How to Order Ball Valves
Ball valves provide fast quarter-turn isolation with low pressure drop in the full-open position, but their specification is more involved than most engineers expect. The choice between floating ball and trunnion-mounted, the bore type, the seat material, and the seal configuration all affect performance, cost, and suitability for the intended service. An incomplete ball valve specification leads to mismatched seat materials, incorrect bore sizes, or a valve that cannot provide double isolation when required.
This checklist covers the parameters required for ordering floating ball, trunnion-mounted, and double block & bleed (DBB) ball valves per API 6D (pipeline), API 608 (metal ball valves), and API 607 (fire-test standard).
Core Attributes
These parameters must appear in every ball valve line item on your RFQ or purchase order.
| Parameter | What to Specify | Example |
|---|---|---|
| Design standard | API 6D (pipeline valves), API 608 (flanged/BW/threaded metal ball valves), API 607 (fire-test standard, referenced but not a design standard) | API 6D |
| Ball valve type | Floating ball (2-piece or 3-piece body), trunnion-mounted (top entry or side entry), double block & bleed (DBB) | Trunnion-mounted |
| Bore | Full bore (FB): bore ID matches pipe ID. Reduced bore (RB): bore is one size smaller than nominal. Specify bore ID in mm if critical. | FB |
| Nominal size | NPS or DN | NPS 10 |
| Pressure class | Class 150, 300, 600, 900, 1500, or 2500 per ASME B16.34 | Class 600 |
| End connection | Flanged (FL) with face type: RF or RTJ. Butt-weld (BW). Threaded (NPT). | FL-RTJ |
| Body material | Cast CS: ASTM A216 WCB/WCC. Low-temp: ASTM A350 LF2 (forged), A352 LCB/LCC (cast). Cast SS: ASTM A351 CF8M. Duplex: ASTM A351 CE8MN (cast), A182 F51 (forged). | ASTM A350 LF2 |
| Seat material | Soft seat: PTFE, RPTFE (reinforced PTFE), PEEK, Devlon, Nylon. Metal seat: Inconel 625 overlay, Stellite 6 overlay, tungsten carbide. Metal-to-metal for high temperature. | RPTFE |
| Seal type | Soft seat, metal seat, double piston effect (DPE) for trunnion valves | Soft seat with DPE |
| Port configuration | Full port, reduced port, V-port (characterized for throttling/control) | Full port |
| Actuation | Lever (small sizes), gear operator, pneumatic actuator (spring-return or double-acting), electric actuator, hydraulic actuator | Gear operated |
Optional / Special Attributes
Include these when the service, project specification, or client requirements demand it.
| Parameter | What to Specify | When Required |
|---|---|---|
| Anti-static device | Anti-static spring between ball and stem, and between stem and body, to dissipate static charge | All hydrocarbon service; required by API 608 and API 6D for flammable fluids |
| Fire-safe certification | API 607 fire-test certification (valve tested to demonstrate metal-to-metal sealing after soft seat destruction) | Hydrocarbon service, offshore, fire-risk areas |
| Cavity relief | Thermal relief hole or self-relieving seat design to prevent trapped pressure buildup in the body cavity between the upstream and downstream seats | Liquid service where thermal expansion of trapped fluid can overpressure the body cavity |
| Double isolation & bleed (DIB/DBB) | Specify DIB (each seat seals independently against body cavity pressure) or DBB (both seats seal against line pressure from one direction). Include bleed valve size and type. | Isolation for maintenance, pigging, pipeline sectioning |
| Stem extension | Specify extension length in mm or inches | Buried valves, insulated valves, underground pipeline valves |
| Locking device | Padlock lugs on lever or gear operator, lockable handle | Safety isolation, lockout/tagout (LOTO) procedures |
| Fugitive emission testing | API 641 or ISO 15848-1 with leakage class (Class A, B, or C) specified | Environmental compliance, volatile organic compounds, toxic service |
| NACE MR0175 / ISO 15156 | Sour service compliance with hardness, chemistry, and material restrictions for all wetted parts | H2S-containing environments |
| Seat overlay / coating | Inconel 625 weld overlay, tungsten carbide HVOF coating, ENP (electroless nickel plating) on ball and seats | Abrasive service, high-cycle, metal-seated applications |
| Certificates | EN 10204 Type 3.1 (MTR) or Type 3.2. Pressure test certificate per API 598 or API 6D Sec. 9. Factory acceptance test (FAT) report. | Always specify; 3.2 for critical and sour service |
Example Line Item
Correct:
4 pcs - Trunnion ball valve, API 6D, NPS 10, Class 600, FL-RTJ, FB, DBB, ASTM A350 LF2 body, Inconel 625 overlay seats, RPTFE seals, gear operated, NACE MR0175, API 607 fire-safe, MTR 3.1
This line item defines: quantity and UOM, valve type and mounting, design standard, size, pressure class, end connection and face type, bore type, isolation configuration, body material, seat overlay material, seal material, actuation, sour service compliance, fire-safe certification, and material certification.
Incorrect:
4 - Ball valve 10 inch 600#
This is missing the valve type (floating vs trunnion), design standard, end connection, face type, bore type (FB vs RB), isolation configuration, body material specification, seat material, seal type, actuation, and all special requirements. The supplier cannot determine whether to quote a floating or trunnion valve, what bore size to provide, or what seat and seal materials are needed for the service conditions.
Common Pitfalls
- Not specifying full bore vs reduced bore. A full bore (FB) ball valve has a bore diameter matching the pipe ID, resulting in negligible pressure drop and allowing pigging. A reduced bore (RB) valve has a bore one nominal size smaller, which is acceptable for many process applications but not for pipeline pigging or high-flow-coefficient requirements. If you do not specify, the supplier may quote RB (lower cost), and the valve will not pass a pig.
- Selecting the wrong seat material for the service temperature. PTFE seats are limited to approximately 200 deg C (392 deg F) continuous service. RPTFE and PEEK extend the range somewhat but still have upper limits. For high-temperature service (above 250 deg C) or fire-safe requirements, metal-to-metal seats are mandatory. Conversely, metal seats have higher operating torque and do not provide bubble-tight shutoff at low pressures. Match the seat material to both the temperature and the shutoff requirement.
- Forgetting cavity relief for liquid service. When a trunnion ball valve is in the closed position, liquid trapped in the body cavity between the upstream and downstream seats can expand with temperature changes (solar heating of an above-ground pipeline, for example). Without cavity relief, this thermal expansion can overpressure the body cavity and damage the seats or body. Specify a self-relieving upstream seat or a dedicated cavity relief valve.
- Confusing DBB with DIB. Double block and bleed (DBB) means both seats seal from the same direction (one upstream, one downstream) and the cavity can be vented. Double isolation and bleed (DIB) means each seat independently seals against cavity pressure, providing true double isolation. API 6D defines both configurations. For critical isolation (e.g., maintenance isolation on a live pipeline), DIB is the safer specification. Always confirm which configuration your project requires.
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