanical changes in the scale and feeding mechanism, it is only the calculation of the weight difference (differential weight), compared with the traditional means of dynamic measurement, its advantages are self-evident. For the control of the object for the flow (t / h, kg / min), and the material can be transported well, the measurement of high precision requirements, the loss-in-weight method of measurement can be used as an optimal program.