Sensors embedded in the extrusion granulator

Thread Content

For work purposes, I have visited many petrochemical and coal chemical plants to see extrusion granulators in person. This thing is quite valuable; it can be considered one of the most important devices in the production of polypropylene (PP) and polyethylene (PE). As the final step in the production process, the steady operation of the extrusion granulation unit directly affects the continuity of production throughout the entire facility. Downtime caused by failures that last more than 10 hours results in the shutdown of the entire production line, with wide-ranging consequences. During the process, it was evident that everyone on site was concerned about the operation of the equipment, but no one could guarantee whether there were actually any problems with it. In most cases, equipment maintenance involves using a vibration meter to check the vibration levels; occasionally, conscientious supervisors will record the vibration trends. However, there is no basis for determining how the internal components are actually functioning, whether there is any damage, or why the vibration is so much greater. Fortunately, this equipment doesn’t usually have any major problems; regular overhauls every few years, during which the bearings and other components are replaced, ensure its proper operation. However, I have also seen several manufacturers experience shutdowns due to shaft breaks or severe wear and tooth damage of the gears; when these problems occur, they can indeed be catastrophic. Basically, the extruders for PP and PE that are available on the market are from three companies: German CWP, Japanese JSW, and Japanese KOBE Steel. In Gansu, I also saw a high-pixel unit that has not yet been put into official operation. I’ve talked to many engineers; some of them installed temperature and vibration sensors of the XXX type, but it was difficult for them to analyze the data obtained from these sensors, or the data wasn’t very accurate – there was a lot of drift – so in the end they stopped using those sensors. In fact, the operation of extruders is special: the speed of the bearings and gearboxes is low, with the output shaft generally rotating at around 200 revolutions per minute ； Affected by the feed conditions, the load on the extruder also changes, resulting in fluctuations in its rotation speed ； It can be considered a low-speed load-changing device. Under complex operating conditions such as low rotational speeds and changing loads, it is difficult to obtain effective signals and to process them. If conventional vibration and temperature monitoring methods are used, the information related to fault characteristics is often obscured by background noise, making it hard to effectively monitor and analyze the operating condition of the gearbox. Frequent cases of underreporting and misreporting occur. In fact, in many cases, the sensors built into the extruder for bearing testing and gear testing are overlooked on site; usually, these sensors have wires leading to a module box or terminal block. Kobelco, Nippon Steel, and Kobe Steel, including those with large pixels, have such features pre-installed in the equipment delivered from the factory. In Kobe, sensors are connected to a conversion module that is integrated into the system. The JSW terminal box, CWP terminal block, conversion modules for Kobe connections, and sensors embedded in the machine units – together with specialized instruments, these can be used to test the condition of the bearings inside the gearbox, the lubrication status of those bearings, as well as the gear meshing condition. Here are some examples of tests: failure of the bearing’s outer ring, bearing rolling elements, gear wear. You can check whether your extruder has such issues; if so, feel free to contact me to discuss them together.