What is a Ball Valve?
A ball valve is a type of valve that utilizes a rotary ball to open and close hydraulic flow. This type of valve is often used in the chemical, petrochemical, and oil and gas industry because it is known to have a long service life and provide reliable sealing. Developed in 1936, ball valves are also among the most cost-effective valves available, and they can be used in a wide range of sizes.
Advantages of Ball Valves
Ball valves have several advantages over other types of valves, including their cost-effectiveness, long service life, and their ability to be used with both liquid and gas services. Additionally, they can be used with vacuum and cryogenic services, making them suitable for a variety of applications.
Uses of Ball Valves
Ball valves are often used in the chemical, petrochemical, and oil and gas industry because of their reliability and long service life. They are also used in applications where precise control and adjustment is not required. Additionally, ball valves can be used for vacuum and cryogenic services as well.
Applications of Ball Valves
Applications of Ball Valves
Ball valves are used in a variety of industries and applications. They are often used as isolation and shut-off valves, as well as for low differential pressure control and emission control. Here, we discuss some of the major applications of ball valves.
Use of Ball Valves in Refineries
Ball valves are used extensively in refineries for a variety of purposes. They are used for tower bottom lines and thermal-cracking units, gas/oil separation lines, gas measuring, metering and pressure regulation stations, oil loading control stations, pumping and compressor stations, emergency shut-down loops, and other refining units.
Use of Ball Valves in Chemical and Petrochemical Complexes
Ball valves are also used in chemical and petrochemical complexes for low differential pressure control, emission control, handling viscous fluids, and abrasive slurries in process and storing facilities.
Power Industry Applications of Ball Valves
In the power industry, ball valves are used for boiler feedwater control, burner trip valves, control and shut-off for steam, and other applications.
Ball Valves in Gas and Oil Production
In gas and oil production, ball valves are used in subsea isolation and shut-down facilities, oil-head isolation, pipeline surge control, processing separation, storage, transmission and distribution, and secondary and enhanced oil recovery.
Use of Ball Valves in the Pulp and Paper Industry
Ball valves are used as shut-off valves in pulp mill digesters, batch-digester blow service, liquor fill and circulation, lime mud flow control, and dilution water control.
Other Uses of Ball Valves
Ball valves are also used in the food, marine and solid transport, and water supply and transport industries.
Ball Valve Standards
Design Standard for Ball Valves
The design of ball valves is guided by several international Codes and Standards, including API 6D, ISO 14313, BS EN 17292, BS 5351, and MSS SP 72.
Testing Standard for Ball Valves
Testing of ball valves is carried out in accordance with API 6D, API 598, BS 6755 Part I, and MSS SP 61.
Fire Testing Standards for Ball Valves
Fire testing of ball valves is conducted as per API 6FA, API 607, ISO 10497, or BS 6755 Part II.
Dimensional Standard for Ball Valves
The dimensional standard for ball valves is ASME B16.10 and API 6D.
Parts of a Ball Valve
Parts of a Ball Valve
Valve Body:
The valve body is the main part of a ball valve, which contains the internal components for on/off control. It is the main characteristic that differentiates these valves from other types of valves.
Rotary Ball:
The rotary ball is the core of the ball valve, which has a hole through the middle that allows the media to flow. The stem is used to control the direction of the ball, which can be free-floating or trunnion-mounted. Trunnion-mounted ball valves reduce the operating torque by two-thirds.
Stem:
The stem of the ball valve links the ball to the external control mechanism. It is also responsible for providing the necessary rotation to the ball valve.
Seats:
Seats are discs that are placed between the ball and the body, which provide a seal and support the ball.
Power Source:
A manual or actuated power source is needed to provide the energy for the stem of the ball valve to rotate. Manual actuation uses levers and handles, while automatic actuators use electric, pneumatic, or hydraulic power sources.
Packing:
Packing provides a seal around the stem to prevent the media from escaping.
Bonnet:
The bonnet is the part of the ball valve body which houses the stem and packing. It is used to seal the valve and protect the internal components.
Ball Valve Working
Introduction to Ball Valves
A ball valve is a rotary motion valve that is used to regulate the flow of fluids in a pipeline. This is achieved by transferring motion from the stem to the connected ball, which then rotates, allowing the bore to open or close and permitting or blocking the flow of the fluid.
