Body: Carbon Steel or Stainless Steel
Disc: Stainless Steel
Wafer: 2″ to 12″
Lugged: 2″ to 12″
-4°F to 450°F
ANSI 150: 285 PSIG
ANSI 300: 740 PSIG
Dead End Service: (Lugged Connections Only)
Pneumatic (spring return)
Pneumatic (double acting)
A double offset butterfly valve is a type of quarter-turn valve that has a disc with two offsets mainly used to regulate or stop media flow through the pipes. A quarter-turn valve operates in a way that when it is turned 90 degrees, the valve is either fully open or fully closed. A metal disc, also known as the butterfly, is found within the valve body that positions perpendicularly to the flow when in a fully closed position. Also known as a double eccentric butterfly valve, double offset butterfly valve is well-suited for shut-off and throttling applications dealing with viscous, corrosive, and abrasive media.
SIO high-performance butterfly valves are equipped with an advanced seat design which can be made either from EPDM or RTFE, both of which are highly-tolerant to low and high temperatures.
SIO double offset butterfly valves also feature a quick-release design that reduces the amount of torque needed to unseat the disc. They are equipped with a high strength 17-4ph stainless steel stem and graphite-reinforced or impregnated 316 stainless steel bearings that provide maximum strength for high-torque applications.
The valve body is made from stainless steel or carbon steel, both of which can withstand demanding applications, including high pressures and temperatures and hazardous media. All of these features contribute to ensuring that our double offset butterfly valves will have a long service life.
Source: Crane Engineering
Double offset butterfly valve and triple offset butterfly valve are both high-performance butterfly valves that are used for shut-off and throttling applications. They are built to handle almost any industrial application including high pressure and temperature, low pressure and temperature, and corrosive, abrasive, and hazardous media. The main difference between the two high-performance butterfly valves is in their structure.
A double offset butterfly valve, which is widely used in different industrial applications, is an improved version of the single offset butterfly valve. It is equipped with an adjustable stem packing that greatly reduces the risk of stem leakage and fugitive emissions.
The stem is found in the center which is veered from both the centers of the valve and disc. With this structure, the disc can leave the seat quickly, significantly reducing the extra scraping and squeezing between these two components and increasing the service life of the butterfly valve.
Although it’s not clear in the diagram, the disc is not completely on the center of the valve seat. This makes the valve operate better in high pressure applications as overpressure caused by compression between the top and bottom of the seat and disc is alleviated.
A triple offset butterfly valve consists of three different offsets, with the two offsets placed in the center while the third one is on the seating surface that creates a cone shape of the seat and the disc. This cone angle, together with the two eccentric offsets, allows the disc to seal the seat without friction. This promotes positive sealing with a metal-to-metal interface and allows the valve to function better in more complex applications, such as higher pressures and temperatures and dirty fluids.
SIO offers two types of seat materials for double offset butterfly valves:
EPDM is an excellent seat material when handling chemicals and other corrosive media. It is a type of terpolymer elastomer made from ethylene-propylene diene monomer (EPDM). It has excellent tear and abrasion resistance and provides good chemical resistance to various alkalis and acids. It also performs well with alcohols and ketones.
RTFE is suitable for applications that deal with severe conditions, such as extremely high pressures and temperatures. Known as Reinforced TFE (Teflon), RTFE is a combination of TFE and a percentage of fiberglass to enhance strength and tolerance to cold flow, abrasive wear, and permeation in molded seats. It can handle higher pressures and temperatures compared to TFE.
SIO offers two types of end connections for double offset butterfly valves:
The wafer body is a one-piece body design that ensures a positive seal against bi-directional pressure to prevent backflow. It is equipped with an O-ring, gasket, precision-machined, and a flat face on the upstream and downstream portions of the butterfly valve.
The lug type features a design similar to a three-piece ball valve wherein one end can be removed without affecting the other end. This is useful when performing repair or maintenance on the valve as it eliminates the need of shutting down the entire system to perform the task. A lug type butterfly valve has protruding lugs surrounding the butterfly valve that will attach to flanges on the pipes to provide a positive seal.
