Knife gate valves are special types of industrial valves developed to safely control fluids containing solid particles, sediment, sludge, or fibers. In standard valve solutions (such as butterfly valves, ball valves, or globe valves), these types of fluids can accumulate inside the valve, making flow control difficult and damaging sealing surfaces. Knife gate valves are designed to eliminate this problem.
In this type of valve, the fluid line is controlled by cutting with a knife or gate. The knife moves up and down perpendicular to the flow direction. When the valve is open, the fluid passes freely; when closed, the knife sits between sealing elements within the body, completely stopping the flow. This ensures the system operates safely in fully open or fully closed positions.
Knife gate valves are generally not suitable for use in intermediate positions. Because in fluids containing particles, if the knife is stopped without being fully closed, turbulence occurs in the flow direction, and particles can damage the valve's working surfaces. Therefore, knife gate valves are preferred in applications that operate on an "open-close" principle.
Ideal Solution for Challenging Fluids
The biggest advantage of knife gate valves is their ability to work without problems in fluids that are not pure and contain solid materials. For example;
• In wastewater lines, they can cut off flow despite sludge and sediments.
• In the paper industry, they work without clogging in controlling pulp fluids with high fiber content.
• In mining and chemical industries, they provide reliable closure in fluids with abrasive particles.
Thanks to these features, knife gate valves are indispensable flow control equipment for many industrial facilities.
Detailed Examination of the Working Mechanism
The working principle of knife gate valves can be summarized in three basic steps:
1. Opening: The knife is moved upward, bringing the valve to a fully open position, allowing the fluid to flow along the line without encountering any obstacles. In this state, the valve keeps pressure loss to a minimum.
2. Closing: The knife moves downward, cutting the fluid path perpendicularly and sitting in a fully closed position. Meanwhile, the sharp edges on the knife pass through the solid particles in the fluid, preventing accumulation on the line.
3. Sealing: Elastomer (EPDM, NBR, NR) or metal seat elements in the valve body ensure that the knife forms a leak-proof surface in the fully closed position. Thus, the fluid does not leak out, and the system remains safe.
Why "Knife" Valve?
These valves are called "knife" valves because the closing element is a thin, flat, and sharp-edged gate. Fibers, particles, or sediments in the fluid are easily overcome by the knife's cutting structure. For example, in butterfly valves, the disk can get stuck among such fluids, making closure difficult; however, knife gate valves do not experience this problem.
Importance in Industry
The reason knife gate valves are preferred is not only their ability to manage challenging fluids. Additionally;
• Their simple designs provide ease of installation and maintenance.
• Their low weight offers an advantage, especially in large diameter pipelines.
• With different control options (manual, pneumatic, electric actuated), they adapt to all kinds of operational needs.
In short, knife gate valves come into play where traditional valve solutions struggle and continue to operate the system safely, durably, and economically.
Structural Features of Knife Gate Valves
The reasons for preferring knife gate valves are not only their resistance to fluid variety but also their specially designed structural features. These valves are equipped with strong materials and a simple yet effective mechanism to work long-lastingly under challenging conditions.
1. Body Design
The body of knife gate valves is generally a single-piece structure. This design provides advantages in terms of both ease of installation and mechanical strength. The single-piece body maintains sealing without deformation even under high pressure. Additionally, the internal structure of the body is designed to allow the fluid to flow continuously and with minimal pressure loss.
Bodies can be made from different materials:
• GGG40 ductile iron → High mechanical strength and long life.
• Stainless steel (AISI 304/316) → Corrosion resistance and applications requiring hygiene.
• Special alloys → For abrasive or corrosive fluids.
2. Knife (Gate)
The most critical part that gives the valve its name is the knife. This gate, made of stainless steel (AISI 304 or AISI 316), moves perpendicular to the flow, opening or closing the line.
• Its thin structure easily cuts fibers and solid particles in the fluid.
• It shows high durability in abrasive environments.
• It is long-lasting due to its resistance to corrosion.
In some special applications, the surface of the knife can be strengthened with additional coatings to provide extra protection against chemical resistance or friction.
