Butterfly valves
Butterfly valves manufacturer
XinHui is an industrial butterfly valve manufacturer from China. The products of our China Butterfly Valve Factory are: Metal Sealed Butterfly Valves for High Temperature and High Pressure Industrial Use and High Performance Butterfly Valves. We are also a supplier of double eccentric and triple eccentric butterfly valves. The double eccentric type is often used in power stations and the oil industry, while the triple eccentric type can meet the higher requirements of industrial applications.
Butterfly valves
-
Butterfly valves
D363H Butt Welded Metal Hard Seat Butterfly Valve
Precautions when buying Butterfly valves
When we select the models we compare ourselves with our customers to know every useful detail about the process, temperature, pressure, fluid and much more, in order to determine the perfect parameters for the realization of their valves, helping them to select the best models for them.
The elements to pay attention to when buying a butterfly valve are mainly 3:
1. Process parameters
Temperatures
The material and seal shape of the valve is decided on the basis of the temperature level. For example if the temperature is above 120 degrees then the throttle valve must be watertight; while if the temperature goes over 400 degrees it is necessary to replace the valve body.
Pressure
The shape of the seal and the method of actuation of the butterfly valve are selected according to the pressure.
Medium
჻ Water: use a soft seal butterfly valve (example: manual D341X, D342X, D372X, D371X, electric: D941X; D942X; D971X; D972X, pneumatic: D641X; D642X; D671X; D672X),
჻ Steam: choose a watertight butterfly valve (example: Manual: D343H; D373H; Electric: D943H; D973H; Pneumatic: D643H; D673H),
჻ Corrosive medium: select stainless steel (example: Manual: D343W; D373W; Electric: D943W; D973W, Pneumatic: D643W; D673W)
2. Valve seat
When selecting a valve, some customers usually don’t know how to choose a butterfly valve seat. In fact, there are many types of valve seats to choose from but the most used is PTFE / NBR / EPDM rubber. For ordinary media such as water, if the temperature is not high, we can use EPDM, while for oily fluids containing water (oil-over-over medium), we must use NBR rubber. If it is a corrosive medium, it is recommended to use the PTFE valve seat.
3. Soft and hard seal
The same is true when choosing whether the throttle valve is an electric hard seal butterfly valve or an electric soft seal butterfly valve. Electric soft seal butterfly valve is mainly midline butterfly valve, while electric hard seal butterfly valve is mainly single eccentric, double eccentric and triple eccentric butterfly valves. The sealing material of the soft seal electric butterfly valve is rubber, PTFE, etc. Due to the limitation of structural characteristics, it is not suitable for areas such as high temperature resistance, high pressure, corrosion resistance and wear resistance.
The soft seal seat is made of non-metallic materials with a certain strength, hardness and temperature resistance. It has good sealing performance and can eliminate losses, but its durability and adaptability to reach temperatures are relatively poor.
The watertight electric butterfly valve has been widely used in many fields such as petroleum, chemical industry, metallurgy, hydroelectric power and so on, as the component used to realize the on-off and flow control of the piping system.
Recommendations for purchasing butterfly valves
1. Since the butterfly valve has a relatively large pressure loss compared to the gate valve and the ball valve, it is suitable for the pipeline system where the pressure loss requirements are not strict.
2. Since the butterfly valve can be used for flow regulation, it is suitable for use in pipelines that require flow regulation.
3. Due to the limitation of structure and sealing material of butterfly valve, it is not suitable for high temperature and high pressure pipeline system. The general working temperature is below 300℃, and the nominal pressure is below PN40.
4. Since the structure length of the butterfly valve is relatively short, and it can be made into a large-mouth meridian, the butterfly valve should be selected in the occasions where the structural length is required to be short or the valve with a large-mouth meridian (such as DN1000 or more).
5. Since the butterfly valve can be opened or closed only by rotating 90°, the butterfly valve should be selected when the opening and closing requirements are fast.
Why choose XinHui Butterfly valves?
