Gas Ball Valve 

What is a gas ball valve?

The gas ball valve is a type of ball valve that is meant for use in gaseous applications. Gas ball valves are mostly two-piece ball valves. Gas ball valves must meet certain standards for them to be used in combustible gas applications. A gas ball valve is known for delivering better performance than other types of ball valves. Gas ball valves are light in weight and of compact design relative to other gas valves. There are various configurations of gas ball valves aimed at suiting specific applications to yield the best performance in different applications such as gas, air, vapor, and hydrocarbon systems. Gas ball valves are designed so that the actuator or handwheel turns the ball to make a quarter turn when closing or opening fluid flow. The design ensures a tight seal to prevent the gas from leaking into the environment. Gas ball valves provide an ideal connection method to the piping system using methods like threads, welding, or bolts and nuts. Most high-pressure and high-temperature applications rely on metallic seated gas ball valves to help them enhance a reliable performance. Gas ball valves are known to open and close quickly which makes them impressive in controlling fluid in high-pressure applications. 

Figure: Gas ball valve.

Components of gas ball valve

Valve body 

The body is the component of the gas ball valve which is used as the base for the whole valve. The valve body is used to house all the internal components of the gas ball valve. The valve body in the gas ball valve serves as the barrier to fluid pressure load. The valve body is tasked with holding together all components of the gas ball valve. The valve body contains the inlet and outlet ports that are connected to the pipeline.

Stem 

 The stem is the component in a gas ball valve that is used to transmit the force used to open or close the valve. The stem is connected to the actuator or the handwheel at the top and connected to the ball at the bottom. When the actuator or handwheel is rotated, the stem rotates to rotate the ball to either open or close the gas ball valve. 

Bonnet 

This is the component of the gas ball valve used to cover the top section of the valve. The bonnet in a gas ball valve is connected to the valve body to also serve as a pressure barrier and support internal components of the valve such as stem and seals.

 Ball

This is the component in the gas ball valve which is used to close or open fluid flow. The ball in the gas ball valve has a bore at the center. This bore or hole is aligned with the piping system to allow fluid flow. The hole turns to be perpendicular to the pipeline to block fluid flow. 

Packing 

Packing refers to a gasket used to keep the stem and bonnet sealed together in gas ball valves. The packing is a very critical component because if it is lost it causes leakage and if it is too tight it inhibits movement. So, the proper tightening of the packing should be followed according to the gas ball valve manufacturer. 

Seat/seat rings

This is the part of a gas ball valve where the ball rests. The seat in a gas ball valve can be attached or not attached to the ball. 

Actuator 

The actuator is the part of the gas ball valve which provides the force to open or close the gas ball valve. For a manually operated gas ball valve, the valve is opened/closed by an operator by turning a handwheel. Other valves use actuators integrated to the gas ball valve to open/close the fluid flow. Such actuators include pneumatic, electric and hydraulic actuators. 

Figure: Components of a gas ball valve.

How does a gas ball valve work? 

Gas ball valves operate by using a ball with a hole at its center to control fluid flow. It is the position of the hole in the ball that determines when the gas ball valve closes and when it opens. The ball of a gas valve is connected to the stem. The stem is connected to the handwheel or actuator. To start a gas ball valve, the handwheel/actuator is rotated a quarter turn that is 90^o. When the handle or actuator turns, at the same time it turns the stem which simultaneously rotates the ball. This makes the hole of the ball to be in line with the pipeline and thus allows fluid to flow through the valve. To stop the gas ball valve, the handwheel or actuator rotates anticlockwise to make a 90^o turn. This makes the stem and the ball turn anticlockwise about 90^o which makes the gas ball valve fully close the fluid flow. The gas ball valve closes the fluid flow because it turns anticlockwise making the hole to be perpendicular to the fluid flow. 

Figure: When the gas ball valve is open the ball bore is in line with the fluid flow.

When the gas ball valve is closed the ball hole is perpendicular to the fluid flow.

Types of gas ball valves 

Forged gas ball valves 

This is a gas ball valve manufactured through the forging process. The gas forged ball valve is made by taking a metallic material and heating it until it becomes soft. Mechanical forces such as that of the press are used to shape the hot material to the required shape of the gas ball valve. Forged gas ball valves are very suitable for high pressure and high-temperature applications due to their high strength. Forged gas ball valves have a higher mass which makes them mechanically strong. 

