Trusted Duplex Valves Manufacturer
NTVAL offers precision-crafted Duplex Valves for high-performance applications, ensuring exceptional durability and reliability. Designed to meet the demanding needs of large-scale projects, our valves deliver quality and performance that set industry standards.
Reliable Duplex Valves
A duplex valve is made from duplex steel, a type of stainless steel that has a unique combination of two metallurgical phases: austenite and ferrite, present in nearly equal proportions. This dual-phase structure gives duplex steel better corrosion resistance and greater strength compared to standard stainless steel, making duplex valves much stronger than typical steel valves.
Due to its high melting point, duplex steel offers excellent thermal resistance, making duplex valves ideal for high-temperature applications such as boilers and power plants. These valves are also recommended for high-pressure environments because of their enhanced strength.
Quality Control
The pmi test checks the duplex valve’s chemical composition, making sure the material matches the required specifications for the application.
PMI Test
The sealing test assesses the valve’s ability to prevent leaks, confirming a tight seal that keeps fluids or gases contained during use.
Sealing Test
A low emission test evaluates how well the valve minimizes the release of harmful gases, supporting safety in sensitive environments.
Low Emission Test
The impact test checks the valve’s ability to withstand sudden force, ensuring it remains intact and functional under high-stress conditions.
Impact Test
Dimension inspection confirms the valve is manufactured to precise size specifications, allowing it to fit and operate properly within systems.
Dimension Inspection
The painting thickness test measures the coating applied to the valve, verifying it’s thick enough to protect against corrosion.
Painting Thickness Test
Penetrant testing (pt) reveals any small cracks or surface defects that could compromise the valve’s performance or durability.
PT
Material inspection involves thoroughly examining the raw duplex material, confirming it meets quality and strength standards before valve production.
Material Inspection
Our Valve Applications in Key Industries
Discover how our advanced valve solutions improve flow control, delivering enhanced efficiency, safety, and strict quality assurance.
Duplex valves resist corrosion from aggressive chemicals, making them ideal for safely managing fluids in chemical processing facilities.
Chemical Processing
In the petrochemical field, these valves perform under extreme pressure and temperature, supporting safe and efficient handling of complex materials.
Petrol Chemical
Duplex valves withstand radiation and high heat, offering reliability and safety in nuclear power and other energy-generating industries.
O.P.G & Nuclear
These valves handle abrasive materials and high pressures in pulp production, providing a strong solution for demanding environments.
Pulp
Duplex valves resist corrosion and damage from abrasive slurries, making them essential for consistent and reliable operations in mining.
Mining
Corrosion-resistant duplex valves are well-suited for water and sewage management, effectively controlling flow even in challenging conditions.
Water & Sewage
Duplex valves are highly heat-resistant, making them ideal for managing steam flow in industrial systems that require dependable performance.
Steam System
In boiling systems, duplex valves safely control pressurized fluids at high temperatures, providing reliable operation in critical applications.
Boiling System
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How Duplex Valves Operate
Duplex valves control, throttle, and stop fluid flow using a disc or ball component. They can operate either manually or automatically:
- Manual Operation: Uses a handle or handwheel.
- Automatic Operation: Uses a pneumatic or electric actuator for remote or automated control.
Duplex valves are widely chosen for demanding industrial applications where durability, high-pressure tolerance, and corrosion resistance are critical.
Types of Duplex Valves
Duplex Globe Valves
Duplex globe valves are ideal for throttling applications due to their precise control of fluid flow. These valves have a spherically shaped body with a disc inside that helps regulate and stop the flow of fluids. The valve body consists of two halves separated by an internal baffle, which directs the flow through the valve.
However, this internal baffle design makes cleaning and repair more difficult and results in higher pressure loss compared to other valve types. Despite this drawback, duplex globe valves are favored for their control capabilities in critical applications.
Duplex globe valves come in several types, including:
- Z-Pattern Type: Features a Z-shaped flow path, commonly used in standard globe valves for efficient throttling.
