keta industry valves resources
industry valve news blog
products catalogues download
Request a free quote
we would like to collaborate with you
Send us a message if you have any requests or need a help with flow control. we will responds within 10 minutes and help you with personalized support with quickly quote .
Email :sales@ketavalve.com
WhatsApp :+8619906653951
guidance of industry valves structure ,size ,type and so on
what is industry valve ?
General explanation
Industrial valves are devices used to control fluid flow, pressure and direction. The controlled fluid can be a liquid, air,powder and liquid mixture, or a solid-liquid mixture. The valve is usually composed of the valve body, valve cover, seat, opening and closing parts (valve disc, plug body, gate, disc and diaphragm, etc.), driving mechanism (valve stem and the valve drive device that drives its movement), seals (packing, gasket, etc.) and fasteners. The control function of the valve depends on the driving mechanism or fluid to drive the lifting, sliding, swinging or rotating movement of the opening and closing parts to change the size of the flow channel area to achieve.
Industry valve applicable industries
The valve is a control component in the fluid delivery system, with truncation, regulation, diversion, prevention of reverse flow, pressure regulation, shunt or overflow pressure relief functions. Valves for fluid control systems range from the simplest globe valves to valves used in extremely complex automatic control systems in a wide variety of varieties and specifications. Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. Nominal diameters of valves range from instrument valves of a few millimeters to industrial pipeline valves of more than 10 meters. The working pressure of the valve can be from 1.3*10-3MPa to 1000MPa ultra-high pressure valves. Operating temperature from -269℃ ultra-low temperature to 1430℃ high temperature. The opening and closing of the valve can adopt a variety of control methods, such as manual, electric, pneumatic, hydraulic, electric-gas or electric-hydraulic linkage and electromagnetic drive; It can also operate according to predetermined requirements under the action of pressure, temperature or other forms of sensing signals, or simply open or close. Valves have a wide range of uses. Whether it is petroleum, petrochemical, metallurgy, electricity, water conservancy, national defense, aerospace, transportation, urban construction, people’s life, etc
A brief history of valve development
Before 2000 BC, the Chinese used bamboo pipes and plug valves in water pipelines, and later used sluices in irrigation canals, plate check valves in smelting bellows, and bamboo pipes and plate check valves for brine extraction in well salt mining. With the development of smelting technology and hydraulic machinery, copper and lead plug valves appeared in Europe. In 1681, the lever and weight safety valve was introduced. Before the advent of the Watt steam engine in 1769, the plug valve and the check valve were the most important valves. Around 1840, there were globe valves with threaded stem and wedge gate valves with trapezoidal threaded stem. After the Second World War, due to the development of polymeric materials, lubricating materials, stainless steel and cobalt-based cemented carbide, the ancient plug valve and butterfly valve have obtained new applications, and the ball valve and diaphragm valve have been rapidly developed. The variety of globe valves, gate valves and other valves has increased, and the quality has improved.ulvinar dapibus leo.
valve types classification
According to the function of the valve:
1.Control valves
2.On /off valves
3.Loading valves
3.Safety valves
4.Check valves
5.Diverting valve
6.Regulate valves
7.0thers special request /customize design valves
Basic valve performance
1.Sealing performance
2.Opening and closing performance
3.Strength performance
4.Valve flow performance
5.Adjustment performance
industry valves category classification
1.Control valve
Control valve is used to regulate the flow, pressure, temperature, liquid level and other process parameters in the field of industrial automation process control, according to the control signal in the automation system, automatically adjust the opening of the valve, so as to achieve the adjustment of media flow, pressure, temperature and liquid level
Control valve classification
1.pneumatic film control valve
2.cylinder type control valve
3.three-way control valve
4 corner control valve
5. Fluorine lined regulating valve
6· Self-operated regulating valve
The control valve belongs to the control valve series, the main function is to adjust the pressure, flow, temperature and other parameters of the medium, and is the final control element in the process loop. Regulating valves play a very important role in the automation control of modern plants, where production depends on the correct distribution and control of flowing liquids and gases. These controls, whether it is the exchange of energy, the reduction of pressure or the simple filling of the container, require the final control element to complete. The final control element can be thought of as the “physical energy” of automatic control. Between the low energy level of the regulator and the high level function required to perform flow fluid control, the final control element performs the necessary power amplification. The regulator is the most widely used form of the final control element.
2. Gate valve
The gate is used as the opening and closing part and moves vertically along the axis of the seat to realize the opening and closing action of the valve. The main advantages of gate valve are smooth flow channel, small fluid resistance, small opening and closing torque; The main disadvantage is that the sealing surface is easy to scratch, the opening and closing time is longer, and the body shape and weight are larger. Gate valves are widely used in pipelines and are suitable for making large diameter valves. Gate valves are usually used to cut off fluid and should not be used to regulate flow. Because when the gate valve is in the half-open position, the gate plate will be damaged by fluid erosion and impact, and the sealing surface will also produce vibration and noise. Gate valves are divided into wedge and parallel types according to different structure of gate plates.
Wedge gate has three kinds of structure: single gate structure is simple, but the wedge Angle processing accuracy is high, easy to happen clamping, chafing phenomenon; The structure of double gate requires lower precision of wedge Angle, and the gate is not easy to wedge dead, but the structure is more complex. Elastic ram has the advantages of single ram and double ram, and can avoid their shortcomings, so it is widely used. Its structure is characterized by a ring groove on the periphery of the gate, so that the gate has appropriate flexibility. Parallel gate valve usually adopts double gate structure; Gate valves for special purposes, such as large-diameter gate valves used in long-distance oil and gas pipelines, use a single gate structure because of the need to clean valves and pipelines.
