The general principle of the selection of the regulating valve is: under the premise of satisfying the function of use, the selected regulating valve should have simple structure, reliable performance, low price, long service life and convenient maintenance. The following highlights the selection and and the type of regulator valve There are many classification methods for regulating valves. At present, a classification method commonly used in China and internationally is divided according to structure, principle and function. There are 9 categories in total, namely, straight-through single-seat regulating valve, straight-through two-seat regulating valve and sleeve adjustment. Valves, angle control valves, three-way control valves, diaphragm valves, butterfly valves, ball valves and eccentric rotary valves are the most basic and common products, often referred to as standard products. Others are based on this. The application is improved and is called a special type product. The straight-through single-seat control valve has only one spool and one seat. It is easy to achieve a strict seal. It can be hard-sealed with metal or metal, or soft sealed with metal and Teflon or other composite materials. The standard leakage is 0.01%. C (C is the rated flow coefficient), allowing the pressure difference to be small, and the flow capacity is small. For example, the allowable pressure difference of the DN100 single-seat control valve is only 120 kPa, and the flow capacity is only 100. The flow path is complicated and the structure is simple. It is suitable for the occasions with strict leakage and clean working medium with small pressure difference. However, small-sized regulating valves (DN1/2, 3/4, 20) can also be used for occasions with large pressure difference. It is one of the most widely used regulating valves and can be used as a shut-off valve when further designed. The shape of the spool determines the flow characteristics, and the original characteristics are lost after flushing. Changing the spool can change the flow characteristics. However, the fluid medium has a large thrust on the valve core, that is, the unbalanced force is large, and an actuator with a large thrust is required. Therefore, in the application of high pressure difference and large diameter, such a regulating valve should not be used. The selection of this valve should pay special attention to the differential pressure check to prevent it from being opened. The straight-through two-seat control valve has two spools and two valve seats. Because the upward thrust of the upper spool and the downward thrust of the lower spool are basically balanced, the imbalance force of the entire spool is small, and the pressure is allowed. The difference is large. For example, the DN100 two-seat regulating valve allows a pressure difference of 280 kPa and has a large flow capacity. Compared with other regulating valves of the same diameter, the two-seat regulating valve can flow more fluid, and the same-caliber two-seat regulating valve has a larger flow capacity than a single seat. The flow capacity of the regulating valve is about 20% to 50% larger. For example, the DN100 two-seat control valve has a flow capacity of 160. Therefore, in order to achieve the same flow capacity, the two-seat control valve can be selected with a smaller thrust actuator. The two-seat control valve adopts double-stage guidance at the top and bottom. Therefore, the modification of the positive-body valve and the reverse-body valve is convenient, that is, the valve body and the valve seat can be reversely installed to change the positive body valve to the reverse body valve, or the reverse body valve. It is changed to a positive valve without the need to re-elect the positive or reactive type of the actuator. The upper and lower spools of the two-seat control valve can not be closed at the same time, the leakage is large, the standard leakage is 0.1% C (C is the rated flow coefficient); the flow path is complicated, it is not suitable for high pressure difference applications, because In this application, the valve is more severely washed by the high pressure fluid, and it is easy to form flashing and cavitation, which increases the flushing of the valve body, and it is also not suitable for the control of the fibrous medium and the high viscosity fluid. The sleeve regulating valve is also called a cage valve. The valve inner part adopts a valve core and a valve cage (sleeve). The sleeve can be a straight-through single-seat regulating valve, or a two-seat regulating valve or an angle regulating valve, etc.: Single seal, double seal two structures, the former is equivalent to a single seat control valve, suitable for single seat control valve; the latter is equivalent to a two-seat control valve, suitable for two-seat control valve occasions. In addition, it has the characteristics of good stability, convenient loading and unloading, convenient maintenance, noise reduction and reduced cavitation effect, but the price is 50%~200% more expensive than single and double seat control valves, and special winding is required. Seals, which are also widely used, are second only to single and double seat regulators, but should not be used for dirty media and for easy crystallization, stuttering, and fouling media. The angle control valve is a single-seat control valve with a special valve body structure. It is suitable for specific piping and fluid applications. It is a valve body that changes the straight-through valve body into an angular shape (equivalent to an elbow), which is throttled and stressed. The form is exactly the same as a single seat regulator. The single-seat control valve has a small leakage and a small differential pressure. In addition, because of its simple "self-cleaning" flow path, it can be applied to dirty media, and can be further improved as an anti-blocking angle valve. It is suitable for working conditions with suspended particle media, especially in the installation space. It is especially suitable for restrictions. The three-way regulating valve uses the valve core to guide itself. When the gas is opened and the gas is closed, the actuator must be replaced. It should be noted that the