Cheap
The butterfly valves we produce have competitive prices, which are cheap without cutting corners and materials, strictly in accordance with production standards, especially for large-diameter butterfly valves;
Good adjustment performance
The butterfly valve we produce has good regulation performance, when it is opened, the flow resistance is small, and it has the characteristics of proportional flow control. It can be used for the regulation process control of low pressure and large diameter conditions.
Simple structure
We produce the most practical butterfly valve with the most reasonable design and simple structure. It has the advantages of small size, light weight, saving consumables without sacrificing quality
Strong sealing performance
Through years of efforts, Xinhui Valve has reformed the sealing performance of the butterfly valve, improved the sealing characteristics of the butterfly valve, and the soft-sealed butterfly valve can achieve zero leakage.
Easy to operate
It can be opened or closed only by rotating 90°, so the opening and closing speed is fast and easy to operate. It is worth mentioning that the valves we produce have many opening and closing times and long service life.
Easy maintenance and installation
The valve body has the function of valve seat, and can use the throttling flushing to flush the inner wall of the valve body, which has a "self-cleaning" effect and can be used for unclean media. And the installation space is small and the maintenance is easy.
More Butterfly valves related articles
We are not only a manufacturer of valves, but also a disseminator of industry knowledge
REQUEST A QUOTE FOR MORE DETAILS
All You Need to Know About Butterfly valves
01
Introduce
what is a Butterfly valve
Butterfly valve, also known as flap valve, is a rotary valve that uses a disc-shaped closing member to rotate about 90 degrees to open and close the valve. The butterfly valve can be used for both adjustment and sealing. Butterfly valve has the advantages of simple structure, not easy to produce thermal deformation, relatively small resistance, rapid opening and closing, low opening and closing power, good sealing performance, long life and so on. Butterfly valve can transport water, sewage, various liquids, air, gas and other gases, as well as dry powder, mud and other mixtures.
What is a Butterfly valve used for?
Butterfly valves are suitable for circulating all kinds of water and some fluid media at normal temperature and pressure. For example, our domestic water pipelines, fire water pipelines, circulating water pipelines, sewage pipelines [etc.], can use butterfly valves as flow control and regulation. In addition, some powder, oil, mud medium pipelines can also use butterfly valves. Even butterfly valves can be used in ventilation ducts. If you are not sure about your working conditions and which butterfly valve to choose, welcome to consult XinHui butterfly valve supplier
02
Introduce
03
Introduce
how does a Butterfly valve work
A butterfly valve is a valve that opens and closes according to a rotating valve stem, which drives a disc plate to rotate. In the cylindrical channel of the butterfly body, the disc rotates around an axis, mainly rotating the plate 90 degrees. When the flow control disc reaches 90 degrees, the valve is fully opened, and the medium flow can be adjusted by changing the angle of the valve. Usually installed in the diameter direction of the pipe. Butterfly valves and stems themselves do not have a locking function. In order to effectively control the flow, a worm gear reducer is required. The butterfly valve with worm gear reducer can not only automatically lock the butterfly valve, but also change the working performance of the butterfly valve and adjust the medium flow more accurately.
Butterfly Valve Structure
The structure of the butterfly valve is quite simple, which is composed of the valve body, the valve stem, the butterfly plate, and the sealing ring, and the closing part of the butterfly valve is called the valve disc or the butterfly plate, and its shape is disc-shaped.
1. Butterfly valve has very distinctive characteristics, that is, it has the characteristics of simple structure, small volume, light weight, very small installation size and very fast switching. The butterfly valve can also be used to cut off, connect and adjust the medium in the pipeline, which shows that the butterfly valve has very good fluid control and closed sealing.
The main structural characteristics of the butterfly valves are:
2. Under the condition of low pressure, the butterfly valve can also achieve very good sealing characteristics, and can also be used when transporting mud, while the amount of liquid accumulated in the pipe mouth of the butterfly valve is very small, so it has a very good adjustment performance .3. Because the butterfly valve adopts a streamlined design, it can reduce the degree of damage to the resistance of the fluid. In this way, the butterfly valve can also be regarded as an energy-saving product.
