Fully welded ball valves (Welded Body Ball Valve) are with the advantages that the ball valve is integrally welded without external leakage path. All welding processes are qualified and performed according to ASME Section IX. The welding for the valve body are to performed with Non-destructive tests.
Fully Welded Ball Valve gives it maximum strength at minimum weight as well as maximum resistance both to pipeline pressures and stresses. The compact, spherical design also eliminates body flanges, thus reducing overall size and leak paths.
Ball Valve Welded body designs are ideal for buried service applications to decrease potential leak points and reduce the potential of fugitive emissions from flanges.
As one of the reliable Fully Welded Body Ball Valve manufacturers in China, Relia supplies welded body ball valves which are used mainly in Gas transmission and distribution pipeline (Mid-stream), typical for underground and buried installation.
Various testing procedures are used to confirm the tightness of the entire ball valve. Furthermore, weld seams undergo visual, magnet particle, ultrasonic and – if requested – radiographic testing.
Fully welded ball valve is trunnion mounted. High-strength forged stems are located in PTfE impregnated stainless steels bearings for smooth operation. Trunnion mounted stems absorb the thrust from line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure, operating torque stays low.
Fully Welded Ball Valve Drawing
The body utilizes forgings, which are available in a large array of materials, making the fully welded ball valves well-suited for special applications as well as standard service. The body is made from three forged parts, and its all-welded construction has fewer leak paths than traditional ball valves. A cavity-relief valve is installed in the body to relieve any overpressurization encountered during service or testing. Integrity of sealing surfaces can be monitored without pressure in the pipeline by pressurizing the body cavity.
All welding processes for the body are suited to the materials of construction and are qualified and performed according to ASME Section IX. Non-destructive tests (NDTS) are performed per ASME VIII Division 1, App. 12 on the circumferential weld joints of the body. The compact shape of the body allows for the easy absorption of the bending loads coming from the pipeline.
The floating seats are free to move slightly along the longitudinal axis of the bi-directional valve. The initial seal at extremely low pressure differential, or vacuum conditions, is obtained through the force of the springs acting on the floating seats. Line pressure, behind the seat ring, supplements the seat spring load to force the seat tightly against the ball. The sealing is performed by PMSS seat to ball. The soft sealing between the seat and the ball is achieved by an elastomeric O-ring, plastic O-ring, or insert, depending on the service conditions. The seat seal is a soft polymeric seal. A secondary sealant injection system is provided for emergency seat sealing. In addition to the seat injection fittings, a check valve installed in the body prevents escape of the internal fluid.
Double Block-and-Bleed – A single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve with a means of venting/bleeding the cavity between the seating surfaces (ISO 14313/API 6D).
Double Piston Effect (DPE) Seat Design - The seat design allows for both seats to seal with pressure acting from the same side of the valve. With line pressure in the body cavity, or in the event of one seat becoming damaged, the user has the added advantage of the opposite seat sealing.