API 6D Ball Valve

What is API 6D ball valve? 

API 6D is a valve specification given by the American petroleum institute. This API 6D standard covers the design and manufacturing, testing, and documentation of pipeline ball valves for pressure ratings. API 6D ball valve means that it is a ball valve that meets the design, manufacturing, and testing specifications of the API 6D standard. API 6D ball valve is a type of ball valve meant for use in power, petrochemical, gas, oil, and liquid applications which makes it one of the most needed ball valves in the market. API 6D ball valves are mostly used in long-distance pipeline for transportation of fluids. These valves are used for on and off applications. API 6D ball valves are strong ball valves aimed for high performance and reliability. API 6D ball valve can employ other designs or materials to achieve excellent sealing performance such as use of a valve body with large storage space and increased body cavity diameter among others. This helps to eliminate stones and sand and other materials in the pipe from staying in the valve cavity for a long duration and thus prevent seat and ball damage. 

Figure: API 6D ball valve.

Components of API 6D ball valve 

Handwheel/actuator 

The handwheel is a component used in manual API 6D ball valves where the valve operator applies torque to open/close the fluid flow. The actuator is used in automatic API 6D ball valves to provide torque necessary for opening or closing fluid flow. 

Valve body 

The valve body in the API 6D ball valve is the component used for holding and protecting the internal components of the valve. The valve body is made of strong metallic materials such as stainless steel, carbon steel, and low-temperature carbon steel among other materials.

Bonnet 

The bonnet forms the top part of the valve body. Bonnet in an API 6D ball valve is placed on top of the valve body and the two parts are connected using bolts and nuts. The bonnet is used to protect the stem and packing seals. 

Stem 

The stem is the component of the API 6D ball valve used to connect the ball to the actuator or the handwheel. The stem is welded to the ball and helps to transmit torque from the actuator/handwheel to the ball. 

Seats

Seats provide sealing between the body and the ball. Seats are also used in the API 6D ball valve to support the ball and prevent fluid leakage. The seat should be made of a material that will not be corroded by the fluid to be used by the valve.

 Ball 

The ball has a hole at its center. The hole in the ball is where fluid flows through in an API 6D ball valve. Just like the seats, the ball should be made of a material that is compatible with the fluid to avoid corrosion damage.

Packing 

This is a sturdy seal placed between the API 6D ball valve stem and the bonnet to prevent fluid leakage. 

Figure: Components of API 6D ball valve.

How does the API 6D valve work? 

API 6D ball valve works by using a ball with a bore at its center. The fluid flowing through the API 6D ball valves flows through the ball bore. To open the API 6D ball valve, the ball is rotated by rotating the handwheel or by using an actuator for actuated valves. The ball is connected to the handwheel or actuator via the stem. The stem transmits the torque needed to open/close the valve to the ball. When the ball is rotated the ball bore becomes in line with the pipeline transporting the fluid. This causes fluid to flow through the valve. To close the API 6D ball valve, the handwheel is rotated in the opposite direction to the direction of opening the valve. This makes the ball bore become perpendicular to the pipeline. In this case, the ball blocks the fluid such that the fluid cannot flow again. API 6D ball valve is connected to the pipeline using bolts and nuts connection or by welding. The bolts and nuts connection helps to make the API 6D ball valve easy to disassemble for cleaning and repairs while the valve is in the field. The welding connection makes the valve hard to open for repairs and cleaning. However, the welded connection makes the API 6D ball valve free from fluid leakage.

Figure: Working of API 6D ball valve.

Types of API 6D ball valve 

Side entry API 6D ball valve 

This is an API 6D ball valve that is assembled from its sides. The side entry API 6D ball valve consists of two or three pieces. The two or three pieces of a side entry API 6D ball valves are made through forging method. After making the pieces through the forging method they are assembled using bolts and nuts as shown in the figure below. One main advantage of the side entry API 6D ball valve is that they can be disassembled for cleaning, repair, and maintenance. The feature of being repairable makes side entry ball valve durable as they can be repaired for reuse. These valves just like other API 6D ball valves are used in offshore and onshore gas and oil, oil processing, refining, and petrochemical industries. 

Figure: Side entry API 6D ball valve.

Top entry API 6D ball valve 

This is an API 6D ball valve that is assembled from the top side. This version of the API 6D ball valve is manufactured through the casting method. The casting method is one of the sure methods to ensure that the valve is free from fluid leakage. The top entry API 6D ball valve body and bonnet are connected using bolts and nuts in a way that ensures there is zero fluid leakage. One of the main advantages of the top entry API 6D ball valve is that the stem, seat, and ball can be accessed from the top side of the valve without removing the valve from the pipeline. Top entry API 6D ball valves can be inspected, cleaned, and repaired while in the field and without removing it from the pipeline. Such features makes a top entry ball valve last longer and is preferred by most valve users in the petroleum and gas industries. 

