What Is The Difference Between A Top Entry And A Side Entry Trunnion Mounted Ball Valve?

Trunnion installation ball valves is suitable for high voltage and large diameter applications because of its low operating torque and excellent sealing performance. It is widely used in oil and gas, petrochemicals, power generation, long distance pipeline transportation and other industries. According to the design and maintenance method of valve body design, there are two kinds of ball valves: ball valve for top top entry trunnion and ball valves for side entry trunnion.
While both designs use a trunnion-supported ball and provide reliable flow control, they differ significantly in structure, maintenance procedures, manufacturing methods and application scenarios. Understanding these differences helps engineers, project managers, and procurement professionals select the most appropriate valve for their working conditions.
What is an overhead tube mounting ball valve?
A top entry trunnion mounting ball valve has a single valve body, allowing internal components to be installed and removed through the top opening.
When repairs are needed, technicians simply remove the top cover to access the spheres, seats, seals and other key internal components. The valve itself has been installed in the pipe throughout the repair process.
This design is particularly appropriate for large industrial facilities in continuous operation, where minimizing downtime and streamlining maintenance are important priorities.
What is a lateral inlet tube mounting ball valve?
Side axial ball valve are usually composed of two or three valve bodies assembled using flanges, bolts, or welded joints.
During manufacture, the valve seats is mounted on the side of the valve body, which is why it is called a lateral entry design.
When repair is required, the valve is usually removed from the pipe before the valve body can be removed for internal repair. Although this maintenance process is more time consuming than the overhead valve maintenance process, the manufacturing process has matured and production costs are generally lower. Therefore, the lateral axial flow ball valves has been widely used in many industrial applications.
Differences in structural design
The most obvious difference between the two valves is the body structure.
A top entry trunnion mounting ball valve is typically made of a whole forged or cast valve body and a removable top bonnet. All interiors are installed and repaired through the top openings.
This integrated structure provides greater mechanical strength and fewer external sealing surfaces, reducing the potential risk of external leakage.
In contrast, a side entry trunnion mounting ball valves consist of multiple body sections connected to bolts or other fastening methods.
While this modular construction simplifies manufacturing and assembly, it introduces additional sealing surfaces that require reliable gaskets and seals to maintain sealing performance.
Differences in maintenance
Maintenance convenience is one of the biggest differences between the two valve designs.
The greatest advantage of the ball valve is its on-line maintenance capability.
When seats, seals or other internal components need to be replaced, the repairman only needs to remove the top cover. Valves remain connected to piping without complete removal.
This maintenance method has the following benefits:
Reduces equipment downtime
Lower maintenance costs
Reduced labour requirements
Improving service efficiency
Ideal for continuous processing
In contrast, repairing a ball valve installed in a lateral ear, nose, and throat unit usually requires the following steps:
Pipeline closure
Decompression and drainage of the system
the flange connections
Remove valve using lifting equipment
Remove valve body for repair
For large transmission pipelines, the process is much more complex and usually requires a long maintenance cycle.
Differences in manufacturing
Because of its integrated valve body structure, the processing accuracy of the top stopper installed on the ball valve is high.
Key dimensions such as top seal, ball positioning, and trunnion alignment must be precisely controlled. As a result, production is more complex and generally takes longer.
The ball valve A side entry trunnion installation adopts modular manufacturing method. Individual components are processed individually and then assembled to make production more efficient and highly standardized.
For mass production, side entrance design usually provides better productivity and lower manufacturing costs.
Cost Comparison
Structural differences can also affect the overall cost of valves.
Installing ball valve at the top stopper requires more more precision machining, more complex manufacturing processes and more stringent quality inspections. As a result, its purchase price is generally higher than the side inlet valve.
A side entry trunnion mounting ball valve benefit from proven manufacturing techniques and standardized components, making them a more cost-effective option for many projects.
If the project budget is limited and maintenance is easy, side entry valve are often a more economical option.
However, if equipment downtime results in significant economic loss, the reduced maintenance time provided by the top entry valve can reduce the overall lifecycle cost of the system.
Differences in Sealing Performance
Both valves have excellent sealing performance with a spherical designsupported by an ear shaft.
However, because there are fewer ball valve body joints installed in a top entry trunnion, fewer potential external leakage points are usually provided. It is therefore particularly suitable for high-pressure systems conveying flammable, explosive or hazardous media.
Modern overhead shaft ball valves are typically equipped with advanced safety and sealing features, including:
Double-seat sealing
Fire Design
Anti-static devices
Double Shielding, Bleed (DBB) capability
Emergency sealant injection systems
These features further improve operating safety and sealing reliability under harsh operating conditions.
Differences in application
Head-in axial ball valves are commonly used for:
Long-distance oil and gas pipelines
Offshore oil and gas platforms
LNG Receiving Terminal
Oil refineries
High-pressure natural gas system
Large industrial facilities with high downtime costs
These applications typically require continuous operations and minimal maintenance interruptions.
Side Inlet Axle Ball Valve is widely used in:
General Industrial Pipeline
Chemical processing plants
Power generation facilities
Water treatment System
Urban gas distribution network
Conventional oil and gas projects
For projects that are relatively easy to maintain and less complicated to valve replacement, side intake valve provides an efficient and economical solution.
How to Choose the Right Axle Flow Install Ball Valve
There are no generally superior options between the ball valves installed at the top inlet and the lateral inlet otolaryngology. The best choice depends on the specific operational requirements of the project.
The ball valve fitted at the top of the inlet otolaryngology is usually recommended when the system involves:
Large pipeline diameters
High operating pressures;
Continuous long-term operation
High costs associated with downtime
Limited maintenance space
Inserting a ball valve in A side entry trunnion is usually a better option when priority is given to:
Reduced initial investment
Standardized system design
Routine maintenance requirements
Bulk purchases
Conclusion:
The ball valves installed at the top inlet and side inlet ear, nose and throat is a high performance industrial valve with the advantages of low operating torque, excellent sealing performance and reliable pressure resistance. Their main differences lie the valve body structure and maintenance methods.
Top entry valves are ideal for critical applications, requiring online maintenance, minimal downtime, and maximum system reliability. Side entry valves, with their proven manufacturing processes, competitive prices and broad applicability, remain the solution of choice for many standard industrial projects.
When selecting an axle-flow installed ball valve, the engineer shall assess operating pressure, pipeline size, process medium, maintenance requirements, project budget, total lifecycle costs, etc., to ensure the best long-term performance and economic value of the valve selected.