Manual Ball Valves
Manual ball valves are used for normal service and utilize a full-port or reduced-port ball. When the port opening is in line with the inlet and outlet ports, flow continues uninterrupted through the valve, albeit with a small pressure drop if a full-port ball is used. 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.
Throttling Applications
With throttling applications, 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.
Quarter-Turn Motion
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.
Full-Port Valves
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.
Characterizable Ball Valves
Characterizable ball valves are designed 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. When the segmented ball is in the full-open position, the flow is restricted by the shape of the flow passageway. 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.
Full-Closed Position
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.
Ball Valve Types | Types of Ball Valves
Types of Ball valves are classified based on various parameters as listed below:
- Overview of Ball Valve Types: Short Pattern vs Long Pattern
Ball valves have two main types: short pattern and long pattern. The end-to-end dimension and weight of short-pattern ball valves are less in comparison to the long-pattern valves. When it comes to piping design, long-pattern valves are selected for their ease of connection to pipe flanges. Additionally, short-pattern valves are not available after a specific size and flange rating, making long-pattern valves the only option in such cases. - Advantages of Long-Pattern Ball Valves
Long-pattern ball valves provide multiple advantages that make them the ideal choice for many applications. They are easier to connect to pipe flanges and are available in larger sizes and with higher flange ratings, making them suitable for a variety of tasks. Additionally, the greater length of the long-pattern valves helps to reduce the risk of leakage. - Considerations When Choosing Ball Valves
When selecting ball valves, it’s important to consider the specific application and the end-to-end dimension and weight requirements. Depending on your needs, short-pattern or long-pattern ball valves may be the best option. It is also important to consider the size and flange rating of the valves and whether the valves can be easily connected to the piping system.
2. Types of Ball Valves: Soft Seated vs Metal Seated
Soft Seated Ball Valves
Soft Seated Ball Valves are a type of ball valve that uses thermoplastic material such as PTFE, NBR, etc. for its seat. These valves are typically used for most applications, however, there are certain situations where the polymeric seals can be damaged due to abrasive media, high pressure, and temperature.
Metal Seated Ball Valves
Metal Seated Ball Valves are a type of ball valve that uses metal as seat material such as 316 SS, Monel, etc. These valves provide a number of benefits such as tight shut-off, no jamming, smooth control, good corrosion and wear resistance, wide temperature range, stability under pressure, etc. Metal Seated Ball Valves were developed in the 1960s as a solution to the limitations of Soft Seated Ball Valves.
The main differences between soft-seated and metal-seated ball valves are tabulated below:
| Soft-Seated Ball Valves | Metal-Seated Ball Valves |
|---|---|
| Made of softer materials such as PTFE or rubber. | Made of hard materials such as stainless steel or chrome. |
| Provide tighter sealing against pressure and higher temperatures. | Provide better flow control and less leakage. |
| More prone to wear and tear due to the soft material. | More durable and can withstand higher pressures and temperatures. |
| More cost-effective. | More expensive. |
Soft Seat Ball Valve Design
Soft Seating Ability and Low Cost
The main features of a soft-seated ball valve are the ability to provide a good sealing ability and a lower cost than metal seated valves. Soft seat materials used for this type of valve include PTFE, Nylon, Devlon, and PEEK. Typically, these valves are rated to a leakage of ISO 5208 Rate A.
Metal Seat Ball Valve Design
Durability and Abrasion Resistance
The main features of metal-seated ball valves are direct metal-to-metal contact between the seat ring and ball. These valves are used for abrasive service and services where soft seated valves cannot be used due to temperature limitations. The ball and seat contact surfaces are hard-faced to improve resistance to wear and prevent scratching caused by solid particles. Metal sealing is achieved through tungsten carbide coating (up to 200 deg. C), chromium carbide coating (above 200 deg. C), electroless nickel plating (ENP), or stellite hard facing. These valves are typically rated to a leakage of ISO 5208 Rate D. However, metal-seated ball valves can be prone to pitting, fretting, stress corrosion cracking, and intercrystalline corrosion damages.
