Ball Valve Maintenance and Troubleshooting Technology in Natural Gas Transmission Pipelines

Abstract: With the growing demand for natural gas, transportation pipelines have expanded rapidly, and ball valves serve as critical components within these systems. This paper analyzes the structure and working principle of ball valves, reviews maintenance practices during both construction and operation, and proposes troubleshooting methods for common faults. The goal is to extend the valve’s service life through scientific management, minimize losses caused by failures, and ensure the long-term, stable operation of natural gas pipelines.

Introduction

As an efficient and clean energy source, natural gas is widely utilized in social development and everyday life. Transportation pipelines are critical infrastructure for ensuring its stable supply. Ball valves are widely used in natural gas pipelines because of their simple structure, fast operation, low flow resistance, and excellent sealing performance. Their functionality directly affects the safety and stability of the entire pipeline system. Therefore, research into ball valve maintenance and troubleshooting technologies is essential for timely issue identification and resolution, enhancing operational reliability, and ensuring the safe, stable operation of natural gas pipelines.

1. Structural Characteristics and Working Principle of Ball Valves

1.1 Basic Structure

A ball valve is a commonly used shut-off valve that mainly consists of a valve body, upper cavity, valve seat, lower cavity, and ball. The valve body serves as the main structure, connecting to the pipeline and ensuring fluid flow. The upper and lower cavities, positioned above and below the ball respectively, accommodate the ball and its associated transmission components. The valve seat is a crucial element that forms a sealing surface with the ball to ensure fluid tightness. The ball, featuring a circular flow channel, is the valve’s core component. The valve opens or closes by rotating the ball 90 degrees. The structure is shown in Figure 1.

Figure 1 Valve Structure

In natural gas transportation pipelines, ball valves are generally classified as fixed ball valves or floating ball valves, depending on how the ball is supported. In a fixed ball valve, the ball is secured within the valve body by upper and lower shafts mounted in bearings. Under fluid pressure, the ball remains stationary laterally and can only rotate around its axis. This design prevents deformation of the valve seat during prolonged operation, ensuring high stability and an extended service life. In contrast, the ball in a floating ball valve is not fixed; it can shift slightly under fluid pressure, pressing firmly against the sealing ring to create an effective single-sided seal. While the floating ball valve has a simpler structure and provides effective single-sided sealing, its valve seat is more susceptible to deformation over time, which can weaken the seal and shorten its service life.

1.2 Working Principle

The fixed ball valve operates by rotating the ball to open or close the flow path. The ball is supported by bearings within the valve body, ensuring stability and preventing displacement under high fluid pressure. In this design, the valve seat is typically a floating type. When pressure is applied, both the spring force and fluid thrust push the seat toward the ball, creating an initial sealing force. The metal valve seat and the ball form the primary seal, ensuring reliable sealing even under fire conditions. In addition, a soft sealing element works in conjunction with the valve seat to form a secondary sealing structure, preventing leakage during normal operation. In fixed ball valves, the valve seat is often designed to be elastic, incorporating components such as spiral springs or disc springs. This elastic design allows the seat to maintain close contact with the ball through the combined action of fluid pressure and spring force, resulting in a stable and reliable seal. The key advantage of an elastic valve seat is its ability to adapt to changes in temperature and pressure while maintaining consistent sealing performance. In contrast, a conventional (non-elastic) valve seat achieves sealing through deformation caused by natural gas pressure and the initial preload. While this type of seat has a simpler structure and is easier to manufacture, its sealing performance may be less stable under high-pressure and high-temperature conditions. The elastic valve seat provides a more stable seal by maintaining uniform contact with the ball, preventing uneven stress distribution. Its simple structure and ease of manufacturing make it especially suitable for long-distance natural gas pipelines. By contrast, while the ordinary valve seat is simple and cost-effective, it may not provide the same level of reliability in demanding environments. Therefore, choosing the right type of valve seat is crucial to ensuring the ball valve’s long-term sealing performance and operational safety.