3. Globe valve
The valve flap is used as the opening and closing part and is moved along the axis of the seat to realize the opening and closing action of the valve. The globe valve is mainly used to cut off the fluid, and it can also be used to adjust the flow rate in the occasions where the adjustment performance is not high. The globe valve is a kind of valve commonly used in pipelines.
Common globe valve body channel forms are straight through, straight flow and right Angle type 3. Straight-through globe valve (Figure 2 straight-through globe valve body channel) has a large fluid resistance, because the shape of the valve body is similar to a sphere, so it is commonly called a spherical valve. In order to reduce fluid resistance,. The direct flow is mostly used for fluids containing solid particles or large viscosity. Right Angle type Used for high and medium pressure right Angle pipe. The sealing surface of the globe valve mainly has two kinds of plane and cone. The width of the contact surface of the cone seal is smaller than that of the plane seal, the required sealing force is small, the tightness is easier to ensure, and the opening and closing force is much lower, mostly used in high-pressure situations. In order to reduce the opening and closing force, a high pressure balanced globe valve has been developed. It uses pressure balanced disc. Fluid enters the upper part of the disc from the lower part through a small hole,
The main advantages of the globe valve are: the opening height is small (generally 1/4 of the diameter of the seat through the hole), so the switch is faster; In the process of opening and closing, there is generally no relative sliding between the sealing surface, so it is not easy to wear and tear; Easy servicing of disc and seat. The disadvantage is that the opening and closing force and fluid resistance are large, so it can not be done too much, the nominal diameter of the general medium and low pressure stop valve is not more than 250 mm, and the high pressure stop valve is not more than 150 mm.
4. Check valve
A valve that automatically prevents the flow back, also known as a check valve. Usually, the fluid under pressure causes the valve disc to open and flows from the inlet side to the outlet side. When the inlet side pressure is lower than the outlet side, the valve disc automatically closes the channel under the action of the fluid pressure and its own gravity, preventing the flow from reversing. According to the different mode of disc movement, check valves are mainly divided into three categories: lift, swing and butterfly
The body of the lift check valve is more similar to the globe valve body, and its fluid resistance is larger. This type of check valve is a high pressure small diameter, often using a round ball disc. The swing check valve has less resistance to the fluid, and is generally suitable for small and medium-sized caliber and low-pressure large-caliber pipelines. Multiple valves are often set on the channel partition of the valve to become multi-valve type. The shape of the butterfly check valve is similar to that of the butterfly valve. It has simple structure and low resistance to fluid. If the check valve is closed too quickly, it may cause a liquid strike in the liquid pipeline, produce noise, and even cause damage to the valve parts. In order to avoid this situation, a check valve with a buffer function can be used when necessary to extend the closing time.
5. Ball Valve
The ball with a round through hole is used as the opening and closing part, and the ball rotates with the valve stem to realize the opening and closing action of the valve. The structure of the ball valve is similar to that of the plug valve, and some people also call it the spherical plug valve. It consists of a ball and two seats (sealing rings) to form a sealing pair. The most commonly used material for the seat is polytetrafluoroethylene plastic.
In all kinds of valves, the ball valve has the least fluid resistance, and it has the advantages of rapid switching and good sealing, so it has become the fastest developing class of valves. It has a wide range of application: the working pressure is from high vacuum to high pressure (the pressure has reached 40 mpa), the working temperature is -253~+450℃, and the maximum caliber has reached 3000 mm. The main disadvantage of ball valve is that the operating temperature is not high. At present, carbon, graphite and other sealing ring materials are being used to improve the service temperature of the ball valve. According to the principle of sealing structure, the ball valve is divided into floating ball valve and fixed ball valve (see the schematic diagram of the ball valve). The former mainly relies on fluid pressure to press the ball on the valve seat at the outlet end, forming a floating seal, so the pressure and caliber used are limited.
6. Butterfly valve
With the circular butterfly plate as the opening and closing parts and rotate with the valve stem, to realize the opening and closing action of the valve. Butterfly valve has simple structure, quick switching, small size, light weight and small opening and closing torque. According to the different requirements for sealing, butterfly valves can be designed to have the function of truncation, adjustment or truncation and adjustment. Butterfly valve is widely used, especially in the low pressure large diameter water supply pipe has gradually replaced the trend of gate valve. The maximum diameter of the butterfly valve has reached 10 meters. Large diameter butterfly valves are generally equipped with slow closing damping devices to prevent water percussion. The sealing material of butterfly valve is usually rubber, which is used for low temperature, high temperature or adjustment conditions of butterfly valve, and metal sealing material is also used.
