When it comes to butterfly valves, there are two main types: double offset and triple offset. The question of whether to use a double offset or triple offset butterfly valve is one that is often debated in the engineering world. Both types of valves have pros and cons, and the decision ultimately comes down to the specific application. In this blog post, we&#;ll explore the key differences between double offset vs triple offset butterfly valve and help decide which is the right choice for the project.

For more information, please visit LEFLOW.

What Is Double Offset Butterfly Valve?

A double offset butterfly valve is a quarter-turn valve that uses a disc to control the flow of fluid. The disc is connected to a rod attached to a lever, and when the lever is turned, the disc rotates to open or close the valve. It means that the disk is not in line with the flow of the fluid. This allows for more precise control of the flow. Double offset butterfly valves are used in various industries, including oil and gas, chemical, and power generation, where a high degree of control is required. 

Advantages Of Double Offset Butterfly Valve

Butterfly valves are frequently used in industrial applications because they offer many advantages over other valve, such as gate and ball valves types. In this article, we will explore five advantages of double offset butterfly valves:

• Double offset butterfly valves have a lower operating torque than other valve types, making them easier to open and close.
• Double offset butterfly valves have a higher flow capacity than other valve types, making them ideal for applications where a large volume of fluid needs to be processed.
• Double offset butterfly valves have a shorter face-to-face dimension than other valve types, making them more compact and easier to install in confined spaces.
• Double offset butterfly valves have a flexible seat design that allows for a tight seal even when the valve is only partially open.
• Double offset butterfly valves can be installed in horizontal or vertical positions, making them versatile for a wide range of applications.

Disadvantages Of Double Offset Butterfly Valve

While the double offset butterfly valve has many advantages, there are also a few disadvantages. Here are five of the most significant disadvantages of this type of valve:

• They can be more expensive than other types of valves.
• They require more maintenance and care than other types of valves.
• They can be more challenging to operate than other types of valves.
• They can be more vulnerable to leakages than other types of valves.
• Double offset butterfly valves can sometimes be less reliable than other types of valves.

What Is Triple Offset Butterfly Valve?

In the world of valves, the triple offset butterfly valve is a specialized type of valve often used in high-pressure and high-temperature applications. Triple offset butterfly valves have three sealing surfaces instead of the usual two, which gives them a tight seal that can withstand high pressures. These valves are also often used in situations where a standard butterfly valve cannot provide a proper seal, such as in high-temperature applications.

While triple offset butterfly valves are more expensive than regular butterfly valves, they are often worth the investment due to their ability to provide a tight seal under challenging situations. For a high-pressure or high-temperature application, a triple offset butterfly valve may be the right choice.

Advantages Of Triple Offset Butterfly Valve

One type of valve that has become increasingly popular in recent years is the triple offset butterfly valve. This valve offers several advantages over other types of valves, including the following:

• Triple offset butterfly valves have a crucial advantage: they seal metal-on&#;metal without friction. They are also more resistant to temperature changes, so they last longer.
• Triple offset butterfly valves have a much lower risk of leakage than other valves.
• They have a very tight seal, which is ideal for applications requiring a high degree of sealing.
• They are available in various sizes and specifications, making them suitable for a wide range of applications.
• They are suitable for high-corrosive and abrasive materials, steam, or high-temperature liquids. They can be found in many industries, including oil and gas processing, pulp and papers, and power generation.

Disadvantages Of Triple Offset Butterfly Valve

A triple offset butterfly valve (TOFV) is a type of butterfly valve that is designed to provide a tight seal even after extended periods of use. The valve gets its name from the three different offsets used in its construction: an offset in the body, an offset in the disc, and an offset in the seat. While a TOFV can provide many benefits, some potential disadvantages should be considered before using one. Here are five potential disadvantages of a TOFV:

• Limited applications &#; Triple offset butterfly valves are not suitable for all applications. They are primarily used in critical applications where a tight seal is required, such as in the oil and gas industry.
• High cost &#; Triple offset butterfly valves are more expensive than other types of valves, such as ball valves. This is because they are more complicated to manufacture.
• High maintenance: Triple offset butterfly valves require high maintenance due to their complex design.
• Susceptible to wear and tear &#; Triple offset butterfly valves are susceptible to wear and tear due to their moving parts.

