Three-Piece Welded Ball Valve
Three-Piece / Welded · DN15–DN100 · PN16 · Tri-Clamp / Welded
Our three-piece ball valve lets you remove the central body for seat or ball service without cutting the pipeline — perfect for frequent cleaning. Welded and tri-clamp versions serve hygienic duty.
SS316 with electropolish option meets food, beverage and pharma CIP/SIP requirements.
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 Three-Piece Welded Ball Valve
A three-piece welded ball valve is chosen where the joint itself must not leak. The body is welded rather than bolted, so the only remaining leak paths are the stem and the pipe welds.
Welded body removes a leak path
A bolted body joint is a potential leak on hazardous, toxic or high-pressure service. A welded three-piece body eliminates it, which is why this design appears on gas and underground lines.
Three-piece means it can still be serviced
Despite being welded into the line, the centre section can be unbolted or the welded ends cut and re-welded, allowing ball and seat replacement without replacing the whole valve.
Buried service is the classic application
A fully welded ball valve with an extended stem is the standard choice for buried gas and fuel lines, where access for maintenance is expensive.
Full bore for pigging
Underground and transmission lines are often pigged. Full bore is normally required, which means the valve is physically larger than a reduced-bore equivalent.
Coating and stem extension go with the job
Buried valves need external coating that survives backfill and, on a rising or extended stem, a seal that keeps groundwater out of the stem housing.
Installation & Maintenance
Weld with the valve open or closed as instructed
Follow the supplier instruction for the specific design. Welding heat is the main risk to the seat during installation.
Purge and cool properly
Oxidation inside the bore and slow cooling both degrade a welded-in stainless valve.
Pressure test the weld, not just the valve
The valve was tested at the factory; the field weld was not. Test the joint before backfilling.
Fit the stem extension before backfilling
And check the operating key reaches the nut from finished ground level.
Common Specification Mistakes
Backfilling before testing the field weld
The weld is the new, untested part of the assembly.
Assuming welded means maintenance-free
The seat still wears; plan for how you would replace it.
Omitting the stem extension on a buried valve
The valve cannot be operated without excavation.
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.
