Attività

The ball is mounted against two seats and has a shaft that connects it to the operating and control mechanism that rotates the ball. When the cross-section of the bore is perpendicular to the area of the flow, the fluid is not permitted to pass through the valve. The fluid flows through from the valve, and the fluid flow rate depends on the area of the bore exposed to the floor.

Ball valves are a type of quarter-turn valve along with plug valves and butterfly valves. They can be operated manually or by using an actuator. The simplest operation of a floating ball valve is through the use of a wrench or a lever manually turned by an operator. Torque is applied to rotate the lever arm by 90° by either clockwise or counterclockwise to open or close the valve. If the lever arm is parallel to the pipe, it indicates that the valve is open. If the lever arm is perpendicular to the pipe, it indicates that the valve is closed.

Ball valves come in many designs and features to satisfy various industrial needs. The standards and specifications for ball valves vary depending on the industry where it is utilized.

The ball is a sphere that has a hole in its center. The hole in its center is called the bore. The bore serves as the flow opening of the fluid when the cross-section of the fluid flow path and the bore is coplanar. Otherwise, the flow is throttled. A ball valve may have a solid ball or a hollow ball. A solid ball has a constant opening diameter throughout its structure, which helps the fluid to smoothly flow at a constant velocity. A hollow ball, on the other hand, has a hollow internal structure, and the space inside it allows more fluid to pass through the valve. However, the larger space creates turbulence and high velocities. A hollow ball is more lightweight and cheap compared to a solid ball.

Shaft

The shaft connects the ball to the control mechanism that rotates the ball. The shaft has seals such as O-rings and packing rings to seal the shaft and the bonnet to avoid leakage of the fluid. The shaft may be manually operated by a lever or a handwheel or operated by an electric, pneumatic, or hydraulic actuation.

Bonnet

The bonnet is an extension of the valve housing that contains and protects the shaft and its packing. It may be welded or bolted to the body. It is also made of hard metal and it covers the opening made from connecting the shaft to the external control mechanism.

Seat

The valve seats provide sealing between the ball and its body. The upstream seat is adjacent to the inlet side of the valve. The downstream seat is found on the opposite side of the upstream seat which is adjacent to the discharge side of the valve.

Two linear variable differential transformers (LVDTs) were installed at the base of the boundary column and at the center line of the top beam.

Table 1 lists the results of the coupon tests of the two materials Q345 and Q235. Three coupons were tested for each material, and the average value is used for the subsequent analytical analyses.

Under pure gravity loads, no buckling occurred in specimens A, B, and C. However, in the case of specimen D, horizontal buckling of the infill steel plate took place. The following described the behaviour of the four specimens.

In the case of specimen A, until the top displacement reached 4 mm, there was no buckling in the infill steel plate. The tension strips, formed from the lower left corner to the upper right corner, have an inclination angle near to 45°. During the first displacement cycle of 8 mm, the first loud bangs occurred. In the subsequent cycles, these noises continued to occur. With an increase of the top displacement, various parts of the infill steel plate progressed to yield. A large residual deformation formed at the end of each pull or push loading with a further increase of residual deformation in the subsequent cycles. The first tear was detected in the upper left corner between the fishplate and the infill steel plate during the first 12 mm displacement load. The tear gradually increased to nearly 30 mm at the end of the first 12 mm cycles, as shown in Figure 3. At the end of the second 12 mm displacement cycle, new tears were detected at the two lower corners. All the tears extended with an increase of the top displacement, but no new tear was observed. During the first 20 mm displacement cycle, the shear resistance of the specimen did not decrease, but the tears grew faster and the specimen was pushed over. The ultimate deformation at the top of the specimen reached more than 50 mm. The force resistance only dropped by about 15%. At the end of the test, all the tears extended to be more than 60 mm. The tension boundary column failed due to the rupture of the weld at the bottom of the column, as shown in Figure 4. Meanwhile, the compression column experienced local buckling in the flange, and only a slight out-of-plane deformation was observed.

In the case of specimen B, i.e., under 600 kN vertical load, no buckling or yielding was detected. Prior to reaching the yield displacement, four load cycles with increasing magnitude from ±50 kN to ±200 kN were necessary to cause the first yielding. At the cyclic load of 150 kN, the first loud bang occurred. These noises also occurred during the unloading phase in the following cycles. However, tension strips first only occurred during the second cycle of the 2 mm level, as indicated by the diagonal lines in Figure 5. The first tear was detected at the upper left corner at the end of the third cycle of 4 mm. The length of the tear was about 10 mm, and this tear gradually grew in the following cycles. At the first 6 mm displacement cycle, new tears of about 15 mm length occurred at the upper right and lower left corners. The length of the tear at the upper left corner extended to about 20 mm. At the end of the second 10 mm displacement cycle, a slight buckling at the support of the boundary column under compression was observed. The length of tear at the upper right corner extended to about 50 mm. At the second 12 mm displacement cycle, as shown in Figure 6, the upper left tear extended to nearly 60 mm, and the shear force resistance did not decrease. During the first 16 mm displacement pull load, the specimen reached a maximum resistance at the top displacement of 13 mm. The shear resistance then began to decrease. At the second 16 mm displacement cycle, the shear resistance decreased rapidly. The failure started at the support of the column under compression where a significant buckling and yield occurred. An out-of-plane deformation increased very fast, resulting in a loss of the in-plane shear resistance.