Electric Operation for Water Treatment Petrochemical HVAC Industrial Piping

I. Product Overview

In the global industrial fluid control system, butterfly valves are recognized for their compact structure, light weight, and efficient flow control capabilities, among which double eccentric butterfly valves stand out with superior sealing performance and long service life. TIANYU’s Ductile Cast Iron Double Eccentric Butterfly Valve, meticulously engineered to comply with API 609 (Butterfly Valves for Industrial Applications), EN 593 (Industrial Valves – Butterfly Valves), and CE PED 2014/68/EU standards, is a high-performance solution tailored for water treatment, petrochemical, HVAC, power generation, and municipal engineering sectors.

Constructed with A536 65-45-12 ductile cast iron (GGG40/50) — a material celebrated for its exceptional tensile strength, impact resistance, and corrosion resistance — the valve features a double eccentric design that minimizes friction between the disc and seat during operation. This core design, combined with versatile sealing options (EPDM/PTFE/VITON), ensures reliable performance across media including water, sewage, steam, gas, oils, and mild corrosives. The valve adopts a flange connection compliant with international standards, enabling seamless integration into existing pipeline systems.

Rated for nominal diameters from DN50 to DN1200 and pressure classes from PN6 to PN25 (Class 150), the valve operates stably across a temperature range of -40℃ to 232℃, depending on the seal material. Available in manual, pneumatic, or electric actuation, it caters to diverse operational needs — from small-scale manual control in municipal water facilities to automated regulation in large petrochemical plants. As a flagship product of TIANYU, it balances durability, cost-effectiveness, and compliance, delivering consistent performance in both standard and harsh working conditions while minimizing lifecycle costs.

II. Important Attribute Specifications

A. Material Composition

Every component is selected based on strict industrial standards to ensure compatibility with diverse media and operating environments, guaranteeing long-term reliability:

Valve Body & Bonnet: A536 65-45-12 ductile cast iron (GGG40/50), a premium ductile iron grade with a chemical composition of C: 3.0-3.8%, Si: 2.0-2.8%, Mn: ≤1.0%, P: ≤0.04%, S: ≤0.02%. It boasts a tensile strength of ≥415MPa, yield strength of ≥275MPa, and impact toughness of ≥12J at -20℃, providing superior structural stability compared to gray cast iron. The inner and outer surfaces are coated with epoxy resin (minimum thickness ≥250μm) to enhance corrosion resistance, suitable for humid or chemically aggressive environments.
Disc: Carbon steel (Q235) or stainless steel (SS304/SS316) as standard, with optional polished surfaces for food-grade or high-purity applications. The disc is precision machined to match the double eccentric design, ensuring uniform contact with the seat and minimizing flow resistance. For abrasive media, a wear-resistant alloy overlay can be applied to extend service life.
Valve Stem: 2Cr13 stainless steel or SS304, featuring an anti-blowout structure to prevent ejection under high pressure. The stem undergoes solution annealing and polishing (surface roughness Ra ≤0.8μm) to reduce friction with packing and enhance corrosion resistance. It is integrally connected to the disc via a keyway, ensuring reliable torque transmission.
Seat: Replaceable soft seal or metal seal options to meet different operating conditions. EPDM (Ethylene Propylene Diene Monomer) seats for general applications (temperature range: -40℃ to 125℃), compatible with water, steam, and weak acids/bases. PTFE (Polytetrafluoroethylene) seats for high-temperature and chemical-resistant service (temperature range: -30℃ to 150℃), suitable for strong acids, solvents, and oils. VITON (fluororubber) seats for extreme temperature and corrosion resistance (temperature range: -23℃ to 150℃), ideal for petrochemical media. All soft seats are bonded to the valve body or disc using high-temperature adhesive, ensuring no detachment during operation.
Packing & Gaskets: Multi-layer flexible graphite packing with PTFE inner rings, complying with ISO 15848-1 Class BH standards to minimize fugitive emissions. Flange gaskets are spiral-wound graphite with SS304 reinforcement (compliant with ASME B16.20), ensuring tight sealing under thermal cycling and pressure fluctuations. O-rings made of EPDM or VITON are used for secondary sealing in bonnet and stem areas.
Fasteners: Carbon steel bolts (ASTM A193 B7) and nuts (ASTM A194 2H) for standard applications. For corrosive environments, SS304/SS316 bolts (ASTM A193 B8/B8M) and nuts (ASTM A194 8/8M) are available, ensuring uniform clamping force and long-term reliability.

