Introdução à comparação: válvula de cunha e válvula de gaveta paralela

Válvula gaveta é uma válvula onde o disco se move na direção vertical ao longo da linha central do caminho. As válvulas gaveta são usadas principalmente para corte na tubulação.

Uma das classificações mais comuns pode ser dividida em válvulas gaveta em cunha e válvulas gaveta paralela de acordo com a configuração da superfície de vedação.

A válvula gaveta em cunha pode ser dividida em: tipo de disco único, tipo de disco duplo e tipo de disco resiliente; válvula de gaveta paralela pode ser dividida em tipo de disco único e tipo de disco duplo.

A superfície de vedação da válvula paralela é perpendicular ao eixo do tubo, aquilo é, as duas superfícies de vedação são paralelas uma à outra válvula de gaveta de importação.

A superfície de vedação da válvula gaveta em cunha está em um ângulo com o eixo do tubo, aquilo é, as duas superfícies de vedação em uma válvula gaveta em forma de cunha. O tamanho do ângulo de inclinação da cunha depende principalmente da temperatura do meio, geralmente quanto maior a temperatura de trabalho, maior deve ser o ângulo tomado, a fim de reduzir a possibilidade de bloqueio do portão quando a temperatura muda.

The design concepts, operating principles, performance characteristics, and suitable applications for these two structures differ significantly. For end-users, a thorough understanding of these differences is key to making informed selection decisions, ensuring system stability, and optimizing procurement costs.

As a globally recognized top-tier valve manufacturer, Farpro YD Valve possesses extensive valve data and information to enlighten our customers on gate valve knowledge. Here, the Farpro YD Team will provide a detailed explanation of the distinctions between parallel gate valves and wedge gate valves, offering valuable insights based on our vast experience. Farpro explicará em detalhes a diferença entre válvulas paralelas e de cunha:

Part One: Gate Valve Fundamentals Recap

Before diving into the comparison, let’s briefly review the basic concepts of gate valves:

1. Operating Principle: By rotating a handwheel or activating an actuator, the valve stem is driven to perform a lifting motion (Outside Screw & Jugo – SO&Y type) or remain in place while the gate moves (Haste Não Ascendente – NRS type). This action drives the connected gate up or down within the valve body, perpendicular to the fluid channel. When the gate is fully lifted, the passage is completely open, offering minimal resistance to flow. When the gate is fully lowered and seals tightly against the valve seat, the passage is completely closed, achieving shut-off.

2. Main Advantages:

   • Low Flow Resistance: When fully open, the gate is completely withdrawn from the flow path, allowing the medium to flow almost straight through, resulting in very low pressure drop.

   • Relatively Low Operating Torque: Compared to globe valves, the gate moves perpendicular to the flow direction, requiring less force to overcome fluid pressure during opening and closing.

   • No Restriction on Flow Direction: Gate valves are typically bidirectional, meaning they can be installed and operated regardless of the flow direction.

   • Wide Range of Applications: Suitable for various media (liquids, gases, vapor, slurries, etc.), pressões, and temperature ranges.

   • Relatively Simple Structure, Manutenção fácil.

3. Main Disadvantages:

   • Not Suitable for Throttling: In a partially open state, high-velocity fluid can easily erode the sealing surfaces, leading to valve damage and leakage. Além disso, the relationship between flow rate and opening percentage is non-linear, making precise flow control difficult.

   • Slow Operation: The gate has a relatively long travel distance, requiring significant time to complete a full open or close cycle.

   • Large Overall Dimensions and Height: Especially for OS&Y types, the rising stem requires considerable overhead space when the valve is open.

   • Sealing Surfaces Prone to Abrasion: During opening and closing, relative friction occurs between the gate and seat sealing surfaces, particularly under pressure or when the medium contains solid particles.

Características das válvulas de gaveta paralela

Válvula de gaveta paralela é o tipo de disco duplo mais comum, a fim de fechar o corpo da válvula e a porta entre as duas superfícies de vedação em contato estanque, frequentemente usado no sanduíche de placa de dois portões com cunha de impulso de dupla face.

Desta maneira, ao fechar a válvula, o contato da cunha de impulso de dupla face com a parte inferior do corpo da válvula é gradualmente tensionado, empurrando para abrir a placa de comporta dupla de modo que a superfície de vedação da comporta e a vedação do corpo da válvula e estanquem. Este tipo de portão paralelo de disco duplo é geralmente aplicado em condições de trabalho que não precisam abrir e fechar com frequência, e mantenha o portão totalmente aberto ou totalmente fechado.

Main Structural Types:

Parallel Slab Gate Valve / Through-Conduit Gate Valve:

• • • Structure: Typically features a single, flat gate (slab) with a bore (port) machined through it, matching the pipeline diameter. The slab slides between two parallel seats.