- Oblique Pattern: Designed with a flow path at an angle, reducing pressure loss and improving flow efficiency.
- Angle Pattern: Redirects the flow 90 degrees, offering better flow control in applications requiring a directional change.
Each type of duplex globe valve is chosen based on specific system requirements for flow control and pressure management.
How Does a Duplex Globe Valve Work?
A duplex globe valve controls the flow of fluids using a handwheel or an actuator (electric or pneumatic) to move the valve stem and disc. The operating principle is the same regardless of the method used to operate the valve.
Advantages of Duplex Globe Valves
- Great for Stopping and Controlling Flow: Duplex globe valves are excellent at both shutting off fluid flow and controlling it, making them versatile in many situations.
- Quick to Operate: These valves respond faster, which is helpful when you need to control the flow quickly.
- Tight Seals: They provide a strong, leak-proof seal when closed, ensuring no fluid gets through.
Disadvantages of Duplex Globe Valves
- Heavier Design: These valves tend to be heavier than other types, which can make them harder to handle or install.
- Higher Flow Resistance: The design creates more resistance to the flow of fluid, which can reduce efficiency in some systems.
Figure: Working of a Duplex Globe Valve
Duplex Gate Valve
A duplex gate valve is used to stop fluid flow by raising or lowering a wedge or rectangular gate. The gate is moved up or down by a stem or shaft, which is controlled by a handwheel or an actuator. This valve is commonly used as an isolation valve in industrial systems because of its simple design, making it easier to repair.
There are different types of duplex gate valves, including:
- Duplex Knife Gate
- Wedge Gate
- Parallel Slide Gate
- Rising Stem Gate Valve
- Non-Rising Stem Gate Valve
Each type has its specific uses, as well as its own benefits and drawbacks.
How Does a Duplex Gate Valve Work?
A duplex gate valve controls the flow of fluids by moving a gate up or down. Here’s how it works:
- Opening the Valve: When the operator turns the handwheel counterclockwise, the valve stem rotates and lifts the gate. As the gate moves up, it opens the flow path, allowing fluid to pass through.
- Closing the Valve: Turning the handwheel clockwise lowers the gate. The gate presses down tightly against the valve seats, creating a seal that stops the flow of fluid completely.
Advantages of Duplex Gate Valves
- Simple Design: Easy to understand and operate, making them user-friendly.
- Easy to Repair: Fewer moving parts mean less complexity, making repairs straightforward.
- Low Pressure Drop: When fully open, these valves allow fluid to pass through with minimal pressure loss.
- Bi-Directional Flow: Capable of handling fluid flow in both directions.
Disadvantages of Duplex Gate Valves
- Not Ideal for Throttling: These valves are not designed for controlling or regulating flow.
- Prone to Noise and Vibration: They can generate more noise and vibration compared to other valve types.
Figure: Working of a Duplex Gate Valve
Duplex Butterfly Valve
A duplex butterfly valve is a special type of valve that opens and closes fluid flow with just a quarter turn of the handwheel, making it one of the easiest valves to operate. It uses a disc positioned at the center of the flow path to control the fluid. This simple design makes the valve easy to repair and lightweight since it uses less material and has a thin construction.
There are different types of duplex butterfly valves, including:
- Rotary
- Lug-Style
- Concentric
- Wafer
- Eccentric
How Does a Duplex Butterfly Valve Work?
A duplex butterfly valve operates by rotating the handle or handwheel. Here’s how it works:
- Opening the Valve: When the operator turns the handle or handwheel counterclockwise by 90 degrees, the valve disc rotates, allowing the fluid to flow through the open passage. The disc is connected to the handwheel by a stem or shaft, which transmits the rotary motion from the handle to the disc.
- Closing the Valve: Turning the handle clockwise for another quarter turn rotates the disc back into place, creating a tight seal with the valve seat, and stopping fluid flow.