4. After quenching and tempering, the valve stem of the butterfly valve also has very good comprehensive mechanical properties, and has good corrosion resistance and scratch resistance, because the valve stem of the butterfly valve is a through-rod structure.
5. There are many connection methods of butterfly valve, which can realize manual, turbine transmission, electric, pneumatic, hydraulic and electro-hydraulic linkage and other driving forms, and can realize remote control and automatic operation.
How to determine the size of the butterfly valve
The diameter of the butterfly valve is described in the form of DN.
For example, DN100 means a butterfly valve with a diameter of 100 mm, which usually represents the inner diameter of the valve. The orifice is usually marked on the body and nameplate of the butterfly valve and can be observed. If you want to replace the old butterfly valve, the surface of the old butterfly valve is rusted and the diameter of the butterfly valve cannot be directly identified. You can remove the valve and measure it with a ruler.
Second, the dimension usually mentioned in the butterfly valve is the structural length, also called the butterfly valve thickness. The long dimension of the structure does not usually appear on the model, valve and nameplate, so the designer must agree with the manufacturer. Some people ask about the standard parts of the butterfly valve and the structural length corresponding to the size of the caliber. In addition, although the butterfly valve standard is not false, there are many standards for butterfly valves, including: national standard, German standard, American standard, Japanese standard [etc.], which can be different according to the length of the standard structure. In addition, some pipes are special, requiring the manufacturer to specially design the structural length to meet the requirements.
04
Introduce
05
Introduce
How to Install a Butterfly valve
Butterfly valve installation, operation and maintenance guide
Supporting tools and corresponding protective gear should be prepared before installing the butterfly valve.
The installation of the butterfly valve on the pipeline firstly uses two screws to penetrate into two symmetrical flange holes respectively, and install two nuts on the screws on the inside of the flange, and then rotate the nuts to the outside to connect the two flanges.
The spacing between them increases until they are slightly wider than the length of the seat structure. Twist the valve handle in both positive and negative directions to check whether the valve opens and closes normally. Slowly install the closed valve into the predetermined position. Carefully confirm that the butterfly
valve is flush with the pipeline, the two flange bosses and the outer edge of the valve body. Whether it is uniform, if it is not uniform, it must be corrected, otherwise when the valve is opened, the valve plate will be damaged and the valve will be scrapped. Align the four bolt holes on the valve with the bolt holes on the flange, then insert the two screws into the two flange holes with symmetrical positions, and install the flat washer, spring washer nut on the outside of the flange, and bolts at both ends. The ammo pads must be installed, otherwise the changes in ambient temperature will cause the bolts to loosen, resulting in water leakage at the flange. Tighten the bolts diagonally one by one, and tighten all the nuts symmetrically and evenly in turn. Be sure to tighten them gradually and repeatedly until the flange sealing surface is in complete contact with the metal valve body and the rubber valve seat is completely compressed and invisible. The installation of the butterfly valve is complete.
Butterfly valve application scenarios
Generally, in throttling, regulating control and mud medium, short structure length and fast opening and closing speed (1/4 revolution) are required. Low pressure cut-off (small differential pressure), butterfly valve is recommended. Butterfly valve can be used in two-position adjustment, constricted channel, low noise, cavitation and gasification, a small amount of leakage to the atmosphere, and abrasive medium. When the butterfly valve is used for throttling adjustment under special working conditions, or requiring strict sealing, serious wear, low temperature (cryogenic) and other working conditions, it is necessary to use a specially designed metal sealing belt adjustment device for triple eccentric or double eccentric. The centerline butterfly valve is suitable for fresh water, sewage, sea water, salt water, steam, natural gas, food, medicine, oil and various products that require complete sealing, zero leakage in gas test, high life expectancy, and working temperature between -10°C and 150°C. Soft-sealed eccentric butterfly valve is suitable for two-way opening and closing and adjustment of ventilation and dust removal pipelines, and is widely used in gas pipelines and waterways of metallurgy, light industry, electric power, and petrochemical systems.