    • Operation: To close, the slab slides down, and its solid portion blocks the flow path. To open, the slab slides up, aligning the through-conduit port with the pipeline, creating a smooth, unobstructed passage. Sealing usually relies on line pressure pushing the slab against the downstream seat (self-sealing), sometimes assisted by spring-loaded seats providing initial sealing force.

    • Advantages:

      • Resistência Mínima ao Fluxo: When fully open, the port matches the pipe bore, offering a smooth, non-restrictive flow path, ideal for pipelines requiring low pressure drop, such as long-distance transport lines.

      • Sealing Surface Protection: In both fully open and fully closed positions, the sealing surfaces are shielded from the main flow, protecting them from erosion and wear, especially suitable for media containing solid particles or abrasives.

      • Suitable for Pigging: The smooth through-conduit allows pipeline inspection gauges (Pigs) to pass through.

      • Relatively Lower Operating Torque: Primarily needs to overcome friction, no wedging force involved.

    • Disadvantages:

      • Sealing tightness at low pressure might be less positive than wedge types, as self-sealing effectiveness depends on sufficient differential pressure.

      • Structural dimensions, particularly face-to-face length, can be larger.

      • Manufacturing costs can be higher, especially for large diameters and high pressure ratings.

Parallel Double Disc Gate Valve:

• • • Structure: Comprises two parallel discs, usually with a spring or spreader mechanism (like a wedge or toggle) located between them.

    • Operation: As the gates descend near the closed position, the spring or spreader mechanism activates, forcing the two discs outwards against their respective upstream and downstream seats, achieving a double seal. During opening, this spreading force is released first, allowing the discs to lift freely.

    • Advantages:

      • Excellent Bidirectional Sealing: Provides effective sealing regardless of the direction of flow or pressure.

      • Reliable Low-Pressure Sealing: The mechanical spreading force ensures a tight seal even at very low differential pressures.

      • Avoids Thermal Binding: The absence of a wedge angle eliminates the risk of jamming due to temperature changes or pressure fluctuations, making it ideal for high-temperature, high-differential pressure, and thermal cycling applications.

      • Potential for Self-Relieving Function: Some designs allow overpressure trapped in the body cavity to automatically bleed off to the upstream side, enhancing safety (specific design must be confirmed).

    • Disadvantages:

      • Relatively complex structure with more parts, leading to higher manufacturing and maintenance costs.

      • Potential for debris accumulation between the discs, which could affect sealing or operation.

      • Typically larger and heavier than wedge gate valves of the same specification.

Parallel Gate Valve Characteristics Summary:

Advantages:

• No risk of thermal binding, suitable for high-temperature and fluctuating temperature service.

• Relatively lower operating torque (especially slab gate type).

• Through-conduit design protects sealing surfaces, suitable for particulate media and pigging operations.

• Double disc design offers reliable bidirectional and low-pressure sealing.

Disadvantages:

• Single-gate self-sealing types may have weaker sealing at very low pressures.

• Double disc types are structurally complex, costly, and bulky.

• High manufacturing precision required, especially for parallelism and flatness.

Typical Application Areas:

• Oil and gas long-distance pipelines (primarily through-conduit parallel slab gate valves, often to API 6D).

• High-temperature steam lines (e.g., main steam lines in power plants, often using double disc parallel types).

• Refineries and chemical plants for high-temperature, high-pressure services or where pigging is required.

• Low-pressure gas distribution lines.

• Applications requiring reliable bidirectional sealing.

Geralmente, no caso de conexão direta com o gasoduto, recomenda-se usar a válvula gaveta paralela, que tem as vantagens da estrutura compacta, peso leve, tamanho pequeno, Manutenção fácil, operação conveniente e flexível, etc..

Características das válvulas gaveta em cunha

Válvula gaveta em cunha tem válvula gaveta de cunha de disco simples/duplo. As vantagens da válvula gaveta de disco duplo são a vedação enquanto o ângulo dos requisitos de precisão é baixo, mudanças de temperatura não são fáceis de fazer a cunha do portão, o desgaste da superfície de vedação pode ser compensado pela adição de juntas.

A desvantagem é que a estrutura é complicada, fácil de colar no meio seco, mais principalmente, a placa defletora superior e inferior é fácil de cair após anos de corrosão.

Portanto, a válvula gaveta de cunha de disco único é usada em grande número devido à sua estrutura simples e uso confiável, especialmente depois de mudar para um portão resiliente, que pode produzir uma ligeira deformação elástica para compensar o desvio produzido no processamento do ângulo da superfície de vedação.

Wedge Angle: The selection of the wedge angle is a critical design parameter, typically dependent on the medium temperature, classificação de pressão, and valve size.

