➢ Correct installation #
Usually, damages of pressure sensor caused by the inappropriate installation. If the sensors installed in the too small hole or irregular shape hole, it could cause damage by the vibration impact for the sensor membrane. Choosing the right mounting processing holes tools are beneficial to control the size of the installation holes. In addition, the right installation torque can help to form good seal. But, the sensors will slip away caused by the high installation of torques. To prevent this kind of phenomenon, usually, the anti-separation compounds should be painted on the thread part of the sensor before installation. After used the anti-separation compounds, even the high installation of torque, it’s different for sensors slipped away.
➢ Checking the size of the installation holes #
If the size of the installation holes are not proper, in the process of installation, the thread portion is susceptible to wear. That will not only influence the sensors’ sealing performances, but also can not play sensors’ full role, and may even cause safe hidden troubles. Only the right installation holes can avoid thread wear (threaded industrial standard 1/2-20 UNF). Usually, it is necessary to test the mounting holes by using installation holes measuring instruments and to make appropriate adjustments.
➢ Keeping mounting holes clean #
It is very important to keep mounting holes clean and prevent melt material blocking to ensure the its normal operation. Before the extruder is cleaned, all the sensors should be removed from the barrel to avoid damage. During the sensor demolition, melt material is likely to flow into the mounting holes and harden. If these remnants melting material is not removed, the top of the sensors may be caused damage when they are installed once again. Using Clean kit can remove these melt material residues. However, if it happened, the repeat cleaning process may deepen installation holes of sensor damage. If it was happened, it is necessary to take some measures to rise the sensors position in the installation holes.
➢ Choosing appropriate position #
When sensor installation position is too close to the upstream of the production line, the non-molten material may wear the top of the sensor. If too close to the downstream, there may appear the molten material dead zone between the sensor and screw line where melting materials may produce degradation and may also cause distortion of pressure signal when transmitted. If too deep installed into barrel, damage may also caused by the touch between the sensor top and screw in its process of rotating. Generally speaking, the sensor can be located in the machine barrel in front of the strainer, or before or after the melt pump, or in the mould
➢ Careful cleaning #
You’d better dismantle all sensors before cleaning by using steel wire brush or special compounds. Because these two cleaning ways may cause the vibration of the sensors’ membranes. When the barrel was heated, sensors also should be dismantled and be wiped with soft cloth. At the same time, the sensor installation holes also need to clean using clean drilling machine and guide sleeve.
➢ Keeping dry #
Although sensor circuit design can endure the harsh extrusion in processing environment, most of the sensors can not absolutely waterproof. And, it will influence its normal operation under damp environment. So, you need to ensure the water- cooling of extruder barrel and water leakage of device, otherwise, it will cause adverse effect for sensors. If sensors have to be exposed to the water or wet environment, you’d better choose the extremely strong water proofing property special sensors.
➢ Avoiding low temperature interference #
In the extrusion production process, for plastic raw materials, it needs plenty of “soak time” from solid to melt condition. If it does not reach operating temperature before extruder starting production, then sensor and extrusion machines will get a certain degree of damage. In addition, if sensors are dismantled from cold extrusion machine , material may adhere to the sensors’ tip to cause damage for vibration film. Therefore, before the sensor demolition, you should confirm the barrel temperature is high enough with softening state of the tube materials.
➢ Preventing overload pressure #
Even if pressure measuring range overload design of sensors can reach the highest overload 50% (beyond the ratio of maximum range), you’d better better choose sensors used to test pressure within its scope range considering safety operation. Normally, the best pressure range of sensors should be 2 times of the tested pressure. Even though extruders are under in high pressure operation, the sensors may not be damaged.
