In the world of piping engineering and fluid control systems, ball valves are a crucial component that plays a vital role in regulating the flow of liquids and gases. These valves are widely used in various industries, ranging from oil and gas to water treatment, due to their exceptional reliability, versatility, and ease of operation. This article provides everything you need to know from ball valve definition, types, parts, working, materials, end connections, specifications, advantages, and standards to testing and uses.
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Types of Pipes | Classification of Pipes (PDF)What is a Venturimeter?
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What is a Venturimeter?A ball valve is a type of valve that uses a spherical perforated obstruction (a rotary ball) to stop and start the hydraulic flow. A ball valve is usually rotated 90° (quarter-turn valve) around its axis to open and close. It is one of the most widely used valve types. Ball Valves are suitable for both liquid and gas services. They are highly popular in the chemical, petrochemical, and oil and gas industry because of their long service life and reliable sealing throughout their service life. Ball valves can even be used for vacuum and cryogenic services. Developed around 1936, Ball valves are among the least expensive valves which are available in extremely wide size ranges.
Ball valves are sometimes used as control valves due to their cost-effectiveness but are not preferred as they don’t provide precise control and adjustments. The ball is positioned within a valve body, and a handle or actuator is used to rotate the ball either perpendicular or parallel to the flow direction, thus controlling the fluid flow. When the hole aligns with the flow direction, the valve is in the open position, allowing fluid to pass through. Conversely, rotating the ball to block the hole closes the valve, stopping the flow.
Ball valves find application across a wide range of industries due to their versatility and ability to handle various types of fluids, from corrosive chemicals to high-pressure gases. Major applications of ball valves include
As shut-off and isolation valves for tower bottom lines and thermal-cracking units; Gas/Oil separation lines, Gas distribution measuring, metering, and pressure regulation stations, Oil loading control stations, Pumping, and compressor stations, Emergency shut-down loops, Refining units, etc.
Ball valves are used for low differential pressure control, emission control, handling highly viscous fluids, and abrasive slurries in process and storage facilities. They are suitable for handling corrosive chemicals and hazardous materials, making them a preferred choice in chemical processing plants.
For boiler feedwater control, such as burner trip valves, for control and shut-off for steam, etc.
In subsea isolation and shut-down facilities, For oil-head isolation, pipeline surge control, processing separation, storage, transmission and distribution, secondary and enhanced oil recovery.
As shut-off valves, In pulp mill digesters, batch-digester blow service, liquor fill and circulation, lime mud flow control, dilution water control, etc.
Municipal water treatment plants utilize ball valves for controlling the flow of water in various processes, such as filtration, chlorination, and distribution.
Heating, ventilation, and air conditioning systems use ball valves for regulating the flow of water and refrigerants in commercial and residential buildings.
Other uses of ball valves include
Below-mentioned international Codes and Standards are used for Ball valve Design
The housing, seats, ball, and lever for ball rotation are the major parts of a standard ball valve. Refer to Fig. 1 below which shows the internal parts of a ball valve.
Fig. 1: Ball Valve PartsBall valves are manufactured with the following crucial parts:
The main part of a ball valve is the valve body which contains all of the internal components for on/off control.
A ball with a center hole through which the media flows is the main characteristic of ball valves that differentiates these valves from other valve types. The hole of the ball through one axis connects the inlet to the outlet. The Stem controls the direction of the ball. The ball may be free-floating or trunnion-mounted. Trunnion-mounted ball valves reduce the operating torque to about 2/3rd that of the floating ball valves.
The stem of a ball valve connects the ball to the external control mechanism.
The seats of a ball valve are discs that lie in between the ball and the body. It provides the necessary seal between the two and also supports the ball.
A manual or actuated power source provides energy to the stem of the ball valve for rotating it. Manual actuation uses levers and handles, which the operator controls during requirements. Automatic actuators use electric, pneumatic, or hydraulic power sources.
Packing is a seal around the stem to prevent the media escape.