The rotary center of the butterfly plate of the butterfly valve (that is, the center of the stem) is located on the center line of the valve body and the sealing surface section of the butterfly plate. When closed, the outer round sealing surface of the butterfly plate squeezes the synthetic rubber seat, which causes the elastic deformation of the seat and forms the elastic force for sealing the butterfly valve. The valve can be designed into flange connection, clamp connection and single clamp connection with the rod can be designed into a through rod, through the pin and two rod hexagonal connection structure
The center of rotation (stem center) of the butterfly plate of a typical single eccentric butterfly valve is located on the center line of the valve body and forms an offset size with the seal section of the butterfly plate! .. Make the sealing surface of the butterfly plate and the valve seat form a complete circle, which is easy to ensure the surface roughness of the butterfly plate and the valve seat. When the butterfly valve is closed, the outer circular sealing surface of the butterfly plate gradually gets close to the valve seat and squeeges the valve seat to produce elastic deformation. The formed elastic force is used as the specific pressure of the seal to ensure that the sealing valve seat should be a soft sealing material, and polytetrafluoroethylene is the best when the valve is fully opened. A gap is formed between the disc and the sealing surface of the seat.”
7. Throttle valve
A control valve for controlling fluid flow or reducing fluid pressure by reducing the cross section of the flow path. The structure of the throttle valve is usually similar to that of the globe valve, the main difference is that the disc shape is changed and the stem with small pitch is used, so it has better adjustment performance than the globe valve. The disc shape of the throttle valve is window shape (for larger calibers), plug shape (for smaller calibers) and needle shape (for small calibers). Throttle valves with needle disc are often called needle valves. Butterfly valves are also commonly used as throttle valves. Due to the throttling action, the flow rate between the valve disc and the seat is very large, and the fluid through the valve disc produces a large pressure drop, the valve disc, the valve seat and the valve body will be damaged by the high-speed erosion of the fluid and the possible cavitation, especially when the fluid is corrosive or the fluid has solid particles more easily damaged
8. Plug valve
A plug body with a through hole is used as a valve for opening and closing parts. The plug body rotates with the valve stem to realize the opening and closing action. The small unpacked plug valve is also called “cock”. The plug body of the plug valve is mostly a cone (also a cylinder), and the conical hole surface of the valve body is combined to form a sealing pair. The plug valve is one of the earliest valves used, with simple structure, fast switching and small fluid resistance. Ordinary plug valves rely on the direct contact between the finished metal plug body and the valve body to seal, so the sealing is poor, the opening and closing force is large, and it is easy to wear, and it is usually only used for low (not more than 1 mpa) and small diameter (less than 100 mm) occasions. In order to expand the application range of plug valve, many new structures have been developed.
9. Diaphragm valve
An elastic diaphragm is used as a cut-off valve for opening, closing and sealing parts. FIG. Typical structure of diaphragm valve is typical structure of diaphragm valve. The valve body is ridge type, and the ridge and diaphragm form a sealing pair. The diaphragm is fixed around the edge, which divides the valve chamber into two parts that are not interconnected. The lower part of the diaphragm is a fluid channel. The disc, stem, cover and other parts are located in the upper part of the diaphragm, isolated from the fluid, not corroded by the fluid, while preventing impurities such as rust from contaminating the fluid. Diaphragm valves do not require stuffing boxes and do not have stem sealing problems. Diaphragm materials are usually rubber and fluoroplastic. The life of the diaphragm valve depends on the fatigue resistance of the diaphragm. It is especially suitable for corrosive fluids and fluids requiring cleaning, such as acetic acid, chemical fiber raw materials and boiler softened water. Its working pressure is generally not more than 0.6 mpa, the working temperature is generally less than 100℃, and the nominal diameter is not more than 350 mm.
10.Plastic valve
Plastic valves service life seal test Fatigue strength test conditions
With the increasing proportion of plastic pipes in cold and hot water supply and industrial pipeline engineering applications, the quality control of plastic valves in plastic pipeline systems is becoming more and more important.
Due to the advantages of plastic valves, such as light weight, corrosion resistance, non-adsorption of scale, integrated connection with plastic pipelines and long service life, plastic valves have advantages in the application of water supply (especially hot water and heating) and other industrial fluids in the plastic pipeline system, which is not comparable to other valves. In the domestic production and application of plastic valves, there is no reliable method to control it, resulting in uneven quality of plastic valves for water supply and other industrial fluids, resulting in lax closure and serious leakage in engineering applications, forming a plastic valve can not be used, affecting the overall development of plastic pipeline applications. China’s national standard for plastic valves is in the process of development, and its product standards and method standards are formulated according to international standards.
The main types of plastic valves in the world are ball valves, butterfly valves, check valves, diaphragm valves, gate valves and globe valves, etc., mainly in the form of two-way, three-way and multi-way valves, raw materials are mainly ABS, PVC-U, PVC-C, PB, PE, PP and PVDF.
In the international standards for plastic valve products, first of all, the raw materials used in the production of valves are required, and the manufacturers of raw materials must have a creep failure curve that meets the standards for plastic pipe products [1]. At the same time, the sealing test of plastic valves, valve body test, long-term performance test of the whole valve, fatigue strength test and operating torque are specified, and the design service life of plastic valves used for industrial fluid transport is 25 years [2]
the main global industry valves standards
Industry Valve global standards and standards code name
GB Chinese nation standard ,standard code HB Chinese industry standard
ISO global standard ,standard code ASTM ,
ANSI America standard standard code AISI
BS British national standard standard code API
DIN Germany national standard standard code MSS
NF French national standard standard code AWS
JIS Japanese national standard standard code ASI
OCT National standard of Soviet Union standard code MIL
ASME American Society of Mechanical Engineers standard standard code JPI
industry valves connections type
1.Internal thread connection (PT pipe thread connection 55° teeth)
2.External thread connection (NPT thread connection 60° teeth)
3.Flange connection;
4.Welding (butt welding “BW” and socket welding “SW “);
5.Wafer
6.Cramp
Flange types
(1) Plane (sealing surface) flange (FF),
1. Commonly used gaskets: commonly used asbestos spot, polytetrafluoroethylene embedded asbestos board, aluminum plate;2 Application range: Suitable for lower pressure valves
(2) raised face (RF) Flange raised face (RF)
(3) ring type jai face (RTJ)31 – groove groove
1, commonly used gaskets metal oval pad, metal octagonal pad.
