In marine, offshore, petrochemical, chemical, and water treatment industries, valves ensure safety, flow control, and plant reliability. Although the valve body and actuator often receive the most attention, the valve disc—the moving component that directly interacts with the flow medium—is the true heart of valve performance.
Whether isolating hydrocarbons in an oil refinery, regulating seawater on a container vessel, or managing corrosive fluids in a chemical plant, the disc determines:
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Flow control accuracy
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Pressure and temperature tolerance
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Erosion, corrosion, and cavitation resistance
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Valve longevity and maintenance intervals
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Ability to meet regulatory codes (ASME, API, ISO, DNV, LR)
As a trusted marine and industrial valve stockist in Singapore, Aik Soon Hardware provides customers with a wide range of valve types and disc configurations. This guide provides an in-depth technical breakdown of every major disc design, its mechanism, advantages, limitations, materials, and selection framework.
This is one of the most comprehensive valve disc guides available online, designed for engineers, plant operators, and procurement specialists seeking technical clarity.
1. What Is a Valve Disc? (Technical Definition)
A valve disc is the movable closure element that:
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Blocks flow
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Modulates flow
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Allows flow
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Prevents reverse flow
Depending on valve design, the disc may:
Disc geometry defines:
Disc failure can lead to total valve failure—making correct design and material selection critical.
2. Complete List of Valve Disc Types and How They Work
Below are ALL major disc types across global industrial valve categories, including advanced and specialty designs.
A. Gate Valve Disc Types
Gate valves use a “gate” that moves up/down to isolate flow. They are not suitable for throttling.
2.1 Solid Wedge Disc
Most common gate disc.
Design
Single-piece wedge disc, tapered.
Mechanism
Seals against angled seats.
Advantages
Where Used
2.2 Flexible Wedge Disc
A solid disc with cut-outs to allow slight flexibility.
Advantages
Applications
2.3 Split Wedge / Parallel Discs
Two-piece disc with spring or pressure balancing.
Advantages
Applications
B. Globe Valve Disc Types
Globe valves are used for throttling and flow control.
2.4 Plug-Type Disc
Key Features
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Conical/tapered plug
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Most common globe disc
Advantages
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Predictable flow control
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Durable in erosive flow
Applications
2.5 Needle Disc
Design
Long, tapered disc resembling a needle.
Advantages
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Ultra-fine throttling
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Ideal for calibration
Applications
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Metering
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Sampling
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Instrumentation lines
2.6 Composition Disc
Design
Metal disc with soft insert (rubber, PTFE).
Advantages
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Tight sealing
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Gentle on seat
Applications
C. Ball Valve Discs
Ball valves use a spherical disc with a bore.
2.7 Floating Ball Disc
Ball “floats” slightly to press against seat.
Advantages
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Tighter sealing
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Simple design
Applications
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Cargo oil systems
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Fuel transfer
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Compressed air lines
2.8 Trunnion-Mounted Ball Disc
Ball held in place by trunnions (shafts).
Advantages
Applications
D. Butterfly Valve Discs
2.9 Concentric Disc
Standard circular disc seated centrally.
Applications
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Seawater
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Chilled water
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HVAC
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Ballast systems
2.10 Double-Offset Disc
Shaft offset from disc center and valve center.
Advantages
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Less seat rubbing
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Higher cycle life
Applications
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Firewater
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High-flow pipelines
2.11 Triple-Offset (TOV) Disc
Seat is cone-shaped; disc rotates eccentrically.
Advantages
Applications
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Gas plants
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Refineries
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High-temperature service
E. Check Valve Disc Types
2.12 Swing Disc
Mechanism
Disc swings open with flow; closes on backflow.
Best For
Applications
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Bilge discharge
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Cooling water lines
2.13 Piston Disc (Lift Check)
Mechanism
Disc lifts vertically via flow pressure.
Applications
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High-pressure oil
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Steam lines
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Boiler feedwater
2.14 Dual-Plate Disc
Two half discs hinged to a central shaft.
Advantages
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Lightweight
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Minimal pressure drop
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Reduces water hammer
Applications
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Ballast systems
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Refinery cooling systems
F. Other Specialty Valve Discs
2.15 Diaphragm Disc
Flexible diaphragm acts as disc.
Applications
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Chemical injection
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Highly corrosive fluids
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Water treatment plants
2.16 Pinch Valve Disc
Elastomer sleeve pinched to stop flow.
Applications
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Slurry
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Sewage
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Mining systems
2.17 Knife Gate Disc
Sharp-edged disc cuts through solids.
Applications
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Wastewater
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Pulp & paper
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Slurry pipelines
3. Valve Disc Materials — Detailed Engineering Breakdown
Material choice directly affects safety, corrosion resistance, and lifespan.
A. Metals
3.1 Bronze / Gunmetal
Properties
Applications
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Marine seawater valves
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Firemain
3.2 Stainless Steel (SS304, SS316, SS316L)
Properties
Applications
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Chemical plants
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Fuel handling systems
3.3 Duplex / Super Duplex
Properties
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High chloride resistance
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High mechanical strength
Applications
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Offshore oil & gas
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High-salinity seawater
3.4 Alloy Steel (ASTM A217 WC9 / Chrome-Moly)
Applications
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High-temperature steam
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Hydrogen service
3.5 High-Nickel Alloys (Hastelloy, Inconel)
Applications
B. Soft Seating Materials (for disc inserts)
3.6 PTFE (Teflon)
Chemical resistant, low friction.
3.7 EPDM / NBR
For water, wastewater, and mild chemicals.
3.8 Viton
For hydrocarbon & chemical compatibility.
4. Valve Disc Failure Modes
Understanding failure helps in selection.
4.1 Erosion
Occurs in high-velocity flow or abrasive fluids.
4.2 Corrosion
Due to chemical attack or chlorides.
4.3 Cavitation
Causes pitting and metal fatigue.
4.4 Thermal Shock
Rapid temperature changes distort the disc.
4.5 Seat Wear
Especially in throttling applications.
5. How to Select the Right Valve Disc (Engineering Framework)
Here is a complete, industry-standard selection flow:
5.1 Match Disc Type to Valve Function
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Isolation: Wedge, ball, triple-offset butterfly
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Throttling: Plug, globe, needle
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Backflow Prevention: Swing, dual-plate, piston
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Slurry: Knife gate, pinch
5.2 Match Disc Material to Fluid
| Fluid |
Recommended Materials |
| Seawater |
Bronze, Duplex |
| Hydrocarbons |
Stainless Steel, Alloy Steel |
| Acids |
PTFE, Hastelloy |
| Slurry |
Rubber-lined, stainless |
5.3 Consider Operating Conditions
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Pressure class (150, 300, 600, etc.)
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Temperature (cryogenic to 600°C+)
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Required shutoff class (API 598 leakage rates)
5.4 Evaluate Environmental Factors
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Marine corrosion
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Salt spray
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Chemical exposure
5.5 Maintenance & Lifecycle
Conclusion
Valve discs are the most critical internal component for ensuring safe, reliable, and long-lasting flow control in marine, offshore, petrochemical, and industrial applications. With a vast range of disc designs—from wedge and plug to ball, butterfly, and diaphragm—engineers must carefully evaluate operating conditions, fluid characteristics, pressure/temperature limits, and classification requirements.
Aik Soon Hardware supports Singapore and global clients with high-quality valves and components built to withstand demanding environments. Whether you’re sourcing valves for a refinery, chemical plant, FPSO, or marine vessel, our expertise ensures you receive the right disc type and material for optimal performance and safety.