3. Ball Valves Types: Reduced bore, Full bore, V-shaped, and Vented ball valves
Reduced Bore (Reduced Port) Ball Valve Design
The reduced bore or reduced port ball valve design is a common choice in the piping industry. This type of ball valve has a bore diameter that is one size smaller than the pipe diameter for valves up to 12” NB, and two sizes smaller for sizes 14” NB to 24” NB. These valves are smaller, have a lower operating torque, and produce a slightly higher pressure drop than full bore valve designs. They are most often seen in one-piece end entry designs for smaller sizes and two or three-piece side entry designs for larger sizes.
Full Bore (Full Port) Ball Valve Design
Full bore or full port ball valve designs are chosen for specific reasons, such as minimal pressure drop, minimal erosion, pigging requirement, and gravity flow. These valves have a bore inside diameter that is the same as the pipe inside diameter, resulting in less pressure drop compared to reduced bore designs. However, due to their larger size and weight, full bore ball valves are more expensive than reduced bore valves.
V-Shaped Ball Valves
V-shaped ball valves have a hole or valve seat with a “V” shaped profile, allowing for more precise control of the flow rate. This design is preferred for applications that require more exact control of the flow.
Vented Ball Valves
Vented ball valve designs have a small hole drilled into the upstream side for eliminating unwanted pressure within the valve. This design is used in applications where it is important to quickly and safely release any built-up pressure.
4. Types of Ball Valves: One-piece, Two-piece, and Three-piece ball valves
Types of Ball Valve Designs
Single Piece Body Design
The single-piece design ball valve has a body cast/forged as one piece. This design eliminates the possibility of external leakage to the atmosphere through-bolted body joints and is restricted to reduced port floating design only (for sizes up to 4” NB).
Two-Piece and Three Piece Ball Valve Design
The two-piece design complements the single-piece design in sizes of 6” & above for both reduced bore and FB design valves. A full bore or reduced bore design is possible in this construction.
The three-piece design ball valve has two end pieces and one centerpiece. This design is the most easily online maintainable. By removing the body bolts and keeping 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 minimizes maintenance downtime. For larger two pieces or three-piece ball valves, the dimensions between the body and flange should be checked to ensure sufficient clearance is available for bolting.
5. Ball Valve Types: Side entry, Top entry, or welded body ball valves
Side Entry or End Entry Ball Valve Design
Side entry or end entry ball valves are a type of ball valve design that feature an assembly of the ball from the side part. These valves have two or three pieces of the body, each part of which is assembled with a bolt/stud similar to joining two pieces of flanges. Side entry ball valves are typically made of forged metal, with each piece of the body being forged separately and then assembled together. This type of valve is robustly designed and helps to minimize defects caused by casting. Additionally, side entry valves are easy to assemble and their trim components are easily aligned. This type of valve is also widely available from vendors.
Top Entry Ball Valve Design
The top entry ball valve design features a flange that can be removed for maintenance and repair without having to remove the valve from its installation. It is available in both welded and flanged end connections, though welded ends are preferred to reduce potential leak paths and minimize the ball valve’s weight. This type of ball valve is the heaviest and most expensive construction available.
Welded Body Ball Valve Design
Welded Body Ball Valve Design: Eliminating Potential Leak Paths
The welded body ball valve design eliminates body flanges, reducing the number of potential leak paths and increasing resistance to pipeline stresses. This is especially beneficial for fugitive emission and vacuum applications. Additionally, the compact and lightweight design makes the valve easy to handle and maintain.
Welded Body Ball Valve Design: Testing and Maintenance
The body draining and venting feature of the welded body ball valve design allows technicians to test each seat ring seal for proper functioning with the ball in either the open or closed position. Sealant injection fittings provide direct access to each seat ring, enabling technicians to top up the lubricant inside the valve sealant injection system and flush out the old grease with valve cleaner. Heavier sealants can also be injected through these fittings in the event of an emergency.
Welded Body Ball Valve Design: Applications
The welded body ball valve design is suitable for a variety of applications, including oil and gas pipelines, compressor stations, and measuring skids.
6. Ball Valve Types depending on the type of ball design: Floating Ball Valve vs Trunnion Mounted Ball Valves
Floating Ball Valve Design
The floating ball valve design features an unrestrained ball that is pressed onto the downstream seat by the fluid pressure from upstream. This allows for pressure sealing of the downstream of the valve when in the closed position. This type of ball valve is typically used for low pressure ratings and small sizes, as the seat loading increases with higher pressure and larger sizes, which can become excessive for soft-seated valves. This design generally requires a higher operating torque and metal-seated floating ball valves often use spring-loaded seats.