- Regulating Flow: To regulate the flow rate, the operator turns the handle slightly less than 90 degrees. This partially opens the valve, allowing some fluid to pass through. Duplex valve manufacturers recommend using this valve for throttling in low-pressure applications.
Advantages of Duplex Butterfly Valves
- Compact and Lightweight: Small size and lighter weight make them easy to handle.
- Handles Sludge and Slurries: Suitable for fluids with sludge and slurries.
- Easy to Operate: Simple to use with minimal effort.
- Simple to Install, Clean, and Repair: The straightforward design allows for quick installation and easy maintenance.
Disadvantages of Duplex Butterfly Valves
- Flow Resistance: The disc remains in the flow path, increasing flow resistance and causing pressure loss.
- Sealing Challenges in High Pressure: Achieving a tight seal in high-pressure applications is difficult.
Duplex Plug Valve
A duplex plug valve uses a conical or cylindrically tapered plug that rotates inside the valve to regulate fluid flow. The plug has one or more holes through its center, and when the valve is open, fluid flows through these holes. This type of valve is simple and highly reliable, especially in high-pressure applications. It can be operated using a handwheel, pneumatic, or electric actuator.
Duplex valve manufacturers produce various types under this category, including expanding valves, non-lubricated valves, lubricated valves, and multi-port valves.
How Does a Duplex Plug Valve Work?
The duplex plug valve operates by rotating the handwheel a quarter turn. The plug, which is connected to the handwheel through the valve stem, rotates 90 degrees when the handwheel is turned counterclockwise. This aligns the holes in the plug with the pipe, allowing fluid to flow through.
To close the valve, the handwheel is turned clockwise for another quarter turn, which rotates the plug back, aligning the plug perpendicular to the flow direction and creating a tight seal with the valve seat to stop fluid flow.
Advantages of Duplex Plug Valves
- Leakage-Proof: The valve design ensures a tight seal, preventing leaks.
- High Strength: Suitable for high-pressure applications due to its robust design.
- Quarter Turn Operation: Easy to open and close with just a quarter turn of the handwheel.
- On-Site Repair: The valve can be repaired and cleaned without removing it from the piping system.
Disadvantages of Duplex Plug Valves
- High Friction: Rotating the plug involves significant friction, making operation harder.
- Flow Resistance: The conical and tapered plug shapes increase flow resistance and cause a pressure drop.
Duplex Check Valve
A duplex check valve is an automatic valve designed to prevent fluid from flowing in the reverse direction. Unlike other valves, it does not require a handwheel or actuator for operation. Instead, it uses a disc or ball component to control the flow.
This type of valve is ideal in systems where reverse flow could cause contamination, such as in water supply lines, boiler systems, food and beverage processing, and pharmaceuticals. Duplex valve manufacturers offer various types of check valves, including swing check valves, spring-loaded valves, ball check valves, and lift-foot valves.
How Does a Duplex Check Valve Work?
Duplex check valves operate automatically, relying on pressure differences between the upstream and downstream sides of the valve. When the pressure on the upstream side is greater than the downstream pressure (such as when a pump is running), the fluid pushes against the valve disc, forcing it open and allowing flow.
Once the pump stops or the upstream pressure drops below the downstream pressure, the fluid tries to reverse flow. In response, the valve disc immediately closes, preventing any reverse flow.
Advantages of Duplex Check Valves
- Cost-Effective: Less expensive than other valves like gate and globe valves.
- No Need for Handwheel or Actuator: Operates automatically without manual intervention.
- Highly Reliable: Provides dependable prevention of reverse flow.
- Prevents Reverse Flow: Ensures fluid flows in only one direction.
- Low Flow Resistance: Offers minimal resistance to fluid flow when open.
Disadvantages of Duplex Check Valves
- Unidirectional: Only allows flow in one direction, making it unsuitable for systems that require bidirectional flow.
- Not Ideal for Pulsating Flow: May not perform well in systems with fluctuating or pulsating flow rates.