meaning of its gas opening and gas closing is different from that of other regulating valves. Its gas opening and gas closing must be Defining which way to go, horizontal or vertical. It has three channels, which can replace two straight-through single-seat regulating valves for shunting and combining two sets of flow and temperature difference ≤150 °C. When DN≤80mm, the confluence valve can be used for shunting occasions. The diaphragm regulating valve is composed of a corrosion-resistant diaphragm and a valve body lining the corrosion-resistant material, and the flow path is simple, and is suitable for two-off occasions of dirty medium and weak corrosive medium. It is one of the earliest regulating valves. Due to its near-fast opening flow characteristics, the adjustment quality is poor, and it is affected by the diaphragm and the lining material. It cannot be used in high temperature and high pressure conditions. The general working pressure is ≤1.6MPa. Temperature ≤ 150 ° C, coupled with the shortcomings of the diaphragm is easy to damage, short life, there are not many occasions. The butterfly valve is equivalent to a section of pipe to make the valve body, and the central valve plate is throttled, which is the most common rotary regulating valve for control. It is suitable for low pressure, medium pressure or very few occasions for high static pressure and large flow, but the pressure difference is limited. Its small size and light weight are 4 to 10 times lighter than the spherical regulators of the same diameter. The caliber and price ratio are small, especially suitable for large diameter applications, and the larger the diameter of the regulating valve, the more significant this feature. Generally, when DN>300mm, it is usually completed by a butterfly valve. The ball valve is a mature old product with "O" shape and "V" shaped ball valve. The flow path is the simplest, the flow resistance is the smallest, the loss is minimal, and the "self-cleaning" performance. The "O" shaped ball valve is a non-resistance regulating valve. Compared with the specification, the rated flow coefficient is the largest. It is often used in large flow and dirty media. The "V" shaped ball valve provides approximate logarithmic flow characteristics and adjustable ratio. The large, "V"-shaped core and the valve seat are sheared when they are relatively rotated, and are especially suitable for the adjustment and cutting of unclean, fibrous media such as high viscosity, suspended flow, pulp, and the like. Ball valves are more expensive. Also known as cam deflection valve, it combines the advantages of ball valve and butterfly valve, simple flow path, "self-cleaning" performance and regulation performance, suitable for crystallization, stuttering and dirty media; the valve body is small in size and light in weight. It can be flexibly assembled according to the position of the site installation without replacing any parts; the rated flow coefficient is large, 10%~30% larger than the single-seat and double-seat regulating valve of the same diameter, the adjustable ratio is large, up to 100:1; the valve seat The sealing is reliable. Due to the disturbing action of the spool support arm and the eccentric rotary motion of the spherical surface of the valve core, the required operating torque is reduced, some asymmetry is compensated, and the operation can be stably performed under flow opening, flow closing and high pressure difference; When adjusting, a positioner is required, and the linear or equal percentage flow characteristics can be conveniently obtained by changing the position of the convex plate in the positioner. For special applications, on the basis of the above-mentioned regulating valve, if the upper bonnet is lengthened, the heat sink can be added for low temperature and high temperature applications; the actuator with multiple springs can reduce the volume and weight of the entire regulating valve; A series of noise reduction measures are designed to form a low noise control valve. In addition, there is a valve body separation regulating valve for the maintenance and cleaning of the valve body separation structure; a quick shut-off regulating valve for the rapid requirement of the interlocking action; a small flow regulating valve designed for the small flow control requirement; The bellows seals the regulating valve and the like. These special types of regulators are non-standard for use in special process manufacturing processes or for special applications. They have the characteristics of complicated working conditions, high requirements for use, and small production batches. These regulating valves are usually evolved and improved according to the requirements of standard type products. Therefore, the basic type should be determined first according to non-speciality, and then the corresponding deformation pattern and material should be determined for specificity. The main accessories of the regulating valve are: valve positioner, position switch, pneumatic retaining valve, pneumatic relay, solenoid valve, air filter reducer, hand wheel mechanism, position transmitter and converter. The valve positioner has an electric valve positioner and a pneumatic valve positioner, which is mainly used to improve the working characteristics of the regulating valve, realize correct positioning, improve the linearity of the position of the regulating valve, reduce the transmission hysteresis of the adjusting signal, and change the flow characteristic of the regulating valve. Change the response range of the regulating valve to the signal pressure to realize the split control and correct positioning. It is one of the most important accessories of the regulating valve, and its quality will directly affect the performance and quality of the regulating valve and regulating system. The following highlights several main factors to consider when choosing a valve positioner: The correct selection of the regulating valve is the first step and the most critical step to apply the regulating valve. The quality of the selection directly affects the use of the regulating valve, which in turn affects the adjustment quality of the system. Of course, the selection work is more complicated, and at the same time it is a learning problem, which needs to be continuously explored and summarized in practical use. Therefore, it is necessary for us to master certain methods and techniques in the selection of regulating valves, and only in this way, we can truly play the role of "hands and feet" in the automation control of industrial processes. Nimonic is a registered trademark of Special Metals Corporation that refers to a family of nickel-based high-temperature low creep superalloys. Nimonic alloys typically consist of more than 50% nickel and 20% chromium with additives such as titanium and aluminium. nimonic 80a round bar,nimonic alloy 80a,nimonic 90 bar,nimonic 90 round bar,nimonic 75 round bar Jiangsu Seonjip Technology Co.,Ltd. , https://www.seonjip.com