• Temperature Influence: Higher operating temperatures lead to more significant thermal expansion differences in materials. To prevent the gate from becoming “wedged shut” or experiencing “thermal binding” at high temperatures, a larger wedge angle is usually chosen. Por outro lado, for ambient or low temperatures, a smaller wedge angle can be used for better sealing and lower operating torque.

• Common Angles: Generally range from 3° to 10°. Por exemplo, API 600 often specifies 5° or higher.

Main Structural Types：

• Solid Wedge Gate Valve:

  • Structure: The gate is a single, solid wedge piece.

  • Advantages: Simplest structure, robust, durável, relatively low cost, less prone to trapping debris, suitable for most general applications, especially in small to medium sizes and low to medium pressures.

  • Disadvantages: Poor adaptability to sealing surface machining inaccuracies and valve body deformation. Temperature changes or pipeline stresses can lead to poor sealing or gate jamming (thermal binding). Closing under high differential pressure can create excessive wedging force, making opening difficult.

• Flexible Wedge Gate Valve:

  • Structure: The main body of the gate is still wedge-shaped, but features cuts, slots, or a specific peripheral design allowing it some elastic deformation capability.

  • Advantages: Can compensate for minor valve body distortions caused by temperature changes or pipeline loads, enhancing sealing reliability. Effectively prevents high-temperature thermal binding. Less demanding on the precision of sealing surface angle machining. Offers better sealing performance than solid wedges. Farpro YD Valve has mature technology in the design and manufacture of high-performance flexible wedge gate valves.

  • Disadvantages: Structure is slightly more complex than a solid wedge, leading to a marginally higher manufacturing cost. Not ideal for media containing significant solid particles or prone to scaling, which could clog the flexible structure.

• Split Wedge / Double Disc Wedge Gate Valve:

  • Structure: Consists of two independent discs (often connected by a mechanism like a ball-and-socket joint, pin, or dovetail) forming a composite wedge shape. Upon closing, external forces (like stem thrust or a bottom spreader) allow the two discs to move slightly apart laterally, pressing independently against their respective seats.

  • Advantages: Both sealing surfaces can achieve independent contact with the seats, providing excellent self-alignment. This offers better adaptability to seat angle variations and body deformation, resulting in superior sealing performance, especially under high pressure and high temperature conditions. Minor sealing surface wear can be compensated for by the outward movement of the discs. Less prone to thermal binding.

  • Disadvantages: Most complex structure, more parts, higher manufacturing cost, relatively more difficult to assemble and repair. Potential for media to become trapped between the discs. In designs with bottom guides, corrosion and detachment of these guides over time can impair function.

Wedge Gate Valve Characteristics Summary:

• Advantages:

  • Excelente desempenho de vedação: Relies on wedging action for positive sealing, providing high sealing pressure and reliability.

  • Relatively compact structure (compared to parallel gate valves of the same size).

  • Wide range of applications: Suitable for various pressures, temperaturas, and media (selection depends on materials and specific structure).

  • Mature technology, highly standardized (e.g., API, ASME standards).

• Disadvantages:

  • Risk of thermal binding: Especially with solid wedges in applications with significant temperature fluctuations or cooling after high-pressure closure.

  • Relatively high operating torque: Must overcome the friction associated with the wedging action.

  • Sealing surfaces prone to wear: Due to relative sliding friction during operation.

  • Not suitable for rapid opening/closing.

Typical Application Areas:

• Power industry (linhas de vapor, feedwater systems, ash handling systems, etc.)

• Óleo e gás (oilfields, refinarias, some pipeline applications)

• Indústria química (various process fluid lines)

• Metallurgy and mining (process water, slurry handling, etc.)

• Municipal water supply and wastewater treatment

• General industrial services

Em geral, a haste da válvula gaveta em cunha é temperada e nitretada na superfície para ter boa resistência à corrosão e anti-arranhões. A porta e a vedação da sede são feitas de soldagem de sobreposição de liga dura, que é resistente ao desgaste, resistente a altas temperaturas, resistente a corrosão, bom desempenho anti-arranhões e longa vida útil. A variedade de materiais do corpo da válvula está completa, embalagem, junta de acordo com as condições reais de trabalho ou requisitos do usuário opcional razoável, pode ser aplicado a uma variedade de pressões, temperatura e condições de trabalho da mídia.

