DN125 PN16 CF8M Stainless Steel Lug-Type Butterfly Valve with PTFE Lining Concentric Line Butterfly Valves

TIANYU DN125 PN16 CF8M stainless steel lug-type butterfly valve is a precision-engineered flow control device designed to address the challenges of handling corrosive, aggressive, and sanitary media in industrial settings. As a midline (centric) butterfly valve, it features a symmetrical disc design that ensures uniform sealing and minimal flow restriction. The lug-type flange connection allows for versatile installation in pipelines, while the PTFE (polytetrafluoroethylene) lining provides exceptional chemical resistance—making it a go-to solution for applications involving acids, alkalis, solvents, and other corrosive fluids.

Constructed from CF8M stainless steel (equivalent to 316 stainless steel), this valve adheres to international standards such as API 609, ASME B16.5, and ISO 5752, ensuring compatibility with global industrial systems. Its soft-sealed, PTFE-lined design delivers bubble-tight performance (ANSI/FCI Class VI leakage), making it suitable for critical processes where media containment and purity are paramount. Whether deployed in chemical plants, pharmaceutical facilities, or water treatment systems, this valve embodies reliability, corrosion resistance, and operational efficiency.

II. Key Attribute Specifications

A. Dimensional & Pressure-Temperature Parameters

Nominal Diameter (Port Size): DN125 (5 inches), a widely utilized size in medium-scale industrial pipelines. This dimension balances flow capacity and installation flexibility, making it ideal for process lines in chemical reactors, pharmaceutical blending systems, and water distribution networks.
Pressure Rating: PN16 (1.6MPa), aligning with industrial medium-pressure requirements. The valve undergoes hydrostatic testing at 1.5× rated pressure for the body and 1.1× rated pressure for the seat, ensuring structural integrity and leak-tight sealing under operating conditions.
Temperature Range: -20℃ to 180℃, enabled by the PTFE lining’s thermal stability and CF8M stainless steel’s resistance to thermal stress. This range accommodates cryogenic fluids, ambient media, and moderately heated corrosive chemicals, ensuring versatility across applications.

B. Material Composition

Valve Body & Disc: CF8M stainless steel (ASTM A351), containing 16–18% chromium, 10–12% nickel, and 2–3% molybdenum. This alloy offers superior corrosion resistance to chlorides, acids, and alkalis compared to 304 stainless steel, making it indispensable for marine, chemical, and pharmaceutical environments.
Sealing Lining: PTFE (polytetrafluoroethylene) lining on the valve body and seat, providing chemical inertness to nearly all industrial chemicals, solvents, and food-grade media. The lining thickness is precision-controlled to ensure uniform coverage and sealing performance.
Valve Stem: 17-4PH stainless steel, heat-treated for strength and corrosion resistance, with an anti-blowout design to meet safety standards.
Gaskets & Packing: PTFE or EPDM gaskets (food-grade compliant) and PTFE-impregnated packing ensure compatibility with corrosive and sanitary media.

C. Connection & Operational Features

Connection Type: Lug-type flange (ANSI B16.5), allowing for bolt-through installation that simplifies alignment and eliminates the need for pipeline rotation during valve maintenance. Lug-style connections are also ideal for retrofitting into existing systems, as they can be installed between standard flanges.
Operation Mode: Manual (lever or gear operator) as standard, with options for electric, pneumatic, or hydraulic actuation for automated control. A lever operator on a DN125 valve enables quick on-off operation, while gear operators reduce torque for ease of use in high-pressure scenarios.
Safety & Compliance Features: API 609-compliant design, with optional fire-safe and low-emission configurations. The valve is marked with permanent identification for material traceability and compliance with industry regulations.

D. Certifications & Compliance

Industry Standards: API 609, ASME B16.5, ISO 5752, ISO 9001.
Material Certifications: ASTM A351 (CF8M), ASTM A564 (17-4PH).
Regional Approvals: CE, FDA (for food-grade applications), and ATEX (optional for hazardous environments).

III. Feature Description

A. Midline (Centric) Design: Uniform Sealing & Flow Efficiency

The midline design positions the disc symmetrically within the valve body, ensuring that the disc edges make equal contact with the PTFE seat during closure. This symmetry eliminates uneven wear and provides consistent, bubble-tight sealing (ANSI/FCI Class VI) across the valve’s service life. In chemical dosing systems, for example, this design prevents costly media leakage and ensures precise flow control.