Metal to metal wire sealed double eccentric butterfly valve is suitable for urban heating, gas supply, water supply and other gas, oil, acid and alkali pipelines, as a regulating and throttling device. In addition to being used as a program control valve for a large pressure swing adsorption (PSA) gas separation device, the metal-to-metal surface sealing triple eccentric butterfly valve can also be widely used in petroleum, petrochemical, chemical, metallurgy, electric power and other fields.
06
Introduce
OEM & ODM XinHui Butterfly valve Applications
D341F Fluorine Lined Flanged Butterfly Valve - Recommended for Chemical Industry
As a component used to realize the on-off and flow control of the pipeline system, the fluorine-lined flange butterfly valve is widely used in the petroleum field. Suitable for various concentrations of aqua regia, sulfuric acid, hydrochloric acid, hydrofluoric acid and various organic acids, strong acids, strong oxidants at -50℃～150℃, FEP flange lined fluorine butterfly valve is suitable for various concentrations of strong alkali organic solvents And other corrosive gas, liquid medium pipeline use.
HBD741X(H) Hydraulic Controlled Slow Closing Check Butterfly Valve-Recommended for power station industry
The hydraulically controlled slow-closing check butterfly valve is also a relatively good pipeline control equipment in China. It is mainly installed at the turbine inlet of the hydropower station industry and used as the turbine inlet valve. Therefore, since the hydraulically controlled slow-closing check butterfly valve has been developed, it has replaced the functions of the gate valve and the check valve. Through the preset opening and closing procedures, in this way, the reliable cut-off of the pipeline is realized, the water hammer of the pipeline is effectively eliminated, and the safety of the pipeline system is protected.
D363H Butt Welded Metal Hard Seat Butterfly Valve-Recommended for metallurgical industry
D363H butt welding hard sealing butterfly valve is widely used in metallurgy, electric power, petrochemical industry, water supply and drainage and municipal construction and other industrial pipelines with medium temperature ≤425℃. It adopts precise J-shaped elastic sealing ring and triple eccentric multi-layer metal hard sealing structure, which is used for regulating flow and load-cutting fluid. The valve seat and disc sealing surface are made of different hardness and stainless steel, which have good corrosion resistance. Long life, the valve has bidirectional sealing function
NKD943X double seal vacuum butterfly valve-recommended for chemical and pharmaceutical industries
NKD343X double-sealed vacuum butterfly valve is a new generation of high-tech products successfully developed by our company in combination with new vacuum technology standards at home and abroad.
The valve structure is designed as: double butterfly plate, double sealing seat, three-dimensional eccentric locking structure, cobalt-based hard alloy surfacing on the sealing surface of the valve body, and the sealing ring is made of temperature-resistant, corrosion-resistant rubber and fluorine rubber pressure plate firmly sealed Pressed on the butterfly plate can be removed and replaced for easy maintenance
Top Entry Type Two-way High Pressure Metal Hard Seal Butterfly Valve-Recommended for Petroleum Industry
The top-mounted two-way high-pressure metal hard-sealed butterfly valve has the advantages of simple structure, low cost, convenient maintenance, and does not affect the normal operation of the pipeline system during maintenance.
Strength customers
Testimonials
Read More
I am very happy to be invited to share our long-term cooperation experience for the xinhui website! Japan is very strict on the production standards of valves, but Xinhui has never let me down in our cooperation for so many years, so I recommend you to start your valve business with them too!
Read More
Hello everyone, I'm Tony, I'm very happy to share the story between us and Xinhui Valve, the CEO of Xinhui company must ask me to shoot this video, I refused at first, but their work is done so well , I think I can't help but tell everyone that my cooperation with Xinhui is really good, so I recommend them! After working with them I believe you are too!
Previous
Next
Butterfly Valves: Ultimate Guide
Why is it called a butterfly valve?
Butterfly valves get their name from the shape and movement of the valve plug. The valve plug is butterfly-shaped, and the valve stem passes through the valve plug, reminiscent of a butterfly. To stop fluid flow, the valve disc rotates 90 degrees on the normal channel where the pipe runs, like butterfly wings.