3. Sealing Elements
The most important factor behind the reliable operation of knife gate valves is the sealing rings. These rings ensure that the fluid completely stops when the knife closes. The material used is selected according to the properties of the fluid:
• EPDM: For hot water and steam applications.
• NBR: In oily or hydrocarbon-based fluids.
• NR (Natural Rubber): In fluids containing abrasive particles.
• Metal seat: For high temperature, high pressure, or aggressive chemicals.
This variety allows knife gate valves to be used safely in different sectors.
4. Operating Mechanism
Knife gate valves can be equipped with different control types:
• Manual (with handwheel): Simple use, low cost.
• Gearbox: Easier use in large diameter valves.
• Chain wheel: Practical solution for valves mounted in high positions.
• Pneumatic actuated: For industrial applications requiring fast opening-closing.
• Electric actuated: For integrated use with automation systems.
Thanks to this variety, knife gate valves can be easily used in both small-scale installations and large industrial facilities.
5. Compact and Lightweight Design
Knife gate valves generally have a compact body structure. This allows them to be easily mounted in tight spaces. They are also lighter than other types of valves, which provides an advantage during both installation and maintenance.
6. Fully Open – Fully Closed Operation
The most distinctive feature of these valves is that they operate only in fully open or fully closed positions, not in intermediate positions. This way, the knife is not affected by particles in the fluid, and the system continues to be operated safely.
Material Options and Durability
The widespread use of knife gate valves in the industry is not only due to their working principles but also their material variety and durability features. Because each sector and each type of fluid has different chemical, mechanical, and thermal requirements. Correct material selection extends the life of knife gate valves while also increasing their reliability.
1. Body Materials
The bodies of knife gate valves are manufactured from different materials according to the needs of the application:
• GGG40 Ductile Iron:
Provides high mechanical strength and is preferred especially in water, wastewater, and general industrial fluids. It offers an economic solution and can be used safely in medium-level corrosion risks.
• Stainless Steel (AISI 304 / AISI 316):
Stands out with its resistance to corrosion. It is used especially in the food, chemical, pharmaceutical, and maritime sectors. AISI 316 offers extra resistance to saltwater and acidic environments thanks to its molybdenum content.
• Special Alloys (Duplex Stainless, Hastelloy, etc.):
Preferred in very aggressive chemical environments, fluids with high chloride content, or abrasive processes. It is high-cost but long-lasting.
2. Knife (Gate) Materials
The knife can be considered the heart of the valve. It directly contacts the particles in the fluid and moves perpendicular to the flow, opening or closing the line. Therefore, it requires high durability.
• Stainless Steel (AISI 304 / 316): The most commonly used material.
• Hardened Steel or Coated Knives: Knives with hardened surfaces or special coatings are used to increase life in abrasive fluids.
• Titanium Knives: Preferred in very aggressive chemicals or environments with high corrosion risk.
3. Sealing Elements
The reliability of knife gate valves largely depends on the sealing elements. The material to be used should be selected according to the type of fluid:
• EPDM: Resistant to hot water, steam, and some chemicals.
• NBR (Nitrile): Suitable for oily fluids and hydrocarbon derivatives.
• NR (Natural Rubber): Used in muddy and particulate fluids with high wear resistance.
• Metal Seat: Preferred in high temperature and pressure or chemically aggressive fluids.
4. Durability Features
Knife gate valves are designed to work without problems for a long time under challenging conditions.
• Maximum Operating Pressure: Generally resistant up to 16 bar levels.
• Maximum Operating Temperature: Can withstand up to 150 °C with elastomer sealing elements, much higher temperatures in metal-seated versions.
• Resistance to Wear: Hardened knives and quality body materials provide long life in particulate fluids.
5. Critical Factors in Material Selection
• Chemical composition of the fluid (acid, base, salt content)
• Temperature and pressure of the fluid
• Particles contained in the fluid and abrasive properties
• Hygiene requirement of the application (food, pharmaceuticals, etc.)
Incorrect material selection can lead to early wear of the valve, corrosion, and increased operating costs. Correct selection provides years of safe and low-cost operation advantage.