Learn More About Duplex Valves
Duplex valves are widely used in various industrial applications due to their numerous advantages over other types of valves. Common applications include:
- Oil and Gas Industry
- Paper and Pulp Manufacturing
- Chemical and Petrochemical Applications
- Food and Beverage Industry
- Pharmaceutical Industry
- Sewage and Wastewater Treatment
- Municipal and Domestic Water Transportation
- Mining Applications
- Steam Power Plants
- Firefighting Applications
- Marine Applications
Advantages & Disadvantages of Duplex Valves
Advantages
- Versatile in Size: Suitable for both small and large flow rates.
- Wide Application Use: Effective in almost all industrial sectors.
- Excellent Corrosion Resistance: Handles corrosive environments well.
- High Strength: Ideal for high-pressure and high-temperature applications.
- Abrasion Resistance: Withstands abrasive wear, enhancing longevity.
- Durability: Built to last, even in challenging conditions.
Disadvantages
- High Cost: The duplex material is expensive, which increases the valve’s price.
- Heavy: These valves are heavier than other types, making them harder to handle.
Troubleshooting Duplex Valves
The Handwheel/Handle is Hard to Operate
- Damage on the Valve Stem: Inspect and repair or replace the stem if necessary.
- Dirt on the Valve Stem: Clean the stem to remove any dirt or debris.
The Valve Does Not Close Completely
- Dirt on the Valve Seats: Clean the valve seats thoroughly.
- Worn-Out Seats: Replace the valve seats if they are no longer effective.
- Worn-Out Disc: Replace the valve disc to restore proper sealing.
Fluid Leakage Inside the Valve
- Damaged or Worn-Out Seats: Replace the seats to prevent internal leaks.
- Damaged or Worn-Out Disc: Replace the disc if it no longer seals properly.
Leakage Between the Valve and the Pipe
- Worn-Out Gasket: Replace the gasket to restore the seal between the valve and pipe.
- High Flow Pressure: If pressure exceeds the valve’s rating, replace the valve with one suited for the system’s pressure. Ensure the valve is used according to the manufacturer’s recommended flow rate and pressure.
The Valve Vibrates a Lot
- High Flow Rate: Ensure the valve is used at the recommended flow rate and pressure.
- The Valve is Not Fully Open: Fully open the valve to reduce vibrations.
All About Duplex Stainless Steels
Duplex Stainless Steels
Duplex stainless steels are strong, corrosion-resistant alloys made from a mix of austenite and ferrite. They are tougher and stronger than austenitic stainless steels, with better resistance to corrosion, especially compared to common grades like 304 and 316. Unlike austenitic grades, duplex steels are magnetic. The most popular type, 2205, contains 22% Chromium and 5% Nickel. Other custom duplex grades are made for specific uses.
Corrosion Resistance of Duplex Stainless Steel
Duplex stainless steels offer excellent corrosion resistance, particularly against intergranular corrosion. They are highly resistant to stress corrosion cracking, even in chloride and sulfide environments. Super duplex grades provide even better corrosion resistance.
Heat Resistance of Duplex Stainless Steel
The high chromium content gives duplex stainless steels their corrosion resistance but leads to embrittlement above 300°C. At low temperatures, duplex stainless steels are more ductile than ferritic and martensitic grades and can be used down to at least -50°C.
Fabrication of Duplex Stainless Steel
Stainless steel should be fabricated using dedicated tools and clean work surfaces to avoid contamination from other metals, which can cause surface discoloration and corrosion.
Heat Treatment of Duplex Stainless Steel
Duplex stainless steels cannot be hardened by heat treatment but can be work-hardened. Solution treatment or annealing involves rapid cooling after heating to around 1100°C.
Machinability
Machining duplex stainless steels is challenging due to their high strength, with machining speeds for 2205 being about 20% slower than for 304. Special machining guidelines should be followed to improve efficiency.
Welding of Duplex Stainless Steel
Duplex stainless steels are weldable using standard welding processes, though not as easily as austenitic grades. Their low thermal expansion reduces distortion and stress after welding. The recommended filler material
for 2205 is 2209.