B. Dimensional & Pressure-Temperature Parameters

Port Size (DN/NPS): DN50 (2”) to DN1200 (48”), full-port design to maximize flow efficiency. The flow coefficient (Cv) ranges from 30 (DN50) to 5200 (DN1200), minimizing pressure drop and energy consumption in high-flow applications such as water supply and drainage systems.
Pressure Rating: PN6 (0.6MPa), PN10 (1.0MPa), PN16 (1.6MPa), PN25 (2.5MPa) / Class 150, aligned with ASME B16.34 and EN 593 pressure-temperature ratings for ductile cast iron valves. At 20℃, PN25 models can withstand a maximum working pressure of 2.5MPa, suitable for medium-pressure industrial pipelines.
Temperature Range: Determined by the seat material. EPDM seats: -40℃ to 125℃; PTFE seats: -30℃ to 150℃; VITON seats: -23℃ to 150℃; metal seats (optional): -40℃ to 350℃. This wide range covers most industrial applications, from low-temperature refrigeration systems to high-temperature steam pipelines.
End Connections: Flange connection compliant with EN 1092-2, ASME B16.5, and ISO 7005-2, with Raised Face (RF) or Flat Face (FF) sealing surfaces. Flange drilling dimensions are compatible with global standards, ensuring interchangeability with valves from other manufacturers.
Face-to-Face Dimensions: Compliant with EN 558-1 Series 14 and DIN 3202-F4, ranging from 140mm (DN50) to 650mm (DN1200). This standardized dimension facilitates easy retrofitting and replacement in existing pipeline systems.

C. Operational Performance Parameters

Sealing Performance: ANSI/FCI 70-2 Class VI (soft-seal) for bubble-tight closure, with a leakage rate ≤0.1×DN mm³/min for liquid media. This ensures zero leakage even when handling toxic, flammable, or high-value fluids, reducing product loss and environmental risks.
Actuation Options:
- Manual: Cast iron handwheel with anti-slip grip, enabling 90-degree rotation for on-off control. A worm gear operator is optional for large-diameter valves (DN500+) to reduce operational torque.
- Pneumatic: Double-acting or spring-return pneumatic actuators (ISO 5211 mounting interface), explosion-proof (Ex d IIC T4) for hazardous environments, with an air supply pressure of 0.4–0.6MPa. Spring-return models provide fail-safe functionality (automatic open or close on air failure) to enhance system safety.
- Electric: AC/DC electric actuators (IEC 60534), equipped with remote control, position feedback, and torque limiting functions. Compatible with SCADA systems for automated process control, suitable for remote or hard-to-reach installations.
Operating Torque: Ranges from 20N·m (DN50, PN6) to 1800N·m (DN1200, PN25) for manual operation. The double eccentric design reduces torque by 30–40% compared to concentric butterfly valves, enabling easy manual operation for medium-diameter valves.
Cycle Life: ≥100,000 open/close cycles under normal operating conditions, with a maintenance interval of 24–36 months. The replaceable seat design further extends the valve’s service life.

D. Certifications & Compliance

Design & Manufacturing Standards: API 609, EN 593:2004, ASME B16.34, ASME B16.5, EN 558-1, DIN 3202-F4, ISO 7005-2, EN 12266 (Testing of Industrial Valves).
Quality & Environmental Certifications: ISO 9001 (Quality Management System), ISO 14001 (Environmental Management System), ISO 45001 (Occupational Health and Safety Management System).
Material & Safety Certifications: EN 10204 3.1/3.2 Material Test Certificates (MTC), CE PED 2014/68/EU (Pressure Equipment Directive), FDA 21 CFR 177.2600 (for food-grade applications with PTFE seats).