2 Application: Mainly used for high temperature and high pressure valves
industry valves operations
Classification of valve drive device According to the movement of the drive mechanism, the valve drive device is divided into two kinds of straight stroke and Angle stroke, and the valve drive device is divided into:
Valve drive device according to the output shaft movement:
(1) multi-turn rotary type;
(2) partially rotary (
3) Linear reciprocating.
Multi-turn rotary type is suitable for valve stem or valve stem nut need to turn multiple turns to fully open or fully closed valves such as gate valves, globe valves, the output torque value of the series is generally 40~10000 n/m (thrust is 20~1100 kN). Partial rotary type is suitable for valves whose stem can be fully opened or fully closed within one turn of rotation, such as ball valves and butterfly valves, and the output torque series is generally 125 ~ 125000 n/m. Linear reciprocation is suitable for valves whose stem can be fully opened or fully closed only by linear reciprocating motion, such as solenoid valves. According to the power source, the valve driving device can be divided into manual device, pneumatic device, hydraulic device, electric device, gas-liquid linkage device, electro-hydraulic linkage device, etc. The most primitive and simplest valve driving device is the handwheel (handle).
Handwheel drive: The handwheel can be made of malleable cast iron, ductile iron or steel or aluminum alloy or plastic and other materials. Hand wheel rotation: clockwise opening valve: counterclockwise closing. Impact handwheel: Impact handwheel is suitable for the globe valve requiring large opening and closing torque. Gear transmission manual device is divided into two kinds, one is to set the gear reduction mechanism on the valve bracket, the other is the gear reduction box type manual device. The former is mostly a first-stage gear reduction, and the latter can be divided into multi-turn manual devices. The connection of the manual device to the valve can be consistent with the electric drive device.
electric actuator
Compared with other valve drive devices, electric drive devices have the characteristics of wide power source, rapid operation, convenient, and easy to meet various control requirements. Therefore, in the valve drive device, the electric device is dominant. Valve electric device according to the output mode is divided into multiple transformation (Z) and partial transformation (Q) two kinds, the former is used for lifting rod valve, including: gate valve, globe valve, throttle valve, diaphragm valve, etc.; The latter is used for rotary rod valves, including ball valves, plug valves, butterfly valves, etc., usually open and close in the 90 degree range. Valve electric device according to the protection type is divided into ordinary type and special protection type two categories.The use environment of the ordinary electric device is as follows: (1) the ambient temperature is -25-40℃; (2) Environmental relative humidity 90% (3.) Altitude ≥1000 meters; (4) The working environment requirements do not contain corrosive, flammable, explosive media. If the working environmental conditions of the valve exceed the ability of the ordinary electric device, special protective products need to be used.
pneumatic actuator
Valve pneumatic drive device is safe, reliable, low cost, easy to use and maintain. At present, pneumatic devices are widely used in the occasions with explosion-proof requirements. The valve pneumatic drive device uses a low working pressure of the air source, generally not more than 0.82MPa, and because the structure size should not be too large, the total thrust of the valve pneumatic drive device cannot be large. Valve pneumatic drive device is divided into three types according to its structural characteristics: (1) film pneumatic drive device, (2) cylinder or pneumatic drive device, (3) swing pneumatic drive device. In addition, there are air motor pneumatic drive devices.
Most of the gas (liquid) dynamic devices are composed of compressed gas or hydraulic driven pressure cylinders (linear reciprocating)), and a few are composed of decelerating mechanisms driven by air motors or hydraulic motors. The former is widely used as partial rotary and linear reciprocating drives; The latter can be used as a multi-turn rotary drive, and some can be used with electric devices. They have the characteristics of compact structure, quick opening and closing, suitable for indoor or corrosive, flammable and explosive environment; Its disadvantage is that the piping is more complex and not suitable for remote control. Hydraulic device adopts higher pressure and larger output.
The hydraulic device is composed of three parts: power, control and actuator. The role of the power part is to convert the effective power on the rotating shaft of the electric or air motor into the fluid pressure energy of the hydraulic transmission. It is composed of a motor or an air motor, a hydraulic pump tank and other parts. The control part is composed of control valves, such as pressure control valves, flow control valves, direction control valves, and electrical control systems. There are two kinds of actuator, one is the hydraulic cylinder actuator, to achieve reciprocating linear motion; The other is a hydraulic motor actuator to achieve rotary motion.
industry valves transport and installment
1. Lift and store full-box valves: crates and wooden cases, loading and unloading with forklift; When loading and unloading with the crane, it is necessary to pay attention to the center of gravity of the wooden box and the strength of the rope, which can not overturn or not break the rope to prevent the occurrence of safety accidents. The whole box of valves can not be stacked in the open air, and should be placed in the field of the site to pay attention to moisture and rain.