Is a butterfly valve a control valve?
Is a butterfly valve a control valve?
Yes, it is a kind of regulating valve with simple structure.
Which valve is best for throttling?
The butterfly valve can be opened or closed only by rotating 90°, so the speed of opening and closing is fast. Between 15 and 70°, it has approximate logarithmic flow characteristics and good adjustment performance.
Can the butterfly valve be used for throttling?
Yes, the function of the butterfly valve is to cut off and throttle on the pipeline.
What are the types of butterfly valves?
Butterfly valves can be divided into segment type and adjustment type according to their use, and can be divided into midline type, single eccentric, double eccentric and triple eccentric butterfly valves according to their structure…
What are the types of butterfly valves?
Butterfly valves can be divided into segment type and adjustment type according to their use, and can be divided into midline type, single eccentric, double eccentric and triple eccentric butterfly valves according to their structure. .
What is the difference between a ball valve and a butterfly valve?
1- For the first tail the method of shutting off the ball valve and the throttle valve is different as the ball valve blocks the channel through the ball to realize the interruption flow of the pipeline. The butterfly valve relies on the wing of the butterfly and the pipeline will not flow if it is stretched and sealed.
2- The second important difference is that the structure of the ball valve and the valve are not the same. The ball valve consists of the valve body, the valve core and the valve stem, and only some parts are visible in the body. Inevce, the butterfly valve consists of valve body, valve seat, valve plate and valve stem and all accessories are visible. Therefore, it can be seen that the sealing performance of the butterfly valve is not as good as that of the ball valve. Butterfly valves are also divided into soft seals and hard seals. The structure of the butterfly valve is relatively simple, it can only be used in low pressure environment, the maximum pressure is only 64kg. Compared with the ball valve, the ball valve can reach up to about 100 kilograms.
3- The third difference lies in the operating system of the ball valve and the butterfly valve. The ball valve has a 90 degree rotation action, precisely because its opening and closing part is a ball, it can only be opened or closed by operating a 90 degree rotation, which is the most suitable for switching. But now the V-shaped ball valve can be used to regulate or control the flow. The butterfly valve is a type of valve that uses a disc type opening and closing element to oscillate approximately 90 ° to open, close or regulate the flow of fluid. It has a good flow regulating function and is one of the fastest growing valve varieties.
What is the difference between gate valve and butterfly valve?
PRINCIPLE
A butterfly valve, also known as a flap valve, is a kind of regulating valve with a simple structure. It can also be used for on-off control of low-pressure pipeline medium, mainly for cutting off and throttling. The butterfly valve is usually less than 90° from fully open to fully closed. The butterfly valve and the butterfly stem have no self-locking ability. For the positioning of the butterfly plate, a worm gear reducer should be installed on the valve stem. The use of worm gear reducer can not only make the butterfly plate have self-locking ability, so that the butterfly plate can stop at any position, but also improve the operation performance of the valve.
The gate valve is an opening and closing gate, which is controlled by the up and down movement of the valve plate to control the opening of the valve. The movement direction of the gate is perpendicular to the direction of the fluid. The gate valve can only be fully opened and fully closed, and it is mainly used for cutting off in the pipeline. Most gate valves are forcibly sealed, that is, when the valve is closed, the gate must be forced against the valve seat by external force to ensure the tightness of the sealing surface.
STRUCTURE
Butterfly valve is mainly composed of valve body, butterfly plate, valve stem, sealing ring and transmission device.
Valve body
The valve body is cylindrical, and the upper and lower parts each have a cylindrical boss for installing the valve stem. Butterfly valves and pipelines are mostly connected by flanges; if they are connected by clips, their structural length is the smallest.