The bonnet is part of the ball valve body that contains the stem and packing.
A ball Valve is a rotary motion valve. When the stem (Item 04 in Fig. 1) transfers the motion to the connected ball (Item 03), the ball rotates. This ball of a ball valve is rested and supported by the ball valve seats (item 05). This rotation of the ball over valve seats allows the bore to open or close helping the fluid to flow or stop.
For manual ball valves with normal service, when the port opening of the ball is in line with the inlet and outlet ports, flow continues uninterrupted through the valve, undergoing a minimal pressure drop if a full-port ball is used. Obviously, the pressure drop increases with the use of a reduced-port ball. When the hand operator is placed parallel to the pipeline, the flow passages of the ball are in line with the flow passages of the body, allowing for full flow through the closure element. As the hand operator is turned to the closed position, the ball’s opening begins to move perpendicular to the flow stream with the edges of the port rotating through the seat. When the full quarter-turn is reached, the port is completely perpendicular to the flow stream, blocking the flow.
In throttling applications, where the ball is placed in a mid-turn position, the flow experiences a double pressure drop through the valve, similar to a plug valve. When a characterizable ball is used to provide a specific flow to position, as the ball is rotated from closed to open through the seat, a specific amount of port opening is exposed to the flow at a certain position, until 100 percent flow is reached at the full-open position.
As with all rotary-action valves, the ball valve strokes through a quarter-turn motion, with 0° as full-closed and 90° as full-open. The actuator can be built to provide this rotary motion, as is the case with a manual hand lever, or can transfer linear motion to rotary action using a linear actuator design with a transfer case.
When full-open, a full-port valve has minimal pressure loss and recovery as the flow moves through the valve. This is because the flow passageway is essentially the same diameter as the pipe inside diameter, and no restrictions, other than some geometrical variations at the orifices, are present to restrict the flow. The operation of throttling full-port valves should be understood as a two-stage pressure drop process. Because of the length of the bore through the ball, full-port valves have two orifices, one on the upstream side and the other on the downstream side. As the valve moves to a mid-stroke position, the flow moves through the first narrowed orifice, creating a pressure drop, and moves into the larger flow bore inside the ball where the pressure recovers to a certain extent. The flow then moves to the second orifice, where another pressure drop occurs, followed by another pressure recovery. This two-step process is beneficial in that lower process velocities are created by the dual pressure drops, which is important with slurry applications. The flow rate of a full-port valve is determined by the decreasing flow area of the ball’s hole as the valve moves through the quarter-turn motion, providing an inherent equal-percentage characteristic with a true circular opening. As the area of the flow passageway diminishes as the valve approaches closure, the sliding action of the ball against the seal creates a scissor-like shearing action. This action is ideal for slurries where long entrained fibers or particulates can be sheared off and separated at closing.
At the full-closed position, the entire face of the ball is fully exposed to the flow, as the flow hole is now perpendicular to the flow, preventing it from continuing past the ball.
With the characterized segmented ball design, only one pressure drop is taken through the valve—at the orifice where the seal and ball come in contact with each other. When the segmented ball is in the full-open position, the flow is restricted by the shape of the flow passageway. In essence, this creates a better throttling situation, since a pressure drop is taken through the reduction of flow area. As the segmented ball moves through the quarter-turn action, the shape of the V-notch or parabolic port changes with the stroke, providing the flow characteristic. Like the full-port design, the sliding seal of the characterizable ball provides a shearing action for separating slurries easily.
Types of Ball valves are classified based on various parameters as listed below:
Depending on the end-to-end dimension of the valves, two types of ball valves are available. They are
The end-to-end dimension and weight of short-pattern ball valves are less as compared to long-pattern ball valves. However, During piping design, a long pattern dimension is selected for ease of connection to pipe flanges. Also, short-pattern ball valves are not available after a specific size and flange rating. So, long pattern ball valves are the only option in such cases.
