A ball valve is a rotational motion valve that uses a ball-shaped disk to stop or start fluid flow. The ball, performs the same function as the disk in the globe valve. When the valve handle is turned to open the valve, the ball rotates to a point where the hole through the ball is in line with the valve body inlet and outlet. When the valve is shut, the ball is rotated so that the hole is perpendicular to the flow openings of the valve body and the flow is stopped.
Most ball valve actuators are of the quick-acting type, which require a 90° turn of the valve handle to operate the valve. Other ball valve actuators are planetary gear-operated. This type of gearing allows the use of a relatively small handwheel and operating force to operate a fairly large valve.
Some ball valves have been developed with a spherical surface coated plug that is off to one side in the open position and rotates into the flow passage until it blocks the flow path completely. Seating is accomplished by the eccentric movement of the plug. The valve requires no lubrication and can be used for throttling service.
A ball valve is generally the least expensive of any valve configuration and has low maintenance costs. In addition to quick, quarter turn on-off operation, ball valves are compact, require no lubrication, and give tight sealing with low torque.
• They provide leak-proof service,
• Open and close quickly,
• Compared to gate valves, they have very small dimensions,
• Compared to gate valves, they are lighter,
• The multi designed flexibility does not exist in the Gate or Globe valve, and hence it lowers the amount of valves needed,
• These valves are manufactured in different sizes and shapes providing flexibility in selection,
• The high quality valves provide safe service under high temperature and high pressure conditions, and
• Compared to other valves, they are controlled with less force.
Conventional ball valves have relatively poor throttling characteristics. In a throttling position, the partially exposed seat rapidly erodes because of the impingement of high velocity flow. There are exceptions though, and ball valves can be used as control valves when modification to characterize the flow port are taken.
• The position of the valve handle is rotated,
• Could not be used for throttling, and
• These valves with drive mechanism should be installed upright.
Ball valves are available in the venturi, reduced, and full port pattern. The full port pattern has a ball with a bore equal to the inside diameter of the pipe.
Balls are usually metallic in metallic bodies with trim (seats) produced from elastomeric (elastic materials resembling rubber) materials. Plastic construction is also available.
The resilient seats for ball valves are made from various elastomeric material. The most common seat materials are teflon (TFE), filled TFE, Nylon, Buna-N, Neoprene, and combinations of these materials. Because of the elastomeric materials, these valves cannot be used at elevated temperatures. Care must be used in the selection of the seat material to ensure that it is compatible with the materials being handled by the valve.
The stem in a ball valve is not fastened to the ball. It normally has a rectangular portion at the ball end which fits into a slot cut into the ball. The enlargement permits rotation of the ball as the stem is turned.
A bonnet cap fastens to the body, which holds the stem assembly and ball in place. Adjustment of the bonnet cap permits compression of the packing, which supplies the stem seal. Packing for ball valve stems is usually in the configuration of die-formed packing rings normally of TFE, TFE-filled, or TFE-impregnated material. Some ball valve stems are sealed by means of O-rings rather than packing.
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Some ball valves are equipped with stops that permit only 90° rotation. Others do not have stops and may be rotated 360°. With or without stops, a 90° rotation is all that is required for closing or opening a ball valve.
The handle indicates valve ball position. When the handle lies along the axis of the valve, the valve is open. When the handle lies 90° across the axis of the valve, the valve is closed. Some ball valve stems have a groove cut in the top face of the stem that shows the flowpath through the ball. Observation of the groove position indicates the position of the port through the ball. This feature is particularly advantageous on multiport ball valves.
When people talk about ball valve advantages and disadvantages, one of the major pros that comes up is the fact that they're highly durable. Ball valves are recognised for their ability to provide many years of reliable service, particularly the plastic variety, which are obviously not prone to rusting like their metal counterparts.
Of course, as with any component that is under constant strain, damage can occur. Another great advantage of some types of ball valves is that they're very simple to repair. Thanks to their basic design, you can easily access seals and seats to fix them as and when you need to. Repairs can take place fairly quickly and without intense workmanship.
It's also worth noting that ball valves, thanks to the regulating elements' design, makes it easy for the component to function without having to worry about side loads, which are often a problem when using butterfly or globe valves. This means that ball valves are less prone to damage than other kinds of valves.
Learn more about types of valves and which to choose for your next project.
In some cases, it's necessary to replace the ball valve altogether. As they're affordable and long-lasting, this is a job that shouldn't cost a fortune or be required too often.
Qingdao Haiying Valve Co., Ltd. which located in Qingdao city, the gold southeast coast of Shandong, where is very near to China Qingdao Port and Airport. We devote to manufacture and supply ball valve, butterfly valve, gate valve, check valve, safety valves, storm valves etc., with cast bronze, cast brass, cast steel, Stainless steel(CF8, CF8M, CF3, CF3M) material. If you are interested in our products, please feel free to contact us!
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