Ball Valves
In a trunnion mounted ball valve the ball is supported on upper and lower stems (trunnions), and line pressure moves the spring-loaded seats against the ball rather than moving the ball. Operating torque therefore stays low, and it is the standard isolation valve for large-diameter, high-pressure pipeline, station and process lines.
Overview
The seats are pressed against the ball by springs and by line pressure: at low pressure the springs provide the seal, at high pressure the pressure force does. This arrangement enables the DBB and DIB functions defined in API 6D, body cavity relief and emergency sealant injection into the seats.
The body is cast steel, two-piece or three-piece (center body plus two end closures). Larger sizes are operated by gear operator or actuator; an extended stem option is available for buried (underground) lines.
Technical specifications
| Size | 2″–60″ (DN50–DN1500) |
|---|---|
| Pressure class | ASME Class 150–2500 |
| End connections | RF / RTJ flanged (ASME B16.5 / B16.47), butt-weld (ASME B16.25) |
| Body | Two-piece or three-piece cast; full bore or reduced bore |
| Seats | Spring-loaded seats; PTFE, RPTFE, PEEK, nylon or metal (hard-faced) |
| Materials | WCB, WCC, LCC, CF8M; duplex (4A/5A) and special alloys |
| Functions | DBB, DIB-1, DIB-2; cavity relief; emergency sealant injection; drain and vent connections |
| Operation | Gear operator, pneumatic (scotch-yoke), electric or gas-over-oil actuator; extended stem |
Key features
- Low operating torque for large sizes and high pressure
- Double block and bleed (DBB/DIB) options
- Emergency sealant injection
- Fire-safe (API 607) and antistatic design
- Extended stem for buried lines
Typical part materials
| Part | WCB | LCB / LCC | CF8M | CF8 |
|---|---|---|---|---|
| Body, end caps (adapters) | A216 WCB | A352 LCB / LCC | A351 CF8M | A351 CF8 |
| Ball, stem, seat ring | A105N + ENP | A350 LF2 + ENP | A182 F316 | A182 F304 |
| Trunnion, gland flange | A105N | A350 LF2 | A182 F316 | A182 F304 |
| Seat insert | PTFE / RPTFE / PEEK | PTFE / RPTFE / PEEK | PTFE / RPTFE / PEEK | PTFE / RPTFE / PEEK |
| O-rings, fire-safe seals | FKM, graphite | FKM, graphite | FKM, graphite | FKM, graphite |
| Anti-static (grounding) spring | SS304 | SS304 | SS316 | SS304 |
ENP: electroless nickel plating. For abrasive or high-temperature service, balls and seats can be supplied metal-seated with tungsten carbide or chromium carbide coating.
Catalog data
| Body construction | 2-piece or 3-piece bolted body, side entry |
|---|---|
| Design features | Anti-blowout stem, anti-static design, fire-safe (API 607 / API 6FA), double block and bleed, cavity pressure relief |
| Maintenance | Emergency sealant injection to seats and stem; drain and vent valves |
| Actuator mounting | ISO 5211 mounting pad; gear operator, pneumatic, electric and hydraulic actuators |
Documentation and testing
On industrial projects the documentation package matters as much as the valve. We confirm the certificate and test scope for every line item at quotation stage:
- EN 10204 3.1 material certificates for pressure-retaining and wetted parts, traceable by heat number
- EN 10204 3.2 with third-party inspection, on request
- Pressure test reports to API 598 or EN 12266-1: shell, seat and, where specified, gas tests
- Fire-test certificates (API 607 / ISO 10497) for fire-safe type-tested designs
- PMI reports for alloy and stainless materials
- Dimensional, visual and coating inspection records
- PED 2014/68/EU CE declaration for equipment within its scope
- NACE MR0175 / ISO 15156 compliance statement for sour (H₂S) service
Technical datasheet
Frequently Asked Questions
When is a trunnion mounted ball valve selected?
When size and pressure class increase (for example above about 6″–8″ in Class 300, and from smaller sizes at Class 600 and above), when DBB/DIB function is required, or when low-torque automation is needed.
What does emergency sealant injection do?
If a seat is damaged, sealant is injected into the seats to restore a temporary seal without removing the valve from the line. On pipeline and station valves this keeps the line in operation until maintenance can be scheduled.
Related products
Floating Ball Valve
½”–10″, Class 150–600; two-piece and three-piece, fire-safe, antistatic.
View details
Forged Steel Trunnion Ball Valve
Class 150–2500, mainly high pressure; A105N, LF2, F316, F51; API 607.
View details
Metal Seated Ball Valve
Tungsten or chromium carbide coated ball and seats; abrasive and high-temperature service.
View detailsRequest a quote: Trunnion Mounted Ball Valve
Share your valve list, datasheet or project specification. We review standards, materials and documentation line by line and return an itemized offer, with any deviation from the specification stated in writing.