Depending on the seat materials of the valve, two types of ball valves are found; Soft Seated and Metal Seated Ball Valves.
Soft, non-metal seated ball valves satisfactorily cover most of the applications. Soft seated ball valves use a thermoplastic material such as PTFE, NBR, etc. However, abrasive media, high pressure, and temperature can severely stress the polymeric seals leading to damage. Because of this reason metal-seated ball valves were developed in the 1960s.
Metal seated ball valves use metal as seat material such as 316 SS, Monel, etc. Tight shut-off, no jamming, smooth control, good corrosion and wear resistance, wide temperature range, stability under pressure, etc. are the advantages that a metal-seated ball valve provides with its soft-seated counterparts.
The main differences between soft-seated and metal-seated ball valves are tabulated below:
Soft Seated Ball ValveMetal Seated Ball ValveElastic non-metallic material like PTFE, Delrin, Nylon, PEEK, etcMetal Alloys like Copper alloy, Nickel based alloy, Chrome Stainless Steel, etc are used as seat materialUsed for low or medium temperature and pressure serviceWidely used for high-pressure and temperature servicesLow costHigh CostHigh level of SealingComparatively poor sealingUsed for clean services like air, water, etcUsed for severe service conditions like hot water, oil, gas, acid, and other chemicals.Lower torque requirement for operation.Higher torque requirementTable: Soft Seated Ball Valve vs Metal Seated Ball ValveThermoplastic or Elastomeric seats are inserted in a metallic holder (seat ring) to provide soft seating action in a ball valve. The main features of a soft-seated ball valve are
The main features of metal-seated ball valves are
Based on the inner diameter of the ball valve two types of ball valves are used in industries; Reduced Bore Ball Valve and Full Bore Ball valve.
Reduced port ball valves are quite common in the piping industry. However, reduced bore ball valves introduce frictional losses. The main design features of such ball valves are
Full bore or Full port valves do not cause extra frictional losses, and the system is mechanically easier to clean as it allows pigging.
In V-shaped ball valves, The hole in the ball or the valve seat has a “V” shaped profile. This design offers more precise control of the flow rate.
Vented Ball Valves: In a vented ball valve design, a small hole is drilled into the upstream side to eliminate unwanted pressure within the valve.
Depending on the body construction of valves, there are three types of ball valve designs; One-piece, Two-piece, and three-piece ball valves
In the single-piece design ball valve, the body will be cast/forged as one piece. The insertion of the ball will be through the end of the body and is held in position by the body insert. This design offers the unique advantage of eliminating the possibility of external leakage to the atmosphere through bolted body joints. This design restricts the ball valve to be of reduced port floating design only (for sizes up to 4” NB).
Fig. 4: Single Piece Ball Valve DesignThe two-piece design complements the single-piece design in sizes of 6” & above for reduced bore and for FB design valves. In a two-piece design, the body is constructed in two pieces and the ball is held in position by the body stud. There can be a full bore or reduced bore design possible in this construction.
In the case of a three-piece design, the body has two end pieces and one centerpiece. Three-piece design ball valves are most easily online maintainable. By removing the body bolts and keeping only one, the body can be swung away using the last bolt as the fulcrum, to carry out any installation or maintenance operation on the valve. This feature reduces maintenance downtime to a bare minimum.
Fig. 5: Multi-piece DesignFor larger 2-piece or 3-piece ball valves, the dimensions between the body and flange should be checked so that sufficient clearance is available for bolting. During the vendor drawing review stage, the same should be checked and ensured.
Fig. 6: Ball Valve DesignFrom the perspective of Ball Valve Body Styles, they are divided into three types of ball valve designs. They are
In the case of a side entry ball valve, the ball is assembled from the side part. They normally have two pieces or three pieces of the body. Each part of the body is assembled by a bolt/stud similar to joining a two-piece of flanges. Side entry ball valves are usually made by forging the metal. Each piece of the body is forged separately and then assembled together to get the complete design. This construction is robust in design and minimizes the defects caused by casting valves. Side entry ball valves are also easy to assemble and the trim component is also easy to align. Another advantage of the side entry ball valve type is that they are easily available from almost all vendors rather than a casting product that still needs some additional testing.
