Trunnion Mounted Ball Valve
Trunnion Mounted · DN200–DN600 · PN16 · High Pressure
For DN200 and above, the trunnion ball is held by top and bottom shafts so line pressure cannot push it off-seat — torque stays low even at PN100.
Metal or soft seats, fire-safe design, with gearbox or actuator for pipeline and tank-farm isolation.
Key Features
Bubble-Tight Shutoff
Soft PTFE seats give zero-leakage shutoff for gas, water and chemical service.
Low Torque
Floating and trunnion designs keep operating torque low for lever or compact actuators.
Anti-Blowout Stem
Stem shoulder and live-loaded packing prevent ejection under line pressure.
Fire-Safe Design
Metal-to-metal backup seat holds line pressure after a fire (design principle; no API 607 certificate held).
Actuator Ready
ISO 5211 flange accepts pneumatic or electric actuators and gearboxes.
Full / Reduced Bore
Full-bore models give unobstructed Cv; reduced-bore saves weight and cost.
Technical Specifications
| Parameter | Specification |
|---|---|
| Body Material | WCB Carbon Steel / SS304 / SS316 / CF8M |
| Ball / Trim | SS304 / SS316 / 17-4PH |
| Seat Material | PTFE / RPTFE / PEEK / Metal |
| Size Range | DN15 – DN600 (1/2" – 24") |
| Pressure Rating | PN16 (ANSI 150 / 300) |
| End Connection | Flanged / Threaded / Welded / Wafer / Tri-clamp |
| Operation | Lever / Gear / Pneumatic / Electric Actuator |
| Bore | Full Bore / Reduced Bore |
| Fire Safe | Fire-safe design with metal backup seat (design principle; no API 607 certificate held) |
| Leakage Class | Bubble-tight, ANSI ISO 5208 Rate A (soft seat) |
| Standards | API 608 / ISO 17292 / GB/T 12237 |
| Certification | ISO 9001:2015, MTC available |
How to Specify a Trunnion Mounted Ball Valve
Trunnion mounting exists to keep ball movement under control at high pressure and large size. Floating ball designs stop being practical around the point where trunnion begins.
Trunnion is for high pressure and large bore
In a floating ball valve the ball is pushed into the downstream seat by line pressure, so seat load rises with pressure and bore. A trunnion-mounted ball is held by bearings top and bottom, so the seat load stays controlled. That is why large or high-pressure ball valves are trunnion mounted.
Double block and bleed is a trunnion feature
Two independent seat seals with a bleed between them lets you prove isolation without draining the line. If DBB is in the specification, it is a trunnion valve you need.
Antistatic and fire-safe construction
A trunnion ball valve in hydrocarbon service normally needs antistatic continuity between ball, stem and body, plus a fire-safe design with a metal backup seat. State both requirements at enquiry stage.
Actuator torque is more predictable
Because the ball is supported, trunnion valves have a more consistent torque curve than floating designs, which makes actuator sizing more straightforward — but confirm the figure with us.
Maintenance access differs
Many trunnion designs allow the ball and seats to be serviced without removing the body from the line. On a pipeline that access is worth a great deal; check whether the design you are quoted offers it.
Installation & Maintenance
Support the valve and the pipe
A large trunnion valve is heavy. It should not be the point that carries the pipeline.
Check the drain and vent ports are accessible
The bleed port is only useful if you can reach it after installation. Plan orientation accordingly.
Align flanges before bolting
A trunnion seat is machined and does not tolerate pipe strain. Pulling flanges together with bolts will produce a leak.
Record the cavity bleed result at commissioning
The double block and bleed test result is the baseline for every future isolation check.
Common Specification Mistakes
Using a floating design for a large or high-pressure line
Seat load becomes excessive and operating torque unmanageable.
Specifying DBB without a trunnion valve
True double block and bleed needs two independent seats.
Skipping antistatic continuity in hydrocarbon service
Static discharge in a ball valve is a genuine ignition risk.
Frequently Asked Questions
What is the difference between floating and trunnion ball valves?
Floating ball valves seat the ball against the downstream seat by line pressure (DN15–DN150). Trunnion-mounted balls are held by top and bottom shafts for larger sizes (DN200+) and higher pressures.
Which seat material should I choose?
PTFE / RPTFE for most chemicals and clean fluids up to +200°C. PEEK for higher temperature. Metal seat for slurry, abrasive or high-temperature service.
Can ball valves be used for throttling?
Ball valves are best for on/off. For modulating duty use our V-port control ball valves or control valves, which keep a stable characteristic curve.
Applications & Use Cases
Oil & Gas
Pipeline isolation, tank farm and loading arms with fire-safe soft seats.
Water & Utilities
Municipal water, HVAC and irrigation with flanged or wafer ends.
Chemical
Corrosive media handled in SS316 or PTFE-seated bodies.
Food & Pharma
Tri-clamp and polished SS316 ball valves for hygienic lines.