Duplex Products
- General Service Alloys: Duplex ferritic/austenitic alloys are designed for use in corrosive environments, offering strong resistance to stress corrosion cracking. They bridge the gap between austenitic stainless steels and nickel alloys.
- Common Grades: The most widely used duplex grades are UNS S31803 and S32205. These are commonly found in the Chemical Process Industry, especially in environments involving sulfuric, nitric, and phosphoric acids.
- Industrial Applications: In addition to chemical processing, duplex materials are widely used in industries like oil and gas production.
- Grade Chemistry: S31803 and S32205 have very similar chemistries, with the same maximum amounts of chrome, nickel, molybdenum, and nitrogen. However, S32205 has higher minimum levels of chrome, molybdenum, and nitrogen, with chromium contents ranging from 21% to 23%.
- Super Duplex Grades: Super duplex grades have even higher chromium contents, typically ranging from 24% to 27%.
- Nickel Content: Duplex 2507 and Xeron 100 have nickel contents that are about 1.5% higher than S31803 and S32205.
- Duplex S31200: This grade has chromium and nickel contents similar to super duplex grades, but its molybdenum content is significantly lower than other common duplex alloys.
Applications of Duplex Stainless Steel
- Chemical Processing, Transport, and Storage
- Oil and Gas Exploration and Offshore Rigs, including refining
- Marine Environments
- Pulp & Paper Manufacturing
- Chemical Process Plants
Corresponding Standards
• EN/DIN 1.4462 X2CrNiMoN22.5.3
• AFNOR Z2CND22.05Az
• AISI A182 F51
• UNS ASTM A276 S31803 / S32205
• BRANDS SAF 2205 – SANMAC
• URANUS 45N
• EN (10283) 1.4470
Duplex stainless steel is a popular choice for corrosion-resistant applications, offering a balance of strength and corrosion resistance. Its machining rate is comparable to 316 stainless steel when using high-speed steel tooling, requiring less labor than high-nickel alloys. While there are many materials for corrosion resistance, duplex alloys perform well in various corrosive environments.
In comparison to the 300 series stainless steels, duplex outperforms in most categories. However, cost becomes a factor when dealing with chlorides and halides. Duplex alloys are nearly as strong as C276 and AL6XN alloys, with only a slight difference in pitting and crevice corrosion resistance. For example, the corrosion rate of duplex is 23 mil/year, compared to 17 mil/year for AL6XN.
The key elements in duplex alloys, such as chromium, nickel, molybdenum, and nitrogen, are more common than the rarer elements found in high-nickel alloys like tungsten (C276), columbium and tantalum (Carpenter 20Cb), or columbium, tantalum, cobalt, and titanium (625 alloy). These elements give duplex its notable strength and resistance to corrosion, making it a cost-effective choice for many industrial applications.
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Specs of Duplex Valves
Material Composition
The Duplex Valves are made from duplex stainless steel, a blend of austenitic and ferritic stainless steel. This material offers superior corrosion resistance and strength, suitable for harsh industrial environments. Its structure allows the valves to handle high stress and chemical exposure, providing durability and reliable operation.
Pressure Ratings
These valves have pressure ratings up to 6000 PSI, depending on the size and model. You won’t believe that they are designed to manage substantial pressure in various applications, such as oil and gas, petrochemical, and chemical processing. At NTVAL, each of our Duplex Valves capability guarantees they can handle the demands of large-scale industrial systems.
Temperature Tolerance
Duplex Valves can operate within a temperature range of -50°C to 300°C. This wide temperature tolerance makes them suitable for extreme conditions, including cryogenic and high-temperature applications. The ability to perform under such varied temperatures ensures their reliability in diverse industrial processes.
Features of Duplex Valves
Compact Grain Structure
The compact grain structure of Duplex valves contributes to their overall durability. This tight grain formation reduces the likelihood of crack propagation and wear, allowing the valves to maintain their integrity even under high-stress conditions or in abrasive environments.
