API 609 ASME B16.5 Class150 NPS10 ASTM B148 C95800 Nickel Aluminum Bronze Manual Double Offshore Eccentric Flanged Butterfly Valve

I. Important Attribute Specifications

A. Material Composition

TIANYU double eccentric butterfly valve is constructed with corrosion-resistant alloy materials that are specially optimized for seawater, salt spray and chloride-containing industrial media. All pressure retaining and wear-critical components are supported by complete mill test certification and verified through strict incoming material inspection before entering the whole production workflow.

• Valve Body: ASTM B148 Grade C95800 nickel aluminum bronze casting. This copper alloy material is widely accepted for marine valve construction, with balanced mechanical strength and outstanding anti-corrosion properties. It delivers stable tensile performance and robust resistance to seawater erosion, cavitation, chloride pitting, crevice corrosion and microbiologically influenced corrosion. The casting blank is processed by shot blasting and full machining to eliminate casting risers, sand inclusions and surface flash, forming a smooth internal cavity to reduce sediment accumulation and medium scouring.
• Valve Disc: ASTM B148 C95800 nickel aluminum bronze, adopting the same alloy grade as the valve body to avoid galvanic corrosion between the disc and body. The disc is precision machined with double eccentric geometric profile, and the sealing contact surface is finely processed to cooperate with the EPDM seat, forming reliable sealing fit. The disc is fixed on the valve stem through high-strength fasteners, maintaining stable coaxiality during rotation, and avoiding local stress concentration under fluctuating pipeline pressure.
• Valve Stem: MONEL K-500 nickel-copper alloy. MONEL K-500 combines excellent tensile strength, high torsional resistance and strong corrosion resistance against brine and marine salt spray. It maintains stable mechanical performance under long-term immersion in chloride media, effectively resisting pitting and stress corrosion cracking which often occur on ordinary stainless steel in marine environments. The stem surface is precision ground, with excellent wear resistance and low friction property during repeated rotational movement.
• Seat Ring: EPDM elastomer seat. EPDM material possesses excellent aging resistance, ozone resistance, water resistance and low temperature performance, and maintains stable elastic sealing performance in fresh water, seawater and neutral aqueous media. It has good rebound characteristics, which can compensate for tiny deformation of the sealing surface, realizing bubble-tight shut-off under rated working conditions.
• Gearbox & Handwheel Assembly: Cast iron gearbox with internal worm and worm gear transmission structure. The black painted spoked handwheel is designed for manual operation, and the gear reduction structure can reduce the operating torque greatly, allowing operators to complete valve opening and closing smoothly with manual force. The gearbox is equipped with position indicator and external limit structure, which can clearly display the rotation angle of the valve disc and limit the full-open and full-close stroke.
• Fasteners: High strength alloy steel studs and nuts, with surface anti-corrosion treatment to resist coastal salt spray corrosion. The fasteners used for disc fixing adopt stainless steel material to adapt to long-term immersion in seawater environment.

B. Dimensional & Pressure-Temperature Parameters

• Nominal Size: NPS 10 inch, matching standard ASME pipeline flange dimension.
• Pressure Class: Class150, complying with ASME B16.34 pressure-temperature rating curve for alloy valves. Under ambient working temperature, the valve can bear the maximum working pressure corresponding to Class150, and the allowable working pressure will derate reasonably with the increase of medium temperature.
• End Connections: Flanged end complying with ASME B16.5 Class150 raised face standard. The flange face is machined to standard raised face profile, with evenly distributed bolt holes on standard bolt circle, convenient for installation and matching with ANSI standard pipeline flanges.
• Face-to-Face Dimension: Fully compliant with API609 and ASME B16.10 standard requirements for butterfly valves, realizing interchangeability with butterfly valves of other brands that meet the same industry specification.
• Flow Path: Full bore design, the disc can be rotated out of the main flow channel when fully opened, minimizing fluid pressure drop and medium turbulence, reducing pumping energy consumption in large flow pipeline systems.
• Eccentric Structure: Double eccentric design, the stem axis deviates from the sealing surface of the seat and the centerline of the valve body bore. This geometric feature makes the disc separate from the seat immediately after the valve starts to rotate, reducing the friction and abrasion between disc and seat during opening and closing cycles.
• Temperature Range: The continuous service temperature range is determined by the performance limit of EPDM seat material, suitable for medium and low temperature aqueous media, and can adapt to temperature fluctuation of seawater circulating pipeline.
• Media Compatibility: Seawater, brackish water, brine, fresh cooling water, fire-fighting water and neutral aqueous medium. It is applicable for non-oxidizing fluid service, and not recommended for strong oxidizing acid and alkali media.