Double Offset Vs. Triple Offset Butterfly Valve

One of the most important decisions one can make when choosing a butterfly valve is deciding between a double offset and triple offset butterfly valve. Both valves have advantages and disadvantages, so it is essential to understand their critical differences before deciding.

Here are the key differences between double eccentric vs triple eccentric butterfly valve:

• Double offset butterfly valves have a higher degree of sealing than triple offset butterfly valves. This is because the double offset design provides better contact between the seat and the disc, which results in a better seal.
• Triple offset butterfly valves have a lower operating torque than double offset butterfly valves. This is because the triple offset design provides less contact between the seat and the disc, which results in a lower operating torque.
• Double offset butterfly valves are less likely to leak than triple offset butterfly valves. This is because the double offset design provides better contact between the seat and the disc, which results in a better seal.
• Triple offset butterfly valves are less likely to be damaged by water or other fluids than double offset butterfly valves. This is because the triple offset design provides less contact between the seat and the disc, which results in a more durable valve.
• Triple offset butterfly valves are more expensive than double offset butterfly valves. This is because the triple offset design is more complex and requires more precision manufacturing.
• Double offset butterfly valves have a two-piece body design, while triple offset butterfly valves have a three-piece body design.

How To Choose The Best Butterfly Valve?

When it comes to butterfly valves, there are a few factors that need to take into account to ensure when choosing the best possible options to the needs. Here are five factors to keep in mind when selecting a butterfly valve:

Pressure Rating

The pressure rating of a butterfly valve is an essential factor to consider, as it will determine the maximum pressure the valve can withstand. Make sure to choose a valve with a pressure rating that meets or exceeds the operating pressure of the system.

Temperature Rating

The temperature rating of a butterfly valve is also an essential factor to consider, as it will determine the maximum temperature the valve can withstand. Make sure to choose a valve with a temperature rating that meets or exceeds the operating temperature of the system.

Material 

When choosing a butterfly valve, it is essential first to consider the materials from which the valve is made. The material of the valve will dictate how well the valve performs and how long it lasts. Some materials are better suited for specific applications than others. For example, a butterfly valve made from stainless steel will be more corrosion-resistant than one made from plastic. It is also essential to consider the compatibility of the materials. Ensure that the materials of the valve are compatible with the fluids or gases flowing through it. If the materials are incompatible, the valve may not work as intended or be damaged.

Type Of Media

Understanding the fluid that flows through the application before purchasing valves is essential. How well the valve seals will be affected by the type of fluid. For gas media, butterfly valves must have a specified minimum leakage pace at a particular operational pressure and temperature. The liquid media valve must have a tight seal to control liquid leakage.

Solids valves should have a seal that fits flush into the pipe. This will prevent obstructions to the flow and keep materials from accumulating in the valve. Solids can also wear down valve seats faster than other materials. Dry materials may get stuck between the seat and the disc, and larger valves are better suited for solid media.

Pressure Drop

A pressure drop indicates a system&#;s energy loss and can cause problems downstream. The pressure drop can be caused by the butterfly valve itself or other system factors, such as the piping or fittings. The pressure drop is an essential factor to consider when selecting a butterfly valve, as it can impact the valve&#;s overall performance. A high-pressure drop can cause the valve to fail to close properly, while a low-pressure drop can cause the valve to leak. The pressure drop should be listed in the specifications for the valve, so be sure to check before making the purchase.

Speed Of Operation

When evaluating butterfly valves, one of the most important factors is the valve speed of operation. The speed of operation is a measure of how quickly the valve can open or close. It is essential to choose a valve with a speed of operation that is appropriate for the application. If the valve is too slow, it may not be able to keep up with the flow demand. If the valve is too fast, it may cause turbulence and chaos in the system. The superior speed of operation for a butterfly valve is typically between 0.5 and 2 seconds.

How To Choose Between Double Offset Vs Triple Offset Butterfly Valve

There are many factors to consider when choosing between a double offset and a triple offset butterfly valve. The most important factor is the application in which the valve will be used. If the application requires a higher degree of precision, then a triple offset butterfly valve may be the better choice. If the application is less demanding, then a double offset butterfly valve may suffice.