Dual Phase Microstructure
Duplex Valves have a dual-phase microstructure, combining both austenitic and ferritic stainless steels. This structure provides a balance of properties, such as improved strength and resistance to stress corrosion cracking, making these valves suitable for various demanding applications.
Low Magnetic
Duplex Valves have low magnetic conductivity, which means they are less likely to be affected by magnetic fields. This feature is important in applications where magnetic interference could cause problems, such as in certain electronic or medical environments.
Benefits of Duplex Valves
Improved Versatility
These valves offer improved versatility, allowing them to be used in a wide range of applications. Whether managing fluids in chemical plants, controlling processes in oil refineries, or handling water treatment systems, their adaptability makes them a valuable component in many industrial settings.
Increased Strength
With increased strength compared to other valves, Duplex Valves can handle higher pressures and more demanding applications without deforming or failing. I discovered that this higher strength makes them suitable for a wide range of industrial uses.
Reduced Maintenance
Requiring less maintenance due to their durable construction and resistance to wear and metal corrosion, Duplex Valves help lower operational costs and minimize downtime. This reduced need for frequent upkeep makes them a practical and economical choice for various industrial applications. If you are looking for the best Duplex Valves that will truly give this benefit, choose NTVAL.
Applications of Duplex Valves
Metallurgy Industry
In the metallurgy industry, Duplex Valves are essential for controlling the flow of molten metals and corrosive substances. They are used in processes such as smelting, refining, and alloy production. The valves’ durability and resistance to extreme temperatures and corrosion make them ideal for maintaining the efficiency and safety of metallurgical operations.
Power Generation
In power generation plants, Duplex Valves from NTVAL are essential for managing the flow of steam, water, and other fluids. Their ability to withstand high temperatures and pressures makes them suitable for use in both fossil fuel and nuclear power plants. They help maintain the efficient and safe operation of turbines and boilers.
Chemical Processing
In chemical processing, Duplex Valves are used to control the flow of aggressive chemicals. Their resistance to corrosion and high strength make them ideal for this industry. These valves help maintain safe and efficient operations in environments where chemicals are frequently handled.
Petrochemical Industry
In the petrochemical industry, Duplex Valves play a crucial role in handling oil, gas, and other volatile chemicals. These valves are designed to manage high-pressure conditions and prevent leaks, making them highly suitable for refining and chemical production. Their strength and corrosion resistance help ensure the safety and reliability of complex processing systems.
Considerations When Buying Duplex Valves
01
Threaded End Connections
When buying duplex valves, confirm they have threaded end connections if your system requires easy installation and maintenance. For example, if your pipeline needs quick disconnections for repairs, threaded connections are ideal because they allow you to remove and reattach the valve without welding or special tools, making maintenance simpler.
02
1/2 inch - 24 inches in Diameter
Look for Duplex Valves in sizes from 1/2 inch to 24 inches in diameter. Let me explain. For example, if your piping system has pipes of different sizes, choosing valves that match these sizes guarantees they fit properly and control the flow of fluids efficiently, preventing any disruptions in your system.
03
API6D Certified
Make sure the Duplex Valves are API6D certified. This certification guarantees that the valves have been tested for quality and safety, making them reliable for critical operations in industries like oil and gas. At NTVAL, all our Duplex Valves are API6D certified, providing assurance of their reliability and performance.
FAQ's
Yes, our Duplex Valves can handle high pressure. This capability is primarily due to their durable design and the materials used in their construction.
We implements a comprehensive quality control system that encompasses various stages of production, testing, and inspection. This rigorous process provides the reliability, durability, and performance of our Duplex Valves, maintaining the highest standards to meet the demanding requirements of our customers.
You can maintain Duplex Valves by regularly inspecting them for signs of wear or corrosion, cleaning any debris, and ensuring all parts are properly lubricated. Also, check and tighten any loose bolts and replace seals as needed to prevent leaks.
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