In short, the durability of knife gate valves starts with the correct material selection. When the body, knife, and sealing elements are selected according to the properties of the fluid, these valves work safely for many years even in the most challenging industrial environments.
Operating Modes: Manual and Automatic Controls
One of the biggest advantages of knife gate valves is that they can be used with a wide variety of operating modes according to different operational needs. This allows them to offer simple solutions in small-scale installations and advanced control options that can be integrated into automation in large industrial systems.
1. Manual Control
The most commonly used and most economical control method.
• Handwheel Operation: The valve is opened and closed with a handwheel turned by hand. Ideal for small diameter valves. It is low-cost and easy to use.
• Gearbox Operation: In large diameter knife gate valves, more force may be required to turn the handwheel. In this case, the gearbox mechanism comes into play. The user can open and close the valve with less effort.
• Chain Wheel Operation: If the valve is mounted at high points (e.g., in high-ceilinged facilities), it may be difficult to reach directly. With the chain wheel mechanism, the valve can be easily controlled remotely with a chain.
Manual solutions are ideal for simple applications but can be time-consuming in large diameter valves or systems with frequent opening and closing.
2. Pneumatic Actuated Control
One of the most preferred automatic control methods in the industry.
• Working Principle: Pneumatic cylinders operate with compressed air. When air pressure is applied, the knife moves up or down.
• Advantages: Provides very fast opening-closing, reliable and durable. Ideal for lines with frequently repeated opening-closing movements.
• Usage Areas: In industries requiring frequent operation such as wastewater treatment plants, paper industry, chemical plants.
3. Hydraulic or Piston Control
In some cases, hydraulic pistons can be used instead of the pneumatic system.
• Offers a stronger solution in applications requiring high torque.
• Suitable for compact designs that take up less space.
• Preferred especially in large diameter valves.
4. Electric Actuated Control
Comes into play when full integration with automation systems is required.
• Working Principle: The electric motor provides the opening-closing movement of the valve.
• Advantages: Can be easily connected to industrial automation systems (PLC, SCADA, etc.). Can be controlled remotely and operating costs are low.
• Usage Areas: Energy plants, large industrial facilities, applications requiring critical process control.
5. Criteria for Selecting Operating Mode
The following criteria should be considered to select the correct control method:
• Valve diameter and pressure in the line (actuated solutions are recommended instead of manual in large diameters).
• Frequency of opening-closing (pneumatic is preferred in frequent operations).
• Need for automation (electric actuated systems if remote monitoring and control are required).
• Budget and ease of maintenance (manual solutions are more economical, actuated systems are faster and more comfortable).
In short, knife gate valves offer a flexible structure suitable for both small installations with manual solutions and large industrial applications with automatic control systems. These features make them widespread and reliable in different sectors.
Advantages: Why Choose Knife Gate Valves?
Knife gate valves are a frequently preferred type of valve in the industry due to their unique advantages, especially under challenging fluid conditions. Knife gate valves stand out with their reliability, durability, and ease of use where traditional valve solutions struggle.
1. Reliable Performance in Challenging Fluids
The biggest advantage of knife gate valves is their ability to work without problems in muddy, sedimentary, fibrous, and particulate fluids.
• Butterfly or ball valves can clog or fail to provide full closure in such fluids.
• The thin and sharp structure of the knife gate valve cuts through the solid particles in the fluid, stopping the flow.
• This feature is especially important in sectors such as wastewater treatment plants, paper and pulp industry.
2. Full Sealing
Knife gate valves provide full closure thanks to elastomer or metal seated sealing elements.
• Elastomer seats (EPDM, NBR, NR) offer excellent sealing in low and medium pressure systems.
• Metal seated options are suitable for high temperatures and aggressive chemicals.
Thus, they create a safe solution according to different industrial needs.
3. Compact and Lightweight Design
Knife gate valves have a more compact body and lightweight structure compared to other valve types.
• Easy to install, can be easily placed in tight spaces.
• Takes up less space even in large diameter applications compared to other valve types.
4. Low Pressure Losses
When the valves are fully open, the knife is retracted from the path of the fluid, allowing the flow to continue with minimal resistance. This increases the energy efficiency of the system and allows pumps to consume less power.