2. Unpacked valves The lifting of these valves should take appropriate means and measures such as the application of pallets, pay attention to the damage to the processing surface, especially the two ends of the valve such as welding end, flange sealing surface, etc.; For large diameter valves, the belt or chain can be lifted around the diameter of the valve body when lifting the valve, and should be balanced to prevent accidental fall or loosening during lifting.
3. Warning A) The size and strength of the lifting equipment (such as belts and chains) should be suitable to withstand the weight of the valve; B) It is forbidden to lift by winding on hand wheels, bolts, motors, electric devices or other valve attachments.
Valve installation Check the valve before installation
1. Open the package carefully, and pay attention to whether the logo and nameplate content on the valve are consistent with the use requirements.
2. Remove the end covers at both ends of the valve channel and remove the protective coating on the end faces. Clean the inside of the valve with compressed air to ensure that no foreign matter such as wood chips, plastic and other packaging materials are attached to the inside of the valve, the seat or the end of the connection.
3. Check the cleanliness inside the valve through the channel at the end of the valve to see if there is any erosion of debris and harmful substances.
4. Check the flow mark of the valve to ensure the correct installation direction of the valve. (for low temperature gate valves, globe valves, check valves) Ensure that the valve is correctly installed in the line and has reliable support, if necessary,
5. Set expansion and bending compensation structure on the pipeline to avoid excessive pipeline stress causing damage to the valve
Valve installation instructions
1. The valve should be installed on the horizontal pipe as far as possible, with the valve stem facing upward.
2. When installing, the gate should be in the closed position to ensure that the valve seat/gate sealing surface will not be damaged during the installation process.
3. When the operating temperature exceeds 200 ° C (392°F), it is recommended to take protective measures for the valve. To prevent high-temperature damage to operation and maintenance personnel.
4. The valve of the electric device should pay special attention to the state of the valve when the electric device fails (such as “on” or “off”).
Flange end valves carefully inspect the surface of the paired flange, and if defects are found that may cause leakage (such as a deep radial groove or knife mark), they should be removed and can be assembled later. Valve flanges and pipe flanges should be well aligned before assembly. The bolt thread can be properly lubricated to avoid biting. When assembling, the bolts should be tightened in sequence (the tightening order of the bolts can be seen in “FIG. 1, Section 5”) so that the force acting on the flange and gasket is as uniform as possible, and the distortion and deformation of one flange relative to another flange should be avoided.
Welded end valves Inspect the surface, size and cleanliness of the welded end and evaluate the various conditions involved in assembly and welding requirements. It is recommended to open the valve slightly to avoid damage to the sealing surface of the valve seat by thermal expansion. When welding, the welding should be carried out with a small current as far as possible to avoid thermal deformation in the sealed area of the valve. For the soft seal valve, effective protective measures must be taken to ensure that the temperature of the soft seal surface area does not exceed 95° C during welding, and too high welding temperature will cause damage to the soft seal.
Threaded end valves Check the form and cleanliness of the connection threads on valves and pairing lines to ensure that there are no visible dents, deformations, and debris attached to the mating surface. The taper pipe thread itself is a slightly loose fit at the beginning of screwing, and excessive tightening torque should be avoided when the thread has been properly engaged. Suitable straps or filaments may be wrapped around the outer surface of the pipe thread (unless specified by the user not to attach sealing material to the thread surface).
Generally speaking, the installation and debugging of the gearbox and electric device has been completed by the valve manufacturer or the manufacturer of the equipment before the valve factory, if the user feels it is necessary to remove the valve, then the drive device should first be removed before the valve can be removed. Before use, the user should ensure that the wire connection and line phase voltage of the electric device are completely correct. For gear and electric drives, the valve channel is ideally horizontal with the stem facing straight up. If other mounting directions are required, the user should consider using the appropriate support fixing method for the transmission and contact the manufacturer for a solution.
Valve maintenance It is recommended that valves be inspected regularly, at a minimum, all valves should be inspected once a quarter to ensure proper operation and prevent valve leakage. The following are the areas that need to be inspected and maintained. Check for damage to the stem threads Check for leaks in the stuffing box Check for leaks at the body/cap joint Check for leaks at all external connections – Operate the valve, check for flexibility in the closing check for working conditions of the gear or electric device (when in use)- Check for visible damage and defects on the outside of the valve
control valve intonation
General explanation
Control valve regulating pressure, flow, temperature parts of the control valve, also known as the control valve, in the field of industrial automation process control, by accepting the control signal output of the control unit, with the help of power operation to change the media flow, pressure, temperature, liquid level and other process parameters of the final control element. It is generally composed of an actuator and a valve. If according to the stroke characteristics, the regulating valve can be divided into straight stroke and Angle stroke; According to the power used by the actuator, it can be divided into three kinds: pneumatic control valve, electric control valve and hydraulic control valve. According to its function and characteristics, it can be divided into linear characteristics, equal percentage characteristics and parabolic characteristics. The regulating valve is suitable for air, water, steam, various corrosive media, mud, oil and other media. English name: control valve, the bit number usually starts with FV. Regulating valve commonly used categories: pneumatic regulating valve, electric regulating valve, hydraulic regulating valve, self-operated regulating valve.