Trunnion Mounted Ball Valve
Trunnion mounted ball valves provide reliable sealing at low pressures with the ball supported by the stem and trunnion and held in place by bearings in the body. The seat is spring-loaded onto the ball and the pressure from the line forces the upstream seat onto the ball to create a seal. This design requires less force due to the smaller area in which pressure is applied, allowing for smaller actuators and gearboxes. Trunnion mounted ball valves are typically used for higher pressure ratings and larger sizes, with single or double-piston effects used for the seat design. Self-relieving seats are also included, allowing for automatic body cavity relief exceeding 1.
7. Types of Ball valves: Single vs Double piston effect design
Single Piston Effect Seat Design
The single piston effect seat design is characterized by seats pressed on the ball by spring load. When the body cavity pressure increases higher than the spring load, the seats are pushed back and the pressure is released in the line. This is referred to as a single-piston effect, as the pressure in the body cavity is the only parameter acting. With this design, the cavity relief is directed to the downstream side if both the ball valve seats are of single-piston effect design, with each seat self-relieving the body cavity overpressure to the line.
Double Piston Effect Seat Design
The double piston effect seat design of ball valves is characterized in that both the medium pressure and body cavity pressure create a resultant thrust that pushes the seat rings against the ball. This is referred to as a double piston effect as the pressure in the pipe and that in the body cavity are both acting parameters. This design requires a cavity pressure relief device in order to reduce the body cavity pressure. Double piston effect is synonymous with “bi-directional” while single piston effect is synonymous with “uni-directional” as defined by API 6D/ISO 14313.
Body Cavity Relief (Pressure Equalisation)
Ball Valves and Pressure Equalisation
Ball valves are double-seated valves which include a cavity between the two seats. When the seats become damaged, the body cavity can become pressurised. Trunnion-mounted ball valves require cavity relief provisions, whereas floating ball valves do not, as the seats are fixed and the ball is floating. When possible, the cavity relief should be to the upstream side of the valve.
DPE – External pressure relief
DPE – External Pressure Relief
When the cavity pressure exceeds the net spring load of the pressure relief valve, the pressure is vented through the Relief Valve. The Relief Valve outlet line can be connected to a vent system, the atmosphere, or back to the upstream piping.
Ensuring Proper Pressure Equalisation in Ball Valves
To ensure proper pressure equalisation within ball valves, trunnion-mounted ball valves must include cavity relief provisions. The cavity relief should be directed to the upstream side of the valve where possible. Additionally, when the body cavity pressure increases beyond the net spring load of the pressure relief valve, the cavity pressure can be vented through the Relief Valve. The Relief Valve outlet line can be connected to an external vent system, the atmosphere, or back to the upstream piping.
Types of Ball Valve Seat Design
Single-Piston Effect Seat:
Single-piston effect seats are used on the upstream side of a ball valve. This type of seat allows for the cavity overpressure to be released to the upstream side of the valve, eliminating the need for an external relief valve. These valves are unidirectional and the flow direction is marked on the valve body.
Double-Piston Effect Seat:
Double-piston effect seats are used on the downstream side of a ball valve. This type of seat provides a single barrier against normal flow conditions and a double barrier against reverse flow from the downstream pipeline. For Emergency Shutdown (ESD) or Protective Shutdown (PSD) valves, a reverse configuration is required with SPE for the upstream seat and DPE for the downstream seat.
Pressure Temperature Ratings of Ball Valves
Pressure-Temperature Ratings of Ball Valves
The pressure-temperature ratings of ball valves are determined based on the materials used for their construction. Soft-seated ball valves utilize sealing materials such as PTFE, 15 to 25% glass-filled PTFE, FPM, NRG, Celastic, POM, Lyton, and Steel. It is difficult to accurately predict the pressure-temperature ratings for all possible media and loading conditions.
Metal-Seated Ball Valve Pressure-Temperature Ratings
The pressure-temperature ratings of metal-seated ball valves are determined by their body ratings. The specific materials used for construction can vary, depending on the application.
Double Block & Bleed (DBB) feature
Double Block & Bleed (DBB):
A double block and bleed (DBB) feature is a type of ball valve that has two independent seals when it is in a fully closed or fully open position. This feature allows for the pressure between the upstream and downstream to be bled off through a drain or vent valve, allowing for in-line inspection of the valves and the checking of sealing integrity when installed in the line. This feature is available with a self relieving seat (SPE) configuration.
