Problems in the application of control valves: 1 There are many varieties of control valves, many specifications and many parameters. Control valves are suitable for the control requirements of different industrial production processes, such as temperature, pressure, medium characteristics, etc. There are nearly a thousand different specifications and different types of products, which makes the selection of control valves inconvenient, inconvenient to install and apply, and inconvenient to maintain. Inconvenient management
1. Problems in the application of control valves: 1 There are many varieties of control valves, many specifications and many parameters. Control valves are suitable for the control requirements of different industrial production processes, such as temperature, pressure, medium characteristics, etc. There are nearly a thousand different specifications and different types of products, which makes the selection of control valves inconvenient, inconvenient to install and apply, and inconvenient to maintain. Management is not convenient. 2 The reliability of the control valve is poor. The characteristics of the control valve at the time of shipment are quite different from those of a certain period of operation. For example, an increase in leakage, an increase in noise, and a deterioration in valve reproducibility cause difficulties in long-term stable operation. 3 The control valve is cumbersome, which brings inconvenience to the transportation, installation and maintenance of the control valve. Usually, the weight of the control valve is several times to several hundred times heavier than the weight of the general instrument. For example, the control valve of a DN200 weighs 700kg. Transportation, installation and maintenance require some mechanical equipment to complete, and the application of the control valve It is not convenient. 4 The flow characteristics of the control valve do not match the characteristics of the controlled object of the industrial process, resulting in poor quality of the control system. The ideal flow characteristics of the control valve have been determined at the time of shipment from the factory, but the characteristics of the controlled objects in the industrial process vary, and the pressure drop ratio on the force port changes, so that the control valve operating flow characteristics cannot be matched with the characteristics of the controlled object, and the control system is controlled. The quality is getting worse. 5 control valve noise is too large. In industrial applications, control valve noise has become a major source of noise for industrial equipment. Therefore, reducing control valve noise has become an important research topic at present, and has received the attention of governments. 6 control valves are energy-consuming devices. In the current shortage of energy, energy-saving technologies should be adopted to reduce the energy consumption of control valves and improve energy utilization. 2. Development direction of control valve: The development direction of control valve is mainly intelligent, standardization, miniaturization, rotation and safety. (1) Intelligentization and standardization. The intelligentization and standardization of control valves have been mentioned on the agenda. Intelligent uses mainly intelligent valve positioners. Intelligentization is reflected in the following aspects. 1 The intelligent function of self-diagnosis of the control valve and remote communication in the running state makes the management of the control valve convenient, the fault diagnosis becomes easy, and the skill requirements for the maintenance personnel are also reduced. 2 Reduce product types and simplify the production process. The intelligent valve positioner not only can easily change the flow characteristics of the control valve, but also improve the control quality of the control system. Therefore, the requirements for the flow characteristics of the control valve can be simplified and standardized (for example, only the linear characteristic control valve is produced). The intelligent function module is used to match the characteristics of the controlled object, so that the type and variety of the control valve product are greatly reduced. The manufacturing process of the control valve is simplified and tested and approved in production and in the market. 3 digital communication. Digital communication will be widely used in control valves. Based on the HART communication protocol, some valve positioners for control valves implement input signals and valve position signals on the same transmission line; based on fieldbus technology, control valves and valve positioners The combination of the PID control function modules enables the control functions to be implemented at the field level, so that the dangers are dispersed and the control is more timely and faster. 4 intelligent valve positioner. The intelligent valve positioner has all the functions of the valve positioner. At the same time, it can improve the dynamic and static characteristics of the control valve and improve the control precision of the control valve. Therefore, the intelligent valve positioner will become an important control valve auxiliary device in the future. widely used. The standardization of control valves is manifested in the following aspects. 1 In order to achieve interchangeability, control valves manufactured by different manufacturers of the same size and specifications can be interchanged, so that users do not have to spend a lot of time to select a manufacturer. 2 In order to achieve interoperability, control valves manufactured by different manufacturers should be able to work with products from other manufacturers without signal mismatch or impedance mismatch. 3 Standardized diagnostic software and other ancillary software enable the control valves of different manufacturers to perform operational status diagnosis, analysis of operational data, etc. 4 standardized selection procedures. Control valve selection is still a matter of great concern to the control designers. Using standardized calculation procedures, according to the data provided by the process, the flow coefficient of the required control valve can be correctly calculated, and the piping and the appropriate valve body, valve core and valve can be selected. Internal materials, etc., standardize the design process and improve design quality. (2) Refinement. In order to reduce the weight of the control valve, facilitate transportation, installation and maintenance, the following measures are taken for the control valve to be refined. 1 Using a small and compact actuator. Using lightweight materials, multiple sets of springs are used instead of a set of springs to reduce the height of the actuator. Usually, the control valve composed of a small and compact pneumatic diaphragm actuator is about 30% lower than the control valve composed of the same type of pneumatic diaphragm actuator. It is reduced by about 30%, and the circulation capacity can be increased by about 30%. 2 change the flow path structure. For example, changing the movement of the spool to the movement of the valve seat, changing the linear displacement to an angular displacement, etc., reduces the volume of the control valve and reduces the weight. 3 using electric actuators. It not only reduces the air supply and auxiliary equipment required for pneumatic actuators, but also reduces the weight of the actuator. For example, Fisher's 9000 series electric actuators, whose Type 20 has a height of less than 330 mm, reduce the overall control valve (with digital controller and actuator) to 20 to 32 kg (3). Rotating due to rotary control valves, for example Ball valves, etc., have the advantages of relatively small volume, small flow path resistance, large adjustable, good sealing, good anti-blocking performance, and large circulation capacity. Therefore, in the new varieties of control valves, the rotary valve The proportion increases. Especially in large-diameter pipelines, ball valve, butterfly valve and other types of control valves are commonly used. From the products of foreign countries in recent years, the proportion of rotary valve applications is increasing year by year. (4) The safety of the safety instrument control system has been paid attention to in all aspects. The safety instrument system (SIS) has higher and higher requirements for the control valve, which is reflected in the following aspects.