Wedge Gate Valve vs. Parallel Gate Valve – In-Depth Comparison

To aid in making a clearer choice, we directly compare these two valve types across several key dimensions:

Selection and Purchasing Guidance – Professional Advice from Farpro YD Valve

Choosing between a wedge gate valve and a parallel gate valve isn’t about determining which one is universally “better,” but rather identifying which one is “more suitable” for a specific application. As a responsible valve supplier, Farpro YD Valve recommends considering the following key factors during selection:

Operating Conditions are Fundamental:

• Media Properties: Is it a clean fluid, gás, vapor, or does it contain solid particles, pasta, viscous material, or crystallizing substances? This directly impacts whether sealing surface protection is needed (advantage: parallel slab gate) or if specific materials and structures are required.
• Classificação de pressão: In high-pressure applications, the positive sealing of a wedge gate valve (especially split wedge) can be very reliable, but consider the operating torque and potential binding issues under high differential pressure. Parallel double disc types also perform well under high pressure.
• Temperature Range & Fluctuation: For high temperatures or significant temperature swings, parallel gate valves (lacking a wedge angle) are the preferred choice to avoid thermal binding. If selecting a wedge type, prioritize flexible wedge or split wedge designs and pay attention to the wedge angle selection.

Functional Requirements Guide the Choice:

• Sealing Level Requirement: Is zero leakage or a very high sealing class required? Split wedge and parallel double disc types generally offer superior sealing performance.
• Operating Frequency: Gate valves are inherently unsuitable for frequent operation. If relatively frequent cycling is necessary, consider a parallel gate valve with lower operating torque or select an appropriate actuation method.
• Need for Pipeline Pigging: For applications like long-distance pipelines where pig passage is required, a through-conduit parallel gate valve is mandatory.
• Need for Automatic Cavity Pressure Relief: Certain parallel double disc gate valves offer this safety feature; confirm based on specific process requirements.

Economic and Maintenance Considerations:

• • Initial Purchase Cost: Geralmente, solid/flexible wedge gate valves have the lowest cost, followed by slab gate and split wedge types, with double disc parallel gate valves typically being the most expensive. No entanto, this is a general guideline influenced by materials, standards, brand, etc..

  • Maintenance Convenience and Cost: Simpler structures usually mean easier maintenance. Consider the valve’s expected lifespan, maintenance intervals, and replacement costs.

  • Space and Weight Constraints: Parallel gate valves are often larger and heavier, requiring consideration of installation space and support structures.

Industry Codes and Standards:

• • Ensure the selected valve complies with relevant industry codes (e.g., óleo & gás, poder, químico) and standards (e.g., API, ASME, EM, GB). All Farpro YD Valve products are designed and manufactured in strict accordance with international and national standards.

Purchasing Recommendations

• Define Needs Clearly, Communicate Thoroughly: Before inquiring or purchasing, provide your supplier (like Farpro YD Valve) with detailed operating parameters and functional requirements. Our technical team will leverage your specific needs to recommend the most suitable valve type and specification.

• Focus on Quality and Brand Reputation: Valves are critical equipment; choosing a reliable brand with a proven quality record is essential. Farpro YD Valve operates under robust quality management systems (e.g., ISO 9001) and utilizes advanced manufacturing and testing equipment to ensure every valve meets high-quality standards.

• Consider Total Cost of Ownership (TCO) / Lifecycle Cost: Look beyond the initial purchase price. Evaluate the valve’s performance, confiabilidade, service life, maintenance costs, and the potential costs associated with failure. Choosing a high-performance, long-lasting valve (even if initially more expensive) often yields better long-term economic benefits.

• Value Technical Support and Service: Select a supplier capable of providing professional technical consultation, selection guidance, after-sales service, and spare parts availability. Farpro YD Valve is committed to offering a seamless and supportive experience for our customers.

Conclusão

Wedge gate valves and parallel gate valves, as two major branches of the gate valve family, each possess unique design philosophies, performance advantages, and application niches.

• Válvulas de cunha, with their powerful wedging seal, relatively compact structure, and broad applicability, dominate many conventional industrial sectors. Derived designs like the flexible wedge and split wedge further enhance performance and reliability.

• Parallel gate valves, characterized by their immunity to thermal binding, suitability for high temperatures and particulate media (through-conduit type), and excellent bidirectional and low-pressure sealing capabilities (double disc type), demonstrate irreplaceable advantages in specific high-end applications and demanding operating conditions, such as long-distance pipelines and high-temperature steam systems.

There is no absolute superiority, only relative suitability. Understanding their core differences and making scientific selections based on specific application requirements are prerequisites for ensuring the safe, eficiente, and economical operation of fluid control systems.

Farpro YD Valve offers a comprehensive product line of both wedge and parallel gate valves, covering various materials, classificações de pressão, actuation methods, and standard compliance. We not only provide standardized high-quality products but also offer customized solutions tailored to your unique needs. Whatever fluid control challenges you face, our professional team is ready to provide the most accurate selection advice and the highest quality valve products.

Choose Farpro YD Valve – Choose Professionalism, Choose Reliability. We welcome you to contact us anytime to discuss your valve requirements!