Double Isolation & Bleed (DIB):
A double isolation and bleed (DIB) is a type of ball valve that has either one or both bidirectional (DPE) seats. This type of valve is different from a DBB in that the downstream seat seals and prevents the upstream pressure from reaching the downstream piping. It is important to note that this type of valve is not able to provide the same pressure relief as a DBB valve.
Blow-Out Proof Stem Design Feature:
The blow-out-proof stem design feature of a ball valve ensures that the top graphite packing rings can be replaced while the valve is under pressure, without the stem being pushed out (blown out). This is achieved by the stem being sealed by o-rings and graphite packing rings and held in position by the stem housing, which is bolted to the body. The graphite packing rings are compressed and held in position by the gland flange, which is bolted to the stem housing. Therefore, when the gland flange is removed to replace the graphite packing rings, the stem is still held securely, by the stem housing.
Stem Sealing:
The stem of a ball valve is sealed by o-rings and graphite packing rings. This creates a tight seal between the stem and the body of the valve, ensuring that the pressure is always acting upon the bottom of the stem and not allowing it to be pushed out (blown out). The o-rings and graphite packing rings provide a secure and reliable seal between the stem and the body, allowing the valve to remain open or closed without any leakage.
Stem Positioning:
The stem is held in position by the stem housing, which is bolted to the body. The graphite packing rings are compressed and held in position by the gland flange, which is bolted to the stem housing. This ensures that the stem is securely held in its position, allowing the valve to remain open or closed without any leakage.
Graphite Packing Ring Replacement:
The graphite packing rings can be replaced while the valve is under pressure, without the stem being pushed out (blown out). This is due to the stem being held securely, by the stem housing, even when the gland flange is removed to replace the graphite packing rings. This feature allows the stem to remain in its position, even when the valve is under pressure, ensuring that the valve remains open or closed without any leakage.
What is an Anti-Static Design Feature of Ball Valves?
Ball valves are used to control the flow of fluids, and the constant rubbing of the ball against the PTFE seats can cause the build-up of static electricity. This can be a potential fire hazard, especially when handling flammable fluids. To prevent this, ball valves feature an anti-static design that includes spring-loaded balls between the ball and stem, and the stem and body, to provide electrical continuity.
Fire Safe Design of Ball Valves
1. Internal Leakage Prevention with Fire-Safe Packing
The internal leakage from the pipeline to the body cavity is prevented by using non-metal resilient seats which, when destroyed in a fire, cause the upstream medium pressure to push the ball into the downstream metal seat lip. This cuts off the line fluid and prevents internal leakage. Furthermore, a fire-safe packing is provided at the seat ring to prevent leakage to the body cavity. This packing is usually made of graphite, a material with a melting point of 1000 degrees Celsius.
2. External Leakage Prevention with Fire-Safe Seals
To prevent external leakage from the body/stem joints to the atmosphere, all possible leakage points between the stem & gland flange, gland flange & body, and body & adapter are sealed with a primary O-ring and then a secondary graphite gasket. The primary O-ring seal is designed to burn out during a fire, while the secondary graphite gasket seal is designed to prevent the process medium from escaping. Fire-safe seals are not designed for fugitive emission performance. The fire testing of valves is done according to API 6FA, API 607, ISO 10497, or BS 6755 Part II standards.
Fire Safe Design
Fire-safe design is a design that is capable of passing a fire test with specified limits on leakage to the atmosphere and downstream after being exposed to fire. This design is not necessarily fire-tested by the manufacturer but is capable of passing the test.
Fire Tested Design
A fire-tested design is a design that has been successfully subjected to a fire test as per the applicable testing standard. This design has been proven to be able to withstand fire and its associated conditions.
Ball Valve Fire Testing Criteria
When testing ball valves, one test valve may be used to qualify valves that are up to twice the size of the test valve. Additionally, the same test valve may be used to qualify valves with higher pressure ratings, but not greater than twice the pressure rating of the test valve. The same basic design and non-metallic materials must be used for the test valve and the valves being qualified.