Basic information :
product name :control valve or regulate valve
function :Change the medium flow, pressure, temperature, etc
Applicable media:Air, water, steam, all kinds of corrosive media
material applicable :Cast iron, cast steel, stainless steel, etc
operations : manual ,pneumatic actuator ,electric actuator ,self operate
Regulation valves play a very important role in the automatic control of modern plants, where production depends on the correct distribution and control of the flowing medium. These controls, whether it is the exchange of energy, the reduction of pressure or the simple filling of a container, require some final control element. The regulating valve acts as a variable resistance in the pipeline. It changes the process fluid
Regulation valves play a very important role in the automatic control of modern plants, where production depends on the correct distribution and control of the flowing medium. These controls, whether it is the exchange of energy, the reduction of pressure or the simple filling of a container, require some final control element. The regulating valve acts as a variable resistance in the pipeline. It changes the process fluid Or in the case of laminar flow provides a pressure drop caused by changing valve resistance or “friction”. This pressure reduction process is often referred to as “throttling”. For gases, it is close to the isothermal adiabatic state, and the deviation depends on the degree to which the gas is not ideal (Joule-Thomson effect). In the case of liquids, the pressure is consumed by turbulence or viscous friction, both of which convert the pressure into thermal energy, resulting in a slight increase in temperature. A common control loop consists of three main parts, the first part is the sensitive element, which is usually a transmitter. It is a device that can be used to measure the process parameters being adjusted, such as pressure, liquid level or temperature. The output of the transmitter is sent to the regulating instrument, the regulator, which determines and measures the deviation between the given value or expected value and the actual value of the process parameter, and sends the correction signal one by one to the final control element, the regulator. The valve changes the flow of the fluid so that the process parameters meet the expected value. The regulating valve belongs to the control valve series, the main function is to adjust the pressure, flow, temperature and other parameters of the medium, and is the final control element in the process loop.
Control valve, also known as control valve, by accepting the control signal output of the control unit, with the help of power operation to change the fluid flow. The regulating valve is generally composed of an actuator and a valve. If the power used by the actuator is used, the regulating valve can be divided into three kinds: pneumatic regulating valve, electric regulating valve, hydraulic regulating valve, in addition, according to its function and characteristics, linear characteristics, equal percentage characteristics and parabolic characteristics.
Valve body type
There are many kinds of valve bodies, commonly used valve body types are straight single seat, straight double seat, corner, diaphragm, small flow, tee, eccentric rotation, butterfly, sleeve, ball and so on.
In the specific choice, you can do the following considerations:
(1) spool shape structure
It is mainly considered according to the selected flow characteristics and unbalance force.
(2) Wear resistance
When the fluid medium is a suspension containing a high concentration of wear particles, the internal material of the valve should be hard.
(3) Corrosion resistance
Because the medium is corrosive, try to choose a simple valve structure.
(4) Temperature and pressure of the medium
When the temperature and pressure of the medium are high and the change is large, the valve core and the valve seat should be selected with small changes in temperature and pressure, and the radiator should be added when the temperature is ≥250℃.
(5) Prevent flash and cavitation
Flash and cavitation occur only in liquid media. In the actual production process, flash and cavitation will form vibration and noise, shorten the service life of the valve, so the valve should be prevented from flash and cavitation when selecting the valve.
Regulating valve actuator
In order for the control valve to work properly, the actuator should be able to produce sufficient output force to ensure the high seal and the opening of the valve.
For double-acting pneumatic, hydraulic and electric actuators, there is generally no return spring. The size of the force has nothing to do with its direction of operation, so the key to selecting the actuator is to find out the maximum output force and the rotational torque of the motor. For single-acting pneumatic actuators, the output force is related to the opening of the valve, and the force appearing on the regulating valve will also affect the motion characteristics, so it is required to establish a force balance in the opening range of the entire regulating valve.
After determining the output force of the actuator, select the corresponding actuator according to the requirements of the process environment. When there are explosion-proof requirements on the site, pneumatic actuators should be selected. From the perspective of energy saving, electric actuators should be selected as far as possible. If the adjustment accuracy is high, the hydraulic actuator can be selected. For example, the speed regulation of the transparent machine in the power plant and the temperature regulation control of the catalytic reactor in the refinery.
The mode of action of the regulating valve is only when the pneumatic actuator is selected, and the mode of action is formed by the combination of the positive and negative action of the actuator and the positive and negative action of the valve. There are four kinds of combination forms, namely, positive and positive (gas close type), positive and negative (gas open type), anyway (gas open type), reverse (gas close type), and the regulating valve formed by these four combinations has two kinds of gas open and gas close.
For the choice of the mode of action of the regulating valve, mainly from three aspects: a) process production safety; b) Characteristics of the medium; c) Ensure product quality and minimize economic losses.
All types of control valves
Electric regulating valve, pressure regulating valve, single-seat regulating valve, pneumatic regulating valve, sleeve regulating valve, two-seat regulating valve, three-way regulating valve, temperature regulating valve, air volume regulating valve, self-operated regulating valve, fire regulating valve, shunt regulating valve, manual regulating valve, cage regulating valve, micro-pressure regulating valve, fine small regulating valve, corner regulating valve, rotary regulating valve, multi-leaf regulating valve, differential pressure regulating valve Section valve, through regulating valve, electronic regulating valve, confluence regulating valve, sealed regulating valve, steam regulating valve, feed water regulating valve, temperature control regulating valve, explosion-proof regulating valve, automatic regulating valve, stainless steel regulating valve, plastic lined regulating valve, locking regulating valve, constant flow regulating valve, flap regulating valve, brass regulating valve, lifting regulating valve, one-way regulating valve, bellows regulating valve, boiler feed water Regulating valve, field bus regulating valve, etc
Regulating valve according to stroke characteristics can be divided into: straight stroke and Angle stroke. Straight stroke includes: single seat valve, double seat valve, sleeve valve, cage valve, Angle valve, three-way valve, diaphragm valve; Angle stroke includes: butterfly valve, ball valve, eccentric rotary valve, full-function ultra-light control valve.