1) Whether the valve positioner can realize the "split" function, that is, the valve positioner only responds to a certain range of the input signal. If the valve positioner can achieve this function, an input signal can be used to control two or more regulating valves according to actual needs;
2) Whether it is easy to adjust the zero point and the range, whether the calibration is independent and how stable it is;
3) What is the accuracy of the valve positioner. Under ideal working conditions, the inner part of the regulating valve (including the valve core of the regulating valve, the valve stem, the valve seat, etc.) should be accurately positioned at the required position corresponding to an input signal, regardless of the direction of the stroke. Or how much load the internals of the regulating valve are subjected to;
4) What is the speed of the valve positioner and the frequency characteristics. Because the valve positioner can continuously compare the input signal and valve position, and adjust its own output according to the deviation between them. If the valve positioner responds quickly to such a deviation, the flow of the medium per unit time is large, and the response system adjusts to the set point and the load change faster, that is, the smaller the system error, the better the control quality. good. In general, the higher the frequency characteristics, the higher the sensitivity to the frequency response and the better the control performance. It should be noted that the evaluation of frequency characteristics should adopt a combination of experiment and theory, rather than relying on theory, and in the evaluation, the experimental method must be stable and scientific, and the valve positioner and the actuator should be combined for consideration;
5) After the combination of the valve positioner and the regulating valve, how does the positioning resolution change? The positioning resolution has a very obvious effect on the control quality of the adjustment system, because the higher the resolution, the closer the positioning of the regulating valve is to the ideal value, and the fluctuation of the fluctuation caused by the overshoot of the regulating valve can be effectively suppressed, thereby finally reaching Limit the purpose of periodic changes in the amount of adjustment.
6) Whether the maximum rated air supply pressure of the valve positioner matches the rated operating pressure of the actuator, whether the installation and connection are convenient, the maintenance amount and maintenance degree, and so on.
In addition to the valve positioner, other types of accessories are relatively simple, and do not need to be repeated here. All accessories have the function of supplementing and ensuring the correct operation of the regulating valve. The principle to be grasped in the selection is necessary increase, unnecessary discarding, otherwise it will only increase the operating cost of the control system and reduce the reliability.
The main use is in gas turbine components and extremely high performance reciprocating internal combustion engines. The Nimonic family of alloys was first developed in the 1940s by research teams at the Wiggin Works in Hereford, England, in support of the development of the Whittle jet engine.
Due to its ability to withstand very high temperatures, Nimonic is ideal for use in aircraft parts and gas turbine components such as turbine blades and exhaust nozzles on jet engines, for instance, where the pressure and heat are extreme. It is available in different grades, including Nimonic 75, Nimonic 80A, and Nimonic 90. Nimonic 80a was used for the turbine blades on the Rolls-Royce Nene and de Havilland Ghost, Nimonic 90 on the Bristol Proteus, and Nimonic 105 on the Rolls-Royce Spey aviation gas turbines. Nimonic 263 was used in the combustion chambers of the Rolls-Royce/Snecma Olympus 593 used on the Concorde supersonic airliner. The heads of the exhaust valves as well as the turbine wheel of its Rajay turbocharger for the Corvair Spyder turbo engine were made of Nimonic 80A. Most Saab cars with high output turbos use exhaust valves made of Nimonic 80A as well.
Nimonic 75 has been certified by the European Union as a standard creep reference material.
How to choose the regulating valve
The regulating valve is the terminal actuator in the industrial process control system. In the industrial process continuous production automatic control system, it is generally necessary to use the regulating valve to control various process parameters in the process production to achieve the pressure, temperature, flow and liquid of the fluid. The adjustment of the parameters such as bits is often referred to as the "hand and foot" in the automated production of industrial processes. Its application quality directly reflects the adjustment quality of the system. As a terminal actuator in process control, people have a deeper understanding of its importance than in the past. In addition to the quality of the control valve and the correct installation, use and maintenance of the user, it is very important to correctly calculate the selection. There are many examples of system instability due to errors in calculation selection, and some even fail to be used. Therefore, users and system designers must fully realize the importance of the regulating valve in the field, and must pay sufficient attention to the selection of the regulating valve.