Additionally, the midline disc minimizes flow restriction, with a flow coefficient (Cv) of approximately 350 for a DN125 valve. This efficiency reduces pump energy consumption by up to 15% compared to valves with offset disc designs, making it a cost-effective choice for energy-conscious operations.

B. CF8M Stainless Steel Construction: Corrosion Resistance in Harsh Environments

CF8M (316 stainless steel) is the material of choice for applications involving chlorides, sulfuric acid, and other corrosive media. In a seawater desalination plant, for instance, a CF8M valve would maintain integrity for over 10 years, whereas a 304 stainless steel valve would corrode within 2–3 years. The alloy’s molybdenum content enhances its resistance to pitting and crevice corrosion, critical for maintaining sealing performance in aggressive environments.

The valve body and disc undergo solution annealing (heat treatment) to restore corrosion resistance after machining, ensuring the material’s full chemical and mechanical properties are retained. This process is particularly important for valves exposed to high-temperature or high-pressure corrosive media, such as in chemical reactors or pharmaceutical sterilization loops.

C. Lug-Type Flange Connection: Installation Flexibility & Maintenance Ease

Lug-type flanges offer distinct advantages over wafer or wafer-style flanges:

Bolt-Through Installation: Lug flanges are drilled to allow bolts to pass through the valve and into the pipeline flanges, simplifying alignment and reducing installation time. This is especially beneficial in confined spaces or when retrofitting into existing pipelines.
Isolation Capability: Lug valves can be installed with blind flanges on one side, enabling easy isolation for maintenance without disrupting the entire pipeline system. In a pharmaceutical batch processing line, this feature allows for quick valve replacement or inspection, minimizing downtime.
Compatibility: Lug flanges conform to ASME B16.5, ensuring compatibility with standard pipeline flanges from other manufacturers. This interchangeability reduces inventory costs and streamlines procurement for multi-vendor projects.

D. PTFE Lining: Chemical Inertness & High-Temperature Stability

PTFE’s chemical resistance is unparalleled, making it suitable for handling nearly all industrial chemicals, including strong acids (e.g., hydrochloric acid), alkalis (e.g., sodium hydroxide), and organic solvents (e.g., acetone). In a chemical plant’s acid waste treatment system, a PTFE-lined valve would resist degradation, whereas an unlined valve would corrode within weeks.

The PTFE lining also maintains its properties at temperatures up to 180℃, making it suitable for hot chemical processing or sanitary applications involving steam sterilization. Unlike rubber seals, PTFE does not degrade or swell in contact with aggressive media, ensuring long-term sealing reliability.

E. Soft-Sealed Performance: Bubble-Tight Leakage Control

The soft-sealed design, with PTFE contacting the disc, achieves ANSI/FCI Class VI leakage performance—meaning “zero leakage” for practical purposes. This is critical for applications where media containment is essential, such as in pharmaceutical manufacturing (to prevent product contamination) or hazardous chemical handling (to avoid environmental spills).

Even under cyclic operation and temperature fluctuations, the PTFE seal retains its elasticity and sealing integrity. In a water treatment plant’s disinfection loop, for example, the valve maintains leak-tight performance after 10,000+ cycles, demonstrating its durability in demanding conditions.

DN125 PN16 CF8M Stainless Steel Lug-Type Butterfly Valve with PTFE Lining Concentric Line Butterfly Valves

IV. Manufacturing Processes

A. Material Inspection & Preparation

CF8M Verification: Raw material billets undergo spectral analysis to confirm chemical composition (Cr: 16–18%, Ni: 10–12%, Mo: 2–3%) and ultrasonic testing to detect internal defects. Mechanical testing (tensile, impact) ensures compliance with ASTM A351 standards.
PTFE Lining Material Testing: PTFE sheets are tested for density, tensile strength, and chemical resistance to ensure they meet FDA and industrial-grade requirements.

B. Valve Body & Disc Machining

Casting: The valve body and disc are produced via investment casting for CF8M stainless steel, ensuring dimensional accuracy and a smooth surface finish. Castings are solution-annealed to restore corrosion resistance.
Machining: CNC turning and milling centers shape the body, disc, and lug flanges. Flange faces are machined to flatness tolerance ≤0.05mm/m and surface finish Ra ≤3.2μm for proper gasket seating. The disc’s sealing edge is precision-ground to ensure uniform contact with the PTFE lining.