C. Operational Performance Parameters

• Sealing Performance: EPDM soft seat sealing, meeting API 598 leakage acceptance criteria for butterfly valves. The elastic deformation of EPDM seat can compensate for the machining tolerance and tiny pipeline deformation, achieving bubble-tight shut-off for liquid service.
• Shell Test Pressure: According to API 598 test specification, the valve body cavity is pressurized to the specified shell test pressure, and hold pressure for required duration, no weeping, sweating or permanent deformation is allowed on pressure retaining components.
• Seat Test Pressure: Apply test pressure from upstream side when the valve is fully closed, inspect the downstream side for medium leakage, and repeat the test in reverse direction to verify bidirectional sealing capacity.
• Operating Torque: The worm gear reduction structure greatly reduces manual operation torque. Operators can complete valve stroke operation by rotating handwheel, no extra heavy-duty tools are required under rated working pressure.
• Cycle Life: Designed for frequent on-off adjustment and isolation service. The double eccentric structure reduces seat friction loss, extending the service life of elastomer seat under repeated opening and closing cycles.
• Position Indication: Visual angle indicator mounted on gearbox top, directly reflecting the real-time rotation position of valve disc for field operators to judge valve opening state.
• Anti-Blowout Stem Structure: The valve stem is equipped with anti-blowout shoulder structure, which can lock the stem inside the valve body when internal pipeline pressure surges, preventing stem ejection accident under abnormal pressure condition.

D. Certifications & Compliance

• Design Standard: API 609 Butterfly Valves, ASME B16.5 Pipe Flanges and Flanged Fittings, ASME B16.10 Face-to-Face Dimension of Valves, ASME B16.34 Valve Pressure-Temperature Rating.
• Testing Standard: API 598 Valve Inspection and Testing.
• Material Standard: ASTM B148 for nickel aluminum bronze casting, MONEL K-500 for valve stem.
• Marking Standard: MSS SP-25 Standard Marking for Valves, Flanges and Fittings.
• Quality Management: ISO9001 certified manufacturing management system.
• Material Documentation: EN10204 3.1 material test certificates can be provided with each valve, recording chemical composition and mechanical property data of all pressure-bearing alloy components.

II. Feature Description

A. Double Eccentric Sealing Geometry

The core feature of this TIANYU butterfly valve is the double eccentric structural layout, which is the key difference compared with concentric and single eccentric butterfly valves. Two offset relationships are adopted in the structural design: the valve stem axis deviates from the center plane of the disc sealing surface, and the stem axis also deviates from the centerline of the valve body bore. When the valve starts to rotate from closed position, the disc can quickly separate from the seat ring without sliding friction between disc edge and seat surface. This design avoids continuous scraping and abrasion of elastomer seat during every opening and closing movement, greatly prolonging the service life of EPDM seat and reducing the maintenance frequency of seat replacement.

In large-diameter seawater pipeline systems, frequent valve operation will cause wear of the sealing pair for concentric butterfly valves, and the elastomer seat is easy to age and fail under repeated friction. The double eccentric structure eliminates sliding friction between disc and seat in the whole rotation stroke except the very small angle near full closed position. When the valve is fully closed, the disc presses evenly on the EPDM seat under pipeline pressure, forming reliable elastic sealing contact. When the pipeline generates thermal expansion, contraction or slight flange misalignment caused by foundation settlement, the EPDM seat can absorb tiny deformation through elastic rebound, maintaining stable sealing performance without permanent sealing damage. The disc contour is precisely machined according to the double eccentric cam curve, so that the contact pressure distribution on the seat is uniform, avoiding local pressure overload which may cause seat extrusion damage.

B. Nickel Aluminum Bronze Body and Disc Construction

The valve body and disc are cast from ASTM B148 C95800 nickel aluminum bronze alloy, which is the preferred alloy material for marine seawater valve products. Nickel aluminum bronze has no zinc element in alloy composition, so there is no risk of dezincification failure which is common in ordinary brass materials in saline environment. This alloy maintains high mechanical strength under long-term immersion in seawater, and can resist pitting corrosion, crevice corrosion and microbiologically influenced corrosion induced by marine organisms. In coastal salt spray atmosphere, the alloy surface will form a stable protective oxide patina, which can slow down the corrosion rate of external valve components, and there is no need for complex anti-corrosion coating maintenance on the outer surface.

