Reduced Bore Ball Valve 

What is a reduced bore ball valve? 

A reduced bore ball valve is a type of ball valve with ball bore diameter less than the pipe diameter. In a reduced bore ball valve, the area of fluid flow is narrower downstream at the outlet. As such, there are frictional losses introduced in the valve resulting in pressure drop. In reduced bore ball valves, the amount of fluid flow remains constant which makes velocity to increase as the flow area decreases. Reduced bore ball valves are commonly used, unlike full bore ball valves. Reduced bore ball valves are used where turbulence and fluid flow rate are not major concerns and where buildup of particles is not likely to occur. Reduced bore ball valves cost less relative to full bore counterparts. The lower cost of reduced ball valves is because these valves have smaller housing and ball size which affects the final product cost. Reduced bore ball valves occupy a smaller volume which makes them consume small space during installation. Reduced bore ball valves are 30% lighter in weight relative to the full bore ball valves. However, reduced bore ball valves are meant for use in fluids that are not very viscous to avoid valve blockage. 

Figure: Difference between full bore and reduced bore ball valve.

Components of a reduced bore ball valve 

Valve body 

This is the component of a reduced bore ball valve which is used to house all the internal parts of the valve. The valve body is always made of strong materials and thus should have higher strength relative to other parts so that it can withstand pressures associated with the fluid. The body serves as the main pressure barrier in a reduced bore ball valve. 

Handle/Actuator 

The handle is a component used for manual reduced bore ball valves while the actuator is a component used for actuated valves. The handle is where the valve operator applies the torque required to open or close a reduced bore ball valve. The actuator is used where the reduced bore ball valve needs to be automated. 

Stem 

The stem is the component of a reduced bore ball valve used to transmit torque applied on the handle to the ball. The stem connects the ball and the handle or the actuator. 

Ball 

This is a component of a reduced bore ball valve which is tasked with opening and closing a reduced bore ball valve. The ball in a reduced bore ball valve has a hole at its center where fluid flows through the valve. 

Seats 

These are discs placed around the ball and the valve body to prevent fluid leakage in a reduced bore ball valve. Seats are also used to support the ball in its position. 

Packing 

Packing refers to seals placed on the valve stem in a reduced bore ball valve to prevent fluid leakage through the stem.

Figure: Components of a reduced bore ball valve.

How does a reduced bore ball valve work? 

 A reduced bore ball valve uses a ball with a bore at its middle section. The ball is connected to the handwheel/hand lever or actuator through the stem. A reduced bore ball valve works by turning the ball for an angle of 90^o. To open a reduced bore ball valve, the handle is rotated for a quarter-turn (90^o) which makes the stem and the ball rotate for the same quarter turn. For an angle of 90^o, the ball bore and the pipeline becomes collinear which makes fluid flow through the valve. To close the reduced bore ball valve, the handle is rotated again for another 90^o. This makes the ball bore and the pipeline to be perpendicular which blocks fluid flow. 

Types of reduced bore ball valve 

Single piece reduced bore ball valve 

Single piece reduced bore ball valve is a valve which consists of one piece of body made through casting. Single body reduced bore ball valves are good in that they are free from leakage. Single-piece reduced bore ball valves are the cheapest of all ball valves! However, single-piece bore ball valves cannot be opened for cleaning or repair and maintenance. Single piece reduced bore ball valves are used in low-demanding applications. These valves are disposed of when they develop problems. 

Figure: Single-piece reduced bore ball valve.

Two-piece reduced bore ball valve 

A two-piece reduced bore ball valve is a valve that consists of two pieces. One-piece contains the end connection and the valve body while the second piece contains the trim and the second connection. The second piece of a two-piece reduced ball valve fits into the first piece. The two pieces of a two-piece reduced bore ball valve can be dismantled for inspection, cleaning, and servicing. A two-piece bore ball valve needs to be removed completely from the pipeline for the two parts to be separated. 

Figure: Two-piece reduced bore ball valve.

Three-piece reduced bore ball valve 

This is a reduced bore ball valve with three pieces that is two end caps and the valve body. The three pieces in this reduced bore ball valve are held together by using bolts connection. All the three pieces of this reduced bore ball valve make the center part of the stem, ball, and seats to be removed easily from the piping system. The three-piece reduced bore ball valve enhances efficient cleaning, replacement of gland packing and seats, and polishing of small scratches on the surface of the ball. Such services can be performed on a three-piece reduced bore ball valve without removing the valve from the pipeline. Three-piece reduced bore ball valves are more expensive relative to other valves like globe valve. 

Figure: Three-piece reduced bore ball valve.

