Development and calibration of pressure sensor for high concentration viscous materials

1. Introduction

The pipeline transportation system of high-concentration viscous materials has been successfully applied in the long-distance transportation of coal slime pipelines. In order to better study the pipeline transportation characteristics of high-concentration viscous materials, we have established a pipeline transportation laboratory for high-concentration viscous materials. One of its purposes is to study the pressure loss of materials during pipeline transportation, so pressure sensors should be installed on the pipeline to obtain the pressure value during pipeline transportation.

However, due to the physical properties of high-concentration viscous materials, such as high viscosity and high abrasion, ordinary pressure sensors cannot be used well. For example, the pressure-inducing hole of ordinary pressure sensors is very small, which is easily blocked when measuring viscous materials, and the pressure cannot be read correctly. In order to ensure accurate pressure transmission, the diaphragm of diaphragm pressure sensors is generally made very thin. If it is used for pressure measurement of viscous materials, the diaphragm will be worn out in a short period of time, and the small solid particles in the viscous materials can also easily penetrate the metal diaphragm during the transportation process. Therefore, this diaphragm pressure sensor can only be used for short-term and intermittent testing of viscous materials (for example, in this article, this sensor is used as a standard sensor to compare with the homemade pressure transmission device). Therefore, we have specially developed a new type of viscous material pressure sensor to solve this problem.

2. Structure of the pressure sensing device for high-concentration viscous material pipeline

The structure of the pressure sensing device is shown in FIG1 .

In Figure 1, both ends of the short tube are connected to the conveying pipeline; the disc-shaped rubber pressure transmission membrane plays the role of isolation and pressure transmission; the oil cylinder is filled with oil; and the pressure transmitter is used to measure the oil pressure. When highly viscous materials pass through the short tube, due to the certain pressure in the pipeline, the materials will fill the short tube and squeeze the rubber diaphragm. The rubber diaphragm transmits the pressure to the oil in the cylinder. The oil pressure in the cylinder is measured by the pressure transmitter, and the pressure in the pipeline can be indirectly obtained. In order to test whether this pressure device can correctly measure the pressure in the pipeline transportation process, we performed static calibration and dynamic calibration.

3. Pressure sensor calibration test

1. Static calibration

The static calibration test is carried out at room temperature and normal pressure. The calibration equipment used is a piston pressure gauge, model YS-600, accuracy: 0.05, measurement range: 0kgf/cm2~600 kgf/cm2 (Note: 0~58.865MPa). The experimental device is shown in Figure 2.

The static calibration test uses the connection flange (as shown in Figure 2) to install the pressure transmission device on the piston calibrator, and calibrates the pressure transmission device with standard weights. The calibration is carried out three times in total, and the test data are shown in Table 1.

By taking the arithmetic average of the six sets of data under the same pressure and then using the least squares method to perform linear fitting on the data, we can obtain the static characteristics of the homemade pressure sensor device. [page]

2. Dynamic calibration

The dynamic calibration test is carried out at room temperature and normal pressure. The equipment used is AK-1 pulsation pressure transmitter with a measurement range of 0MPa ~25MPa and an accuracy level of 0.5.

The pipeline transportation system uses a double-cylinder hydraulic plunger pump to deliver power, and each hydraulic stroke is 6s to 40s, so the requirements for the dynamic response characteristics of the pipeline pressure sensor device are not high. However, since there is a transient reversing process between the reciprocating motion of the double cylinders, this requires the pressure sensor device to accurately reflect the transient characteristics of the reversing process, so that it can be considered that the dynamic response characteristics of the pressure sensor device can meet the measurement requirements during pipeline transportation. For this reason, the comparative calibration method is adopted, that is, a diaphragm pressure sensor with high accuracy and good dynamic response characteristics and a homemade pressure transmission device are installed at the same pressure measurement point. During the test, the pressure signals of the two are collected to the computer and displayed in real time. If the two data curves have the same shape in the steady state and transient process, it can be considered that the pressure sensor device has good dynamic response characteristics. In order to be able to show it clearly, the zero point of the standard sensor is deliberately adjusted to 0.2MPa. Figure 3 shows the pressure signal curves of the two sensors collected during the pipeline water delivery experiment. The upper one is the pressure curve of the standard sensor, and the lower one is the pressure curve of the homemade pressure transmission device. It can be seen from the figure that the curves of the two sensors have good consistency during the water delivery process. FIG4 is a partial enlarged view of FIG3, reflecting the pressure situation of this measuring point during the reversing process of the hydraulic cylinder. The two are also very consistent in subtle details.

Figure 5 is a pressure signal curve of two sensors collected when the pipeline transports urban "dewatered sludge", and Figure 6 is a partial enlarged view of Figure 5, which is the curve of the two pressure sensors during the hydraulic cylinder reversal process. It can also be seen from the figure that the curves of the two sensors have good consistency.

IV. Conclusion

After comparing the static calibration and dynamic calibration, we can see that our self-made pressure sensor has high accuracy and good dynamic response characteristics, which can well meet the pressure measurement in the process of high-concentration viscous material pipeline transportation.

The pipeline transportation tests of thick materials (coal slime, dewatered sludge, papermaking waste sludge, etc.) have shown very good results.

References:

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