C. PTFE Lining Application

Preparing the Substrate: The valve body and seat surfaces are sandblasted to create a rough texture, enhancing PTFE adhesion.
Lining Application: PTFE is applied via spray coating or press-fitting, depending on the valve size and complexity. For a DN125 valve, the lining thickness is typically 2–3mm, with a tolerance of ±0.2mm to ensure uniform coverage.
Curing: The lined valve is heated in an oven to cure the PTFE, ensuring it bonds securely to the stainless steel substrate.

D. Assembly & Testing

Component Assembly: The disc, stem, and sealing components are assembled into the valve body. The stem is torqued to ensure proper disc alignment and sealing pressure.
Hydrostatic Testing: The valve undergoes shell and seat tests at 1.5× and 1.1× rated pressure, respectively, with no leakage allowed.
Operational Testing: The valve is cycled 100 times to verify smooth operation, torque consistency, and seal integrity. Leakage is measured using a bubble counter to confirm ANSI/FCI Class VI performance.

V. Product Advantages

A. Unmatched Corrosion Resistance

CF8M stainless steel and PTFE lining combine to resist nearly all industrial chemicals, making the valve suitable for the most aggressive environments. In chemical processing plants, this translates to a service life of 8–10 years, compared to 2–3 years for unlined or lower-grade stainless steel valves.

B. Versatile Lug-Type Installation

Lug-type flanges simplify installation and maintenance, reducing downtime and labor costs. In retrofitting projects, they eliminate the need to modify existing pipelines, saving time and resources.

C. Bubble-Tight Sealing

ANSI/FCI Class VI leakage performance ensures media containment, critical for sanitary, hazardous, or costly media applications. This reduces the risk of environmental spills, product contamination, and regulatory non-compliance.

D. Energy-Efficient Flow Control

The midline design minimizes pressure drop, lowering pump energy consumption by up to 15%. For facilities with multiple DN125 valves, this results in significant annual energy savings.

E. Cost-Effective Longevity

The combination of corrosion-resistant materials and durable sealing ensures minimal maintenance and replacement costs over the valve’s service life, delivering a favorable total cost of ownership.

VI. Product Applications

A. Chemical Processing

Acid/Alkali Handling: Controls flow of sulfuric acid, hydrochloric acid, sodium hydroxide, and other corrosive chemicals in reactors, storage tanks, and transfer lines.
Solvent Recovery: Regulates flow of organic solvents (e.g., ethanol, acetone) in distillation and recycling systems, with PTFE ensuring chemical inertness.

B. Pharmaceutical & Biotechnology

API Manufacturing: Handles active pharmaceutical ingredients (APIs) and process fluids in sterile environments, with FDA-compliant PTFE and CF8M ensuring product purity.
Clean-in-Place (CIP) Systems: Controls flow of cleaning agents (e.g., nitric acid, sodium hypochlorite) in sanitary processing lines, resisting corrosion and maintaining hygiene.

C. Food & Beverage Industry

Beverage Production: Regulates flow of juices, carbonated drinks, and dairy products in bottling and processing lines, with PTFE meeting FDA food contact standards.
CIP for Food Processing: Handles cleaning solutions in meat, poultry, and dairy facilities, ensuring sanitary conditions and corrosion resistance.

D. Water Treatment & Desalination

Seawater Desalination: Controls flow of seawater and brine in reverse osmosis systems, with CF8M resisting chloride-induced corrosion.
Wastewater Treatment: Manages flow of corrosive effluents in chemical and industrial wastewater plants, preventing system degradation.

E. General Industrial Applications

Pulp & Paper: Controls flow of bleaching agents (e.g., chlorine dioxide) in paper manufacturing, with PTFE resisting chemical attack.
Marine & Offshore: Regulates seawater and ballast water in marine vessels and offshore platforms, with CF8M ensuring long-term corrosion resistance.

VII. Summary & Customization

TIANYU DN125 PN16 CF8M lug-type butterfly valve with PTFE lining delivers corrosion resistance, bubble-tight sealing, and versatile installation for chemical, pharmaceutical, and industrial applications. It combines CF8M stainless steel, PTFE lining, and midline design for reliability and efficiency, backed by API/ASME standards.

Customize with 316L/2205 duplex steel for extreme corrosion, extended temperature (-40℃~200℃) with modified PTFE, electric/pneumatic actuators, or sanitary polished finishes. Tailor to your media, pressure, and hygiene requirements for optimal performance.