Long-distance pipelines are integral to transporting natural gas, petroleum, chemicals, and other essential media, where valves play a critical role in regulating flow, providing safety, and ensuring the system operates efficiently and reliably. These valves are categorized into on-off and safety protection valves and flow control valves, each serving unique functions depending on the requirements of the pipeline system. Common types include slab gate valves, ball valves, check valves, and pressure relief valves, each with distinct structural features and applications. Material selection, inspection, and testing standards are vital in ensuring the durability, sealing performance, and safety of these valves in challenging environments. Through advanced design, rigorous testing, and optimal material choice, long-distance pipeline valves ensure stable operations, even in high-pressure, high-temperature, and harsh conditions.
Long-distance pipelines are used to transport various media that require flow control, such as natural gas, petroleum, and chemicals. In the transportation process, valves, as critical components, play a vital role. The primary functions of valves are to regulate, control, or cut off the flow of media, ensuring the efficient, safe, and stable operation of the pipeline system. Depending on the requirements, valves on long-distance pipelines can be divided into two main categories:
On-Off and Safety Protection Valves: Located at the mainline and the inlets/outlets of various systems, these valves serve to open, close, and provide safety protection, preventing abnormal conditions such as media leakage or overpressure in the pipeline.
Flow Control Valves: Installed at the starting stations and intermediate booster stations of the pipeline, these valves are used to regulate and control the flow rate, pressure, and other parameters of the medium, ensuring the stability and efficiency of the transportation process.
In long-distance pipelines, commonly used valve types include slab gate valves, ball valves, emergency shut-off ball valves, check valves, and quick-acting ball control valves. Each type of valve has its unique features and functions. The structural characteristics of common valves are as follows.
Structural Features: Slab gate valves have a short structural length and excellent sealing performance. They require low torque for opening and closing, with minimal flow resistance and uniform operating force. Their design does not require abnormal pressure relief devices, and some slab gate valves with diversion holes can be cleaned using pipeline cleaners.
Application: Primarily used in pipelines that require frequent opening and closing and stable fluid flow, especially suitable for low and medium-pressure pipelines.
Structural Features: Ball valves have a compact structure and excellent sealing performance, with a 90-degree rotation for quick opening and closing. They have a short operation time and can use injected sealing grease to form a secondary auxiliary seal. The fire-resistant seat structure ensures good sealing in case of fire. When equipped with a quick shut-off device, they can achieve emergency closure.
Application: Ball valves are commonly used in pipelines that require rapid opening and closing and precise fluid flow control, especially suitable for natural gas, petroleum, and high-pressure applications.
Structural Features: Ball control valves have large flow capacity, simple structure, and good stability. They can withstand large pressure differences, have low flow resistance, low noise, and excellent anti-cavitation performance. They offer minimal flow resistance when fully open and are easy to operate and maintain.
Application: Suitable for applications requiring precise flow control, widely used in industries such as petroleum, chemical, and liquefied natural gas.
Structural Features: Check valves typically have a damping structure that effectively eliminates pipeline vibration and reduces flow resistance. They use a dual-seal design (elastic seal for low pressure and metal-to-metal seal for high pressure) to ensure good sealing performance. They can also be cleaned using pipeline cleaners.
Application: Suitable for preventing backflow of pipeline media, commonly used in water pumps and oil and gas transportation systems to protect the safety of pumps and systems.
Structural Features: Designed to mitigate pressure fluctuations and shock waves caused by pump start-up or shutdown, pressure relief valves ensure the stability of the pipeline system.
Application: Commonly used in high-pressure pipelines and transportation systems to prevent system damage due to sudden pressure fluctuations.
Structural Features: Pressure reducing valves are used to regulate pressure at pipeline branches, ensuring constant medium pressure for downstream users. Pilot-operated pressure reducing valves are commonly used, offering high pressure control accuracy and stability, with low requirements for medium cleanliness.
Application: Widely used in liquid and gas pipelines, especially in applications requiring high-precision pressure control.
The material selection for long-distance pipeline valves is crucial, as the quality of the materials directly affects the valve's durability, sealing performance, corrosion resistance, and wear resistance. Commonly used valve materials include:
Valve Body and Bonnet: Typically made of WCB (cast steel), WCC (corrosion-resistant steel), or stainless steel to ensure strength, corrosion resistance, and long-term stability.
Gate: The gate of slab gate valves is usually made of stainless steel, with surface treatment to further enhance corrosion resistance.
Ball: The ball of ball valves is typically made of stainless steel or alloy steel to ensure sealing performance and corrosion resistance.
Sealing Ring: Materials such as reinforced PTFE are often chosen for their corrosion resistance and high-temperature tolerance, ensuring good sealing performance.
Stem: The stem is generally made of stainless steel, offering good strength and corrosion resistance.
Gasket: Stainless steel graphite or PTFE spiral wound gaskets are commonly used to ensure good sealing.
Connection Bolts: High-quality alloy steel is often used for its strong tensile and corrosion resistance.
Due to the need to withstand climatic temperature differences, terrain changes, and potential earthquakes, the inspection and testing standards for long-distance pipeline valves are very stringent. Common inspection items include:
Shell Strength Pressure Test: Ensures the valve can withstand high-pressure working conditions.
Sealing Test: Verifies the valve's ability to maintain an effective seal and prevent media leakage.
Operational Performance Test: Confirms the valve's opening and closing actions are flexible and precise.
Bending and Tensile Tests: Checks the valve's strength and stability under external forces.
Fire Resistance and Durability Tests: Ensures the valve can operate normally under extreme high-temperature conditions.
Cold and Heat Resistance Tests: Simulates extreme temperature changes that long-distance pipelines may encounter, ensuring the valve operates stably in both freezing and high-temperature environments.
Additionally, for valves transporting media containing particles, wear resistance tests are required to ensure the valve does not wear out during long-term use, maintaining efficient operation.
As an indispensable key component in pipeline systems, long-distance pipeline valves bear the responsibility of media flow regulation and system protection. With technological advancements, valve design requirements have become increasingly complex, necessitating excellent sealing, fire resistance, corrosion resistance, and wear resistance to ensure the safe and stable operation of pipeline systems. Through strict material selection, optimized design, and systematic testing, long-distance pipeline valves can not only meet the demands of high pressure, high temperature, and harsh environments but also adapt to ever-changing working conditions, providing strong support for energy transportation.