Regulating valve according to the driving method can be divided into: manual regulating valve, pneumatic regulating valve, electric regulating valve and hydraulic regulating valve, that is, pneumatic regulating valve with compressed air as power source, electric regulating valve with electricity as power source, hydraulic regulating valve with liquid medium (such as oil, etc.) pressure as power;
According to the regulation form can be divided into: regulation type, cut off type, regulation cut off type;
According to the flow characteristics can be divided into: linear, logarithmic (percentage), parabola, fast opening.
considerations of buying valve
1. Accurately match valve specifications and system requirements: Valve specifications, categories and models must strictly comply with the requirements of pipeline design documents. At the time of inquiry or order, a comprehensive and necessary description should be provided, including the working pressure of the valve, which should be greater than or equal to the actual working pressure of the pipeline, and the valve should be able to withstand higher pressure to adapt to possible changes in working conditions without affecting the cost.
2. Material selection and working condition adaptability: The material selection of the valve should be based on its contact medium characteristics, working pressure, temperature range and expected service life. For example, ductile iron is suitable for water, steam, air and oil and other media, while stainless steel is more suitable for corrosive media.
3. Performance testing and quality assurance: the valve should undergo strict performance testing before leaving the factory, including opening and closing torque, sealing and flow resistance coefficient. These test results should comply with relevant industry standards, such as ISO15848-1, API 622, etc., to ensure that the valve can operate reliably in practical applications.
4. Follow the latest industry standards: Valve procurement should follow the latest industry standards, such as the 18 valve industry standards implemented from January 1, 2021, covering many aspects from pressure relief valves to Marine valve electric devices.
5. Supplier selection and evaluation: It is very important to choose a reputable and qualified valve supplier. Suppliers should be able to provide high quality valves that meet industry standards and have timely and effective communication skills to ensure that the specific needs of the purchaser are understood and met.
6. Fluid characteristics and valve matching: according to the physical characteristics of the fluid, such as viscosity, density, etc., select a valve with an appropriate Cv value to achieve accurate flow control and ensure the stability of the system. For compressible fluids, the calculation and application of Cv is more complex, but it is still an important basis for selecting valves.
7. The control function and operation method of the valve: clear the control function of the valve in the system, such as whether it is necessary to adjust the flow rate, control the flow direction or prevent the backflow of the medium. The operation method can be manual, electric, and pneumatic, and should be selected according to the actual application scenario and operation convenience.
8. Pressure-temperature rating and sealing materials: pay special attention to the pressure-temperature rating of the valve, as well as the choice of sealing materials and gasket materials, which determine the temperature and pressure resistance of the valve, and affect its sealing and reliability.
9. Connection and installation integration: Consider the connection between the valve and the pipe, such as flange, welded or threaded connection, etc., to ensure that it is suitable for system pressure and temperature, while simplifying installation and avoiding additional leakage points.
10. Comprehensive consideration of the fluid characteristics of the valve: When purchasing the valve, consider the fluid characteristics of the valve, such as the accuracy of flow control, the reliability of the sealing mechanism, and the ease of operation and maintenance requirements of the valve.
Through these detailed precautions, you can ensure the professionalism and efficiency of valve procurement, while ensuring the performance and life of the valve in industrial applications.
one
General requirement
1.1 Valve specifications and categories shall comply with the requirements of pipeline design documents.
1.2 The valve model should indicate the national standard number requirements based on. If it is the enterprise standard, the relevant description of the model should be indicated.
1.3 Valve working pressure, requirements ≥ pipeline working pressure, without affecting the price of the premise, the valve can withstand the working pressure should be greater than the actual working pressure of the pipeline; Any side of the valve closed condition should be able to withstand 1.1 times the valve pressure value without leakage; When the valve is open, the valve body should be able to withstand the requirements of twice the working pressure of the valve.
1.4 Valve manufacturing standards, should indicate the national standard number based on, if the enterprise standard, the procurement contract should be attached to the enterprise document.
2
Valve quality standard
2.1 The body material should be mainly ductile iron, and indicate the grade and the actual physical and chemical test data of the cast iron.
2.2 Valve stem material, strive to stainless steel valve stem (2CR13), large diameter valves should also be stainless steel clad valve stem.
2.3 The nut material shall be cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem.
2.4 Valve stem bushing material, its hardness and strength should not be greater than the valve stem, and under the condition of water immersion with the valve stem, valve body does not form electrochemical corrosion.
2.5 Material of sealing surface
① Different types of valves, sealing methods and material requirements are different;
② Ordinary wedge gate valve, copper ring material, fixing method, grinding method should be explained;
③ Physical, chemical and health test data of soft seal gate valve and valve plate liner material;
④ The butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material on the butterfly plate; Their physical and chemical test data, especially the sanitary requirements of rubber, anti-aging properties, wear resistance; Usually use butadiene rubber and EPDM rubber, etc., it is strictly prohibited to mix recycled rubber.
