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Pressure instrumentation industry in Petrochemical Industry
Release time:2016-04-26   Clicks:1117

Pressure instrumentation industry in Petrochemical Industry
Pressure transmitter is one of the largest petrochemical industry measurement device used automatic control. In large chemical projects, it contains virtually all the pressure transmitter applications: differential pressure, absolute pressure, gauge pressure, pressure, differential pressure, high temperature, low temperature, as well as a variety of materials and special processing of remote flange Pressure Transmitters. Yangzi-BASF Styrenics project as an example, which uses nearly 480 sets of various types of pressure instruments. In the project planning stage, experts and engineers to build part of the project hope that all of the pressure transmitter on reliable operation for at least two years, without failure.
Currently, a large number of China's petrochemical industry pressure transmitter used mainly rely on imports, in terms of product range and performance and abroad there is a gap of domestic pressure transmitter. Pressure sensors achieve localization, economic and defense security of the country, to revitalize national industry so important. By contrast study abroad in the petrochemical field using several typical pressure transmitter, pressure sensor analyzes the localization of the key. Through these efforts, the pressure transmitter can break the monopoly of foreign-based MEMS sensors, pressure sensors petrochemical industry to achieve localization.
Requirements petrochemical industry demand for pressure transmitters and pressure sensors
In the modernization process of continuous production, stable and reliable pressure transmitter is a strong guarantee of the production process. Once measurement error, or even downtime, the ensuing economic losses will not be counted. Stability and reliability of the pressure transmitter petrochemical industry has become the primary demand for pressure transmitters.
Typically, measuring the pressure transmitter will vary the working environment and the static pressure and drift. In some small pressure or differential pressure measurement occasions, this drift is likely to be more serious. Under different operating conditions, to obtain the most accurate measurement of the relative, so as to maintain stability and ensure the consistency of the production process, it is the embodiment of the pressure transmitter stability, but also the stability of the petrochemical industry requirements for pressure transmitters.
On the basis of stability and reliability, precision is higher demand for petrochemical industry pressure sensor that pressure gauge. The accuracy of control depends on the accuracy of the measurement process control. The higher the accuracy, the control accuracy is higher. Currently, most of the pressure transmitter accuracy reached 0.075 percent, the petrochemical industry to meet the accuracy requirements.
In addition, the petrochemical industry on the pressure transmitter, there are many other needs. For example: increased range, add flexibility than the pressure transmitter can be used to design and application convenience. When some of the design process in the reaction conditions change, such as, if the transmitter has a greater range than the means with good versatility, changes in process conditions do not substantially affect the transmitter model, greatly reducing the workload of design changes. Meanwhile, a large number of process engineering than can reduce the kind used in the transmitter, reduce spare parts inventory, also reduced the backlog of funds.
Petrochemical industry demand for pressure transmitter is mainly concentrated in the reliability, stability and high precision three aspects. Among them, the reliability and many additional requirements, such as turndown ratio, bus type, etc., depend on the transmitter design, machining technology level and structure of materials. Stability and high accuracy pressure transmitter is mainly guaranteed by the stability and accuracy of the pressure sensor. Measurement accuracy pressure transmitter is to measure the corresponding pressure sensor accuracy and response speed, stability and corresponding pressure transmitter is temperature characteristics and hydrostatic pressure sensor characteristics and long-term stability. Petrochemical industry demand for pressure sensors is reflected in the measurement accuracy, fast response, temperature characteristics and static pressure characteristics, long-term stability of the four aspects.
Micro pressure sensor is a pressure sensor using new semiconductor materials and MEMS manufacturing process. Compared with traditional pressure sensors, micro pressure sensor with high accuracy, high sensitivity, good dynamic characteristics, small size, corrosion resistance, and low cost. Pure single crystal silicon material fatigue small, the use of long-term stability of this material micro pressure sensor. Meanwhile, the micro pressure sensor easily integrated with micro temperature sensor, temperature compensation increases accuracy, a substantial increase in temperature characteristics and measuring accuracy of the sensor. If the two micro pressure sensor integration, and static pressure compensation can be achieved, thereby improving the static pressure characteristics of the pressure sensor. Thus, many of the traditional micro pressure sensor with pressure sensors do not have the advantage, can satisfy the needs of the petrochemical industry pressure sensor.
Current MEMS sensor and its structure is being used in the field of petrochemical analysis
Fuji FCX-AⅡ series pressure transmitter
After the 20th century, half of the 1980s, the company began selling Fuji intelligent transmitters. At present, the world has more than 500,000 sets of FCX series products used in various industrial processes. FCX series of products using Fuji's original "advanced floating mold box" structure, with excellent reliability and good performance. It is one of China's petrochemical industry pressure transmitter is widely used.