Flanged end gas ball valve 

Flanged gas ball valves are gas ball valves with flanged ends for connecting the valve to the piping system using bolts and nuts. These gas ball valves are made of metallic material making them safe against combustible gases and increasing their strength to work at high-pressure applications. The flanged gas ball valves are used for on/off fluid flow applications. Flanged gas ball valves are used in several applications such as heat exchanger stations, natural gas transportation among others. 

Figure: Flanged gas ball valve.

Welded end gas ball valves

This is a gas ball valve with the ends connected to the pipeline through welding. These gas ball valves are used where frequent maintenance is not expected. These gas ball valves are very reliable as they do not cause any leakage through the pipe and valve joint. Welded end gas ball valves are made of metallic materials and connected to metallic pipes to enhance perfect and strong weldment. The gas ball valves have strong joints and strong bodies which makes them reliable for use in high pressure and high-temperature applications. 

Figure: Welded ends gas ball valves.

Ductile iron gas ball valves 

These are gas ball valves made of ductile iron material. As the name suggests, ductile iron gas ball valves are made of ductile material which makes them safe against external impact which can cause damage to the valve body. External impact due to, for example, a falling object can cause damage in terms of cracks and thus cause leakage in the valve body. However, with a ductile iron gas ball valve, the valve is safe from external damage as it has enhanced impact resistance due to the ductile alloy used. This valve uses a stainless steel stem and ball with seats made of other materials like PTFE or elastomers. 

Applications of gas ball valve 

• Used in natural gas systems. 
• Compressed air systems. 
• Transporting hydrocarbons. 
• Control the flow of liquefied petroleum gas and natural gas. 
• Control of chemical vapors. 
• Control of hot fluids in residential and commercial heaters. 
• Boilers, gas stoves, and furnaces. 

Advantages of gas ball valves 

• Light in weight relative to other ball valves. 
• Excellent opening and closing features. Gas ball valves operate quickly in response to pipeline pressure conditions. This feature is very important because it helps to prevent backflow and fluid contamination. 
• Versatile. Gas ball valves employ a compact design with a strong valve body suitable for various industrial applications. 
• Efficient. These valves close/open by applying low torque and or a simple actuation mechanism. 
• Durable. These valves can be used for a long duration as long as the valve is used for the correct media and for on/off applications only. 
• Minimal maintenance interventions. 
• Strong. These valves are made of metallic components which makes them strong even when operating at high pressure and high temperatures. 
• Cheap relative to other valves. 

Disadvantages of gas ball valves 

• Welded gas ball valves are difficult to clean. 
• Can be fatal when they leak combustible fluids. 

Troubleshooting gas ball valve 

Gas ball valve leakage 

• Leakage through the packing. Loose packing; tighten the packing. 
• Leakage through the threaded connection. Tighten the threaded connection. 
• Leakage through flanged end bolts and nuts. Tighten the bolts and nuts. Check the flange gasket and if it is damaged replace it. 
• Leakage through the valve body. Valve body is damaged. Repair the valve for example through welding. 

The handwheel is hard to turn 

• The stem is damaged. Check the media compatibility with the gas ball valve to ensure it does not damage the stem. Replace damaged stem. 
• Clogged material. Remove/clean the foreign materials in the valve.

Summary 

A gas ball valve is a type of ball valve used for opening/closing flow of gaseous fluids. Gas ball valves are mostly two-piece ball valves. Gas valves use a ball with a hole at its center. The hole allows for fluid flow. When the hole is collinear to the pipeline, fluid flows and the gas ball valve is said to be open. When the ball valve is turned to make the ball bole perpendicular to the pipeline, the fluid flow is stopped and the gas ball valve is said to be closed. Gas ball valves are made of strong metallic materials to make them suitable for high pressure and high-temperature applications. Gas ball valves are connected to the pipeline using different connection methods such as welding, threads, bolts, and nuts. There are various types of gas ball valves such as welded end gas ball valves, flanged end gas ball valves, forged gas ball valves, ductile iron gas ball valves among others. Gas ball valves are used in various applications such as natural gas systems, compressed air systems, transportation of hydrocarbons, control of LPG and natural gas flow, chemical vapors, commercial and residential heaters, in boilers, and furnaces among others. Advantages of using gas ball valves are high efficiency, durability, versatility, high strength, quick operation, ease of use and lightweight.