Ningbo Ruican supplies investment cast triple-offset butterfly valve discs to valve OEMs and engineering contractors in duplex 2205 and CF8M stainless steel, covering the laminated seal seat geometry, conical sealing surface and tapered hub bore in a single near-net-shape casting. Duplex 2205 combines roughly twice the yield strength of CF8M with a PREN above 34, which allows a lighter disc section while resisting chloride pitting and stress corrosion cracking in seawater and process duty. All sealing geometry is finish machined in-house on CNC turning and multi-axis milling equipment, so discs arrive ready for seat assembly, lapping and shell testing.
Key Features
- Laminated seal seat geometry — the cast seat retaining pocket and machined groove accept a laminated metal and graphite seal ring, held by a bolted or clamped retainer without distorting the disc body.
- Machined conical sealing surface — the triple-offset cone angle is machined to ±0.05 degrees with a surface finish of Ra 0.8 µm or better, then lapped to support zero-leakage seating.
- Tapered hub bore — taper-matched bore machined to H7 with seat-to-bore runout held to 0.03 mm; keyway, spline and cylindrical stem bore variants supplied to the stem drawing.
- Duplex 2205 strength and corrosion resistance — high yield strength permits thinner disc vanes and lower operating torque, while high pitting resistance handles chloride, seawater and sour service.
- Near-net-shape investment casting — hollow hub and balanced vane geometry cast close to final form, reducing machining allowance, material waste and lead time against fabricated or fully machined blanks.
- Documented material verification — positive material identification on every disc, with ferrite measurement and mechanical certification for duplex grades supplied per heat lot.
Materials & Heat Treatment
| Material | Standard | Condition | Application note |
|---|---|---|---|
| Duplex stainless steel 2205 | ASTM A995 Grade 4A (UNS J92205) / EN 1.4470 | Solution annealed at 1120 C minimum, water quenched | Default grade for seawater, chloride-bearing and sour process duty; PREN above 34 |
| Stainless steel CF8M | ASTM A351 CF8M (cast 316 / EN 1.4401 equivalent) | Solution annealed, water quenched | General chemical, marine and process duty; castable alternative to wrought 316 |
| Super duplex 2507 (optional) | ASTM A995 Grade 5A (UNS J93380) | Solution annealed, water quenched | Higher pitting and crevice resistance for aggressive chloride and hot seawater service |
| Stainless steel CF3M (optional) | ASTM A351 CF3M (cast 316L equivalent) | Solution annealed | Low-carbon grade for welded assemblies and post-weld service without sensitisation |
| Hardfacing / seal overlay (optional) | Stellite 6 or customer-specified alloy | As-welded, finish machined and lapped | Build-up on the conical sealing face for high-cycle, high-temperature or erosive service |
Specifications
| Parameter | Value |
|---|---|
| Casting process | Silica sol investment casting (lost wax); water glass route offered for larger, cost-driven part families |
| Casting weight range | 0.8 kg – 65 kg per piece (typical DN100-DN900 triple-offset disc 3 – 25 kg) |
| Dimensional tolerance | ISO 8062 CT4-CT6 (silica sol process); CT7-CT8 available via the water glass route |
| Minimum wall thickness | 4 mm nominal on disc vanes, thinner locally after engineering review |
| As-cast surface roughness | Ra 6.3 – 12.5 µm, improved to Ra 0.8 µm or better on the conical sealing face |
| Machining capability | CNC turning plus 4-axis and 5-axis machining centres; conical seat angle ±0.05 degrees, seat-to-bore runout 0.03 mm, tapered hub bore to H7, stem keyway and retainer threads machined to drawing |
| Pressure and seat testing | Shell and seat test support to API 598 / ISO 5208 leakage class as specified by the valve design |
| Inspection and testing | CMM dimensional layout, positive material identification, ferrite measurement on duplex grades, dye penetrant, ultrasonic testing where specified |
| MOQ | 100 pieces per part number for series production; prototype and single-piece validation runs negotiable |
| Tooling lead time | 20-30 days for wax die, core tooling and first article samples |
| Production lead time | 35-50 days after sample approval, depending on size, volume and machining content |
Applications
- Chemical and petrochemical process lines requiring zero-leakage shut-off on corrosive media
- Marine seawater cooling, ballast and bilge systems on commercial vessels and offshore units
- Oil, gas and product pipeline isolation valves and metering skids
- Desalination and water treatment plants handling chloride-rich and abrasive water
- Power generation cooling water, flue gas desulphurisation and auxiliary steam service
Product Gallery
Quality & Documentation
Ningbo Ruican operates an IATF 16949 certified quality management system, and valve disc programmes run under documented process discipline: controlled melting practice, solidification simulation before tooling release, defined gating and feeding to keep the sealing zones sound, and full heat-lot traceability from charge material through heat treatment to the packed part.
Process selection — silica sol vs. water glass. Silica sol investment casting is the recommended route for triple-offset butterfly valve discs because the laminated seat pocket, conical sealing face and tapered hub bore demand CT4-CT6 accuracy, clean near-net-shape vane geometry and high surface integrity. Water glass casting is offered for larger, low-pressure disc families and simpler geometries where tolerance is less demanding and unit cost is the priority. The process route is confirmed with the customer at quotation stage against drawing tolerance, annual volume and total cost targets.
Documentation supplied:
– EN 10204 3.1 material certificates covering chemical analysis, mechanical properties, solution annealing condition, hardness and ferrite content for duplex grades (EN 10204 3.2 certification arranged on request)
– First Article Inspection (FAI) dimensional reports against ballooned drawings, with CMM data for every drawing-numbered characteristic including cone angle and runout
– Non-destructive testing records: dye penetrant on machined sealing faces, ultrasonic testing and positive material identification results retained per batch
– Heat-treatment charts with recorded solution annealing temperature and quench data for every duplex heat lot
– Third-party inspection options including SGS, BV, TUV and DNV, with witness testing, shell and seat test attendance and document review available
Why Ningbo Ruican
- 17 years of casting experience supplying valve, marine and industrial components to export customers worldwide.
- One-stop casting plus CNC machining in a single facility, protecting cone angle, seat runout and hub bore datum integrity while shortening lead time and removing split-vendor risk.
- OEM and ODM programmes from drawings or samples, covering tooling design, casting simulation, prototyping, validation lots and series production.
- IATF 16949 certified quality system, delivering documented process control, full traceability and repeatable series delivery performance.
Request a Quote
Send your drawings to Wendy She — sales@cnsandcasting.com | WhatsApp +86-13777124360