As a professional industrial valve manufacturer, SIO’s double offset butterfly valve may be actuated in two ways:
A valve with an electric actuator is a cost-effective and safe solution when valve automation is needed as it allows operators to control the valve remotely. It uses electricity to produce mechanical energy to actuate butterfly valves and other industrial valves that need automation.
Pneumatic actuation also provides a safe working environment as it uses compressed air, which is non-toxic and non-flammable, to produce mechanical energy. Since it uses air to actuate the valves, it is sustainable and readily available. Pneumatic actuation can be achieved in two mechanisms:
Spring-return mechanism only supplies air to one section of the piston, and the energy that moves the mechanism is from the spring on the other section.
Double-acting mechanism supplies air to both sections of the piston, with one end having more pressure that permits movement required to actuate the butterfly valve.
The main function of a butterfly valve is similar to a ball valve, it allows for a quick and tight shut-off. A double offset butterfly valve is a type of quarter-turn valve that performs a 90-degree rotation to open or close media passage. It features a flat and circular disc, more known as the butterfly, situated at the center that functions as the closing device of the valve.
In a double offset configuration, the butterfly valve uses an eccentric disc or offset from the valve seat. As the disc begins to rotate, it veers away from the valve seat instead of across it and uses the line pressure to help achieve its seal. This means that in a typical butterfly valve, the disc rotates horizontally, while a double offset rotates vertically.
When the valve disc is turned a full 90 degrees, the double offset butterfly valve opens and provides unobstructed flow or closes and shuts media passage. When the valve disc does not rotate a full 90 degrees, the valve will remain slightly open or closed and will allow small amounts of media to go through.
Power generation plants use many valves to manage flows of steam and water, such as in chemical treatment, cooling water, and relieving a pipe system from pressure. These applications deal with different pressures and temperatures as well as corrosive and abrasive media.
SIO double offset butterfly valves are made with either stainless steel or carbon steel to withstand such demanding conditions. These materials have high tolerance properties to abrasion, corrosion, and extreme temperatures and pressures that ensure a long service life for butterfly valves.
Hydrocarbon processing involves a lot of demanding applications, such as petroleum refining, liquefied natural gas (LNG) operations, and gas refining, that are usually associated with high-pressures and high fugitive emissions.
SIO’s double offset butterfly valve is supplied with an adjustable stem packing that ensures a tight seal and greatly reduces emissions. The valve’s stem is made from stainless steel, which is durable enough to handle high pressures.
Chemical and petrochemical industries cover a range of applications that usually handle hazardous, corrosive, and abrasive process media, such as ethylene, propylene, and petroleum. These applications require valves that guarantee positive sealing and durable enough to withstand such severe conditions.
A double offset butterfly valve has valve seats made from EPDM, a strong material that can withstand different types of chemicals, solvents, oils, and fatty acids. The valve body is made from stainless steel, also durable to withstand severe conditions, such as severely high pressures and temperatures, low pressures, cryogenic conditions, and toxic media. These materials allow the valve to function effectively even with excessive use.
Water and wastewater treatment applications deal with various fluid flows, such as water, slurries, wastes, and other dirty flows. Wastewater treatment is an essential option for water supply which is why it’s a must that the right valves are used to maintain the integrity of the operation.
Double offset butterfly valves are well-suited for handling applications with pressures up to 285 PSI for pressure rating #150 and 740 PSI for pressure rating #300 and temperatures between -4°F to 450°F. These make them ideal for the different conditions in water and wastewater treatment applications. Double offset butterfly valves can ensure reliable and safe operations for the entire system.
Components involved in pulp and paper industries, such as liquid chlorine, hydrogen peroxide, chlorine dioxide, and other industrial chemicals, are considered dangerous, corrosive, abrasive, and involve high pressures. The design and make of SIO’s double eccentric butterfly valve are suitable for such conditions.
The bi-directional interference feature of double offset butterfly valves ensures a tight seal and prevents the risk of leaks to maintain safe and smooth operations. The valve body, either made from stainless steel or carbon steel, is capable of handling different properties of media, both critical and non-critical. The valve seat can be made from RTFE, a strong material that is non-reactive to various chemicals, which is ideal for pulp and paper industries.
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