Valve stem
The valve stem is the rotating shaft of the butterfly plate, and the shaft end adopts the packing box sealing structure, which can prevent the leakage of the medium. The upper end of the valve stem is directly connected with the transmission device to transmit torque. Butterfly plate The butterfly plate is the opening and closing part of the butterfly valve. The gate valve is generally composed of valve body, valve seat, valve stem, gate plate, valve cover, and sealing ring. It can be transformed into a variety of electric gate valves and pneumatic gate valves by equipping the transmission device and gate valve.
Flow characteristic curves The gate valve has small resistance and good shut-off, good airtightness after closing, less internal leakage, but not conducive to flow regulation, often used for shut-off of main pipes.
The butterfly valve has small size, combined with the advantages of globe valve and ball valve. The shape of the valve disc can be adjusted to design valves with different flow characteristics, and it has good shut-off performance, large pipe diameter, and a wide range of applications, including hot water and cold water.
APPLICATION
Gate valve is one of the commonly used shut-off valves. It is mainly used to connect or cut off the medium in the pipeline, and is not suitable for regulating the flow of the medium. Butterfly valve is suitable for a wide range of pressure, temperature and diameter, especially for medium and large diameter pipelines.
Butterfly valve is suitable for pipelines conveying various corrosive and non-corrosive fluid media in engineering systems such as producer, coal gas, natural gas, liquefied petroleum gas, city gas, hot and cold air, chemical smelting and power generation environmental protection, building water supply and drainage, etc. The characteristics of the industrial butterfly valve are high temperature resistance, high applicable pressure range, large nominal diameter of the valve, carbon steel for the valve body, and metal ring instead of rubber ring for the sealing ring of the valve plate. Large high temperature butterfly valve is made of steel plate welding, mainly used for flue air duct and gas pipeline of high temperature medium.Generally speaking, in order to reduce the soil covering depth of the pipeline in the water supply network, butterfly valves are generally selected for pipes with larger diameters.
For those with little influence on the soil covering depth, gate valves should be selected, but the price of gate valves of the same specification is higher than that of butterfly valves. As for the demarcation line of caliber, it should be considered on a case-by-case basis. From the perspective of use in the past ten years, the failure rate of butterfly valves is higher than that of gate valves, so it is worthy of attention to expand the scope of use of gate valves when conditions permit.
INSTALLATION & MAINTENANCE
Gate valve installation and maintenance
o The handwheel, handle and transmission mechanism are not allowed to be used for lifting, and collision is strictly prohibited
o The double gate gate valve should be installed vertically, that is, the valve stem is in a vertical position and the handwheel is at the top
o The gate valve with a bypass valve should open the bypass valve before opening to balance the pressure difference between the inlet and outlet and reduce the opening force
o The gate valve with transmission mechanism shall be installed according to the provisions of the product instruction manual
o If the valve is frequently switched on and off, lubricate it at least once a month
Butterfly valve installation and maintenance
o During installation, the valve disc should stop in the closed position
o The opening position should be determined according to the rotation angle of the butterfly plate
o For butterfly valves with bypass valves, the bypass valve should be opened before opening
o It should be installed according to the manufacturer’s installation instructions. For butterfly valves with heavy weight, a firm foundation should be set up.
What are the advantages of a butterfly valve?
Butterfly valves are lighter, smaller and lighter than other types of control valves and are the best choice for regulating flow in many applications. Traditionally, standard butterfly valves have been used for automatic on/off applications and they are well suited for this role. However, some engineers consider them unacceptable when regulating flow in closed-loop systems.
Butterfly valves use rotating discs to control flow through pipes. The disc usually rotates 90 degrees, so it is sometimes called a quarter turn valve. Usually, they are used when economy is considered. When tight shutoff is required, butterfly valves with soft elastomeric seals and/or coated discs can be used to provide the required performance. High Performance Butterfly Valves (HPBVs) – or Double Offset Butterfly Valves – are now the industry standard for butterfly control valves and are widely used for throttling control. They are useful for applications with relatively constant pressure drop or slow process cycles.The advantages of HPBV include a straight flow path, high capacity, and the ability to easily pass through solid and viscous media. They generally have the lowest installed cost of all valve types, especially in NPS 12 and larger sizes. Their cost advantage over other types of valves has resulted in a dramatic increase in valve sizes over 12 inches. They provide good shut-off performance over a wide temperature range and are available in different body designs including wafer, lug and double flange. They are much lighter in weight and more compact than other types of valves.