The main design features of top-entry ball valve types are
The main design features of this type of ball valve design are
Depending on the supporting and positioning of the ball, two types of ball valves are used; Floating Ball Valves and Trunnion Mounted Ball Valves
In a floating ball valve, the ball is not fixed in place and is free to move slightly within the valve body. Sealing is achieved through the pressure of the fluid against the ball.
The major design features of a floating ball valve are
Trunnion ball valves have a fixed ball with a shaft extending through it. This design provides more support to the ball, making it suitable for high-pressure and large-diameter applications. Trunnion ball valves are known for their increased durability and reliability in demanding conditions.
The major design characteristics of a trunnion-mounted ball valve are
Based on the pressure relieving capability of the ball valve seats, two types of ball valves are designed; Single Piston Effect Design and Double Piston Effect Ball Valve Design
The important design features of single piston effect seat design are
The design characteristics of a double piston effect seat design ball valves are
The pressure-temperature ratings of ball valves are decided based on the valve body and sealing materials used for soft-seated ball valves. Sealing materials may be PTFE, 15 to 25% glass-filled PTFE, FPM, NRG, Celastic, POM, Lyton, and Steel. It is very difficult to pre-determine exact pressure-temperature ratings for all kinds of media under all imaginable loading conditions.
The pressure-temperature rating for metal-seated ball valves is decided based on body ratings.
When the ball valve is in a fully closed or fully open position, each seat seals off the process medium independently at the same time between the up/downstream and body cavity; it allows bleeding of the cavity pressure through a drain or vent valve. This DBB feature permits in-line periodic inspection of the valves and the checking of sealing integrity when the valve is installed in the line. This feature is available with self relieving seat (SPE) configuration.
The integrity of stem seals at very low temperatures (-30 degrees C & below) is the major hurdle that must be overcome. Specially designed extended bonnets installed to valves offer a safe & efficient method to accomplish stem seal integrity.
The bonnet extension provides a gas column that allows the gas to vaporize from contact with the warm ambient temperature outside the service line. This vapor column insulates the stem seal and maintains the seal integrity. Bonnet extension also helps with thermal insulation installation.
Fig. 21: Extended BonnetSealing areas & other wetted parts of the ball valve can be cladded in case of corrosive service. More frequently used materials for the overlay process are stainless steel, DSS & high nickel alloys. This technology is cost-effective for ball valves in highly corrosive or erosive services. Considerable cost saving without sacrifice to service life or performance. It can be done cost-effectively for sizes 8” and larger. Welding is performed in accordance with ASME BPV section 9.
Fig. 22: Weld OverlayDevlon V: Temp. Range -100 deg. C to 150 deg. C
O-rings are used for below applications:
Materials are generally as follows:
O-rings are not allowed in the seat ring-body joint as well as for the body-bonnet joint. The ball valve seat ring shall have a primary lip seal with a fire-safe graphite ring.
On the stem side, if the seal material specified in the requisition as thermoplastic, it shall be of lip seal type with Inconel 718 spring. If the seal material is specified as elastomeric, it shall be of AED type.
The type of ball valve ends are as follows:
Ball Valves can be operated by a lever, wrench, or hand wheel or they can be pneumatic, hydraulic, or motor-operated. A ball valve is rotated in a clockwise direction to close & anti-clockwise direction to open. The maximum lever length shall not exceed 450 mm & maximum handwheel diameter shall not exceed the valve face-to-face dimension of 800mm whichever is smaller. A gear operator is required to be provided for valves as per the below criteria:
Ball valves as ESD valve application shall be of trunnion mounted type with metal seat design. The minimum size shall be 2” NB. Upstream seats of such ball valves shall be with a single-piston effect and downstream seats with a double-piston effect.