III. Feature Description

API 609 EN 593 CE Certified DN50-DN1200 PN6-PN25 Class 150 Ductile Cast Iron Double Eccentric Butterfly Valve

A. Double Eccentric Design: Reduced Wear & Low Torque

The double eccentric design is the core advantage of this valve, setting it apart from traditional concentric butterfly valves. The first eccentricity refers to the offset of the valve stem axis relative to the center of the valve seat; the second eccentricity is the offset of the valve stem axis relative to the center of the disc. This dual-offset structure ensures that the disc only contacts the seat at the final stage of closing, minimizing friction between the disc and seat during opening and closing.

This design not only reduces operational torque by 30–40% but also significantly reduces seat wear, extending the seat’s service life by 50% compared to concentric designs. In applications with frequent on-off operations (e.g., water treatment plants), this feature minimizes maintenance frequency and operational costs. Additionally, the double eccentric design enables bidirectional sealing, eliminating the need for check valves and simplifying pipeline design.

B. Ductile Cast Iron Construction with Epoxy Coating: Durability & Corrosion Resistance

The valve body and bonnet are made of A536 65-45-12 ductile cast iron, which offers superior mechanical properties to gray cast iron. Ductile cast iron’s spherical graphite structure enhances its tensile strength, impact resistance, and ductility, making it resistant to cracking under pressure surges and thermal cycling — critical for harsh industrial environments.

To further enhance corrosion resistance, the inner and outer surfaces of the valve body are coated with high-quality epoxy resin. The coating thickness is strictly controlled at ≥250μm, forming a seamless barrier against moisture, chemicals, and abrasive media. This coating ensures the valve maintains structural integrity in humid, corrosive environments such as sewage treatment plants and coastal areas, with a service life of 8–12 years.

C. Replaceable Seat Design: Maintenance Flexibility

The valve adopts a replaceable seat design, allowing on-site seat replacement without removing the valve from the pipeline. This significantly reduces downtime during maintenance — a key advantage for continuous-process facilities such as petrochemical plants and power stations. The seat is easily accessible by removing the bonnet or end flange, and no special tools are required for replacement.

TIANYU offers a range of seat materials to match specific media and operating conditions, enabling users to adapt the valve to changing process requirements without replacing the entire valve. This flexibility not only reduces maintenance costs but also extends the valve’s overall lifecycle.

D. Versatile Actuation Options: Adaptable to Diverse Systems

The valve is available in three actuation types, catering to the unique needs of different applications:

Manual actuation: Cost-effective for small-to-medium diameter valves (DN50-DN300) or systems with infrequent operation. The anti-slip handwheel provides clear visual confirmation of the valve’s position (parallel to the pipeline = open; perpendicular = closed).
Pneumatic actuation: Ideal for automated systems requiring fast, reliable operation (e.g., batch processing lines in chemical plants). Spring-return actuators ensure fail-safe operation, preventing system overpressure or media leakage in the event of air supply failure.
Electric actuation: Suitable for remote control and precision regulation (e.g., SCADA-integrated water supply networks). The electric actuator features adjustable torque limits and position feedback, enabling real-time monitoring and control of the valve’s status.

E. Bubble-Tight Sealing: Reliable Performance

Equipped with high-quality soft seals (EPDM/PTFE/VITON) or metal seals, the valve achieves ANSI/FCI Class VI sealing performance (for soft seals), ensuring bubble-tight closure. The combination of the double eccentric design and preloaded seat ensures uniform sealing pressure across the entire seat surface, even under fluctuating pressure and temperature conditions.

For applications requiring strict leakage control (e.g., handling toxic or flammable media), the valve can be equipped with a secondary sealing system, further enhancing sealing reliability. This feature makes the valve suitable for critical service in petrochemical, pharmaceutical, and food processing industries.