In FCX ??series pressure transmitter, based on Fuji developed the FCX-AⅡ series. This series of products is also based on "advanced floating mold box" structure based on silicon micro sensor unit uses a capacitive sensor and a newly developed detection circuit (ASic), to achieve a high precision sensor unit and having a compensation based on the temperature dual temperature sensor unit, accuracy up to 0.1%, long-term stability within 0.1% URL (measured 3 years).
Fuji's micro-capacitance silicon sensor uses a symmetric differential capacitance structure, the upper and lower capacitor electrode coating sensitive conductive layer leads through the guide hole on the sensor. When filled with silicone oil guide hole, acting on the floating mold box by the external pressure to both ends of the conductive silicone sensor, extruded silicon deformed, thereby changing the pitch of capacitor plates, resulting in a change in capacitance. Another effect of silicone oil acts as a dielectric between the capacitor plates.
The body of the sensor is made of monocrystalline silicon, aluminum electrode side is, for the transfer capacitance and the lead connecting signals to the outside world. Group to the rest of the conductive portion of the sensor components are gold. Differential capacitance between three insulating plates made of a ceramic material.
In the sensor capacitance sensing circuit, Fuji uses mixed digital / analog circuits ASIC, not only to achieve the high speed testing, but also to reduce detection errors caused by electromagnetic interference circuit, while improving detection accuracy, long-term stability and reliability.
Another original technology FCX-AⅡ Series transmitter is based on the temperature-compensated two temperature sensors. Through the built-in sensor unit temperature sensor and built-in electronic devices temperature sensors, respectively, the sensor portion and circuit portion temperature compensation, the temperature characteristic of the transmitter.
Siemens SITRANSPDSⅢ series pressure transmitter
Siemens patented technology of silicon sensors, DSⅢ series pressure transmitter is suitable for all kinds of pressure, differential pressure, absolute pressure and level measurement. It uses a modular design, the sensor unit and electronic amplification unit. The sensor unit includes a differential pressure sensor, absolute pressure sensor and a temperature sensor. By absolute pressure sensor and a temperature sensor for static pressure and temperature characteristics over the entire range of the differential pressure sensor adequately calculate the compensation, so DSⅢ series differential pressure transmitter has a very excellent static pressure and temperature characteristics.
DSⅢ series pressure transmitter 300 yearly failure rate, is applied to the high security and reliability requirements of the occasion and design. Just a DSⅢ series pressure transmitter can be obtained with two conventional transmitters same level of security. This means that the installation, operation and maintenance costs are significantly reduced. Accuracy DSⅢ series pressure transmitter up to 0.075%, five-year long-term drift of less than 0.25% (measured for 1 year).
DSⅢ Series Intelligent differential pressure transmitter, which has an independent central diaphragm pressure measurement sensor and can not afford to measure the effect of a unique structure. Both ends of the pressure measuring cell through the seal diaphragm and filling liquid is passed to the silicon pressure sensor. When the pressure exceeds the measurement limit, overload diaphragm is deformed until it is attached to the inner wall of the measuring element, in order to protect the silicon pressure sensor to avoid overvoltage damage. The center can not afford to measure the effect of the diaphragm structure makes DSⅢ series pressure transmitter has excellent overvoltage protection. Siemens piezoresistive silicon sensor design. Due to the differential pressure measuring diaphragm imposed deformation, mounted above it four resistance strain gauge resistance change with, and so that the output voltage of the differential pressure is proportional to the change in resistance of the bridge with.
During absolute pressure measurement, DSⅢ Series transmitter requires absolute pressure measuring element. Measured pressure passes through diaphragm and fill fluid to the absolute pressure sensor, the measurement diaphragm is deformed. Piezoresistive absolute pressure sensor design, measurement principles and the same differential pressure sensor.
Domestic pressure transmitter
Domestic pressure transmitter, such as Xi'an Jiaotong University Wiener instruments limited liability company in MEMS pressure sensor research and industrialization of a series of attempts, the production of WYB1 type piezoresistive pressure transmitter with semiconductor diffused silicon pressure Sensors and dedicated amplification circuit, with high precision, easy debugging circuit, high reliability, strong anti-interference ability and other characteristics, and has integrated structure, easy to install and use the site, compact appearance, with a variety of forms and knot mouth multiple lead the way.
This paper analyzes the petrochemical industry demand for pressure transmitter pressure gauge, micro-pressure sensor with pressure sensors do not have many of the traditional advantages of the petrochemical industry to meet the requirements of a pressure sensor. It describes the structural characteristics of MEMS pressure sensor and its petrochemical industry is currently being used; compare domestic and foreign manufacturers of pressure sensor performance, a clear key pressure sensor localization problem is how to improve the long-term stability of the sensor.
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