The casting adopts resin bonded sand casting technology to guarantee dimensional stability and good surface quality of casting blank. The inner cavity of valve body is fully machined to remove casting defects and rough surface, reducing the dead zone where marine sediment and biological attachments accumulate. The flange end is processed to ASME B16.5 raised face specification, and the bolt holes are processed on standard bolt circle, which can be matched with standard ANSI flanges. The valve body is permanently marked with TIANYU logo, nominal size, pressure class and material grade in accordance with MSS SP-25 marking specification, realizing permanent product traceability.

C. MONEL K-500 Valve Stem and Anti-Blowout Protection

The valve stem adopts MONEL K-500 nickel-copper alloy material. MONEL K-500 has excellent combination of high tensile strength and corrosion resistance, which can resist stress corrosion cracking and pitting corrosion in seawater and brine media. In offshore and coastal environments, chloride ions in seawater and salt spray will cause pitting damage to ordinary stainless steel stems, while MONEL K-500 can maintain stable performance under long-term exposure to chloride medium. The stem surface is precision ground to reduce friction with the bushing during rotation, and the surface is free of machining burrs and micro cracks that may induce stress corrosion.

The anti-blowout shoulder is integrated on the valve stem. This shoulder structure is clamped inside the valve body cavity after assembly. When the pipeline internal pressure suddenly rises, the shoulder will bear the upward axial force, preventing the stem from being ejected out of the valve body, which effectively improves the safety performance of the valve under abnormal working conditions. The stem and disc are connected by high-strength pin structure, which can transmit torque stably without relative rotation slip between stem and disc. The bushing between stem and valve body is made of corrosion-resistant alloy material, which reduces rotation friction and isolates galvanic corrosion between stem and bronze body.

D. EPDM Elastomer Seat and Worm Gear Handwheel Actuation

The replaceable EPDM elastomer seat ring is installed in the valve body seat groove. EPDM material has outstanding resistance to water aging, ozone and ultraviolet aging, and can maintain stable elastic performance in long-term contact with seawater. The seat ring is fixed in the valve body through mechanical clamping structure, which can be disassembled and replaced on site without removing the whole valve from the pipeline. When the valve is closed, the disc presses on the seat ring, and the elastic deformation of EPDM fills the tiny gap between disc and seat, realizing bubble-tight sealing. The seat material has good low temperature resistance, and will not harden and lose elasticity rapidly under low ambient temperature in coastal areas.

The manual operation system adopts worm and worm gear reduction gearbox, matched with cast iron handwheel. The worm gear transmission converts the rotation of handwheel into the rotation torque of valve stem, and the reduction ratio reduces the manual operation torque, making the operation of large diameter NPS10 butterfly valve labor-saving. The gearbox is equipped with external mechanical limit screws, which can limit the rotation stroke of disc at full open and full closed position, preventing over rotation damage of valve internal components. The visual position indicator on the top of gearbox rotates synchronously with the valve stem, and the pointer points to the scale mark, which can directly display the opening percentage of the valve disc for field operators to read the valve state quickly.

E. ASME B16.5 Raised Face Flanged End Connection

Both ends of the valve adopt ASME B16.5 Class150 raised face flanged connection. The raised face provides stable compression area for flange gasket, and the flange thickness and hub structure are designed to bear the load under Class150 pressure rating without plastic deformation. Flanged connection is widely selected in marine and offshore large diameter pipeline systems. It supports convenient disassembly for valve maintenance and seat replacement, and avoids the crevice corrosion risk of threaded connection. Plastic protective caps are installed on flange sealing faces during transportation, to prevent scratch and impact damage of machined raised face surface in transit and storage.

III. Manufacturing Process & Product Advantages

A. Raw Material Procurement & Verification

TIANYU purchases nickel aluminum bronze castings and MONEL K-500 alloy bars from qualified alloy foundries and metal material suppliers, and all raw materials are accompanied by official mill test reports meeting EN10204 3.1 standard. Before casting blanks and alloy bars enter the machining workshop, TIANYU incoming inspection laboratory carries out strict verification work for each batch of raw materials.

