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Three-piece ball valve 

April 3, 2022

What is a three-piece ball valve?

A three-piece ball valve is a type of ball valve with three pieces which are the body, and two end caps. The end joints or end caps are joined to the pipeline by threading, using bolts and nuts, or by welding. The three pieces are connected together using bolts and nuts which makes it easy to remove the main valve body for repairs and cleaning without removing the pipe connectors or end joints. After installing a three-piece ball valve, valve components that experience wear like balls, stem, and seats can be replaced independently and quickly. One of the benefits of using a three-piece ball valve is that it can be removed for maintenance and cleaning making it very cost-effective for the long term. Changing seals and seats makes a three-piece ball valve more affordable than replacing the whole valve. Also, not removing the pipe connectors in a three-piece ball valve helps to prevent production shutdown in case of maintenance. 

Three Piece Body Ball Valve

Figure: Three-piece ball valve.

 

Components of a three-piece ball valve 

Handwheel/actuator 

The handwheel is the component on a three-piece ball valve on which the valve operator applies torque to open or close the valve. A handwheel is used where the three-piece ball valve is manual. If the valve is not manual, then it is operated by an actuator. An actuator is a device integrated with the three-piece ball valve to provide torque for opening and closing the valve. Some of the available actuators for a three-piece ball valve are pneumatic, hydraulic, and electrical actuators. 

Valve body 

The valve body is the main component of a three-piece ball valve as it serves as the main barrier against pressure and it houses all the internal parts of the valve. The valve body is made of strong materials relative to other parts of the valve like seats and seals to ensure it has high strength enough to withstand high pressure and high temperatures. Most three-piece ball valves are used in high-pressure applications and thus their bodies are made of strong materials like stainless steel, carbon steel, and cast iron, among others. 

Stem/shaft

A stem/shaft is the component of a three-piece ball valve that is used to connect the ball and the actuator so that it can transmit the force or torque required to open/close the valve. The stem is also made of strong materials like steel, bronze, and brass to help it withstand high temperatures and pressure as well as enable it to transmit high torque for large three-piece ball valves. 

Ball 

This is the component of a three-piece ball valve meant for closing/opening the ball valve. The ball has a bore or hole at its center. The fluid flows through the 3 piece ball valve via this hole.

Seats

Seats are internal components between the ball and the body of a 3 piece ball valve. Seats are used to provide a seal between the ball and the valve body as well as support the ball. 

Packing 

Packing is a seal placed around the stem to prevent fluid from escaping. 

Trim 

Trim refers to components in the three-piece ball valve such as sleeves, ball, stem, seats, seating surfaces, and seal rings. 

Figure: Components of a three-piece ball valve.

 

How does a three-piece ball valve work? 

A three-piece ball valve works by using a ball that is responsible for opening and closing fluid flow. This ball in a three-piece ball valve that has a hole in its middle section. It is through the hole where the fluid passes through the valve. A three-piece ball valve has the ball connected to the stem. The stem is then connected to the handwheel or the actuator. The actuator or handwheel makes a quarter turn (90o degree angle) to open/close the ball valve. When the handwheel/actuator rotates by 90o, it makes the stem and the ball rotate at the same 90o. The quarter-turn of the ball makes the ball hole collinear with the pipeline which allows the fluid to flow through the valve. In this case, the three-piece ball valve is said to be closed. To block the fluid flow, the ball is then turned in an anticlockwise direction for 90o. This makes the ball hole perpendicular to the fluid flow or the pipeline and thus ensuring fluid does not fluid. 

 

Types of three-piece ball valve 

Full bore three-piece ball valve 

A full bore 3 piece ball valve is a valve in which the ball bore diameter is the same as that of the pipe diameter. The advantage of a full bore 3 piece ball valve is that it does not have additional friction losses and it is easier to clean. However, a full bore 3 piece ball valve has a bigger housing and bigger ball relative to a reduced bore ball valve. As such, the cost of a full bore 3 piece ball valve is higher which is a challenge for many manufacturers. Full bore 3 piece ball valves are used where low fluid flow resistance is needed for example, in pump suction pipes in which pressure drop can affect pump performance. 

Reduced-bore three-piece ball valve 

A reduced bore 3 piece ball valve is a valve with a smaller ball bore diameter than the pipe diameter. In a three-piece ball valve, the area of fluid flow becomes narrower at the valve outlet downstream. As such, frictional losses are introduced resulting in pressure drop. Because the fluid discharge remains constant, flow velocity increases as the flow area decreases. However, despite frictional losses and pressured drop, reduced bore 3 piece ball valves are more commonly used relative to the full bore 3 piece ball valves. Reduced bore 3 piece ball valves are used where turbulence and flow rate are not main concerns and build-up of particles is not likely to occur. The cost of a reduced bore 3 piece ball valve is lower because these valves use smaller housing and ball size. 

 

Reducedbore 3 piece ball valve

Figure: Reducedbore 3 piece ball valve.

V-port 3 piece ball valve 

This is a three-piece ball valve with a ball having a “V” shaped bore. The V shape also denotes the seat design. A V-port 3 piece ball valve offers more control to close and open fluid flow efficiently. The flow in a V-port 3 piece ball valve is almost linear. V-port three-piece ball valves are made stronger since they are meant to work in high-velocity fluid flow which can damage standard ball valves. 