Ball Valve Sealant Injection System
Ball valves may be equipped with a sealant and lubricant injection connection located at the stem and seat area if specified by the purchaser. This connection is integrated with a check valve to provide backup sealing and a check valve is also equipped at the front of the seat sealant injection to avoid blowing out in the case of incorrect operation. In the event of soft sealing materials (seat inserts and o-rings) being damaged and leakage occurring due to fire or other accident, the sealant can be injected through the injection fittings.
Extended Bonnet Ball Valves: Ensuring Seal Integrity at Low Temperatures
An extended bonnet installed to valves is an effective way of ensuring seal integrity at low temperatures (-30°C and below). This bonnet extension provides a gas column that vaporizes from contact with the warm ambient temperature outside the service line. This vapor column acts as an insulation for the stem seal, maintaining its integrity and allowing for thermal insulation installation.
Weld Overlay: Cost-Effective Corrosion Protection
Weld overlay is often used to clad the sealing areas and wetted parts of a ball valve in corrosive services. The most commonly used materials for this process are stainless steel, duplex stainless steel, and high nickel alloys. This technology is cost-effective for ball valves in highly corrosive or erosive services, allowing for considerable cost savings without sacrificing service life or performance. Weld overlay is typically cost-effective for sizes 8″ and larger, and welding is performed according to ASME BPV Section 9.
Ball Valve Seat Insert Materials
Ball valve seat inserts are essential components of ball valves, used to create a tight seal between the valve body and the ball. They are available in a variety of materials, each offering unique benefits for different applications.
Thermoplastic seat/seal inserts
Devlon V: Temp. Range -100 deg. C to 150 deg. C
Devlon V is a thermoplastic material that is designed to be used in extreme temperature environments, ranging from -100°C to 150°C. It is highly resistant to wear and has excellent chemical resistance, making it ideal for applications in harsh environments. It is also easy to machine and shape, making it a great choice for complex designs.
Elastomeric seat/seal inserts
Types of Seals for Zero Leakage
When trying to achieve zero leakage, elastomeric seals are generally the best option as they are softer and can provide a better seal. However, for more resistance against scratches and other environmental factors, thermoplastic seals are the better option.
PTFE Seals
PTFE seals are a good option for a wide range of temperatures and are resistant to many fluids. However, PTFE is not recommended for high pressure applications (class 900 or higher).
Nylon 12G Seals
Nylon 12G seals are more suitable for high pressure applications than PTFE and are able to withstand a wide range of temperatures. However, Nylon 6 should not be used as it absorbs moisture.
Devlon V Seals
Devlon V seals are similar to Nylon 12G, but are able to withstand a wider range of temperatures both higher and lower.
PEEK Seals
PEEK seals are recommended for high temperature applications up to 260 degrees Celsius, but they are much harder than other non-metallic materials.
Kel-F Seals
Kel-F seals are ideal for cryogenic services and provide excellent resistance to extreme temperatures.
O-Rings: Elastomeric Seals for a Variety of Applications
O-Rings are commonly used for stem seals, seals between seat and body/closure, and seals between body and bonnet/closure. The materials used for these seals are typically Viton (fluor elastomer), NBR (nitrile butadiene rubber), and HNBR. O-rings are not suitable for seat ring-body joint or body-bonnet joint, as these applications require a primary lip seal with a fire-safe graphite ring.
Thermoplastic Seals for Stem Side
For the stem side, if the seal material specified in the requisition is thermoplastic, it should be of lip seal type with Inconel 718 spring. If the seal material is specified as elastomeric, it should be of AED type.
Lip Seal
Control valves are used to regulate the flow of liquids or gases in various industries. In order to effectively control the flow, the valves must have a secure seal between the body and the stem. To ensure that the seal is effective, there are two common types of seals that are used: elastomeric O-rings and lip seals. Both of these seals have their own benefits, depending on the application.
Benefits of Elastomeric O-Rings
Elastomeric O-rings are a type of seal that is commonly used in control valves. They are made of a flexible rubber material that can easily stretch and form a tight seal. This type of seal has the advantage of being easy to install and replace. Additionally, elastomeric O-rings are generally less expensive than other types of seals.
Advantages of Lip Seals
When elastomeric O-rings are not reliable for a given application, lip seals are used for body and stem sealing. Lip seals are self-energized seal systems that consist of a Teflon cover and a spring made from the Inconel 718 material. The spring provides the initial load due to the low elasticity of the Teflon, while the fluid pressure provides the load to force the lips on the sealing surfaces. To ensure a secure seal, the lip seal housing on CS valves is typically made of SS316 weld overlayed material that is 3mm thick.