2. Maintenance Technology of Ball Valves for Natural Gas Transmission Pipelines

2.1 Maintenance During Construction

During valve procurement and installation, the involvement of professional technicians is essential. At the early procurement stage, technical personnel conduct thorough research on product specifications and performance in the building materials market and then enter into legally binding procurement agreements. Strict packaging protocols are adhered to during logistics to prevent damage during transportation. Upon arrival at the construction site, quality control specialists conduct a thorough inspection to verify the valve’s quality, specifications, and performance. In accordance with installation requirements, close coordination between manual labor and machinery is essential—especially during lifting operations. Operators must exercise caution and perform multiple checks to ensure the valve remains undamaged. When using wire ropes for tail suspension, gentle handling is necessary to avoid stressing or damaging the valve. Before installation, blind flanges are installed on both ends of the valve to prevent dust, moisture, and debris from entering, thereby protecting the sealing surfaces. Additionally, grease is applied promptly during installation, and both the sealing performance and fluid flow are carefully inspected to ensure overall installation quality. During commissioning, the valve must be fully opened and closed to ensure smooth operation. For hydrostatic testing, water inside the valve cavity should be completely drained to prevent internal corrosion. The sealing surfaces must be carefully inspected for leaks, and the valve should only be commissioned after successfully passing the pressure test.

2.2 Maintenance During Operation

To ensure the stable operation of ball valves and minimize long-term maintenance costs, a systematic maintenance plan must be implemented. Key valve components—such as seals—should be regularly inspected for signs of wear, corrosion, or damage. Early identification and resolution of potential issues can greatly reduce maintenance time and prevent unplanned downtime. Regarding lubrication management, the amount of grease injected should be adjusted based on the valve’s operating frequency. The grease volume should correspond to the actuation rate, ensuring that at least one-eighth of the sealing system’s total volume is filled. This prevents dust and contaminants from entering, thereby protecting the valve’s functional integrity. For valves operated infrequently, it is advisable to apply grease after manual actuation to minimize internal mechanical wear and extend service life. Cleaning should focus on removing dust, debris, and accumulated water from the valve cavity to prevent rust and freezing. Valves in regular use should receive routine cleaning and maintenance to keep the interior clean and preserve sealing performance by minimizing friction-related wear. The valve’s gear transmission mechanism should be re-greased annually. A thorough inspection must be performed to identify and address any issues that could compromise long-term reliability. Gears should be checked for wear and replaced promptly if found to be damaged or deteriorated. External rust on the ball valve not only impacts its appearance but can also reduce its service life. Regular cleaning with suitable tools and chemical agents is necessary to remove surface rust. After cleaning, apply an anti-corrosion coating or rust-proof paint to prevent further oxidation. Regular external inspections help detect emerging issues early, enabling timely corrective actions and ensuring the valve remains in good working condition.

3. Troubleshooting Technology for Ball Valves in Natural Gas Transmission Pipelines

3.1 Internal Leakage of Ball Valves

Internal leakage in ball valves is mainly caused by poor construction practices and insufficient maintenance during later stages of operation. Construction-related issues include mechanical mishandling that damages the valve; failure to properly dry and apply anti-corrosion treatment before installation; improper transportation or storage allowing dust and debris to enter the valve cavity; lack of grease injection during installation; and poor site management that damages the sealing surface. These factors can cause internal leakage from the moment of installation. The internal leakage paths are shown in Figure 2. Improper maintenance is another major cause of internal leakage. This can result from weak management oversight, insufficient maintenance funding, improper operational procedures, poor-quality grease, or degradation of internal grease over time. These factors can lead to progressive internal leakage during service, compromising the valve’s sealing performance and reducing its service life.

Figure 2: Internal Leakage Pathways

Treatment Methods for Internal Leakage
To address internal leakage, several corrective measures can be taken: verifying valve position, injecting cleaning fluid, applying standard grease, and using sealing grease.

Valve Position Adjustment
Inspect and adjust the valve stops to ensure the sealing surfaces align properly and remain within the specified operational range.

Cleaning Fluid Injection
Inject cleaning fluid into the valve to soften and dissolve hardened grease within the sealing passages and to remove debris or foreign matter from the sealing surfaces.