IV. Manufacturing Process & Quality Control

A. Raw Material Procurement & Inspection

TIANYU adheres to strict raw material sourcing and inspection protocols to ensure product quality and traceability:

Material Sourcing: Ductile cast iron blanks, stainless steel components, and seal materials are sourced exclusively from ISO 9001-certified suppliers. Each batch of raw materials is accompanied by a Material Test Certificate (MTC) detailing chemical composition, mechanical properties, and heat treatment history.
Material Verification: Incoming ductile cast iron blanks undergo spectral analysis (XRF) to confirm compliance with A536 65-45-12 standards. Tensile, yield, and impact tests are performed on sample specimens to ensure mechanical properties meet requirements (tensile strength ≥415MPa, impact toughness ≥12J at -20℃).
Non-Destructive Testing (NDT): Cast components (body, bonnet) undergo ultrasonic testing (UT) to detect internal defects such as porosity and cracks, and magnetic particle testing (MPI) to inspect surface flaws. Only defect-free materials proceed to the next manufacturing stage.

B. Casting & Heat Treatment

Casting and heat treatment are critical to ensuring the structural integrity of the valve:

Precision Casting: Ductile cast iron billets are melted in an electric arc furnace and poured into sand molds using the lost foam casting process. This process ensures dimensional accuracy and surface smoothness, reducing the need for subsequent machining. The casting process is strictly controlled to minimize internal defects such as shrinkage and porosity.
Heat Treatment: Cast components undergo normalization (850–900℃, air-cooled) to relieve casting stress and refine the grain structure. This treatment enhances the material’s toughness and ductility, ensuring the valve can withstand pressure surges and thermal cycling. Post-heat treatment hardness is controlled between 170–230 HB.
Descaling & Cleaning: Cast parts are shot-blasted to remove surface oxide scale and sand, then cleaned with ultrasonic baths to eliminate residual contaminants. This ensures clean surfaces for subsequent coating and assembly.

C. Precision Machining

Machining is performed using high-precision CNC equipment to meet tight tolerances:

Body & Bonnet Machining: CNC lathes and milling machines process flange faces, seat pockets, and stem bores. Flange faces are machined to a flatness tolerance of ≤0.02mm/m and surface roughness Ra 1.6μm to ensure tight sealing. Seat pockets are honed to a coaxiality tolerance of ≤0.01mm relative to the valve bore, ensuring uniform contact between the disc and seat.
Disc Machining: The disc is precision turned and milled to match the double eccentric design. The sealing surface is lapped to Ra ≤0.4μm to enhance sealing performance. For full-port designs, the disc bore is machined to match the nominal pipe size, minimizing flow resistance.
Stem Machining: The stem is turned and ground to a diameter tolerance of ±0.01mm and polished to Ra ≤0.8μm. The anti-blowout shoulder is precision-machined to engage securely with the valve body, preventing stem ejection under high pressure.

D. Coating Process

The epoxy coating process is critical to the valve’s corrosion resistance:

Surface Preparation: Machined components are degreased and sandblasted to achieve a surface roughness of Ra 40–80μm, ensuring strong adhesion between the coating and the substrate.
Coating Application: High-quality epoxy resin is applied using electrostatic spraying, ensuring uniform coating thickness. The coating thickness is measured at multiple points to ensure it meets the minimum requirement of 250μm.
Curing: Coated components are cured in an oven at 180℃ for 2 hours, forming a hard, wear-resistant coating. Post-curing inspection ensures no pinholes, cracks, or delamination.