V-port three-piece ball valve

Figure: V-port three-piece ball valve.

Trunnion 3 piece ball valve 

This is a three-piece ball valve where the valve ball rotates in a fixed position. The ball in a 3 piece ball valve is held in position by a shaft on the bottom and topsides such that it cannot move in a lateral direction. A trunnion ball valve creates a seal by pro-stressing the ball and seats or by forcing the seat against the ball using fluid pressure. The trunnion component absorbs the fluid flow pressure and thus the contact between the seat and ball is not stressed excessively. This makes the operating torque in a trunnion 3 piece ball valve lower which makes it easier to open/close the ball valve. The concept of trunnion ball valves is used to make large three-piece ball valves and valves used in high-pressure applications. 

Trunnion 3 piece ball valve

Figure: Trunnion 3 piece ball valve.

Floating 3 piece ball valve 

A floating three-piece ball valve is a valve that has the ball suspended in the fluid and held in its position by two seal rings. The valve ball is supported in its place by seats and it can move in a lateral direction freely. Fluid pressure acts on the ball forcing the ball into the seat and thus providing a tight seal. Floating 3 piece ball valves are mostly used in low and medium-pressure applications. Floating 3 piece ball valves have good sealing and a simple design structure. Floating ball valves are not used in large sizes and high-pressure applications because the high force on the ball can deform the seats and impact the low-pressure sealing properties of the valve. The other reason is that the high force on the ball makes the 3 piece ball valve hard to operate which necessities high values of torque to overcome seat force at high pressure. 

 

Applications of three-piece ball valve 

  • Three-piece ball valves are used in water control in irrigation systems. 
  • Three-piece ball valves are used in pharmaceutical manufacturing processes. 
  • 3 piece ball valves are used in power generation plants. 
  • These valves are used in chemical industries. 
  • These valves are used in oil and gas plants. 
  • Three-piece ball valves are used in food and beverages processing for sanitary purposes because of ease to cleaning necessary for maintaining high hygienic conditions. 

 

Advantages of three-piece ball valves 

  • The three pieces in these valves are connected by use of bolts and nuts. This connection is very convenient as it makes installation and disassembly of the valve easier.
  • Three-piece ball valves are quick to operate. 
  • Three-piece ball valves have low fluid resistance.
  • Cleaning, repair, and maintenance can be done easily on three-piece ball valves. 
  • Three-piece ball valves employ a simple design structure. 
  • These valves are of various types which suits them to various applications. 
  • Three-piece ball valves have long service life because they can be repaired instead of buying a new valve in case a component of the valve breaks down.  
  • 3 piece ball valves can be connected to the pipes using various connection methods according to the user’s preferences. 

 

Disadvantages of three-piece ball valves 

  • Three-piece ball valves are expensive relative to one-piece and two-piece ball valves. 

 

Troubleshooting a three-piece ball valve 

Leakage at the connections 

  • Misaligned end connectors. Check the end connector alignment to ensure they are parallel. 
  • O-rings damaged or displaced or particles in the O-ring groove. Inspect the valve O-rings for chemical and physical damage to ensure they are compatible with the media. If O-rings are damaged, replace them. If there are particles in the groove, clean them. 
  • Bots and nuts are loose; tighten them.

Stem leakage 

  • The stem O-ring is damaged. Replace the O-ring. Check the O-ring is compatible with the media. 
  • Broken stem. Repair or replace the stem as necessary.  

Leakage through the ball 

  • Obstruction on the ball. Verify that the 3 piece ball valve is in its full close position. If not in full close position, check for debris clogging the ball port. Remove obstructions and reinstall the valve. 
  • The ball is damaged. Replace the ball. 

Leakage through the seat 

  • The seat is damaged; replace it. 
  • The seat is debris-laden. Remove debris from the seat. Check the seat compatibility with the media. 

The handle is hard to operate

  • Clogged debris. Check the handle for obstruction by solids. Remove any foreign materials. 
  • Broken. Repair the handle or replace it if necessary. 

 

Summary 

Three-piece ball valves are valves that have three pieces that is the body and two end-caps. The three pieces are connected using bolts and nuts. Three-piece ball valves are very strong but they are costly relative to other valves like two-piece ball valves. 3-piece ball valves employ a ball with a bore at its center. The ball is responsible for opening/closing the fluid. The fluid flows through the three-piece ball valve via the ball hole.

Three-piece ball valves work by aligning the ball hole in line with the pipe in which the fluid passes through the ball hole and the pipe is said to be open. The 3 piece ball valves are closed when the handle or actuator is turned 90o in the anti-clockwise direction where the ball becomes perpendicular to the pipe blocking fluid flow. Three-piece ball valves are used in wide applications in different manufacturing industries such as pharmaceuticals, food and beverages, power generation, irrigation, oil, and gas among others. The advantages of using a three-piece ball valves include quick operation, suitable for cleaning, repair, and maintenance, can be used in different applications, and are made of strong materials for high-pressure applications among others. 

 

 

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