A trunnion ball valve is a type of valve that uses a rotating ball as its core control element. The flow of media is controlled by the contact or separation of the ball and the valve seat. The "trunnion" in its name refers to the support shaft structure located on both sides of the ball. This design gives it unique advantages in high-pressure, large-diameter, and complex operating conditions, making it a key piece of equipment in the field of industrial fluid control.
A trunnion ball valve mainly consists of a valve body, valve cover, valve ball, valve seat, valve stem, and operating device.
The valve body is the main component, usually made of cast iron or stainless steel, offering good corrosion resistance. The valve cover connects to the valve body and secures the valve ball and seat. The valve ball is the key component of the trunnion ball valve, typically made of stainless steel, providing excellent sealing performance.
The valve seat mates with the valve ball, usually made of an elastic material, ensuring the valve's sealing performance. The valve stem connects the valve cover and valve ball, transmitting the operating force. The operating device can be manual or automatic, used to control the opening and closing of the valve.
Large Bore Trunnion Ball Valves (Up to 60") for High-Pressure Pipelines
Components of a Trunnion Mounted Ball Valve
| Component Category | Part Name | Description & Function | Common Materials |
| Pressure Containing | Valve Body | The main enclosure that holds all internal parts and connects to the pipeline. | ASTM A105, A216 WCB, A350 LF2, A182 F316 |
| Adaptor / End Cap | Bolted or welded to the body to secure the internals (in 2-piece or 3-piece designs). | Matches the Body material | |
| Core Flow Control | The Ball | A fixed-axis sphere with a bore. Rotates 90° to open or close the flow. | A105+ENP, F316, F51 (Duplex), F22 |
| The Stem | Connects the actuator/lever to the ball. Transmits torque to rotate the ball. | 4140+ENP, 17-4PH, XM-19, SS316 | |
| The Trunnion | A lower support pin (or plate) that keeps the ball fixed on its vertical axis. | Matches Stem or Ball material | |
| Sealing System | Seat Rings | Floating rings that move against the ball under spring and fluid pressure. | Carbon Steel + ENP, Stainless Steel |
| Seat Inserts | The soft or hard material inside the seat ring that contacts the ball. | PTFE, Nylon, Devlon, PEEK, Stellite | |
| Seat Springs | Coil or Wave springs that ensure a tight seal at low pressure (Pre-loading). | Inconel X-750, Stainless Steel 316 | |
| Friction & Support | Bearings / Bushings | Reduces friction between the stem/trunnion and the body for lower torque. | PTFE-lined Steel, Stainless Steel |
| Thrust Washer | Prevents friction and wear between the stem shoulder and the bonnet. | PTFE, Graphite, Nylon | |
| Seals & Gaskets | O-Rings / Lip Seals | Provides primary dynamic sealing for the stem and seats. | Viton (FKM), NBR, HNBR, AED (Anti-Explosive Decompression) |
| Body Gasket | Static seal between the body and the end cap (often Fire-safe). | Spiral Wound (SS316 + Graphite) | |
| Safety & Auxiliaries | Sealant Fittings | Injection nipples for emergency grease/sealant to stop leaks. | Stainless Steel |
| Drain & Bleed Valves | Used to vent pressure from the body cavity for Double Block & Bleed (DBB) testing. | Stainless Steel | |
| Anti-Static Device | A spring-loaded ball ensuring electrical continuity between ball, stem, and body. | Stainless Steel |
Trunnion vs. Floating Ball Valve Components
| Component | Trunnion Mounted (Fixed) | Floating Ball Valve |
| Ball Support | Stem (Top) & Trunnion (Bottom) | Stem (Top) only |
| Seat Type | Spring-loaded (Floating Seats) | Fixed Seats |
| Operating Torque | Lower (Ideal for large sizes) | Higher (Increases with pressure) |
| Size Range | Typically 2" to 60" | Typically up to 10" or 12" |
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FAQ
What size are trunnion mounted ball valves?
Range GNEE Valves manufactures a comprehensive range of Trunnion- mounted Ball Valves in sizes up to 56" (1400 mm) in ASME classes from 150 to 2500. The valves are offered in a variety of body styles, materials, trims and actuation options to address critical services in hydrocarbon, power and allied industries.
When to use a trunnion mounted ball valve?
Trunnion mounted ball valves are perfect for a wide range of applications among several oil and gas industries. Examples of oil and gas industries that utilize trunnion mounted ball valves include gas feed lines, field gas plants, industrial gas processing plants, oil refinery feedstock lines, and crude oil plants.