Balls 101

Ball valves are produced in several configurations depending on the mechanical support of the ball, bore geometry, and flow control requirements. The floating ball valve relies on pressure-induced downstream sealing, making it ideal for small to medium sizes and low to medium pressures. The trunnion-mounted ball valve, on the other hand, uses upper and lower trunnions to absorb hydraulic loads, maintaining alignment and reducing seat wear. Trunnion designs are standard in high-pressure pipeline applications (e.g., API 6D valves above DN150), where predictable torque and double block-and-bleed functionality are required. From an engineering and procurement perspective, the choice between floating and trunnion-mounted configurations determines actuator sizing, stem torque margins, and sealing integrity under differential pressure.

Flow capacity and control characteristics are defined by bore geometry and angular travel. A standard on/off ball valve operates through a 90° rotation, moving the bore from fully open (0°) to fully closed (90°) with a quarter-turn motion. This design enables rapid shut-off and compact actuation. In contrast, V-port (or segment) balls introduce a machined V-shaped bore—typically 30°, 60°, or 90°—allowing controlled, non-linear flow regulation. The V-profile ensures precise modulation: a 30° V-port provides fine low-flow control (linear characteristic), while a 90° port offers a higher capacity with an equal-percentage curve suitable for proportional control loops. Actuators used in such applications often feature positioners or feedback systems to achieve accurate flow modulation across the full 0–90° rotation range, while the valve’s Cv (flow coefficient) curve must be verified against process requirements.

Material and surface engineering considerations are critical for long-term performance and lifecycle cost. Soft-seated valves (PTFE, RPTFE, PEEK) are appropriate for clean service and low torque applications, while metal-seated valves—featuring tungsten carbide, chromium carbide, or Stellite coatings—are required for high-temperature, abrasive, or throttling duties. In modulating service, hard-coated balls paired with metal seats prevent erosion at partial openings. Procurement specifications should therefore explicitly define the V-angle, rotation range, seat material, coating specification, and applicable standards (e.g., API 6D, ISO 5208, NACE MR0175). Matching the valve configuration, flow geometry, and materials to service conditions ensures reliable sealing, predictable torque behavior, and optimized total cost of ownership.