Double offset butterfly valves are more commonly used because they provide a better seal and are less likely to leak. They are also easier to maintain and repair. However, they are not as well suited for high-pressure applications.

Triple offset butterfly valves are less common, but they are better suited for high-pressure applications. They provide a tighter seal and are less likely to leak. However, they are more difficult to maintain and repair.

So, which type of butterfly valve is right for you? It all depends on your specific application.

Bottomline

In conclusion, double offset and triple offset butterfly valves are excellent choices for various applications. Double offset valves have a lower initial cost and are easier to maintain, while triple offset valves provide superior performance and are more durable. Ultimately, the best choice for a particular application depends on the project&#;s specific needs. Contact the best industrial valves manufacturers for purchasing the reliable butterfly valve for all industrial uses.

Butterfly valves control fluid flow in a pipe by using a disc attached to a central shaft. This disc controls the amount of fluid passing through the valve by creating a variable opening.

Butterfly valves can be classified according to the alignment of the disc with respect to the valve body:

• Zero offset,
• Double offset, and
• Triple offset.

Majority of butterfly valves with plastic linings are zero offset. Those that are made of metal and some with rubber lining are either double or triple offset butterfly valves. If you&#;re really interested and want to have a solid grasp of butterfly valve types, components and major parts, you can read our ultimate guide for high performance butterfly valves.

In this article, however, we will only discuss what a double offset butterfly valve. Let&#;s start with the differences between the aforementioned butterfly disc alignment types.

Differences Between Zero, Double, and Triple Offset Butterfly Valves

Zero Offset Butterfly Valve (Concentric)

Disk Alignment

The disc and stem of zero offset butterfly valves are situated at the center of the valve seat which is centered in the valve body. The disc rotates on the central axis which allows a 360° rotation. A sealing is done when the disc deforms the soft seat causing full friction during the whole operating cycle.

Common Applications

Zero offset butterfly valves are common in liquid and gas applications under 250 PSI and up to 400° Fahrenheit. These valves are able to handle food, coatings, chemicals, abrasive, and some solid applications.

A notable advantage of opting for zero offset valves is that the flowing media on the valve is not going to get into contact with the body because the valve seat is covering it.

Double Offset Butterfly Valve (Double Eccentric)

Disk Alignment

Double offset butterfly valve is popularly known as a high-performance butterfly valve and has two offsets from the valve body&#;s center:

Are you interested in learning more about 2-Offset Butterfly Valve? Contact us today to secure an expert consultation!

• The shaft axis is offset from the disc&#;s seat and body seal&#;s centerline, and
• The shaft axis is eccentric to the pipeline&#;s/valve&#;s center line.

The position of the disc in a double offset butterfly valve creates a cam action when the valve operates. The seat is lifted from the seal which results to the occurence of friction on the first 10° and final 10° of the opening and closing operations.

Common Applications

Double offset butterfly valves are best suited for pressures higher than zero offset butterfly valves can handle.

Triple Offset Butterfly Valve (Triple Eccentric)

Disk Alignment

A triple offset butterfly valve has three offsets two of which are the same as the double offset butterfly valve. The third offset is on the geometry of the valve&#;s seating surface instead of the shaft position.

The components of the sealing are machined into the valve to create a conical profile of the valve seat and disc. The disc only gets into contact with the seat in the first and last 1° of the opening and closing operations.

Common Applications

Triple offset butterfly valves are used in applications similar to double offset butterfly valves but are preferred in tighter and more demanding applications.

High-Performance Double Offset Valves

Double offset butterfly valves are widely known as high-performance butterfly valves. They are one of the most available eccentric-type butterfly valves in the market aside from triple-offset ones. Additionally, they are also called the elite type of butterfly valves.

Material Composition

Double offset butterfly valves can be found in higher pressures compared to zero offset ones. They are made from materials with ANSI Class ratings of up to 600 such as Hastelloy, stainless steel, carbon steel, and others. Their rigid Polytetrafluoroethylene (PTFE) seats (ANSI class butterfly valve), usually from Teflon, can be varied and they also come in Fire Safe designs with metal seats as back ups.

Major Components

Double offset butterfly valves have the following major components:

• Body,
• Seat,
• Seat retainer,
• Disc,
• Shaft,
• Shaft packing,
• Operator, and
• Bearings or bushings.