5. Various Control Options
Knife gate valves can be equipped with different control methods:
• Manual (handwheel, gearbox, chain wheel)
• Pneumatic actuated
• Electric actuated
This flexibility makes them usable in both small facilities and large automation systems.
6. Ease of Maintenance
Thanks to their simple designs, maintenance processes are quite easy.
• Sealing elements and the knife can be quickly replaced when necessary.
• They have low failure rates as they do not have complex internal mechanisms.
• Maintenance costs remain low even in long-term use.
7. Application Variety
Knife gate valves have a wide range of applications, from water and wastewater management to the food industry, from chemical plants to power plants. This versatility has made them a standard solution in different sectors.
In conclusion, the reason knife gate valves are preferred is not only their ability to work under challenging conditions; they also offer full sealing, low maintenance needs, compact design, and flexible control options. Thanks to these advantages, knife gate valves are among the indispensable equipment of reliability and efficiency-focused projects in the industry.
Limitations: Points to Consider in Use
Although knife gate valves stand out with many advantages, they are not a universal solution for every system. If not used correctly, they may not deliver the expected performance and may even lead to undesirable results in the system. Therefore, it is important to know the limitations of knife gate valves and the points to be considered.
1. Not Suitable for Precise Flow Control
Knife gate valves are designed to operate only in fully open or fully closed positions.
• When left in intermediate positions, the turbulent movement of the fluid strains both the knife and the sealing elements.
• This can lead to early wear.
• Additionally, they cannot provide sufficient accuracy in precise adjustments such as flow control.
Therefore, knife gate valves should be used as open-close valves and should not be preferred for flow adjustment tasks.
2. Pressure Limits
Most knife gate valves are suitable for low and medium pressure systems.
• Maximum operating pressures are generally at the 10–16 bar level.
• When used in high-pressure lines, the body and knife can be excessively strained.
• Therefore, alternatives such as globe or ball valves should be preferred in high-pressure processes.
3. Sensitivity of Sealing Elements
Valves with elastomer seats may experience performance loss in case of chemical incompatibility or high temperature.
• Incorrect material selection can lead to the deterioration of sealing and fluid leaks.
• While metal-seated knife gate valves are advantageous at high temperatures, they may have lower sealing sensitivity compared to elastomer models.
4. Maintenance Need in Abrasive Environments
Knife gate valves are successful in particulate fluids, but such fluids can cause wear on the knife over long-term use.
• Especially in muddy and chemical fluids, if regular maintenance is not performed, the knife may lose its sharpness and the effectiveness of sealing surfaces.
• This can shorten the life of the valve.
5. Operational Difficulties in Large Diameter Valves
As the diameter increases, more force is required to move the knife.
• In manual use, this can make operation difficult.
• Therefore, pneumatic or electric actuated solutions should be preferred in large diameter lines.
6. Risk of Unidirectional Use
Some knife gate valve models can only provide sealing in one direction. This can lead to performance loss in lines where bidirectional flow is involved. Models providing bidirectional sealing should be selected according to the need.
Application Areas of Knife Gate Valves
Knife gate valves are used safely in many industries due to their resistance to different fluid properties. Their performance in fluids containing solid particles, fibers, or sludge distinguishes them from other types of valves. Here are the prominent application areas:
1. Paper and Pulp Industry
In paper production, there are highly fibrous fluids in the pulp preparation and processing stages.
• Butterfly or ball valves can lose their function in this environment due to fiber entrapment.
• Knife gate valves easily cut through fibers, ensuring the continuity of flow.
• Additionally, low pressure losses increase the efficiency of production lines.
2. Wastewater and Treatment Plants
In wastewater lines, sludge, sediment, and foreign materials are common.
• Knife gate valves operate without clogging in such fluids.
• When used with sludge pumps, they increase system reliability.
• Models providing bidirectional sealing eliminate the risk of backflow.
3. Food Industry
Knife gate valves are also used in food processes where hygiene and safety are prioritized.