Grease Injection
Inject high-quality grease to enhance sealing, lubricate the sealing surfaces, reduce operating torque, and minimize resistance during valve operation.

Sealing Grease Injection
Based on the sealing mechanism, inject a specialized sealing grease that remains fluid, contains appropriate granularity, and resists solidification for at least three years. During the injection process, keep the sealing grease in continuous motion and monitor it closely to prevent further leakage.

3.2 Stem Leakage

Stem leakage is another common issue in ball valves used in natural gas transmission pipelines. It often results from long-term wear and aging. Specific causes include degradation of sealing materials, poor sealing performance of the stuffing box, corrosion or wear on the valve stem surface, and grease failure or insufficiency. Aging of sealing materials causes the seal between the stem and valve body to break down. Poor sealing of the stuffing box allows external contaminants to enter the space between the valve stem and valve body. Surface corrosion or wear on the stem damages the sealing interface. Grease failure or insufficient lubrication accelerates mechanical wear, further increasing the risk of leakage.

Treatment Methods for Stem Leakage
The primary solution for stem leakage is grease injection. Injecting high-quality sealing grease fills the gap between the valve stem and the stuffing box, restoring sealing integrity. Once leakage stops, immediately stop grease injection and apply compaction sealing to ensure a tight seal. Additionally, the valve stem should be regularly inspected for signs of wear, and any worn or damaged components should be replaced promptly to ensure reliable operation and prevent leakage from recurring.

3.3 Abnormal Operation

Abnormal operation is a common fault in ball valves used in natural gas transmission pipelines. It can cause the valve to become difficult to open or close, or even jam during operation.

The main causes of abnormal operation include the following aspects:

• Infrequent use of the ball valve combined with inadequate routine maintenance, leading to increased resistance during operation.
• Ingress of external impurities, dust, and moisture into the pipeline, which can cause grease to accumulate around the valve seat ring and lead to operational difficulties. Excessive moisture content in the natural gas can result in internal corrosion and freezing, further hindering smooth valve movement.
• Improper tightening of the valve stem bolts, which can impair valve operation.
• Wear or breakage of valve stem transmission components—including gear wear, failure of the worm safety pin, bearing damage, and insufficient lubrication—can cause operational problems.

To address these issues, targeted technical improvements should be implemented to improve the stability of ball valve operation and reduce the risk of failure.

Treatment Measures for Abnormal Operation

Inject cleaning fluid to soften and dissolve hardened grease inside the sealing passages. Allow the fluid to remain for a specified period, opening the valve at regular intervals to dislodge and flush out foreign matter. Repeated valve cycling helps clear debris and impurities from the sealing surfaces. During this process, monitor the pressure with a gauge to detect any leakage. Inject grease to enhance sealing, lubricate the surfaces, reduce operating torque, and minimize resistance. Adjust the tightness of the valve stem bolts to ensure they are neither too loose nor overtightened, allowing for smooth valve operation. Inspect the valve stem transmission components for wear or damage, and promptly replace any faulty parts. Use a pressure gauge during routine inspections to verify that the air and oil circuits are unobstructed, the air source pressure is sufficient, and the internal sealing devices function properly. If necessary, vent any trapped air pressure within the valve cavity to ensure normal operation.

4. Conclusion

The structure and working principle of a ball valve directly affect its performance and reliability. Fixed ball valves offer greater stability and longer service life, whereas floating ball valves have a simpler design and provide effective sealing. Throughout the construction process—including selection, transportation, installation, commissioning, and hydraulic testing—strict control over every step is essential.

To extend the valve’s service life and reduce failures, a systematic inspection plan should be established. Regular checks of sealing integrity, corrosion, and damage are essential, with any abnormalities addressed promptly. Key maintenance measures include grease injection, cleaning, anti-corrosion treatment, gear mechanism upkeep, and rust removal to ensure the valve’s long-term stable operation. Internal leakage can be addressed by injecting cleaning fluid, grease, and sealing grease, while stem leakage is typically resolved by applying high-quality grease. In cases of abnormal operation, faults can be addressed by injecting cleaning fluid and grease, adjusting valve stem bolts, replacing worn components, and inspecting the gas and oil systems.