Body Types

High-performance butterfly valves are available in three basic body designs:

• Wafer,
• Lug, and
• Double flanged.

Wafer

Wafer body types has two or more holes for easier installation. They are cheaper and lighter but cannot be installed at the end of pipes or as end-of-line services.

Lug

Lug-style double offset butterfly valves have bolt holes where pipe flanges can be connected. Their threaded bolts on the whole area makes them a better option. This is because wafer valves users can switch to a lug valve design but not the other way around.

Unlike wafer types, lug types can be used at the end of pipes or as end-of-line services. However, because of some body materials that have lower strengths, the threads of the lug are weak. This results in bolt torque ratings that are lower compared to water.

Double Flanged

Double flanged types have a pair of flanges on the sides of the butterfly valve. This body design are common in large valve sizes. Some manufacturers use U-shaped valves which are more affordable but the flanges aren&#;t always parallel which causes problems when bolting on the flanges of the pipe.

Operation

High-performance double offset butterfly valves can be operated using gears, handles, or actuators. They move the disc of the valve to its optimal position to fully seal or open the valve during operation.

Moreover, operation by actuation can use either one of the three types of actuators:

#1 Electric actuator

Electrically-operated butterfly valve convert electrical energy into torque. An electrical motor that is mechanically connected rotates a screw and a threaded ball nut with threads matching those of the screw is kept from rotating with it. The nuts move along the threads once the screw is rotated. The direction of the nut movement depends on the direction the screw has rotated.

#2 Pneumatic actuator

Pneumatically-actuated butterfly valves are air-driven or air actuated. A pneumatic linear actuator has a hollow cylinder with a piston inside. A pneumatic pump or external compressor drives the piston. The cylinder will move along the piston&#;s axis to create a linear force as the pressure increases. The piston will return to its default position when a fluid or other force is applied to the opposite side of the piston.

#3 Hydraulic actuator

A hydraulic linear actuator operates similar to a pneumatic actuator but rather than a pressurized air, an incompressible fluid supplied by a pump drives the cylinder.

If you want to know more about the advantages and disadvantages of each actuator type, you can read this article.

How Double Offset Butterfly Valves Work

The movement of a double offset butterfly valve follows a conic profile in sealing the valve. The arrangement of the offsets of the disc and the shaft generates a cam action of the disc into the seat, reducing the required torque to close or open the valve.

This offset geometry also allows the 90° rotation of the disc to get into contact with the seat on the first 1° to 3° of rotation only. Moreover, the design of double offset butterfly valves minimizes wearing at the touch points of the seat and disc which happens in conventional butterfly valves.

For a more detailed explanation on how a double offset butterfly valve works, you can go to this video:

Applications

High-performance double offset butterfly valves are popular because they can be used in a wide range of applications. They can survive extreme pressures and temperatures and are suitable for handling gas, oil, steam, and water in a light weight and cost-effective design compared to triple offset butterfly valves.

The corrosion resistance and design strength of double offset butterfly valves allow them to be used either as buried valves or as parts of plants. Below are some of the most common applications and industries that use these kinds of butterfly valves.

• Caustic,
• Corrosive,
• Dry Chlorine,
• Oxygen,
• Seawater,
• Sour Gas,
• Steam,
• Toxic
• Ultra Pure Water,
• Vacuum, and

• Wastewater.

Industries

• Chemical,
• Food and Beverage,
• HVAC,
• Mining,
• Oil and Gas,
• Petrochemical,
• Pharmaceutical,
• Power Generation,
• Pulp and Paper,
• Refining,
• Sugar Processing, and
• Water Filtration.

Conclusion

Industrial valves have higher requirements regarding pressure and temperature ranges compared to traditional butterfly valves. This gave to the rise of high-performance butterfly valves that can handle high pressure and high temperature, one of which is a double offset butterfly valve.

Huamei, a high performance valve manufacturer in China, has just what you need. We offer double offset butterfly valves along with other industrial valves in various material body, disc, seat, and end-type connection designs. For more information, you can explore our website or reach out to us.

Want more information on Cast Steel Globe Valve-DIN? Feel free to contact us.