• Spectrometric chemical composition analysis is carried out to verify that the element content of nickel aluminum bronze and MONEL K-500 is within the range of corresponding material specifications.
• Visual inspection and dye penetrant non-destructive inspection are performed on bronze casting blanks to detect surface cracks, shrinkage porosity and sand inclusion defects which may affect pressure bearing integrity.
• Mechanical performance sampling test is conducted on raw material samples, including tensile strength, yield strength and elongation test, to confirm that the mechanical properties of alloy materials meet design requirements. Any raw material batch failing the inspection items will be rejected and returned to the supplier, and will not flow into the subsequent machining and assembly process.

B. Precision Machining

All pressure-bearing components and sealing related parts are processed on CNC machining centers and CNC lathes with high machining precision.

• Valve Body Machining: CNC equipment processes flange face, bolt holes, body inner cavity and seat installation groove. The flatness and surface roughness of flange raised face are strictly controlled to ensure uniform gasket compression during pipeline installation. The seat groove is machined according to tolerance requirement to ensure that EPDM seat can be installed tightly without gap or extrusion deformation.
• Valve Disc Machining: The disc blank is processed to double eccentric cam profile, the sealing edge of disc is finely ground to form smooth continuous sealing contour, matching with EPDM seat ring. The pin hole for stem connection is reamed to precise tolerance to guarantee coaxiality of disc and stem assembly.
• Valve Stem Machining: MONEL K-500 bar is processed into stem blank, and the outer circle surface is precision ground. The pin groove and anti-blowout shoulder are machined to the design dimension, and the surface is polished to reduce friction during rotation.
• Gearbox and Bushing Machining: The cast iron gearbox blank is machined to install worm, worm gear and bearing components, ensuring stable meshing of transmission pair and low rotation noise. The corrosion-resistant bushing is processed to fit the outer diameter of valve stem, forming low-friction rotating pair.

After machining, all parts go through ultrasonic cleaning to remove metal chips, cutting fluid and residual machining debris. The cleaned components are classified and protected to avoid scratch on sealing surface before assembly.

C. Assembly & Pressure Testing

After cleaning and inspection of all machined parts, the assembly work is carried out in a dust-controlled assembly workshop, following standardized assembly operation procedure.

• Install EPDM seat ring into the valve body seat groove, check the clamping state of seat ring to ensure no distortion or dislocation.
• Put the valve stem and bushing assembly into the valve body, install the disc and connect the stem and disc with fixing pin, check the rotation flexibility of disc in the valve body cavity.
• Assemble the worm gear box on the top of valve body, adjust the meshing clearance of worm and worm gear, install the handwheel and position indicator, debug the mechanical limit structure of full open and full close stroke.
• Rotate the handwheel repeatedly for multiple stroke test, check whether the disc rotates smoothly, without jamming or abnormal friction noise.

All finished valves are required to carry out pressure test in accordance with API598 specification.

• Shell Hydrostatic Test: Fill the valve body cavity with test medium, pressurize to the specified shell test pressure and hold pressure for required time. Inspect the whole valve body, flange and stem penetration position for weeping, sweating and permanent deformation.
• Seat Hydrostatic Test: Close the valve disc completely, apply test pressure to upstream side, observe the downstream side for leakage through sealing pair, and reverse the test direction to verify bidirectional sealing ability.
• Functional Stroke Inspection: Under pressure holding state, rotate handwheel to complete full open and full close operation, check the rotation torque change and position indicator feedback.

Once the valve fails pressure test or functional inspection, disassemble the valve to find the root cause of failure, replace damaged parts or rework sealing surface, then carry out pressure test again. Only valves passing all test items can enter the final marking and packaging process.

D. Product Advantages

• Low Seat Wear and Long Service Life: The double eccentric structure eliminates sliding friction between disc and EPDM seat in most of the rotation stroke, greatly reducing wear of elastomer seat. This advantage is especially prominent for large diameter butterfly valves which need frequent switching operation in seawater pipeline, lowering the frequency of seat replacement and reducing long-term maintenance cost.
• Excellent Chloride Corrosion Resistance: The combination of ASTM B148 bronze body and disc plus MONEL K-500 stem provides multi-level anti-corrosion protection in seawater and salt spray environment. The alloy material can resist pitting and microbiological corrosion, and the service life is far longer than carbon steel and ordinary stainless steel butterfly valves in marine service.
• Bubble-Tight Soft Sealing Performance: EPDM elastomer seat can compensate for tiny machining deviation and pipeline deformation, achieving reliable bubble-tight shut-off for liquid medium. It is suitable for pipeline systems requiring strict isolation to prevent seawater leakage.
• Labor-Saving Manual Operation: Worm gear reduction mechanism reduces operation torque of large size NPS10 butterfly valve. Operators can realize valve opening and closing only by rotating handwheel manually, no pneumatic, hydraulic or electric actuator is required, adapting to remote field sites without power supply.
• Visual Position Feedback: The gearbox mounted position indicator can directly display valve opening degree, helping field operators quickly judge valve state, reduce human operation error and improve system operation safety.
• Replaceable Seat Design: The EPDM seat can be replaced on site without removing the valve from pipeline. When seat aging occurs after long time operation, maintenance technicians can complete seat replacement with simple tools, shortening pipeline downtime.
• Global Standard Compatibility: API609, ASME B16.5 and API598 compliance make the valve widely accepted by shipyards, EPC contractors and classification societies. Complete material test documents can be provided for project approval and site acceptance.
• High Safety Anti-Blowout Stem: Integrated anti-blowout shoulder structure of MONEL K-500 stem prevents stem ejection under unexpected pipeline pressure surge, improving equipment safety in offshore and marine fluid pipeline.