1 The requirements for the diagnosis and treatment of the control valve fault information are improved, not only the passive maintenance of the control valve after the fault occurs, but also the preventive maintenance and predictive maintenance before the fault occurs. Therefore, it is more important to perform statistics and analysis on the components that make up the control valve, and to make maintenance recommendations in a timely manner. 2 For the control valves used in emergency stop systems or safety interlock systems, timely, reliable and safe action requirements are required. Ensure that these control valves are responsive and accurate. 3 For control valves used in hazardous locations, the certification procedure should be simplified. For example, fieldbus instruments for intrinsically safe applications can be simplified to use the FISCO fieldbus intrinsic safety concept to simplify the certification process for intrinsically safe products. 4 Similar to the safety of other field instruments, the safety of the control valve can be achieved by flameproof technology, fire protection technology, increased safety technology, intrinsic safety technology, non-sparking technology, etc. For fieldbus instruments, entity concepts can also be used. Intrinsic safety concept, FISCO concept and non-flammable (FINCO) concept. (5) Energy saving Reduce energy consumption and improve energy efficiency is a development direction of control valves. There are mainly the following development directions. 1 Control valve with low pressure drop ratio. The control valve is reduced in proportion to the pressure drop of the entire system, thereby reducing energy consumption. Therefore, designing a control valve with a low pressure drop ratio is one of the development directions; another development direction is to use a low impedance control valve, such as a butterfly valve, eccentric Rotary valve, etc. 2 Adopt self-operated control valve. For example, the pressure of the medium after the valve is directly used to form a self-operated control system, and the post-valve pressure control is realized by the energy of the controlled medium. 3 The control valve of the electric actuator is used. Pneumatic actuators require a certain amount of air pressure during the operation of the entire control valve. Although an amplifier with a small consumption can be used, the gas consumption is still huge. With the electric actuator, when the opening of the control valve is changed, the power supply is needed, and the power supply can be stopped when the required opening degree is reached. Therefore, from the viewpoint of energy saving, the electric actuator has obvious energy saving advantages over the pneumatic actuator. 4 uses a piezoelectric control valve. Piezoelectric control valves are used in intelligent electric valve positioners, which only consume air when the output signal increases. 5 Use a valve core with a balanced structure to reduce the thrust or thrust of the actuator, reduce the bubble head chamber, and reduce energy requirements. 6 uses variable frequency speed control technology instead of control valve. For the application of high pressure drop ratio, if the energy consumption is very large, the frequency conversion speed regulation technology can be adopted, and the frequency converter is used to change the rotation speed of the running equipment to reduce energy consumption. (6) Protection of environmental and environmental pollution has become a public hazard. The pollution of the control valve to the environment mainly includes control valve noise and leakage of the control valve. Among them, the pollution of the control valve noise is very serious. 1 Reduce the control valve noise. Various methods for reducing the noise of control valves have been developed, ranging from control valve flow path design to control valve trim design, from noise source analysis to noise reduction measures. There are mainly design noise reduction control valves and noise reduction control valve trims; reasonable distribution of pressure drop, use of external noise reduction measures, such as increased isolation, the use of muffler. 2 Reduce the air pollution of the control valve. The air pollution of the control valve refers to the "running", "rising", "dropping", and "leaking" of the control valve. These leakages not only cause waste of materials or products, but also cause pollution to the atmospheric environment, and sometimes cause personnel. Accidents such as casualties or equipment explosions. Therefore, the development of control valve packing structure and packing type, the development of control valve sealing, etc. will be an important research topic for control valves in the future. The development of high-tech science and technology such as computer science, control theory and automation instrumentation has promoted the development of control valves, such as the development of fieldbus control valves and intelligent valve positioners, and the realization of digital communication in control valves. The development of control valves has also driven the development of other scientific technologies, such as the study of corrosion-resistant materials, the study of methods for weakening and reducing noise, and the study of fluid dynamics. With the development of fieldbus technology, the control valve will also be open, intelligent and more reliable. It will have a higher degree of control and more obvious effects, and play a more important role in China's modernization. Other industrial automation instruments and computer control devices Together, the functions of industrial production process control are more perfect and the control is fine.
Http://news.chinawj.com.cn Submission:

Solid Phase Extraction (SPE) is a column chromatographic analysis process bearing much similarity to high performance liquid chromatography (HPLC) in the mechanism of Separation And Choice Of Reagents and solvents.In the past, monodisperse sorbents are only used in high-end chromatography and analysis columns. Under optical microscope, the first generation silica sorbents are irregular in shape and the second generation spherical polymer particles are broad in size distribution. The new generation Uni series SPE sorbents by Nano-Micro Tech is spherical with a uniform particle size. They also have a high surface area and high density of functional groups on the particle surface.

Solid Phase Extraction (SPE) Sorbent

Solid Phase Extraction (Spe) Sorbent,Separation And Choice Of Reagents,Separation And Choice Of Solvents

Suzhou Nanomicro Technology Co., Ltd. , http://www.nanomicro-technology.com