What's Different About Zero, Double and Triple Offset ...

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 valvedouble offset vs triple offset butterfly valve and help decide which is the right choice for the project.

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?

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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

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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.

Zero Offset

Also known as a concentric design, this is common in general service &#;resilient seated&#; or &#;rubber seated&#; butterfly valves. The stem and disc are centered in the seat of the valve, all of which are centered in the body of the valve. The disc is in constant contact with the seat. 

An advantage of this valve is the media going through the valve will not contact the body, since the seat is constructed as a sleeve or cartridge inside of the body.

Zero offset butterfly valves are used in basic and specialty liquid and gas applications up to 200 PSI and up to 400 deg F. The zero offset butterfly valve can handle chemicals, coatings, food, some solids, and abrasive applications.  

The zero offset butterfly valve is available in epoxy coated cast iron and stainless steel with multiple seat materials such as Buna, EPDM, VITON, Teflon, Natural rubber and others. 

Double Offset Butterfly Valve

This popular valve is also known as a high performance butterfly valve. This valve has two stems offset from the center.  This creates a cam action during the application's process.

• 1st offset: The axis of the shaft is behind the centerline of the sealing point of the disc to seat.
• 2nd offset: The axis of the shaft is eccentric to the center of the valve/pipe line.

The double offset butterfly valve is generally used in: 

• Power generation
• Pulp and paper
• HVAC
• Chemical
• Oil and gas
• Water and wastewater treatment
• Shipbuilding   

Double offset butterfly valves are available in higher pressures than the zero offset style.  The double offset is up to ANSI Class 600 rating in carbon steel, stainless steel, Hastelloy and other body material, with variations of Teflon seats and also Fire Safe design with metal back up seats.   

Triple Offset Butterfly Valve

With the triple offset butterfly valve there are three offsets.  Two are placed in a similar position to the double offset butterfly valve, while the third offset is the geometry of the seating surface, creating a type of cone shape of the disc and seat. This cone angle, along with the two eccentric shaft offsets, allows the disc to seal against the seat with no friction.

This seat design also allows for uniform sealing, and thus a tight shutoff in a metal seat design. This design is a lower cost, lower torque option (easier to automate), than alternative style metal seated valves.

Triple offsets are generally used in applications similar to gate valves, where a metal seat is required, and tight shutoff and/or quarter turn actuation is desired. Applications like high pressure steam (over 150 PSI), superheated- steam, high temperature gases and oils, high temperature applications are good for this type of valve because a metal seat is required over a soft seat. 

The triple offset valve is used in similar industries as the double offset butterfly valve, but in more demanding applications.  

If you have any further questions, don&#;t hesitate to contact us! Our valve team has over 20 years of experience and is happy to help! 

Double Offset Vs Triple Offset Butterfly Valve