Fully Welded Ball Valve Series

What is a fully welded ball valve?

A fully welded ball valve has a completely welded body with no bolted flanges, threaded connections, or gasketed joints. The valve body is welded shut after assembly, creating a monolithic hermetic seal. This design eliminates all external leakage paths — there is no stem packing bolt, body-bonnet gasket, or end-connection seal to fail. Fully welded ball valves are designed for 30+ years of maintenance-free service in buried pipeline applications where access for repair is impossible.

Why choose a fully welded ball valve for buried pipelines?

Fully welded ball valves are the preferred choice for buried pipelines because: (1) Zero external leakage — no bolted connections means no leak path to the environment, critical for natural gas and oil pipelines; (2) No maintenance — once buried, the valve must operate for 30+ years without access; (3) Corrosion protection — welded body eliminates crevice corrosion at bolted joints; (4) Reduced cathodic protection complexity — monolithic body is easier to protect; (5) Lower total lifecycle cost — despite higher initial purchase price, the elimination of inspection, maintenance, and potential repair over decades makes them the most economical choice.

What is the service life of a fully welded ball valve?

TANGGONG fully welded ball valves are designed for a minimum 30-year maintenance-free service life, matching the design life of transmission pipelines. The welded body eliminates gasket degradation and bolt relaxation — the common failure modes in bolted-body valves. Double piston seat rings with self-compensating design ensure long-term sealing performance. Extended stem design with triple-seal system (PTFE + O-ring + graphite fire-safe packing) protects the stem seal from groundwater ingress.

How is a fully welded ball valve installed underground?

TANGGONG fully welded ball valves are installed by: (1) Butt-welding the valve ends directly into the pipeline; (2) Extending the valve stem through a vertical extension pipe to above-ground level; (3) Mounting the operator (gearbox or actuator) above ground for access; (4) Applying fusion-bonded epoxy (FBE) or 3-layer polyethylene (3LPE) anti-corrosion coating to the buried body; (5) Backfilling with compacted sand around the valve body; (6) Connecting cathodic protection cables before backfill. The valve itself requires no underground vault or pit — only the operator extension breaks the surface.

Does TANGGONG provide cathodic protection coatings?

Yes. TANGGONG fully welded ball valves are available with fusion-bonded epoxy (FBE), three-layer polyethylene (3LPE), or coal-tar enamel anti-corrosion coatings for cathodic protection compatibility. The valve body casting is prepared to SSPC-SP10 (near-white metal blast) standard before coating application. Coating thickness and holiday testing are conducted per project specifications. We also provide electrical bonding lugs for cathodic protection cable connection.