What is a lockable ball valve? 

A lockable ball valve is a type of ball valve with a lock mechanism. As the name suggests, a lockable ball valve uses a hollow ball and locking mechanism to control fluid flow and lock the valve in an open/closed position. The hole in the valve ball is where the fluid flows through in a lockable ball valve. The lock mechanism is used to ensure valve personnel safety as well as secure the valve in an open or closed state. The lock mechanism covers the stem nut to ensure the lockable ball valve lever cannot be removed which helps to avoid valve interference or tampering. Also, using a lockable ball valve in controlling fluid flow helps to ensure that the valve cannot open by mistake when it needs to be closed and vice versa. Lockable ball valves are important as they help protect people working in pressure relief devices from malfunctions.

Figure: Locking ball valve.

 

Components of a lockable ball valve 

Handle 

The handle is the component of a lockable ball valve where the valve operator applies force to open or close the valve. The handle should be made strong enough to withstand the torque required to open the locking ball valve.

Valve housing/valve body 

The valve body is the main component of a lockable ball valve which is used to serve as the pressure barrier. This helps to protect the internal components of the lockable ball valve against external damage and holds them tight in position. The valve body is very critical because it needs high strength to make it withstand high pressure.

Stem 

The stem is the part of a lockable ball valve that aids in transmitting torque applied by the valve operator on the handle to the valve ball. The stem connects the ball and the handle in a locking ball valve.

Ball 

The ball is the component tasked to open or close the locking ball valve. The ball has a hole at its middle part where the fluid flows through. The ball should be made of material that enhances compatibility with the fluid.

Lock mechanism 

This is the component of a lockable ball valve which is used to lock the valve in one state that is open or closed state.

Seat 

Seats refer to discs used between the body and valve ball in a lockable ball valve meant for providing a seal between the body and the ball and also enhancing ball support against fluid pressure.

Packing 

Packing is a component that forms a pressure seal on the valve stem to ensure the fluid does not leak through the locking ball valve.

Figure: Components of a lockable ball valve

 

How does a lockable ball valve work?

A lockable ball valve is a ball valve with a lock mechanism. The working of a lockable ball valve depends on the ball of the valve. A locking ball valve has a ball with a bore at its middle section. It is the ball that is tasked to open or close the fluid flow. The ball is connected to the handle through the valve stem. To start the lockable ball valve, the handle is rotated for a quarter turn which then rotates the stem and ball at the same 90^o angle. In this case, the ball bore becomes in line with the fluid flow from the pipeline which makes fluid flow through the valve. To close the lockable ball valve, the handle is then rotated in the opposite direction for 90^o. This then makes the stem and ball rotate for the same quarter turn angle. In this case, the ball bore becomes perpendicular to the fluid flow from the pipeline which makes the valve to be closed. The lock-in of a lockable ball valve is used to close or open the valve when the valve operator finds it necessary.

 

Types of lockable ball valves 

Two-piece lockable ball valve 

This is a lockable ball valve with two pieces. One of the two pieces has the body and one connection end while the other piece holds the valve trim and fits into the first piece with its end connection. The two-piece lockable ball valve can be disassembled for inspection, cleaning, and servicing. However, in a two-piece lockable ball valve, the valve must be removed completely from the pipe to separate the two pieces. In most cases, two-piece lockable ball valves have a standard bore or reduced bore ball diameter.

Figure: Two piece locking ball valve.

Three-piece lockable ball valve 

A three-piece lockable ball valve is a valve with three pieces that is the body and end caps. The three pieces are held together using bolts and nut connections. The three-piece lockable ball valve is designed such that the central components of the valve that is seats, stem, and ball can be removed easily from the pipeline. This helps to enhance effective cleaning of debris, replacement of gland packing and seats, polishing scratches on the ball without the need to remove the valve body from the pipeline. However, comparing a three-piece locking ball valve to the other valves, this valve is more expensive.

Figure: Three-piece lockable ball valve.

Three-way lockable ball valve 

This is a lockable ball valve with three ports. A three-way lockable ball valve can have an L shape or T shape configuration. With an L shape configuration, the lockable ball valve can be used to mix two fluid streams into one stream. The T-shaped lockable configuration of a ball valve can be used as a fluid diverting or fluid mixing valve. When the T-shaped configuration is used as a diverting valve, it is arranged such that the fluid stream from one port is divided into two ports. When the T-shaped configuration of a three way ball valve is used to mix fluids, it combines two fluid streams from two ports to form one fluid stream.

Figure: Three-way lockable ball valve.