2.6 Valve shaft packing
(1) Because the valve in the pipe network is usually opened and closed infrequently, the packing is required to be inactive for several years, the packing is not aging, and the sealing effect is maintained for a long time;
② Valve shaft packing should also withstand frequent opening and closing, sealing effect is good;
(3) In view of the above requirements, the valve shaft packing should not be replaced for a lifetime or more than 10 years;
④ If the packing needs to be replaced, the valve design should consider the measures to be replaced under the condition of water pressure.
3
Variable speed transmission box
3.1 The material and internal and external corrosion requirements of the box are consistent with the principle of the valve body.
3.2 The box should have sealing measures, and the box can withstand soaking of 3 meters of water column after assembly.
3.3 The opening and closing limit device on the box, the adjustment nut should be located in the box or outside the box, but special tools are required to operate.
3.4 Transmission structure design is reasonable, opening and closing can only drive the valve shaft to rotate, do not make it move up and down, the transmission parts bite properly, do not produce load when opening and closing separation slip.
3.5 Transmission box and valve shaft seal can not be connected into a leak-free whole, otherwise there should be reliable anti-leakage measures.
3.6 There is no debris in the box, and the gear bite part should be protected by grease.
4
Operating mechanism of valve
4.1 The opening and closing direction of the valve operation should be closed clockwise.
4.2 Because the valve in the pipe network is often manually opened and closed, the number of opening and closing revolutions should not be too much, even the large diameter valve should also be within 200-600 revolutions.
4.3 In order to facilitate the opening and closing operation of one person, the maximum opening and closing torque should be 240N-m under the condition of plumber pressure.
4.4 Valve opening and closing operation end should be square tenon, and standardized size, and face the ground, so that people can directly operate from the ground. Valves with roulette disks are not suitable for underground pipe networks.
4.5 Display panel of valve opening and closing degree
① The scale line of the opening and closing degree of the valve should be cast on the gearbox cover or the shell of the display panel after the conversion direction, all facing the ground, and the scale line is brushed with phosphor to show the eye-catching;
② The material of the indicator dial needle can be used in stainless steel plate under better management, otherwise it is painted steel plate, do not use aluminum skin production;
③ Indicator disc needle eye-catching, fixed firmly, once the opening and closing adjustment is accurate, it should be locked with rivets.
4.6 If the valve is buried deeply and the distance between the operating mechanism and the display panel and the ground is ≥1.5m, the extension rod facility should be provided and fixed firmly so that people can observe and operate from the ground. In other words, the valve opening and closing operation in the pipe network is not suitable for well operation.
5
Valve performance testing
5.1 When the valve is manufactured in batches of a certain specification, the following performance testing should be commissioned by an authoritative organization:
① Opening and closing torque of the valve under working pressure;
② Under the working pressure condition, it can ensure the continuous opening and closing times of the valve close tightly;
③ Test the flow resistance coefficient of the valve under the condition of pipeline water transmission.
5.2 The valve should be tested as follows before leaving the factory:
① When the valve is open, the valve body should withstand the internal pressure detection of twice the valve working pressure value;
② Under the closed condition of the valve, both sides are subjected to 1.1 times the working pressure value of the valve, without leakage; However, the leakage value of the metal sealed butterfly valve is not greater than the relevant requirements.
6
Internal and external corrosion protection of valves
6.1 Inside and outside the valve body (including the variable speed transmission box), the first thing should be shot blasting, sand cleaning and rust removal, and strive to electrostatic spraying powder non-toxic epoxy resin, the thickness of more than 0.3mm. When it is difficult to electrostatic spray non-toxic epoxy resin on oversized valves, similar non-toxic epoxy paint should also be brushed and sprayed.
6.2 The inside of the valve body and various parts of the valve plate require comprehensive anti-corrosion, on the one hand, it will not rust in water, and there will be no electrochemical corrosion between the two metals; The smooth surface of the two aspects reduces the water resistance.
6.3 The sanitary requirements of the anticorrosive epoxy resin or paint in the valve body shall be tested by the corresponding authority. Chemical and physical properties should also meet the relevant requirements.
7
Valve packing and transportation
7.1 Light plugging plates should be installed on both sides of the valve to seal.
7.2 Medium and small diameter valves should be tied with straw ropes and transported in containers.
7.3 Large diameter valves also have simple wooden strip frame solid packaging to avoid damage during transportation.
8
Valve factory
Valve is equipment, in the factory manual should be marked with the following relevant data: valve specifications; Model number; Working pressure; Manufacturing standards; Body material; Valve stem material; Sealing material; Valve shaft packing material; Valve stem sleeve material; Internal and external anticorrosive material; Operation starting direction; Revolutions; Opening and closing torque under working pressure; Name of the manufacturer; Date of delivery; Factory number; Weight; The aperture of the connecting flange, the number of holes and the center hole distance; The control dimensions of the overall length, width and height are indicated in the graphical form; Valve flow resistance coefficient; Effective opening and closing times; Related data of valve factory testing and precautions for installation and maintenance.
request a free quote
we would like to collaborate with you
Send us a message if you have any requests or need a help with flow control. we will responds within 10 minutes and help you with personalized support with quickly quote .
Email :sales@ketavalve.com
WhatsApp :+8619906653951