(For example, a 12-inch ANSI Class 150 double-flange segmented ball valve weighs 350 pounds and has a face-to-face dimension of 13.31 inches, while a 12-inch drag butterfly valve weighs only 200 pounds and has a face-to-face dimension of 3 inches.)
Limitation of butterfly valve
Butterfly valves do have limitations that make them unsuitable for flow control in certain applications.
Compared to globe valves, they have limited pressure drop capability and have a greater potential for cavitation or flashing. Standard butterfly valves are generally not used in high pressure applications because the larger surface area of the disc acts like a lever, applying the power of the flowing medium to the drive shaft. If so, actuator size and selection becomes critical.
Butterfly control valves can sometimes be oversized, which can negatively impact process performance. This may be due to the use of line-sized valves, especially high-capacity butterfly valves. It can increase the variability of the process in two ways. First, oversizing increases the gain of the valve, while lacking flexibility in adjusting the controller. Second, oversized valves may work more frequently at lower valve openings, while butterfly valves may have more sealing friction. Because an oversized valve produces a disproportionately large flow change for a given increment of valve travel, this phenomenon greatly exaggerates the process variability associated with deadband due to friction. Specifiers sometimes use butterfly valves for economic reasons or to fit a given line size without considering their limitations. There is a tendency to oversize butterfly valves so as not to undersize pipes, which can lead to poor process control. The biggest limitation is that the ideal throttle control range is not as wide as a globe valve or segmented ball valve. Butterfly valves generally do not perform well in the control range of about 30% to 50% open.
How to obtain the best control performance
Typically, the loop is easiest to control when the control loop operates in a linear fashion and the process gain is close to unity. Therefore, a process gain of 1.0 becomes a target for good loop control, with an acceptable range of 0.5 to 2.0 ( 4:1 range).
The best performance is obtained when most of the loop gain comes from the controller. Process gain defines the relationship between process output and input change. A stroke where the process gain remains between 0.5 and 2.0 is the optimum control range for the valve. When the process gain is not in the 0.5 to 2.0 range, poor dynamic performance and loop instability can occur.
The design of the butterfly valve disc has a great effect on the flow of the valve as the valve goes from closed to open. Disks with inherent percentage characteristics can better compensate for changes in pressure drop as flow changes. Equal percent trim will provide linear mounting characteristics for varying pressure drops, which is ideal. The result is a more precise, one-to-one change between flow and valve travel.
Butterfly valves have recently become available for discs with inherent equal percentage flow characteristics. This provides mounting characteristics that allow the mounting process gain to be in the desired 0.5 to 2.0 range over a wide travel range. This significantly improves throttle control, especially in the lower driving range.
This design provides good control with an acceptable gain of 0.5 to 2.0 from approximately 11% opening to 70%, a nearly three-fold increase in control range compared to a typical high performance butterfly valve (HPBV) of the same size. Therefore, equal percentages of disks provide overall lower process variability.
Butterfly valves with inherent equal percentage characteristics, such as control disc valves, are ideal for processes that require precise throttling control performance. They can be controlled closer to the target set point without process disturbance, reducing process variability.
How to improve control
If the butterfly valve is not performing well, simply replacing it with an appropriately sized valve will fix the problem. For example, a paper company is using two oversized butterfly valves to control the removal of moisture from pulp. Both valves were operated at less than 20% stroke, resulting in process variations of 3.5% and 8.0%, respectively. They spend most of their life in manual mode. Two appropriately sized NPS 4 Fisher Control-Disk butterfly valves with digital valve controllers were installed. These loops are now running in automatic mode, increasing the process variability from 3.5% to 1.6% for the first valve and from 8% to 3.0% for the second valve without any special loop tuning . Poor water pressure and flow control in the steel plant’s coolant system resulted in inconsistent end products.