Types of Ball Valve Ends
There are a variety of end connections available for ball valves. These include flanged ends with raised face or ring joint face, threaded ends, socket weld ends and butt-weld ends.
Flanged Ends
Flanged ends are the most common type of end connection used with ball valves. They can come with either raised face or ring joint face.
Threaded Ends
Threaded ends are used when the ball valve needs to be connected to another component with a threaded connection.
Socket Weld Ends
Socket weld ends are used when the ball valve needs to be connected to another component with a socket weld connection.
Butt-Weld Ends
Butt-weld ends are used when the ball valve needs to be connected to another component with a butt-weld connection. Soft and metal seated butt-welding end valves should be provided with butt-weld pup pieces to avoid damage to the ball valve seat and soft seal materials due to welding heat. The pup piece length varies depending on the size of the ball valve, with 200mm for sizes up to 2” NB, 400mm for up to 12” NB size and 800mm above 12” NB sizes.
How to Operate a Ball Valve
A ball valve can be operated using a lever, wrench, or hand wheel and also using pneumatic, hydraulic, or motorized mechanisms. To close the valve, the user must rotate it in a clockwise direction, and to open it, the user must turn it in an anti-clockwise direction. The maximum lever length should not exceed 450mm, and the maximum handwheel diameter should be smaller than the valve’s face-to-face dimension, which should not exceed 800mm.
Gear Operators for Different Valve Sizes
For certain valve sizes, a gear operator must be provided. The size of the valve determines the size of the gear operator that must be used. For class 150 ball valves, a gear operator of 6” or larger must be used. For class 300 and 600 valves, the gear operator must be at least 4” or larger. Lastly, for class 900 valves and higher, the gear operator must be 3” or larger.
Ball Valves as ESD Valve
Ball valves are often used as emergency shutdown valves (ESD) due to their superior shutoff performance. The minimum size of such ball valves should be 2” NB. These valves have a single-piston effect upstream seat and a double-piston effect downstream seat. The SPE and DPE should be clearly marked on the respective seat side and the flow arrow should be embedded in the body of the valve. The valve should also be suitable for bi-directional flow isolation. The seat ring should have 2 primary lip seals with a fire-safe graphite ring. The stem should have a minimum of 2 primary lip seals or U or V-shaped packing with fire-safe secondary seals. Additionally, a grease injection fitting should be provided between the primary and secondary seals on the stem side with 2 in-built check valves.
Ball Valve Lifting and Supporting Provision
Ball valves of 8” NB and above, or 250 Kg and heavier should be equipped with lifting lugs. Tapped holes and eye bolts are not acceptable. Ball valves that weigh more than 750 kg should have support lugs to take care of both vertical and lateral loads. The support height should be as minimal as possible.
Other Requirements of Ball Valves
Drain & Vent Connections for Ball Valves Up to 900# Pressure Class and Sizes Less Than 6” – FB & 8” – RB
For ball valves up to 900# pressure class and for sizes less than 6” – FB and 8” – RB, the drain and vent connections shall be drilled and threaded. These connections shall be fitted with a threaded plug and suitably locked with a locking ring to prevent loosening.
Drain & Vent Connections for Ball Valves Above 900# Pressure Class and 6” – FB / 8” – RB & Above Sizes
For ball valves above 900# pressure class and 6” – FB / 8” – RB & above sizes, the drain and vent connections shall be fully welded flanged type, fitted with a blind flange. It is important to ensure that the orientation of the connections is accessible at the site in case of drain/vent/sealant injection. Vendor drawing review should include checking the orientation of the connections.
Ball Valve Specification
Size and Pressure Class of a Ball Valve
When purchasing a ball valve, the size and pressure class rating should be provided to the vendor/manufacturer. This will ensure that the valve is suitable for the desired application.
Types of Ball and Pattern
The type of ball (floating or trunnion mounted design) and the pattern of the ball valve (standard or short) must also be specified.
Bore Type and End Connection
The bore type (full or reduced bore) and the end connection type of the ball valve should also be provided.
Drain Connection, Sealant Injection, and Locking Device
It is important to mention whether a drain connection, sealant injection system, and/or locking device is required.