The SPE & DPE shall be marked permanently on the respective seat side and the flow arrow shall be embedded on the ball valve body. However, the valve shall be suitable for bi-directional isolation. The seat ring shall have 2 primary leap seals with a fire-safe graphite ring. The stem shall have a minimum of 2 primary lip seals or U or V-shaped packing with fire-safe secondary seals.
Grease injection fitting shall be provided between primary & secondary seals on the stem side with 2 in-built check valves. No seat sealant injection shall be provided for ESD valves.
Ball Valves of sizes 8” NB and above or 250 Kg & heavier shall be equipped with lifting lugs. Tapped holes & eye bolts are not acceptable. Ball valves weighing more than 750 kg shall have support lugs and these should be designed to take care of the vertical & lateral loads of valves. The support height shall be as minimum as possible.
Drain and Vent connections shall be drilled & threaded for ball valves up to 900# pressure class & for sizes less than 6” –FB & 8”-RB. The connections shall be fitted with a threaded plug. The plug shall be suitably locked by a locking ring to prevent loosening.
The drain & vent connections for ball valves above 900# pressure class & 6” –FB / 8” -RB & above sizes shall be fully welded flanged type, fitted with a blind flange. If drain/vent/sealant injection is asked, ensure the orientation of the connections is accessible at the site. During the ball valve vendor drawing review, the same should be checked.
While purchasing a ball valve, the following information should be provided to the vendor/manufacturer:
The important Advantages of a Ball valve are listed below
Because of all these benefits, ball valves find wide application in the following industries.
However, there are a few disadvantages of ball valves like
The major differences between a Ball Valve and a Gate valve are tabulated below:
Ball ValveGate ValveBall Valve uses a ball for opening or closingGate valve used a gate or wedge for opening or closingThe ball Valve is a quarter-turn rotary motion valveGate valve uses a gate or wedge for opening or closingThe sealing capacity of Ball Valves is comparatively higherComparatively less sealing.Durability moreLess durabilityQuick operation, prone to surgeOperation is slow hence, less probability of surge creation.More number of valve configurations Less number of valve configurationsMore expensiveComparatively low costLess CorrosionHigher CorrosionLow-Pressure DropHigh-Pressure DropTable 1: Ball Valve vs. Gate Valve TableIn the realm of fluid control, ball valves stand as a testament to the ingenuity of engineering. Their versatile design, reliable operation, and ability to withstand challenging conditions make them an indispensable component across industries. Whether in oil and gas pipelines, chemical plants, or everyday household systems, the unassuming ball valve plays a crucial role in ensuring the smooth and efficient flow of fluids that power our modern world.
A ball valve is a type of valve used to control the flow of fluids. It operates by rotating a spherical ball inside the valve body. When the hole in the ball aligns with the flow direction, the valve is open, allowing fluid to pass through. Rotating the ball to block the hole closes the valve, stopping the flow.
There are two primary types of ball valves:
Ball valves are widely used across various industries, including:
Some key advantages of ball valves include:
Yes, ball valves are suitable for both on/off and throttling (partial flow control) applications. However, for precise control in throttling situations, it’s important to choose the right type of ball valve and size it appropriately.
Trunnion ball valves, with their fixed ball and additional support, are well-suited for high-pressure applications. Floating ball valves are generally used in lower-pressure situations.
While ball valves can handle some solid-laden fluids, they are not the best choice for controlling highly abrasive or viscous slurries. In such cases, specialized valves like knife gate valves or pinch valves may be more appropriate.
Yes, ball valves can be equipped with actuators (electric, pneumatic, or hydraulic) for remote control and automation. This is especially useful in industrial processes where precise control and monitoring are essential.
To select the right ball valve, consider factors like the type of fluid, operating temperature and pressure, pipe size, the specific application, end connections, material requirements, flow control requirements, actuation types, etc
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