The nine installed HPBVs were unable to effectively control the water flow as required. The plant wanted to install valves that could better control the process and needed to keep installation costs to a minimum. If each valve is switched from HPBV to segmented ball valve, the factory will spend $10,000 for pipe replacement. Instead, we recommend its control disc butterfly valve to fit current HPBV face-to-face dimensions. A control disc valve was tested side-by-side with one of nine existing HPBVs and met specified requirements.
The plant replaced the remaining eight HPBVs within a year, each with a control disc valve, saving the $90,000 in pipe replacement costs for segmented ball valves, which cost about 25 percent more relative to butterfly valves.
Control disc valves provide precise control and help eliminate end-product variability. The mill is estimated to have installed nine control disc valves, resulting in annual savings of about $1 million.
CONCLUSION
The initial installation cost of an HPBV with a digital positioner is lower than most other valve types, and when properly sized can provide adequate control range. They have high capacity and minimal flow restrictions. Butterfly valves with inherently equal percent adjustment offer the opportunity to extend the control range, similar to globe or ball valves, and take up only the space of an HPBV. When selecting valves, especially HPBVs, make sure they are the correct size, otherwise they may be manually controlled from the control room. It is important to consider the style, inherent characteristics and valve size of the valve that will provide the greatest range of control for the application.
Do butterfly valves need gaskets?
Yes, when installing the butterfly valve, it is necessary to install a flat washer and a spring washer nut on the outside of the flange, and spring washers must be installed at both ends of the bolt, otherwise the change in ambient temperature will cause the bolt to loosen, resulting in water leakage at the flange.
Are butterfly valves suitable for isolation?
Yes, the main function of the butterfly valve is to cut off and throttle.
How to test butterfly valve?
Butterfly valve inspection shell test
First, open the butterfly valve to the half-open and half-closed position, then place the butterfly valve on the test bench, seal it with a gland, and clamp it with three claws. Then the pressure tester pressurizes to 1.5 times the nominal pressure of 2.4 mpa, and maintains the pressure for one minute at this time. Check whether there is leakage around the shell, and finally check whether the pressure gauge has leakage. If there is no leakage, the shell inspection is qualified.
Butterfly valve sealing test
Open the butterfly valve to the half-open and half-closed position, then place the butterfly valve on the test bench, seal it with a gland, clamp it with three claws, pressurize it, and fill it with water. Close the valve and drain off excess water to avoid affecting seal detection. Add 18kg to the pressure tester and keep the pressure for one minute. The third-party inspection personnel will supervise the inspection on site, check whether the seal is leaking, confirm that the inspection is correct, drain the pressure, and open the valve. Loosen the three claws, remove the gland, take out the valve, seal without leakage, and complete the test.
How much pressure can the butterfly valve withstand?
In the earliest days, the butterfly valve was an ordinary flap valve with a very single function. It could only be used to control the size of the water flow, and the pressure it could withstand was very small. With the advancement of science and technology, the manufacturing process of butterfly valves has become more and more mature, and there are more and more types of butterfly valves, which also enables butterfly valves to be used in different types of working conditions. How much pressure can butterfly valves withstand?According to the pressure of the valve, we divide the valve into vacuum valve, low pressure valve, medium
pressure valve, high pressure valve, ultra-high pressure valve and so on. Therefore, butterfly valves can also be classified according to pressure.
1. The working pressure of the vacuum butterfly valve is lower than the standard atmospheric pressure butterfly valve.
2. Butterfly valve with nominal pressure PN < 1.6MPa.
3. The medium pressure butterfly valve is a butterfly valve with a nominal pressure PN of 2.5- 6.4MPa.
4. The high-pressure butterfly valve is a butterfly valve with a nominal pressure PN of 10.0- 80.0MPa.
5. Ultra-high pressure butterfly valve with nominal pressure PN>100MPa.
Are butterfly valves cheaper than ball valves?
Butterfly valves should be the cheapest, followed by ball valves and gate valves, and then globe valves are relatively expensive.