V-Segment Ball Valve — CF8M Body (SS316), Stellite Seat, Modulating Control up to 350 °C

The V-segment ball valve is the benchmark modulating control component for the industry's toughest fluids: fiber slurries, abrasive solid-laden slurries, viscous fluids with suspended particles, and high-temperature services where conventional globe valves fail due to wear, fouling, or thermal limitations. Its V-segment provides an equal percentage control characteristic with a shearing effect upon closing — fibers and solids are cut by the V-segment's edge instead of being trapped between the seat and the ball.

The V-segment — why it's different from a standard ball

The standard ball valve has a spherical ball with a circular bore designed for ON/OFF operation, not for proportional modulating control. Its effective rangeability for proportional control is 3:1 to 5:1. The V-segment ball is different in three fundamental aspects:

• Equal percentage control characteristic with 50:1 to 100:1 rangeability: The V-profile generates a predictable relationship between the opening angle and the flow rate — similar to the equal percentage characteristic of a globe valve, but in a quarter-turn format. The PID controller can precisely follow this characteristic across the entire opening range.
• Shearing effect upon closing: The sharp edge of the V-segment cuts fibers, particles, and solids that remain in the flow path when the valve closes — preventing the fouling that would impede the tight shut-off of a standard ball. This is why the V-segment ball is the first choice for cellulose pulp, slurries with fibers, and any fluid where debris would block closure.
• Stability in intermediate positions: It operates stably between 5° and 90° of opening without the cavitation and vibration that a standard ball would generate in partial opening. This stability is essential for the PID control loop to reach and maintain the setpoint without oscillations.

Stellite (STL) Seat — hardness for severe service

Stellite (cobalt-chromium-tungsten alloy) is the most wear-resistant seat material available in standard industrial valves:

• Hardness: 40–55 HRC — with greater toughness and impact resistance to particles than hard ceramic coatings.
• Abrasion Resistance: Excellent resistance to wear from abrasion, erosion, and adhesive wear — the dominant mechanism in fluids with solids and slurries.
• High-Temperature Corrosion Resistance: Stellite's chromium and cobalt content provides oxidation and corrosion resistance up to temperatures where SS316 would begin to degrade.
• Impact Resistance: Unlike brittle ceramic coatings that chip upon impact, Stellite better resists impacts from large particles without fracturing.

Ball with hard chrome coating (HCr)

The V-segment ball has a hard chrome coating (HCr) over a CF8M (SS316) substrate:

• Hardness: 65–70 HRC — the highest surface hardness available to resist scratching and wear in each operating cycle.
• Surface Finish: Ra ≤ 0.2 µm — mirror finish that ensures effective metal-to-metal seal with the Stellite seat.
• Abrasion Resistance: Hard chrome is the industry standard coating for surfaces subject to abrasive wear — hydraulic rods, rolling mill rollers, compressor cylinders.

High Bracket — actuator protection in severe services

• Actuator Thermal Isolation: In high-temperature services (150–350 °C), the high bracket creates the necessary distance between the hot body and the actuator. Without a high bracket, a standard actuator mounted directly on the body would be damaged in weeks in high-temperature service.
• Protection against splashes and vapors: In slurry and pulp services, the high bracket moves the actuator away from the area of greatest exposure, protecting it from corrosion, mechanical jamming, and splash damage.
• Improved Mechanical Alignment: The longer bracket reduces bending stresses on the stem and improves alignment between the valve stem and the actuator shaft — reducing coupling wear and improving positioning repeatability.

Two temperature configurations available

Standard Configuration — up to 180 °C

• O-ring: Viton (FKM)
• Stem Packing: RTFE
• Operating Temperature: -29 °C to +180 °C
• Application: Slurries and pulps at moderate temperatures, viscous fluids, corrosive fluids without high temperatures

Very High Temperature Configuration — up to 350 °C

• O-ring: Expanded graphite
• Stem Packing: Expanded graphite
• Operating Temperature: -29 °C to +350 °C
• Application: High-temperature steam, thermal oils, elevated temperature process fluids

V-segment ball vs. globe valve — when to choose each

Equal percentage flow characteristic and Cv coefficient

Automation — 4–20 mA positioner for modulating control

The V-segment ball is a modulating control component — its value lies in operating at precise intermediate positions, not in ON/OFF mode. To take advantage of its control capability, the assembly must include:

• Pneumatic quarter-turn actuator + 4–20 mA electro-pneumatic positioner: Standard configuration for modulating control. The positioner receives the signal from the PID controller and precisely positions the V-segment. For high-temperature services, the pneumatic actuator with a high bracket is the first choice — no electronic components exposed to the heat of the body.
• 4–20 mA modulating electric actuator: For installations without a compressed air network. The electric actuator with a 4–20 mA signal positions the V-segment directly without an additional positioner. Verify temperature compatibility at the installation point — the high bracket helps to isolate the actuator from the heat of the body.
• HART digital positioner: For control loops with online diagnostics, remote calibration, and communication with DCS or SCADA systems. Allows monitoring the actual valve position, detecting seat wear, and performing partial stroke tests (PST) without interrupting the process.

Technical Specifications

• Type: V-segment ball, quarter-turn
• Body Design: Two-piece body
• Body Material: CF8M (ASTM A351) — cast SS316 equivalent
• V-Segment (ball): CF8M (SS316) with hard chrome coating (HCr)
• Seat: SS316 + Stellite (STL) — metal-to-metal seal
• Stem: SS316
• O-ring: Viton up to 180 °C · Expanded graphite up to 350 °C
• Stem Packing: RTFE up to 180 °C · Expanded graphite up to 350 °C
• Connection: ANSI 150 RF flanges — face-to-face ASME B16.10
• Flange Drilling: ASME B16.5
• Nominal Pressure: ANSI 150 — up to 290 psi (20 bar) at 38 °C
• Operating Temperature: -29 °C to +180 °C (standard) · -29 °C to +350 °C (high temperature)
• Flow Characteristic: Equal percentage — effective rangeability 50:1 to 100:1
• Actuator Mounting: ISO 5211
• Bracket: High — thermal insulation and actuator protection included

Main Industries and Applications

• Pulp and Paper: Control of cellulose pulp in digesters, washers, refiners, and distribution systems. Cellulose pulp (2–15% solids, fibers up to 3 mm) is the fluid for which the V-segment ball was originally developed. Control of black liquor, white liquor, and bleaching fluids in the Kraft process.
• Wastewater Treatment: Control of primary, activated, and thickened sludge in municipal and industrial plants. Sludge with 2–8% solids and abrasive fine sand particles are incompatible with conventional globe valves.
• Mining — Mineral Slurries: Flow control in flotation circuits, thickeners, and filters. Mineral slurries with 30–60% solids and abrasive quartz and pyrite particles are the most demanding service — the hard chrome of the ball and the Stellite of the seat are the correct materials.
• Power Plants — Steam and Condensate: Control of high-temperature process steam, condensate regulation, and boiler water control in thermoelectric and cogeneration plants. The high-temperature configuration with graphite covers up to 350 °C.
• Chemical Industry: Control of viscous fluids with solids in polymerization reactors, neutralization systems, and intermediate product transfer lines. The CF8M body resists corrosive fluids and Stellite withstands the abrasion of suspended particles.
• Steel Industry: Control of cooling water with suspended solids, hydraulic oils contaminated with metallic particles, and fluids in environments with intense mechanical vibration.
• Food and Beverage — Non-Sanitary Auxiliary Services: Control of heating steam, caustic CIP cleaning solutions, and auxiliary process fluids where chemical resistance and durability in frequent cycles are required.

Data Sheet