IV. Product Applications

A. Marine & Shipbuilding Industry

TIANYU double eccentric butterfly valves are widely applied in various types of vessels, including bulk carriers, container ships, offshore support vessels and floating production units. Typical application systems include ship seawater cooling pipeline, ballast water pipeline, fire water main system, deck washing pipeline and bilge water treatment pipeline. Large diameter NPS10 butterfly valve is suitable for main pipeline branch isolation and flow regulation of seawater system on board. The C95800 bronze alloy can resist long-term seawater immersion and deck salt spray corrosion, and the double eccentric structure adapts to the vibration and thermal cycle of ship pipeline. Shipyards can obtain complete material certificates and test reports, which meet the audit requirements of major marine classification societies.

B. Offshore Oil & Gas Facilities

On offshore fixed platforms, FPSO and other offshore topside facilities, this butterfly valve is used for seawater lift pump outlet pipeline, firewater deluge system, cooling heat exchanger isolation and utility water pipeline control. The offshore environment is featured with high humidity, salt aerosol and alternating splash immersion condition. The nickel aluminum bronze body and MONEL K-500 stem can withstand this harsh corrosive environment. The manual worm gear operation is suitable for hazardous area without electric power supply, and the mechanical limit and position indicator help operators to complete safe valve operation on platform topside.

C. Seawater Desalination Plants

In seawater desalination projects including reverse osmosis and multi-stage flash desalination process, raw seawater intake pipeline, pre-treatment filter system, backwash pipeline and brine discharge pipeline need large-diameter isolation and regulating valves. TIANYU Class150 double eccentric butterfly valve serves for these pipeline systems. The full bore design reduces pressure drop of high flow seawater transmission, saving the energy consumption of water pump unit. EPDM soft seat realizes tight shut-off for raw seawater containing suspended sediment and marine organism, and the replaceable seat structure reduces maintenance workload of desalination plant.

D. Coastal Power Generation Plants

Coastal thermal power plants and combined cycle power stations use seawater as circulating cooling medium for condenser cooling loop. This butterfly valve is installed on cooling water main pipeline, condenser isolation branch and fire protection water system of coastal power plant. The valve can run stably under long-term standby and intermittent operation condition. The alloy material resists corrosion of circulating seawater and salt spray in coastal power plant, and the double eccentric structure reduces seat wear caused by frequent switching of cooling water pipeline.

E. Coastal Industrial & Municipal Water System

Coastal chemical factories, salt production plants, coastal municipal waterworks and aquaculture water supply systems adopt this butterfly valve for brine delivery, seawater intake and neutral aqueous medium pipeline isolation. The nickel aluminum bronze material can resist chloride corrosion in coastal atmosphere and process fluid. The manual worm gear handwheel operation is suitable for outdoor unattended pump station and remote water pipeline, and the bubble-tight sealing reduces medium leakage risk of water pipeline system.

TIANYU ASTM B148 C95800 double eccentric flanged butterfly valve with MONEL K-500 stem and EPDM seat is a reliable large diameter isolation and flow regulating valve for seawater and chloride-containing medium. Built to API609, ASME B16.5 and API598 standards, this manual worm gear operated butterfly valve combines double eccentric low-wear sealing design, high anti-corrosion alloy construction and convenient on-site maintenance function. It has become the preferred valve product for marine, offshore, desalination, coastal power and coastal industrial piping projects where reliable shut-off performance and excellent chloride corrosion resistance are the core requirements.

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