• With stainless steel bodies and easy-to-clean designs, they are preferred in the production of milk, juice, beer, and beverages.
• They work in harmony with CIP (clean-in-place) systems, meeting hygiene standards.
4. Automotive Sector
In production lines, paint shops, and test systems, fluid management plays a critical role.
• Knife gate valves provide reliable solutions, especially in the control of paint and chemical liquids.
• Their compact structures allow them to be mounted in tight spaces.
5. Maritime
In the maritime sector, fluids often contain saltwater, leading to a high risk of corrosion.
• AISI 316 stainless steel knife gate valves are resistant to saltwater.
• They are widely used in cooling systems, ballast water management, and wastewater lines on ships.
• Low maintenance needs provide an advantage on long voyages.
6. HVAC Systems
Knife gate valves may be needed in building comfort air conditioning and hot water systems.
• They provide reliable solutions against sediments accumulating in heating and cooling lines.
• Their compact structure offers easy installation in mechanical installations.
7. Petrochemical and Pharmaceutical Industry
In these sectors, it is necessary to work with aggressive fluids.
• Knife gate valves offer high temperature and chemical resistance with metal-seated options.
• Stainless or special alloy body options provide reliability in corrosive environments.
8. Metal Industry
In metal processing processes, there is a combination of high pressure and temperature.
• Knife gate valves show reliable performance in the control of particulate fluids.
• They offer long-lasting solutions, maintaining the continuity of production lines.
9. Energy Sector
In energy production, especially in cogeneration and heat recovery systems, fluid management is of critical importance.
• Knife gate valves are used in water and steam lines containing solid particles.
• They provide reliability thanks to their materials resistant to high temperature and pressure.
10. Textile Industry
In printing, dyeing, finishing, and washing processes, fibrous and particulate fluids are common.
• Knife gate valves control the flow in this environment without the risk of clogging.
• They increase energy efficiency, reducing operating costs.
The Importance of Knife Gate Valves in Industrial Processes
The fluids used in industrial facilities are not always clean and pure. Often, these fluids contain mud, sand, sediment, fiber, particles, or chemical components. Managing such fluids poses significant challenges in terms of system efficiency and safety. Knife gate valves are one of the most suitable solutions developed to overcome these challenging conditions.
1. Process Reliability
The smallest disruption in flow control in industrial production lines can lead to the entire process stopping.
• Knife gate valves enable processes to work uninterruptedly by providing quick opening-closing even in difficult fluids.
• Their ability to fully close even in muddy or particulate fluids creates a safe working environment.
2. Production Efficiency
Valve clogging or sealing loss causes time and cost loss in production.
• The cutting knife structure of knife gate valves allows the flow to continue by easily overcoming solid materials in the fluid.
• This feature increases production efficiency, especially in challenging environments such as the paper industry, mining sector, and wastewater treatment plants.
3. Energy Savings
When knife gate valves are fully open, there is almost no obstacle in front of the fluid.
• This keeps pressure loss at a minimum level.
• Pump systems consume less energy, and operating costs decrease.
4. Contribution to Safety Standards
In some industrial applications, fluids are quite dangerous (e.g., aggressive chemicals or high-temperature fluids).
• Knife gate valves ensure the safe control of these fluids when the correct material is selected.
• Especially models providing bidirectional sealing eliminate the risk of backflow, contributing to operational safety.
5. Flexible Usage Opportunity
In industrial facilities, there may be fluids with different properties in the same line.
• Knife gate valves easily adapt to different types of fluids with elastomer or metal seat options.
• They can be integrated into any automation system with their manual, pneumatic, or electric actuated versions.
6. Long Life and Low Maintenance Cost
The durability of equipment used in the industry is of great importance.
• Knife gate valves require little maintenance due to their simple designs.
• With regular control and correct material selection, they work without problems for many years.
• This provides an advantage in the total cost of ownership for businesses.
Maintenance and Operational Ease
In industrial systems, not only durability but also maintenance ease and operational continuity are among the most critical factors. Because the failure of a valve can cause the entire line or process to stop. Knife gate valves provide significant advantages for businesses with their simple and practical structure in this regard.
