I. The difference between a gate valve and a ball valve.
Gate valve: It is an opening and closing member of the gate, the direction of movement of the gate is perpendicular to the direction of the fluid. Depending on the parameters, the Gate valve can only be fully open or fully closed. The gate valve is usually 5°, or 25.2° when the medium temperature is not too high. This can improve its craftsmanship to make up for the angle of the sealing surface in the processing of the deviation, this gate is called elastic gate.
When the gate valve is closed, the sealing surface can only rely on media pressure to seal. Relying only on the media pressure to the sealing surface of the gate to the other side of the valve seat, so that the sealing surface can ensure the closure of the sealing surface, this is the self-sealing. Most gate valves have a forced seal. That is, when the valve is closed, to rely on external forces to force the gate to the valve seat, to ensure that the sealing surface of the sealing.
Ball valve: opening and closing parts are (ball) driven by the valve stem, and around the axis of the ball valve for rotary motion of the valve. It has a rotary 90 degrees of action, the plug body is a sphere, it has a round hole and channel through its axis, can be used for fluid regulation and control. Ball valves have a hard seal V ball valve, its V-shaped ball core, and surfacing hard alloy metal seat has a strong shear force, especially for fibers, tiny solid particles, and other media.
Ball valves have a hollow sphere that allows the medium to pass through. If you view the cross-section of the ball valve below, the operation is achieved by rotating the shaft or stem a quarter turn. The stem is perpendicular to the ball portion of the valve.
When the stem is at right angles to the disc, fluid is allowed to pass through. The lateral movement of the medium plays an important role in the closing principle. Ball valves use fluid pressure to act on the valve or seat to provide a tight seal, depending on the ball valve configuration.
Ball valves are available in full bore and reduced bore. A full-bore ball valve means that its diameter is the same as the pipeline. This can achieve a lower operating torque and pressure drop. However, there are also reduced bore types where the valve size is one size smaller than the pipe size.
Gate valves work by lifting a gate or flap to allow the medium to pass through the valve. These types of valves only allow unidirectional flow with a small pressure drop. You will often see gate valves with a handwheel. The handwheel is attached to the package.
There are two types of gate valve stem designs. When this handwheel is rotated, the stem rises to the outside environment and lifts the gate at the same time. The other type of gate valve is the non-rising gate valve. It is characterized by a stem that is screwed into the wedge, thereby exposing it to the medium.
When the gate is opened, the path becomes larger. The flow path is not linear in the sense that the medium can occupy the gap, as shown in the diagram below. If the gate valve is used as a throttling valve, the flow will be uneven. This causes vibrations. This vibration can cause damage to the gate.
By convention, ball and gate valves are bi-directional. This means that the ball valve can stop the medium from both the upstream and downstream ends.
3. Valve Sealing Capability.
For ball valves, floating ball valves are designed to have a fixed seal, while trunnion-mounted ball valves have a floating seal. Since ball valves are often used in low-pressure applications, the main seal is usually made of a related material such as PTFE, given the nature of its operating mechanism.
While the rapid closing and opening of a ball valve can be advantageous, it can also lead to several problems. Ball valves are susceptible to water hammer or sudden pressure surges when the valve is closed. This can damage the seat of the ball valve.
In addition, the water hammer increases the pressure inside the ball valve. In applications where this can occur, i.e. combustible materials, there is an emergency seat seal, usually made of metal. This is a second barrier in case the resilient seal is damaged in high-pressure service. To relieve pressure, ball valves can be fitted with a pressure relief valve.
Gate valves minimize pressure drop when fully open. This is achieved by using a full-bore port design. This means that the size of the valve is equal to the size of the pipe. It is this characteristic of gate valves that gives them an advantage over ball valves. Water hammer will not occur in gate valves.
The disadvantage of gate valves is the high differential pressure that often occurs when they are closed. Friction can cause wear of the valve seat and disc.
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III. Applications and Cases.
Gate Valve Uses | Ball Valve Uses |
Shutoff and isolation service for: · Wastewater Plants · Power Plants · Mining · Process Plants · Large Water Supply Lines Gate valves are commonly found in older residential plumbing systems. | On/off control for specialized industries including: · Oil & Gas · Food & Beverage Equipment · Automotive · Vehicle Wash Systems · Power Processing · Pharmaceutical · Chemical Admixtures & Treatment · Irrigation & Water Treatment Equipment · Manufacturing Facilities Ball valves can also be found in newer domestic plumbing systems. |
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