Graeff Graff NTX technology replaces mercury containing melt pressure sensor
In extrusion equipment and high-temperature fluid measurement system, if the operation is improper, the high-temperature melt pressure sensor containing mercury will pollute the environment and endanger health; Graeff Graf China's newly developed mercury free melt pressure sensor based on NTX technology will not cause health problems, and the measurement results are highly accurate. In addition, the product is extremely durable and has a long service life. The high-temperature melt pressure sensor plays a core role in controlling the extrusion process. Without accurate pressure measurement, it is almost impossible to control the production process in most cases. The measured melting pressure value is not only used to control the rotation speed of extruder and pump, but also represents an indispensable control variable when achieving high-quality melt filtration. Despite this core function, the importance of high temperature melt pressure sensors is almost ignored in many extrusion operations: little attention is paid to quality characteristics during purchase. Untrained personnel often operate incorrectly, resulting in rapid damage to the high temperature melt pressure sensor. In real life, the impact of failure or low-quality pressure sensors on cost is usually underestimated. In many cases, only direct costs are considered when purchasing new sensors. However, the indirect costs caused by production difficulties due to lack or incorrect pressure measurement or production interruption when the sensor must be replaced are more important.
Graf (Jiaxing) Instrument Co., Ltd. is a Chinese subsidiary of Graff GmbH limited, a European enterprise, which is 100% FS controlled in China (hereinafter referred to as Graff China). Graf (Jiaxing) Instrument Co., Ltd. (Graff China) is the official organization of Graff GmbH limited in China; Graeff China has experience in the design, development and production of various industrial pressure sensors, temperature sensors, melt pressure sensors, instruments, industrial control systems and automation products, covering various fields that need to detect temperature, pressure and control of automation systems.
In August 2020, the headquarters of Graeff announced the establishment of Graf (Jiaxing) Instrument Co., Ltd., a Chinese subsidiary controlled by 100% FS in China. In November 2021, the factory of Graf (Jiaxing) Instrument Co., Ltd. was officially settled in the national Xiuzhou high tech Development Zone in Jiaxing, Zhejiang, China.
Since 1983, the core technical members of Graeff Graf company began to study the mercury free filled melt pressure sensor. Prof Zhao (Graeff lifelong technical consultant), nearly 90, talked about the research process of mercury free filled melt pressure sensor.
Graeff Graff NTX technology replaces mercury containing melt pressure sensor
Mercury containing pressure sensors can meet high quality standards. However, if not handled correctly, this heavy metal will cause serious harm to the environment and great harm to health. As early as 2007, the European Parliament passed a bill to "restrict the commerce of some mercury measuring instruments". In the coming years, the EU plans to take additional comprehensive measures to reduce the risk of exposure to mercury as part of the agreed strategy. Graeff Graff has developed a new generation of mercury free pressure sensors using NTX technology. Compared with mercury containing sensors, these sensors do not cause health problems and do not need to be disposed of as special waste. Other advantages of the product include low zero offset and accuracy up to 0.1% FS of the final value. These sensors can be used at temperatures up to 500 ℃, and are also suitable for the fields of medicine and food processing. Figure 1 shows a zero offset free pressure sensor using different filling media between room temperature and 200 ℃. It is obvious that the zero offset of melt pressure sensor using NTX technology is lower than that of mercury containing pressure sensor. Therefore, the melt pressure sensor based on NTX technology represents not only an alternative to mercury containing sensor.
Failure cause of high temperature melt pressure sensor
The focus of Graeff Graff's investigation among high temperature melt pressure sensor users is to analyze the sensor faults and the causes of these faults. A total of 78 companies participated in the survey. When asked about frequency issues related to sensors, about half (52%) of companies said they rarely encountered faulty sensors. The situation becomes even more critical about the consequences of a faulty sensor: almost three-quarters of companies (72%) said there was a fairly serious or at least more serious problem when the sensor failed.
The item shown in Figure 2 is the failure cause of the provided high temperature melt pressure sensor. It is worth noting that installation and removal of the sensor is the most frequent cause of damage to the provided high temperature melt pressure sensor. The damage caused by pollutant particles in the melt glue accounts for a small proportion.
In this context, the sensor damage type shown in Fig. 3 can now be explained.
The most frequent damage so far is located in the most sensitive part of the sensor, namely the diaphragm. Contaminants, particles, etc. in the melt will cause damage to the diaphragm. However, diaphragm failure is most common when the diaphragm is bonded to the cooled plastic during disassembly, or when the cooling melt shrinks and the diaphragm tears. This type of damage usually results in contamination of the relevant area due to leakage of the filling medium when using mercury containing sensors. About two-thirds of the companies that reported diaphragm failures said they had such problems quite frequently or more frequently. In comparison, most companies rarely have problems related to other faults, although in this regard, the sensor head is the next most vulnerable component, which may be due to the use of plug-in connectors.
Extremely strong and precise
In the context of the above problems, a high-temperature melt pressure sensor has been developed, which is extremely strong and durable on the one hand, and easy to install and disassemble at the same time. On the other hand, the purpose is to achieve technical improvement. During development, Graeff Graf was able to draw on its decades of experience as a manufacturer of pressure and temperature sensors. The result of the development is the introduction of a new DA series melt pressure sensor (Fig. 4). This sensor is characterized by a significant improvement in accuracy (± 0.2% FS) and integrity that could not be achieved before. Due to the newly developed diaphragm technology, this development result can be obtained.
In addition, this high temperature melt pressure sensor also shows a very long service life. The special surface features make the high temperature melt pressure sensor rod extremely strong and durable. This property is only used in particularly strong metal plug-in connections. Due to the unique extremely durable spring design, the flexible capillary made of special materials can be protected in an ideal way, so the load can be several times higher than the traditional design. The sensor is also equipped with a built-in amplifier.
Heating sensor tip
The investigation results show that the high temperature melt pressure sensor faces a particularly high risk of damage during installation and disassembly. In order to significantly reduce the risk of diaphragm damage, the new sensor is equipped with heating capacity (Title photo). This allows the sensor tip to heat up in a few minutes. Therefore, removing the sensor from the cooled system will not cause problems. The sensor can also be heated to avoid diaphragm damage due to the expected problems caused by glue shrinkage when the system is shut down. Heater controller is used to prevent overheating of high temperature melt pressure sensor. Built in thermocouples are extremely helpful in this regard because they can provide control variables. Therefore, the risk of diaphragm damage or sensor failure is minimized. This can greatly prolong the service life of the sensor.
conclusion
Graeff Graf China's newly developed DA series melt pressure sensor can provide extremely high accuracy. Due to the mercury free design based on NTX technology, the product can meet the most stringent environmental protection standards. In addition, the sensor is characterized by being particularly strong and durable and long service life. This can reduce the cost of replacing the sensor and prevent the indirect cost caused by production loss due to production interference or even sensor failure.
