Pneumatic-Hydraulic Actuator: Choice for Natural Gas Pipeline Safety

In the operation of natural gas pipelines, safety is always the top priority. Pneumatic-hydraulic actuators, as key devices for ensuring pipeline safety, are of undeniable importance. This article will delve into the functions, components, application scenarios, and maintenance tips of pneumatic-hydraulic actuators, helping you gain a comprehensive understanding of this efficient and reliable equipment.

The core function of a pneumatic-hydraulic actuator is to open and close valves. This seemingly simple function plays a crucial role in the complex environment of natural gas pipelines. It not only enables local manual operation but also allows for remote control of valve opening and closing, significantly enhancing the flexibility and convenience of operations.

In modern natural gas pipeline systems, the application of remote control technology is already very widespread. The remote operation function of pneumatic-hydraulic actuators allows operators to easily open and close valves from a distance through commands from the control center. This remote control method not only saves labor and time but also ensures the safety of operators in hazardous environments.

During the operation of natural gas pipelines, various unexpected situations may occur, such as pipeline ruptures. The automatic rupture protection function of pneumatic-hydraulic actuators can automatically trigger valve actions to quickly close or open valves when the pipeline pressure or pressure drop rate exceeds the set value, preventing natural gas leakage and ensuring the safe operation of the pipeline.

The ESD (Emergency Shutdown) function is another important safety feature of pneumatic-hydraulic actuators. In emergency situations, such as fires at the station or power outages, the ESD function can quickly cut off the inlet and outlet valves to minimize the danger. Compared with electric ball valves, pneumatic-hydraulic actuators do not require external power in emergency situations and can more reliably perform emergency shutdown operations to ensure the safety of the station.

Pneumatic-hydraulic actuators consist of several key parts, each of which plays an indispensable role in realizing their powerful functions.

The mechanical drive mechanism is the link between the pneumatic-hydraulic actuator and the valve. It receives hydraulic power and converts it into the torque required to drive the valve open and close. The design of this part directly affects the reliability and efficiency of valve operation, so it is usually made of high-strength materials to ensure it can withstand long-term high-load operation.

The pneumatic-hydraulic conversion unit is one of the core components of the pneumatic-hydraulic actuator, mainly including the air storage tank and the pneumatic-hydraulic tank. Its main function is to convert the power of the air source into hydraulic power, providing strong power support for the mechanical drive mechanism. When the actuator operates, the pneumatic-hydraulic conversion unit can respond quickly to ensure the rapid and accurate opening and closing of the valve.

The fluid control unit is responsible for controlling the flow of the pneumatic-hydraulic circuit, thereby achieving various valve opening and closing methods. Through precise control, it can realize functions such as remote operation, rupture protection, and ESD emergency shutdown. This part usually consists of multiple valves and control elements, which can flexibly adjust the flow path of the pneumatic-hydraulic fluid according to different operational requirements.

The electronic control unit is the "brain" of the pneumatic-hydraulic actuator. It continuously monitors pipeline pressure parameters and performs automatic cutoff operations in emergency situations. In addition, the electronic control unit also has human-machine interaction and data recording functions. Operators can conveniently check the equipment status and historical data through it, promptly identifying and addressing potential problems.

Pneumatic-hydraulic actuators are widely used in various aspects of natural gas pipelines, especially in key locations where their role is particularly prominent.

Installing pneumatic-hydraulic actuators at the mainline valves and station inlet and outlet valves of natural gas pipelines can achieve emergency shutdown and rupture protection functions. When a pipeline rupture or other emergency occurs, the actuator can quickly respond and close the valve to prevent natural gas leakage and protect the safety of personnel and equipment.

When the pipeline pressure is too high or too low, the pneumatic-hydraulic actuator can automatically trigger the high and low pressure shutdown function to cut off or open the valve, ensuring that the pipeline pressure always remains within a safe range. This function is crucial for ensuring the stable operation of the pipeline.

At the venting and bypass valve locations of natural gas stations, pneumatic-hydraulic actuators can achieve remote control and automatic protection functions. Through remote operation, operators can easily complete venting and bypass operations from the control center, improving work efficiency. At the same time, in emergency situations, the automatic protection function of the actuator can prevent safety accidents caused by operational errors.

At the inlet and outlet locations of natural gas stations, the pneumatic-hydraulic actuator's ball valve control function is comprehensive, capable of performing ESD actions and remote control in emergency situations. In emergencies such as station fires or power outages, the actuator can quickly shut off the inlet and outlet valves to ensure the safety of the station.

For pipeline valves that require remote monitoring and operation, the bidirectional remote control function of pneumatic-hydraulic actuators can achieve remote valve opening and closing operations. Operators can easily open and close valves from the control center through remote commands, greatly enhancing the convenience and flexibility of operations.

When natural gas pipelines cross rivers or other special sections, installing pneumatic-hydraulic actuators can achieve remote monitoring and automatic protection functions. Through remote operation, operators can always keep track of the pipeline's operating status and quickly take measures in emergencies to ensure the safe operation of the pipeline.

In locations where high-torque drive is required for valves, pneumatic-hydraulic actuators can serve as an alternative to high-torque pneumatic actuators. They have the advantages of high output torque and comprehensive functions, meeting the opening and closing requirements of high-torque valves.

During the loading and unloading process of natural gas compressors, pneumatic-hydraulic actuators can achieve rapid valve opening and closing operations to ensure the safe operation of the compressors. Through precise control, the actuators can timely adjust the valve opening during compressor loading and unloading, ensuring the stable operation of the compressors.

The ESD (Emergency Shutdown) function is an important safety feature of pneumatic-hydraulic actuators. In the event of an emergency, the ESD function can quickly place the pneumatic-hydraulic actuator in a fail-safe position to protect the system.

The ESD function of pneumatic-hydraulic actuators can be divided into single ESD and ESD interlock. Single ESD refers to the emergency action of the pneumatic-hydraulic actuator involving only one device itself, while ESD interlock treats the pneumatic-hydraulic actuator as one of the control objects, providing protection for the entire system when it operates. In complex environments such as stations, the ESD interlock function can effectively prevent the escalation of accidents and ensure the safety of the entire system.

To ensure the normal operation of the ESD function, pneumatic-hydraulic actuators require a continuous and stable 24VDC power supply and a reliable air source. Meeting these conditions is the basis for realizing the ESD function.

Pneumatic-hydraulic actuators can achieve the fail-close function of single-acting pneumatic actuators. Through air circuit control, when power loss or air loss occurs, the pilot air is expelled, completing the fail-close function. This function can quickly cut off the valve in emergencies to ensure pipeline safety.

Pneumatic-hydraulic actuators can be equipped with both ESD and remote valve switching functions. The ESD function is usually power-loss activated, suitable for protection in emergency situations, while remote switching is equivalent to remote operation of local pneumatic devices, allowing operators to open and close valves from a distance. The combination of these functions greatly enhances the flexibility and safety of operations.

As an important device in natural gas pipeline systems, pneumatic-hydraulic actuators play an irreplaceable role in ensuring the safe operation of pipelines with their powerful functions, reliability, and flexibility. By gaining a deep understanding of their basic functions, components, application scenarios, and maintenance tips, we can better select and use this equipment to ensure the safe and stable operation of natural gas pipelines. In the future, with continuous technological advancements, pneumatic-hydraulic actuators will become more intelligent and efficient, providing stronger support for the safe operation of natural gas pipelines.