E. Assembly & Comprehensive Testing

Assembly and testing adhere to EN 12266 and API 598 standards to ensure reliable performance:

Component Cleaning: All parts (body, disc, seat, stem, packing) are degreased and ultrasonic-cleaned to remove oil, debris, and metal particles, preventing contamination of sealing surfaces.
Assembly Sequence: The seat is first installed in the valve body, followed by the disc, stem, packing, and bonnet. Fasteners are tightened in a crisscross pattern to uniform torque (per ASME B18.2.1) to ensure even clamping force. Actuators (pneumatic/electric) are mounted in accordance with ISO 5211 standards, and the connection is tested for torque transmission.
Pressure Testing:
- Hydrostatic Shell Test: 1.5× rated pressure is applied to the valve body cavity for 30 minutes. No leakage, deformation, or pressure drop is permitted.
- Hydrostatic Seat Test: 1.1× rated pressure is applied to each seat (bidirectional) for 15 minutes. Leakage is measured using a bubble counter, complying with ANSI/FCI Class IV/VI.
- Pneumatic Test (Optional): 0.6MPa air pressure is applied to the body and seats for 10 minutes. No audible leakage is permitted.
Operational Testing: The valve is cycled 50 times (open-close) to verify smooth operation, consistent torque, and correct actuator performance (for pneumatic/electric models).
Specialized Testing:
- Fugitive Emissions Test: ISO 15848-1 Class BH compliance is verified using methane and a flame ionization detector (FID).
- Low-Temperature Test: For valves used in cold environments, testing at -40℃ ensures sealing performance and operational reliability.

F. Final Inspection & Packaging

Before shipment, each valve undergoes a final inspection and careful packaging:

Visual Inspection: Each valve is inspected for surface defects (scratches, dents), proper machining, and correct marking (DN, PN, TIANYU logo, certifications). Valves with surface scratches deeper than 0.05mm are rejected.
Documentation: Each valve is shipped with a comprehensive Documentation Package, including MTC, Hydrostatic Test Certificate, EN 10204 3.1/3.2 Certificate, and CE PED Declaration of Conformity.
Packaging: Valves are packaged in plywood crates with foam insulation to prevent damage during transportation. Flange ends are capped with plastic protectors, and actuators are wrapped in waterproof film. Crates are labeled with handling instructions, product information, and warning signs for safe delivery.

V. Product Advantages

A. Superior Durability & Long Service Life

The combination of A536 65-45-12 ductile cast iron construction and epoxy coating ensures the valve can withstand harsh industrial environments. The double eccentric design minimizes wear between the disc and seat, extending the valve’s service life to 8–12 years — significantly longer than the 3–5 years of standard concentric butterfly valves. In a case study at a municipal sewage treatment plant, TIANYU’s double eccentric butterfly valves maintained reliable performance for 10 years without major maintenance, reducing replacement costs by 60%.

B. Low Operational & Maintenance Costs

Low Torque Operation: The double eccentric design reduces operational torque by 30–40%, enabling manual operation for medium-diameter valves and reducing energy consumption for pneumatic/electric actuators. For a DN600 PN16 valve, this translates to annual energy savings of $2,000–$3,000 for electric actuation.
Easy Maintenance: The replaceable seat design allows on-site maintenance without removing the valve from the pipeline, reducing downtime by 70% compared to non-replaceable seat valves. The 24–36 month maintenance interval minimizes operational disruptions and labor costs.
Cost-Effective Material: Ductile cast iron offers a balance of performance and cost, providing superior mechanical properties to gray cast iron at a lower cost than stainless steel. This makes the valve an economical choice for large-diameter applications.

C. Reliable Sealing & Operational Safety

Bubble-Tight Sealing: ANSI/FCI Class VI sealing performance prevents media leakage, critical for handling toxic, flammable, or high-value fluids. This eliminates product loss and environmental contamination risks, ensuring compliance with global safety regulations.
Safety Features: The anti-blowout stem design prevents stem ejection under high pressure, and spring-return pneumatic actuators provide fail-safe operation. The valve’s compliance with CE PED 2014/68/EU ensures it meets strict safety standards for pressure equipment.
Bidirectional Sealing: The double eccentric design enables reliable sealing in both flow directions, eliminating the need for check valves and simplifying pipeline design. This reduces the number of components in the system, lowering potential failure points.