Valve Support and Anti-Static Device
The need for valve support and/or an anti-static device should also be indicated.
Operator Details and Material
The operator details (lever/gear/actuator) and the material of the valve body, seat rings, trunnion, trim, seals, gaskets, bolts, nuts, and packing material must be provided.
Seating Type and Valve Orientation
The seating type (soft or metal seated) and the valve orientation should be specified.
Certification Requirements and Fire-safe Test
The specific certification requirements and the need for a fire-safe test should also be indicated.
Painting Details and Integral Bypass Connection
The applicable painting details and the need for an integral bypass connection should be provided.
Lugs or Lifting Arrangements
Finally, the requirement for lugs or lifting arrangements must be specified.
Advantages of Ball Valves
Ball valves offer a range of benefits that make them ideal for many industrial applications. These advantages include:
Quarter Turn Straight Through Valve:
Ball valves are designed to open and close quickly with a quarter turn. This makes them ideal for emergency shutdowns and fast-paced industrial operations.
Tight Shutoff and Easy to Use:
Ball valves provide a tight shutoff, making them suitable for use in a range of applications. They are also easy to use, making them a popular choice for many industrial operations.
Multi-Design Flexibility:
Ball valves come in a variety of designs and configurations. This makes them suitable for a range of different industrial applications and operating conditions.
Compact, Economical Designs:
Ball valves are designed to be compact and economical. This makes them an ideal choice for a range of industrial operations.
Suitable for High-Pressure Service Conditions:
Ball valves are designed to handle high-pressure service conditions. This makes them suitable for a range of industrial applications.
Long Service Life:
Ball valves are designed to last for a long time. This makes them suitable for a range of industrial applications.
Applications for Ball Valves
Ball valves are suitable for a range of industrial applications, including:
Oil & Gas, Chemical, Petrochemical, Refinery:
Ball valves are suitable for use in the oil and gas, chemical, petrochemical, and refinery industries. They are designed to handle high-pressure service conditions and provide a tight shutoff.
Food & Beverage Equipment:
Ball valves are suitable for use in food and beverage equipment. They are designed to open and close quickly and provide a tight shutoff.
Vehicle Wash Systems:
Ball valves are suitable for use in vehicle wash systems. They are designed to be compact and economical and provide a tight shutoff.
Automotive: Ball valves are suitable for use in automotive applications. They are designed to open and close quickly and provide a tight shutoff.
Home Appliances:
Ball valves are suitable for use in home appliances. They are designed to be compact and economical and provide a tight shutoff.
Power Processing:
Ball valves are suitable for use in power processing applications. They are designed to open and close quickly and provide a tight shutoff.
Manufacturing Facilities:
Ball valves are suitable for use in manufacturing facilities. They are designed to be compact and economical and provide a tight shutoff.
Pharmaceutical:
Ball valves are suitable for use in pharmaceutical applications. They are designed to open and close quickly and provide a tight shutoff.
Irrigation & Water Treatment Equipment:
Ball valves are suitable for use in irrigation and water treatment equipment. They are designed to be compact and economical and provide a tight shutoff.
Chemical Admixtures & Treatment:
Ball valves are suitable for use in chemical admixtures and treatment. They are designed to open and close quickly and provide a tight shutoff.
Disadvantages of Ball Valves
While ball valves offer many advantages, there are also some drawbacks to using them. These include not being suitable for throttling, having fluid trapped in the body cavity, and having limited working temperature ranges.
Disadvantages of Ball Valves -Not Suitable for Throttling -Fluid Trapped in Body Cavity -Limited Working Temperature Range.
Ball Valve vs Gate Valve
| Ball Valve | Gate Valve |
|---|---|
| Ball Valve uses a ball for opening or closing | Gate valve used a gate or wedge for opening or closing |
| The ball Valve is a quarter-turn rotary motion valve | Gate Valve is a linear motion valve |
| The sealing capacity of Ball Valves is comparatively higher | Comparatively less sealing. |
| Durability more | Less durability |
| Quick operation, prone to surge | Operation is slow hence, less probability of surge creation. |
| More number of valve configurations | Less number of valve configurations |
| More expensive | Comparatively low cost |
| Less Corrosion | Higher Corrosion |
| Low-Pressure Drop | High-Pressure Drop |