Figure: Top entry API 6D ball valve.

Welded body API 6D ball valve 

This is an API 6D ball valve that has its body made through welding only. This method of making this type of API 6D ball is very reliable as it ensures nowhere the fluid can leak through as it can happen through valve body made through bolts and nuts connection. However, welded body API 6D ball valve cannot be repaired while in the field. In case the valve needs to be repaired or cleaned, it has to be removed from the pipeline. Welded body API 6D ball valves are suitable in applications where cleaning or maintenance is not desirable. Welded body API 6D ball valve needs to undergo non-destructive tests on the perimeter of welded joints of the valve body to ensure that indeed it has zero leakage. 

Figure: Welded body API 6D ball valve.

Manual API 6D ball valve 

This is the type of API 6D ball valve which is operated manually. In this type of API 6D ball valve, a valve operator is needed. The valve operator is tasked with applying the torque required to open or close the valve. The valve operator applies the torque on the valve handwheel. One of the main advantages of the manual API 6D ball valve is that it is cheaper compared to the automatic one. However, manual API 6D ball valve requirements may be exhausting to the valve operator where the valve has to be operated frequently because of the high levels of torque required in every closing/opening instance. 

Figure: Worm Op API 6D ball valve.

Actuated API 6D ball valve 

Actuated API 6D ball valve is a valve that is operated by using an actuator. The work of the actuator is to provide the torque needed to open or close the valve. Actuated API 6D ball valves are automatic valves that eliminate the work of the valve operator. The actuators that can be used with API 6D ball valves are hydraulic, electric, and pneumatic. One of the main advantages of actuated ball valves is that they are very safe, unlike their manual counterparts. However, the actuated API 6D ball valves are more expensive relative to their manual counterparts. 

Figure: Actuated API 6D ball valve.

Applications of API 6D ball valves

• Used in the gas and oil industries. 
• They are used in petroleum applications. 
• Chemical admixtures and treatment plants. 
• Steam power plants. 

Advantages of API 6D ball valves 

• Quick to operate. 
• Durable. 
• Versatile as they can be used in different applications. 
• Very strong for high pressure and high-temperature applications. 
• Can be opened for cleaning, inspection, repair, and maintenance. 
• Free from leakage. 
• They are fire-proof.

Disadvantages of API 6D ball valves 

• Very expensive relative to other ball valves.
• Close quickly which can cause hammering and overpressure. 

Troubleshooting API 6D ball valve 

Fluid not flowing through the API 6D ball valve 

• Obstruction in the valve or pipeline. Remove the API 6D ball valve from the pipeline and clean the obstructing materials. 

Leakage through the ball seat 

• The seat is damaged by foreign materials. Clean any foreign material in the API 6D ball valve and replace the seat. 
• Improper seat material. Replace the seat with the correct seat to ensure compatibility with the fluid and working pressure and temperatures. 

Fluid leakage through the gasket 

• Insufficient bolting torque on the bolts. Tighten the bolts and nuts to increase bolting torque as recommended by the API 6D ball valve manufacturer. 
• The body gasket is damaged due to overpressure in the body cavity. Replace the gasket after body cavity pressure has been relieved. 

Gland packing leakage 

• Insufficient torque on the gland bolts. Increase torque on the gland bolts as recommended by the API 6D ball valve manufacturer.
• The packing is worn out. Replace valve packing. 

API 6D ball valve cannot open/close

• Foreign materials in the valve body. Remove foreign materials and replace seats. 
• The seats are worn out. Replace the seats and if necessary the ball as well. 

Summary 

API 6D ball valve is a type of ball valve designed, manufactured, tested, and documented as specifications. They are preferred for use in long-distance transportation of fluids. These valves are best suitable for on and off applications with high reliability and performance. API 6D ball valves employ a ball component with a bore at the center. The ball is used for closing and opening fluid flow. Fluid flows through the ball bore. To block the fluid flow, the ball is rotated to make it perpendicular to the pipeline. These valves are used in industries such as petroleum, oil and gas, steam power plants, and chemical industries. The various types of API 6D ball valves include side entry API 6D ball valve, top entry API 6D ball valve, manual API 6D ball valve, and automatic API 6D ball valve. The advantages of API 6D ball valves are durable, fire-proof, versatile, repairable, high strength, quick operation, and zero leakage. However, they are expensive relative to other ball valves and they must always be installed vertically.