Daily maintenance of pressure sensors Chengdu JRT Meter Technology Co., Ltd , https://www.jrt-measure.com
Pressure sensor installed correctly
Usually the damage of the pressure sensor is caused by the improper installation position. If the sensor is forcibly installed in a hole that is too small or has an irregular shape, it may cause the shock film of the sensor to be damaged by impact. Selecting a suitable tool for machining the mounting holes facilitates the control of the size of the mounting holes. In addition, a suitable mounting torque facilitates the formation of a good seal. However, if the installation torque is too high, it can easily cause the sensor to slip off. To prevent this from happening, the anti-detachment compound is usually applied on the threaded portion of the sensor prior to installation. After using this compound, the sensor is difficult to move even if the mounting torque is high.
â— Check the size of the mounting hole
If the size of the mounting hole is not appropriate, the threaded portion of the sensor during the installation process is susceptible to wear. This will not only affect the sealing performance of the equipment, but also make the pressure sensor unable to fully function, and may even cause potential safety hazards. Only suitable mounting holes can avoid thread wear (Thread Industry Standard 1/2-20 UNF 2B). Mounting holes can usually be used to test mounting holes to make appropriate adjustments.
â— Keep the mounting holes clean
Keeping the mounting holes clean and preventing clogging of the melt is important to ensure proper equipment operation. Before the extruder is cleaned, all pressure sensors should be removed from the barrel to avoid damage. When the sensor is removed, the molten material may flow into the mounting hole and harden. If these residual melts are not removed, the top of the sensor may be damaged when the sensor is installed again. The cleaning kit can remove these frit residues. However, the repeated cleaning process may deepen the damage caused by the mounting hole to the sensor. If this happens, steps should be taken to increase the position of the sensor in the mounting hole.
â— Choose the right location
When the pressure sensor is installed too close to the production line, the unmelted material may wear out the top of the sensor; if the sensor is installed too far, a stagnant area of ​​molten material may be generated between the sensor and the screw stroke. The molten material may be degraded there, and the pressure signal may also transmit distortion; if the sensor is too deep into the barrel, the screw may touch the top of the sensor during rotation and cause damage. In general, the sensor can be located on the barrel in front of the screen, in front of the melt pump, or in the mold.
â— Carefully clean
Before using a wire brush or special compound to clean the extruder barrel, all sensors should be removed. Because both of these cleaning methods may cause damage to the sensor's diaphragm. When the barrel is heated, the sensor should also be disassembled and wiped on top using a soft cloth that will not wear, and the holes in the sensor also need to be cleaned with a clean drill and guide bush.
â— Keep dry
Although the sensor's circuit design can withstand harsh extrusion processing environments, most sensors are not absolutely waterproof and do not work well in a wet environment. Therefore, it is necessary to ensure that the water in the water cooling device of the extruder barrel does not leak, otherwise it will have an adverse effect on the sensor. If the sensor has to be exposed to water or a humid environment, special sensors with extremely high water resistance must be selected.
â— Avoid cold interference
In the extrusion production process, there should be sufficient "saturation time" from the solid to the molten state for the plastic raw material. If the extruder has not reached operating temperature before starting production, both the sensor and the extruder will suffer some degree of damage. In addition, if the sensor is removed from the cold extruder, the material may adhere to the top of the sensor causing damage to the diaphragm. Therefore, before removing the sensor, make sure that the temperature of the barrel is sufficiently high and the material inside the barrel is in a softened state.
â—Prevent pressure overload
Even if the overload design of the pressure measurement range of the pressure sensor can reach 50% (the ratio beyond the maximum range), it should be avoided from the safety point of view of the equipment operation. It is better to select the sensor whose measured pressure is within the measuring range. Under normal circumstances, the optimal range of the selected sensor should be twice the measured pressure, so that the pressure sensor can be protected from damage even if the extruder is operated under extremely high pressure.