Three-way reduced bore ball valve 

These are reduced bore ball valves with three ports. Three-way reduced bore ball valves can have either an L shape configuration or a T shape configuration depending on what flow pattern is needed. Three-way reduced bore ball valves are suitable for diverting and mixing fluid flow. The T-shaped configuration is suitable for mixing and diverting fluid. When used to mix fluid flow, two streams from the inlet ports are merged to form one fluid stream at the outlet. When used to divert fluid flow, one fluid stream from the inlet port is divided into two streams to flow in two outlet directions at the same time. The L-shaped configuration of a three-way ball valve allows fluid diverting. 

Figure: Three-way reduced bore ball valve.

Metallic reduced bore ball valves 

These are reduced bore ball valves that are made of metallic materials such as stainless steel and or brass. Metallic reduced bore ball valves are known for high strength to withstand high pressure and high resistance to temperature. Also, metallic reduced bore ball valves are known to have corrosion resistance. Each metallic material has unique characteristics transferred from the respective metal or alloy to the entire valve. For example, stainless steel reduced bore ball valve is made of a higher amount of chromium and a lower amount of nickel. The chromium content adds corrosion resistance to the reduced bore ball valve. Stainless steel reduced bore ball valves have superb strength, durability, and toughness. Stainless steel reduced bore ball valves are used for example, in swimming pools to control chlorinated water as they can resist corrosion associated with chlorine. Reduced bore ball valves made of brass materials are more common as they also guarantee high strength, toughness, and durability. Brass reduced bore ball valves are distinguished by their dull yellowish to reddish color. Brass reduced bore ball valves are resistant to corrosion, and chemical and biofouling resistance. One main advantage of the brass reduced bore ball valve is that it is cheaper than the stainless steel counterpart. Brass reduced bore ball valves can be used in applications such as gas and oil, chemical, drinking water, and food industries. 

Figure: Metallic reduced bore ball valve

Plastic reduced bore ball valves 

These are reduced bore ball valves made of plastic materials such as polyvinyl chloride PVC and polypropylene (PP). Plastic reduced bore ball valves are cheaper compared to their metallic counterparts. Plastic reduced bore ball valves consume less energy to manufacture and are also easier to produce. Plastic reduced bore ball valves are more resistant to corrosion than metallic ones. However, plastic reduced bore ball valves have low strength at high pressure and they easily get distorted at high temperatures of 82^o. Plastic reduced bore ball valves are used in applications such as fertilizers, chemicals, sugar, and paper among others. 

Figure: Plastic reduced bore ball valves.

Applications of reduced bore ball valves 

• Used in oil and gas transfer. 
• Water supply applications. 
• Steam boiler systems. 
• Food processing and beverages. 
• Chemical production plants. 
• Used in washing machines. 

Advantages of reduced bore ball valves 

• Cheaper compared to other ball valves. 
• Small size and light in weight compared to full bore ball valves
• Durable since most of them can be repaired which increases their service life. 
• Versatile since they can be used to serve different industrial applications. 
• Open and close quickly. 
• Can be inspected, repaired, and cleaned. 
• Easy to repair and assemble. 
• These valves have a perfect seal that prevents fluid leakage. 

Disadvantages of reduced bore ball valves 

• Have frictional losses due to unequal pipe and ball bore diameters. 
• Get blocked by solids easily. 
• Not suitable for throttling applications. 

Troubleshooting reduced bore ball valves 

Reduced bore ball valve having leakage when it is closed

• Damaged seats. Replace the seats. 
• Damaged ball. Replace the ball. 
• The ball is not fully closed. Check the opening/closing settings of the ball. 
• Debris clogging the ball and or seats. Clean the debris. 

Reduced bore ball valve having irregular ball movement

• Impurities between the seat and the ball or between the body and the seats. Flush the interior of the ball and clean seal surfaces. Replace seats if necessary. 

Reduce bore ball valve needs too high torque to open/close 

• Damaged seats. Replace seats and seals. 
• Foreign materials in the valve. Clean the interior of the valve. 
• Broken stem. Replace the stem. 

Reduced bore ball valve experiencing leakage through the valve stem 

• Loose gland cap screw. Tighten the screw. 
• Damaged stem and sealing surface. Replace stem and seals. 

Summary 

The reduced bore ball valve is a type of ball valve that has a ball bore diameter less than the pipe diameter. The design makes the valve experience frictional losses and turbulence due to unsmooth fluid flow which causes pressure loss through the valve. They are suitable for use in applications where turbulence and flow rate are not concerns for valve working and where solids accumulation is not likely to occur. Reduce bore ball valves are used in various applications such as water supply, oil and gas, food and beverages, chemicals, boiler systems, and washing machines among others. There are various type of reduced bore ball valves which include single-piece reduced bore ball valve, two-piece reduced bore ball valve, three-piece reduced bore ball valve, three-way reduced bore ball valve, metallic reduced bore ball valve, and plastic reduced bore ball valve. Reduced bore ball valves have several advantages such as they are durable, they are small in size and have low weight, they are versatile, they open and close quickly, they are of various types for different pressure and temperature applications, and they can be cleaned, inspected and repaired.