Regulating valve how to select intelligent coal air permeability tester using regulating valve, to meet the pressure and flow requirements
Regulator is the terminal actuators in industrial process control systems, industrial continuous production process automatic control system in general need to use the regulator to control the process in the production of various process parameters, to achieve the fluid parameters such as pressure, temperature, flow rate and liquid level of adjustment, is commonly known as “hands and feet” in industrial process automation production. The quality of its application is directly reflected in the quality of system regulation. As a terminal execution element in process control, people have more profound understanding of its importance than before. Regulating valve application is good or bad, in addition to product quality and users are correct installation, use and maintenance, correct calculation and selection is very important. Due to the error of calculation and selection, the system runs unstable, and some even can not be used in many examples. Therefore, users and system designers to fully realize the importance of regulating valve in the field, must cause enough attention to the selection of regulating valve.
The general principle of regulating valve selection is: under the premise of meeting the use function, the selected regulating valve should be simple structure, reliable performance, low price, long life, convenient maintenance and so on. The following focuses on the selection and control valve type
Selection of attachments.
1 regulating valve valve type selection
Regulator classification method are many, the current domestic and international on a classification method is usually adopted by the structure, principle and function division, a total of 9 kinds big, namely through single-seat regulating valve, pass-through two-seater regulator, sleeve valve, Angle valve, three-way valve, diaphragm valve, butterfly valve, ball valve and eccentric rotary valve, the nine product is basic, common products, Usually also called standard products, other based on the combination of practical application improvement, called special products.
1.1 Characteristics and correct selection of standard type regulating valve 1.1.1 Straight through single seat regulating valve
Straight through single seat regulating valve only a spool and a seat, easy to achieve strict sealing, metal and metal hard seal, or metal and PTFE or other composite materials soft seal, standard leakage of 0.01%C (C is rated flow coefficient), allow small pressure difference, small flow capacity, For example, DN100 single seat regulating valve allowed differential pressure *120kPa, flow capacity * 100. The flow path is complex, simple structure, suitable for strict leakage requirements, working pressure difference is small, clean medium occasions, but the small specification of the regulating valve (DN1/2, 3/4, 20) can also be used for the occasion of large pressure difference, is applied as one of the best regulating valve, when further designed, can be used as a cut-off valve. The shape of the spool determines the flow characteristics. It loses its original characteristics after being washed out. Replacing the spool can change the flow characteristics. However, the thrust of the fluid medium on the spool is large, that is, the unbalance force is large, and the actuator with large thrust is needed. Therefore, in the application of high pressure difference and large caliber, it is not suitable to use this kind of regulating valve. Select this valve should pay special attention to the differential pressure check to prevent being jacked open.
1.1.2 Straight through two-seat regulating valve
The straight through two-seat regulating valve has two spool 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 whole spool is small and the allowed pressure difference is large. For example, the DN100 two-seat regulating valve allows the pressure difference of 280kPa, and the flow capacity is large. Two-seat regulating valve can flow through more fluid, the same caliber two-seat regulating valve flow capacity than a single seat regulating valve flow capacity of about 20% ~ 50%. For example, the flow capacity of DN100 two-seat regulator is 160. Therefore, in order to obtain the same flow capacity, the two-seat regulator can choose a smaller thrust actuator. Double seat regulating valve using the top and bottom double guide, therefore, the body valve and the reverse body valve refitting convenient, that is, only the spool and seat installed in reverse can change the body valve to the reverse body valve, or the reverse body valve to the positive body valve, without the need to change the type of positive or negative action of the actuator. Double seat regulating valve, the spool 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 complex, and is not suitable for high pressure applications, because in this kind of application, the valve is scour by high pressure fluid is more serious, and easy to form flash and cavitation, aggravating the scour of the valve body, it is also not suitable for the control of fibrous media and high viscosity fluid.
1.1.3 Sleeve regulating valve
Sleeve regulating valve is also known as cage valve, its valve inner parts using spool and valve cage (sleeve), sleeve can be straight through single seat regulating valve, can also be a double seat regulating valve or Angle regulating valve, etc. : a single seal, double seal two structures, the former is equivalent to a single seat regulating valve, suitable for a single seat regulating valve occasions; The latter is equivalent to a two-seat regulating valve, suitable for two-seat regulating valve occasions. In addition, it also has good stability, convenient loading and unloading, convenient maintenance, has the characteristics of reducing noise and reducing the impact of cavitation, but the price of single and double seat control valve expensive 50% ~ 200%, also need special winding gasket, its application is also relatively superior, inferior to single and double seat control valve, However, this valve should not be used for unclean media and easy to crystallize, stutter and scale media.
1.1.4 Angle regulating valve
Angle regulating valve is a single seat regulating valve with a special body structure, suitable for specific pipe and fluid occasions, it is the straight through the body to change the Angle (equivalent to an elbow) body, the throttling, force form is completely equivalent to a single seat regulating valve. Retain the single seat control valve leakage, small allowable pressure difference. In addition, because of its simple flow path has “self-cleaning” performance, can be applied to unclean media, but also can be further improved to prevent blocking Angle valve, suitable for the working conditions containing suspended particles medium, especially in the installation space is limited, especially suitable for occasions.
1.1.5 Three-way regulating valve
The three-way regulating valve uses the spool itself to guide, and the actuator must be replaced when the air opening and gas closing are replaced. It should be noted that the meaning of its air opening and gas closing is not the same as that of other regulating valves. Its air opening and gas closing must be clear to which way, namely the horizontal position or the vertical position. It has three channels, can replace two straight through single seat regulating valve for shunt and confluence two groups of flow and temperature difference ≤150℃ occasions, when DN≤80mm, confluence valve can be used for shunt occasions.
1.1.6 Diaphragm regulating valve
Diaphragm regulating valve by corrosion resistant diaphragm and lined with corrosion resistant material body composition, simple flow path, suitable for unclean medium and weak corrosive medium two cut off occasions. It is one of the early regulating valve, due to the flow characteristics of approximately fast opening, the quality of regulation is poor, and affected by the diaphragm and lining material, can not be used for high temperature and high pressure conditions, the general working pressure is less than 1.6mpa, the working temperature is less than 150℃, coupled with the diaphragm is easy to damage, short life of the shortcomings, now the occasion is not much.
1.1.7 butterfly valve
Butterfly valve is equivalent to a section of pipeline to do the valve body, ** set the valve plate throttle, is used for control of the common rotary regulator. Suitable FOR LOW PRESSURE, MEDIUM PRESSURE OR, IN RARE CASES, HIGH STATIC PRESSURE, large FLOW, but THE differential pressure is limited. Its small size, light weight, light 4 ~ 10 times than the same caliber spherical type regulating valve, caliber and price is small, especially suitable for large caliber occasions, and the larger the caliber of the regulating valve, the more this feature. Generally, when DN>300mm, it is usually completed by butterfly valve.
Post time: Sep-06-2022