Full port lockable ball valve 

A full port is also known as a full bore lockable ball valve. This is a valve with its ball bore diameter equal to the pipe diameter. One benefit of a full port locking ball valve is that it does not cause losses due to friction and that the valve can be cleaned easily. When used in large manufacturing systems, the advantage of inspection and cleaning without dismantling the lockable ball valve and without loss of production cannot be underrated. One of the main challenges of a full port ball valve is that the valve body and the valve ball need to be bigger relative to those of a standard lockable ball valve. As such, the cost of a full port ball valve becomes higher. Despite the cost, full port lockable ball valves are useful where low flow resistance is important for example in a pump suction piping system, where pressure loss can lower pump performance.

Reduced port lockable ball valve 

A reduced port lockable ball valve is a type of ball valve which has a ball bore diameter less than the pipe diameter. The reduction in ball bore diameter relative to the pipe diameter introduces losses due to friction and turbulence in a locking ball valve. As such, reduced bore lockable ball valves are preferred in cases where turbulence, pressure drop, and material characteristic are not major challenges. A reduced port ball valve is of lower cost and smaller size.

Threaded end lockable ball valve 

This is a lockable ball valve that is connected to the pipeline using threads. The threaded connection on a lockable ball valve will be either male or female. A lockable ball valve with a female threaded end connection will need a male threaded pipeline and vice versa. Threaded end lockable ball valves can be disassembled from the pipeline for inspection, repair, and cleaning.

Flanged end lockable ball valve 

This is a locking ball valve that has flanged ends for connecting the valve to the pipeline using bolts and nuts. Both the pipeline and the lockable ball valve need flanged ends with holes for the bolts. These lockable ball valves provide a tight seal and they can be dismantled for inspection, repair, and cleaning.

Figure: Flanged end lockable ball valve.

 

Applications of lockable ball valves 

• Lockable ball valves are used in water supply and irrigation systems.
• Lockable ball valves are used in air, liquids, and gaseous applications that need bubble-tight service.
• Locking ball valves are used in feed water and cooling water systems.
• These valves are used in steam services.
• They are used in oil and gas industries.
• Locking ball valves are used in different manufacturing industries.

 

Advantages of lockable ball valves 

• Lockable ball valves provide a lock mechanism when in an open or closed state.
• These valves enhance the safety of valve operators and personnel.
• Lockable ball valves are quick to operate.
• These valves have high strength for high pressure and high-temperature applications.
• Lockable ball valves are versatile as they can be used in different industries.
• Lockable ball valves are small in size and weight.
• Lockable ball valves have a simple and compact design structure.
• A small amount of torque is required to open/close a lockable ball valve unlike other valves like globe valve or gate valve.
• Locking ball valves can be used for fluid mixing and fluid diversion.
• These valves have a perfect seal that prevents fluid leakage.
• Locking ball valves have low-pressure drop and a high fluid flow rate.

 

Disadvantages of lockable ball valves

• Lockable ball valves can have suspended dirt build up between the ball and the body which can cause erosion, leakage, and valve failure which necessitates frequent maintenance.
• Locking ball valves are not suitable for throttling applications.

 

Troubleshooting lockable ball valve 

Leakage at the thread/bolt connection 

• Loose thread connection. Tighten the connection.
• Improper threads. Check threads for proper sizes. Replace the connections if necessary.
• Loose bolts and nuts. Tighten the bolts and nuts.
• Worn out or damaged gasket. Replace the gasket.

Leakage at the stem 

• Stem O-ring damaged. Replace the O-ring.
• Broken stem. Replace the stem.

Ball leakage 

• Ball obstruction. Check for solids blocking the ball and remove them.
• Damaged ball. Replace the ball.

Leakage through the seat 

• Worn out seats. Replace the seats.
• Debris-laden seat. Clean the debris.
• Displaced or damaged seat O-ring. Adjust the seat ring or replace it as necessary.

The handle is difficult to close/open 

• Over-tight seal carrier. Loosen the seal carrier slightly.
• Internal obstruction. Disassemble the lockable ball valve and check for segments blocking handle rotation. Clean the segments.
• Broken handle. It could be due to external impact. Replace the handle.
• Broken or sheared stem. This could be due to external impact. Replace the stem as necessary.

 

Summary 

A lockable ball valve is a ball valve with a lock mechanism that can be used to lock the valve when it is in a closed or open state. The lock mechanism is used to help valve personnel to isolate the valve while carrying out valve work which enhances safety in the hope that the valve cannot be used. The ball has a bore at its center which is used to open or close fluid flow. The lock is activated according to the operator’s intended use either in an open or closed state.

There are various types of locking ball valves such as three-piece lockable ball valves, two-piece lockable ball valves, three-way lockable ball valves, flanged lockable ball valves, threaded end lockable ball valves, reduced port lockable ball valves, and full port lockable ball valve. Locking ball valves are used in various applications such as oil and gas, chemical industries, water supply, steam services, air, gaseous and liquid applications among other manufacturing applications. The advantages of lockable ball valves include ease of operation, versatility, high strength for high pressure and high temperature, they have a lock mechanism, and they have perfect seals preventing fluid leakage.