Installation and maintenance of high temperature melt pressure sensor
Core Tip: In the extrusion line, high temperature melt pressure sensors play an important role in improving melt quality, improving production safety and protecting production equipment. At the same time, the high-temperature melt pressure sensor is a very sensitive component, and only proper installation and maintenance can fully play its role.
It is understood that safety and protection of production equipment play an important role. At the same time, the high-temperature melt pressure sensor is a very sensitive component, and only proper installation and maintenance can fully play its role.
In the extrusion process, some quality standards of the product (such as dimensional accuracy or surface flatness of mineral filler parts) require optimal control of the extrusion pressure, which is achieved by a high temperature melt pressure sensor. Important components required. By providing a melt pressure sensor and a pressure control device at the mold inlet connection, the yield can be made more stable while reducing material waste. Melt pressure sensors play an important role in improving melt quality, increasing production safety, and protecting production equipment and extending their service life.
In addition, measuring the pressure through the filter and the melt pump is also important to ensure production safety and to optimize the performance of the equipment. If the melt is blocked when it flows into the mold, the sensor under the filter will alert you to the operator. When the sensor on the filter screen gives an alarm, it indicates that the internal pressure of the extruder is too high, which may cause excessive wear on the screw. For the manufacturer of the melt pump, it is necessary to measure the inlet pressure and outlet pressure of the melt to ensure that the melt can continuously flow into the mold, as any hindrance can cause damage to the melt pump.
The high temperature melt pressure sensor assembled on the extrusion line can be a single sensor that measures only one point pressure, or a series of sensors that measure the entire production line. The melt pressure sensor is connected to the data logger and the audible alarm device, and the processing parameters of the extruder can be adjusted by the processing control system. At the same time, the pressure sensor is also a very sensitive component that can be easily damaged if it is not properly installed and maintained. The following simple methods are helpful to extend the life of the pressure sensor and help the user to obtain accurate and reliable measurement results.
Install correctly
Usually the damage of the high temperature melt pressure sensor is caused by improper installation position. If the sensor is forcibly installed in an excessively small hole or an irregularly shaped hole, the vibration film of the sensor may be damaged by impact. Choosing the right tool to machine the mounting holes will help control the size of the mounting holes. In addition, suitable mounting torque facilitates the formation of a good seal. However, if the installation torque is too high, it is easy to cause the high temperature melt pressure sensor to slip. To prevent this, it is common to apply the anti-separation compound to the threaded portion before the sensor is installed. After using this compound, the sensor is difficult to move even if the mounting torque is high.
Check the size of the mounting hole
If the size of the mounting hole is not suitable, the threaded portion of the high temperature melt pressure sensor is susceptible to wear during installation. This not only affects the sealing performance of the device, but also prevents the sensor from functioning fully and may even pose a safety hazard. Only the proper mounting holes can avoid thread wear (Thread Industry Standard 1/2-20UNF2B). Mounting holes can usually be tested with a mounting hole gauge to make the appropriate adjustments.
Keep the mounting holes clean
Keeping the mounting holes clean and preventing clogging of the melt is important to ensure proper operation of the equipment. All high temperature melt pressure sensors should be removed from the barrel to avoid damage before the extruder is cleaned. When the sensor is removed, the melt may flow into the mounting hole and harden. If the residual melt is not removed, the top of the melt may be damaged when the high temperature melt pressure sensor is installed again. The cleaning kit removes these melt residues. However, repeated cleaning processes have the potential to deepen the damage caused by the mounting holes to the high temperature melt pressure sensor. If this happens, measures should be taken to raise the position of the high temperature melt pressure sensor in the mounting hole.
Choose the right location
When the high temperature melt pressure sensor is installed too close to the upstream of the production line, the unmelted material may wear the top of the sensor; if the high temperature melt pressure sensor is installed in the too late position, the high temperature melt pressure sensor and the screw There may be a stagnant zone of molten material between the strokes, where the melt may degrade and the pressure signal may transmit distortion; if the high temperature melt pressure sensor is too deep into the barrel, the screw may touch the high temperature during the rotation. The top of the melt pressure sensor causes damage. In general, high temperature melt pressure sensors can be located on the barrel in front of the screen, in front of or behind the melt pump, or in the mold.
Carefully clean
All high temperature melt pressure sensors should be removed before cleaning the extruder barrel with a wire brush or special compound. Because both cleaning methods may cause damage to the diaphragm of the high temperature melt pressure sensor. When the barrel is heated, the high temperature melt pressure sensor should also be removed and wiped with a soft cloth that does not wear out. The hole in the high temperature melt pressure sensor also requires a clean drill and guide sleeve. Clean up.
Keep dry
Although the circuit design of the high temperature melt pressure sensor can withstand the harsh extrusion processing environment, most high temperature melt pressure sensors are not absolutely waterproof, and are not conducive to normal operation in humid environments. Therefore, it is necessary to ensure that the water in the water-cooling device of the extruder barrel does not leak, which may adversely affect the sensor. If the sensor has to be exposed to water or moisture, choose a special high temperature melt pressure sensor that is extremely water resistant.
Avoid low temperature interference
In the extrusion production process, for plastic raw materials, there should be sufficient "soaking time" from solid to molten state. If the extruder does not reach the operating temperature before starting production, the high temperature melt pressure sensor and extruder will be damaged to some extent. In addition, if the high temperature melt pressure sensor is removed from the cold extruder, the material may adhere to the top of the high temperature melt pressure sensor causing damage to the diaphragm. Therefore, before removing the high temperature melt pressure sensor, make sure that the barrel temperature is high enough and the material inside the barrel is softened.
Prevent pressure overload
Even if the overload design of the sensor's pressure range can reach 50% (out of the maximum range ratio), it should be avoided as far as possible from the safety point of operation of the equipment. It is best to choose the high temperature melt pressure within the range of the measured pressure. sensor. Under normal circumstances, the optimum range of the selected high-temperature melt pressure sensor should be twice the measured pressure, so that the high-temperature melt pressure sensor can be prevented from being damaged even if the extruder is operated at extremely high pressure.
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