1. Simple Design – Easy Intervention
The design of knife gate valves is quite simple due to the low number of moving parts.
• They have a compact structure consisting of the body, knife, and sealing elements.
• This makes it easy to disassemble and reassemble during maintenance.
• The low risk of failure offers the possibility of long-term uninterrupted use.
2. Replaceability of Sealing Elements
The elastomer or metal seats used in knife gate valves are selected according to the fluid properties.
• These sealing rings can wear out or deform over time.
• However, thanks to the modular design, only the sealing element can be replaced; there is no need to renew the entire valve.
• This significantly reduces maintenance costs.
3. Knife Control and Cleaning
The knife (gate) needs to be regularly checked as it directly contacts the fluid.
• In abrasive fluids, there may be deformation on the knife surface.
• Stainless steel knives offer high durability; their life can be extended with sanding or surface cleaning when necessary.
• Some models allow the knife to be easily removed and cleaned.
4. Low Maintenance in Automation Systems
Pneumatic and electric actuated knife gate valves are integrated into automation systems and controlled remotely.
• This reduces the need for manual intervention.
• Control systems monitor the opening-closing status of the valve and notify possible failures in advance.
• This prevents unplanned shutdowns.
5. Operational Continuity
One of the most important contributions of knife gate valves to businesses is maintaining system continuity.
• The low risk of clogging ensures the line operates continuously.
• During maintenance, the valve can be easily taken out of service and a spare valve can be installed.
• When used with auxiliary equipment such as an accumulator tank, flow can be continued even during short-term shutdowns.
6. Cost Advantage
Easy maintenance directly affects not only continuity but also costs.
• Requires less labor.
• Spare part needs are limited.
• As the life of the valve extends, the return period of the total investment shortens.
Criteria for Selecting the Right Knife Gate Valve
Selecting a knife gate valve is a critical step for the safety and efficiency of the system. A wrongly chosen valve can lead to failures, loss of sealing, and high maintenance costs in a short time. Therefore, when making a selection, the properties of the fluid, pressure and temperature values, the diameter of the line, and the purpose of valve use should be carefully evaluated. In muddy or fibrous fluids, elastomer-seated valves provide high sealing, while in environments containing aggressive chemicals, stainless steel-bodied and metal-seated models offer a safer solution. Additionally, as the valve diameter increases, turning to pneumatic or electric actuated solutions instead of manual use provides an advantage in terms of both operational ease and continuity. A knife gate valve with the right material and control method contributes to the system's trouble-free operation for many years.
Truevalve Knife Gate Valve Solutions
The Truevalve brand stands out with its wide product range and durable material options in knife gate valves. The AISI 304, AISI 316 stainless steel, and GGG40 ductile iron used in the bodies provide long-lasting use by adapting to different industrial needs. The knife parts are made entirely of stainless steel, ensuring reliable performance even in abrasive fluids. Truevalve knife gate valves, which can withstand temperatures up to 150 °C and pressures up to 16 bar, can be used safely in both low and medium pressure systems. Control options are also quite diverse; in addition to manual handwheel models, they can be easily integrated into automation systems with pneumatic piston or electric actuated solutions. Truevalve knife gate valves, offering high standards in terms of durability, sealing, and flexibility, guarantee process safety and operational efficiency in different sectors.
Conclusion: A Reliable, Durable, and Long-Lasting Flow Control Solution
Knife gate valves hold a special place in the industry with their durability and reliability offered in systems with challenging fluids. Their ability to work without problems in muddy, sedimentary, fibrous, or abrasive fluids is the biggest advantage that sets them apart from other valve types. With the correct material selection, they increase operational safety by providing full sealing, contribute to energy efficiency with low pressure losses, and simplify maintenance processes thanks to their simple design.
The high-quality knife gate valve solutions offered by Truevalve meet user expectations in terms of both performance and longevity in different sectors. These valves, which have a wide range of applications from industrial facilities to infrastructure systems, are not just equipment for businesses but also a strategic investment that provides efficiency and continuity. In conclusion, knife gate valves are one of the most effective ways of reliable, durable, and economical flow control in modern industrial processes.