Fully Welded Ball Valve

One of the most trusted valves in the petroleum industry, the fully welded ball valve combines the strength of forged steel components with a lightweight and compact spherical design.The distinctive design of the Qilong 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 potential leak paths

Valve Range

Size ： 1/2”~56”（DN15~DN1400）

Rating ： 150~2500LB（PN16~PN420）

Body Materials ： Carbon Steel, Stainless Steel, Alloy Steel, Duplex Steel

Trim ： Carbon Steel, Stainless Steel, Duplex Steel

End Connection ：RF，BW

Fully welded ball valves are used mainly in Gas transmission and distribution pipeline (Mid-stream), typical for underground and buried installation The ball is fixed and the seat rings are floating, free to move along the valve axis.

Side load generated by pressure acting on the ball is absorbed by bearings.

At low pressure the seat sealing acting is achieved by the thrust of the springs acting on the seat. As the pressure increases the fluid pressure pushes the seat rings against the ball, making the sealing more reliable.

Features and Benefits

Upstream Sealing At low pressure, seat-to-ball contact is maintained by Belleville springs. At higher pressures, seat contact is reinforced by line pressure.

Automatic Internal Relief of Body Pressure Relief of excess body cavity pressure is automatic, avoiding dangerous pressure buildup. Any pressure exceeding downstream line pressure by approximately 200 psi pushes the downstream seat away from the ball, allowing the pressure to relieve into the pipeline.

Rotating Seat Rings The exclusive rotating seat feature is standard in the fully welded ball valve sizes 14” (350 mm) and larger. Both seats rotate 15 degrees each time the valve is closed, exposing a new pinch point and evenly

Distributed Seat Wear

The pinch point is the area of the seat insert that experiences an increased velocity when the valve is seated closed and unseated open. This is where the seat seal experiences the most wear, and in most valves, where a leak path begins. By rotating the seat ring, the pinch point wear is distributed throughout the seat seal, providing an increase in seat life.

Prevents Buildup

In some services, a valve can experience harmful sediment buildup around the seat ring. This can cause the seat to stick and not seal properly. The QiLong fully welded ball valves, with exclusive rotating seat, can handle these harsher services. As the seat rotates, it will prevent any buildup, or breaks up existing buildup.

Stem Seals

Delta seals and lip seals made of PTFE are incorporated in the upper stem area. PTFE is a low-friction, non-deteriorating material that is not subjected to rapid decompression explosion. Most valve sizes have a provision for sealant injection to establish a secondary seal.

Trunnion-supported Ball Allows

Low-torque Operation

Regardless of size or pressure rating, every 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.

Double Block-and-bleed

Whether in the fully open or fully closed position,pressure on each side of the ball is blocked from the body cavity by the seat ring. The body cavity can then be bled down or drained through the body port. When you block-and-bleed a fully welded ball valve, the following can be accomplished:

Test Valve Integrity

When the valve body is vented, the seat seal’s integrity is verified. This test can be performed with the valve open or closed prior to facility maintenance. By verifying valve integrity,unforeseen valve leakage can be prevented.

Secondary Seat Seal

The sealant injection system provides a fast, simple way of restoring tight shutoff if any foreign object should damage the sealing surfaces. The injection system also can be used for routine flushing of the seat ring area in services where this may be required