D. Wide Application Range & Versatility

The valve’s diverse material options, pressure-temperature range, and actuation choices make it suitable for a wide range of applications, from water treatment and HVAC to petrochemical and power generation. It can handle media including water, sewage, steam, gas, oils, and mild corrosives, eliminating the need for multiple valve types across different process lines. This versatility reduces inventory costs and simplifies procurement for end-users.

E. Global Compliance & Interchangeability

Compliance with API 609, EN 593, ASME B16.34, and CE PED ensures the valve can be used in global markets, from North America and Europe to Asia. The standardized flange dimensions and face-to-face dimensions ensure interchangeability with valves from other manufacturers, facilitating easy retrofitting and replacement. This global compliance makes the valve an ideal choice for multinational companies and export-oriented projects.

VI. Product Applications

A. Water Treatment Industry

The valve is widely used in water treatment plants, including raw water intake, coagulation, sedimentation, filtration, and disinfection processes. Its corrosion-resistant epoxy coating and EPDM seats are suitable for handling water and chlorine-containing disinfectants. The full-port design ensures high flow rates, meeting the large-volume water supply needs of municipal and industrial water treatment facilities. Manual or electric actuation options cater to different control requirements, from small-scale booster stations to large water treatment plants.

B. Petrochemical Industry

In petrochemical plants, the valve is used in crude oil processing, refined product transportation, and chemical reagent handling. PTFE or VITON seats are selected for their chemical resistance to oils, solvents, and weak acids/bases. The bubble-tight sealing performance prevents leakage of flammable and toxic media, ensuring operational safety. Pneumatic or electric actuation with explosion-proof features is suitable for hazardous environments in refineries and chemical plants.

C. HVAC & Building Services

For heating, ventilation, and air conditioning (HVAC) systems, the valve is used to control the flow of hot and cold water, steam, and air. EPDM seats are ideal for this application, with a temperature range of -40℃ to 125℃ covering typical HVAC operating conditions. The low torque design enables easy manual operation or integration with building automation systems (BAS) via electric actuators. The valve’s compact structure saves installation space, making it suitable for commercial buildings, shopping malls, and industrial workshops.

D. Power Generation Industry

In thermal power plants and nuclear power plants (non-radiation zones), the valve is used in cooling water systems, feedwater systems, and steam auxiliary systems. Metal seats or PTFE seats are selected for high-temperature service (up to 350℃), withstanding the high-pressure and high-temperature conditions of steam pipelines. The reliable sealing performance ensures efficient heat transfer and prevents energy loss. Electric actuation with remote control enables precise regulation of flow rates, optimizing power plant efficiency.

E. Municipal Engineering

The valve is widely used in municipal infrastructure, including water supply and drainage networks, gas distribution systems, and sewage treatment plants. The epoxy-coated ductile cast iron body resists corrosion from soil and groundwater, ensuring long-term reliability in buried pipelines. The flange connection facilitates easy installation and maintenance, reducing construction costs. For gas distribution systems, VITON seats are used for their compatibility with natural gas and propane.

F. Food & Beverage Industry

In food and beverage processing plants, the valve is used to control the flow of water, juices, dairy products, and cleaning agents. SS304/SS316 polished discs and PTFE seats are selected for their food-grade compliance (FDA 21 CFR 177.2600), ensuring no contamination of food products. The easy-to-clean design and smooth surfaces prevent bacterial growth, meeting strict hygiene standards for the food industry.

VII. Customization Advantages

TIANYU’s API 609/EN 593-certified ductile cast iron double eccentric butterfly valve delivers reliable flow control for water treatment, petrochemical, and HVAC sectors. Its double eccentric design reduces wear and torque, epoxy-coated body resists corrosion, and versatile seats cover -40℃ to 232℃. Customize with SS316 disc for harsh corrosion, metal seats for high temps, or smart electric actuators for automation. Tailored to your media and system, it balances safety, durability, and cost-effectiveness — your trusted valve solution for diverse industrial needs.

API 609 EN 593 CE Certified DN50-DN1200 PN6-PN25 Class 150 Ductile Cast Iron Double Eccentric Butterfly Valve