Inherently Safe Explosion Protection

At the bustling gas station, we routinely pump fuel into our vehicles. Yet behind this seemingly simple operation lies a complex system integrating precision metering, intelligent control, and intrinsic safety explosion-proof technology. Modern fuel dispensers, especially those compliant with China's new national standard (GB/T 9081-2023), have evolved far beyond mere mechanical devices. They now represent sophisticated electronic equipment critical to safety, environmental protection, and data management. This article will take you on an in-depth exploration, particularly decoding the most crucial design—the intrinsic safety explosion-proof system—which serves as the cornerstone safeguarding gas station safety.

1、 How Does a Fuel Pump Work? — A Symphony of Fluids, Data, and Control

Before delving into explosion-proof technology, it is essential to first understand the basic working principles of fuel dispensers. Depending on the method of driving the fuel, they are primarily divided into two types: self-priming pumps and submerged pumps.

(1) Self-priming pump fuel dispenser:

When you turn on the fuel nozzle switch, the explosion-proof motor starts, driving the oil pump to operate. The fuel is drawn from the underground tank and first enters the vapor separator, where the gas mixed in the oil is separated and expelled through the exhaust pipe. The purified fuel then flows through the filter, flow measurement transducer (flow meter), control valve, and finally is injected into your fuel tank via the nozzle.

Core Process: As the oil flows through the flow meter, it drives a digital encoder to generate pulse signals. These signals are continuously captured by the "brain" of the dispenser—the control motherboard. The metering MCU (microcontroller unit) within the control motherboard performs real-time data comparison with another independent monitoring MCU. This "dual-core verification" mechanism is crucial for ensuring measurement accuracy and preventing fraud. Finally, the verified fuel dispensing data is transmitted to the indicator device (display screen) for display.

(2) Submersible pump fuel dispenser:

The pump of this model is directly installed inside the fuel tank. The fuel pickup signal triggers the submersible pump to operate, pressurizing the fuel and delivering it through pipelines to the flow meter and subsequent components of the fuel dispenser. Its measurement and data processing process is identical to that of the self-priming pump, relying on the coordinated operation of the flow meter, encoder, and control motherboard.

Regardless of the type, the fuel dispenser's electronic system adopts an advanced CAN bus architecture. This architecture clearly divides the system into the legal metrology section (e.g., metering MCU, monitoring MCU, encoder) and the non-legal metrology application section (e.g., human-machine interaction, payment, communication). Two independent CAN buses (CAN0 and CAN1) ensure the security and integrity of core measurement data, effectively meeting the stringent software evaluation requirements of the national fuel dispenser model approval outline (JJF1521-2023).

2、 The cornerstone of safety: why fuel dispensers must be "inherently safe and explosion-proof"?

(1) Severe environment: ubiquitous' invisible bombs'

Gas stations are typical explosive hazardous environments in Zone 1 and Zone 2. Volatile gasoline or diesel vapors mix with air to create an explosive gas environment. Any tiny spark, arc, or high-temperature surface can become the "fuse" that ignites this mixture of gases, causing catastrophic consequences. The fuel dispenser integrates various electrical devices such as motors, circuit boards, relays, switches, etc., which inevitably generate electric sparks during normal operation (such as circuit switching and motor commutation). Therefore, how to make these electrical equipment work "safely" in hazardous environments has become the primary issue in the design of fuel dispensers.

(2) The ultimate concept of explosion prevention: intrinsic safety explosion prevention

Among various explosion-proof technologies, intrinsic safety explosion-proof (referred to as "intrinsic safety explosion-proof") is considered one of the most reliable and safe forms of explosion-proof. Its core concept is not to "resist" or "isolate" explosions, but to "fundamentally eliminate" the possibility of explosions.

l Core principle: Through precise circuit design, the energy of any electrical sparks or thermal effects generated by electrical equipment under normal and specified fault conditions is strictly limited to a level low enough to ignite specific explosive gas mixtures in the surrounding area.

l Limiting voltage and current: Intrinsic safety circuits use components such as safety barriers and current limiting resistors to ensure that even in the event of a short circuit fault, the voltage and current in the circuit are limited below safe values.

l Control capacitors and inductors: The energy stored in the energy storage components (capacitors, inductors) in the circuit is also strictly controlled to prevent their instantaneous release from generating high-energy sparks.

Simply put, it is to 'strangle' the possible electric sparks inside the device in the cradle, making it so weak that it cannot even ignite the slightest gasoline vapor.

(3) Practice of intrinsic safety design in fuel dispensers

In the design of the Belin refueling machine, the concept of intrinsic safety runs through the entire process:

l Power board (DY300): As the energy source of the entire system, the power board is designed to provide multiple independent, stable, and energy limited DC power sources (such as+5V,+8V, S+5V). The internal fuse tubes (F401, F402) and filtering circuit not only ensure stable operation, but also serve as the first line of defense to limit the impact of abnormal energy.

l Control motherboard and communication board: The integrated circuits on these core boards operate in a low voltage, low power consumption state. The communication interface between it and peripherals such as encoders, display boards, and keyboards has been designed with intrinsic safety to ensure that the energy on the signal transmission line is within a safe range.

l Wiring and explosion-proof box: All wires entering hazardous areas must pass through sealed explosion-proof junction boxes. After cable connection, the plug must be tightened and the cable clamped to ensure the explosion-proof performance of the junction box and prevent explosive gases from entering the equipment through gaps.

3、 Passport to the Global Market: Explosion proof Certification System

In order for a fuel dispenser to be sold and used in the market, it must pass inspection and certification by a nationally designated explosion-proof certification agency.

l China: NEPSI certification - inspected and issued by China's national level instrument explosion-proof safety supervision and inspection station. Fuel dispensers must comply with the requirements of the GB3836 series standards (equivalent to the IEC60079 series international standards) in order to obtain an explosion-proof certificate. This is a mandatory admission requirement for sales in the Chinese market.

l EU: ATEX certification - According to the EU ATEX Directive (2014/34/EU), it is the legal threshold for products to enter the European market.

l North America: UL/cUL certification - issued by Underwriters Laboratories in the United States, in compliance with explosion-proof standards in North America (such as UL 916).

These certifications are not just empty words, they provide detailed and strict regulations for product design, materials, processes, and inspection. There are differences in standards in different regions, which requires manufacturers to have a global perspective when designing products, and to design and certify accordingly for the target market. This directly affects the selection of components, circuit board layout, and overall structure.

4、 Beyond Explosion proof: Intelligence and Compliance of Modern Fuel Dispensers

In addition to ultimate safety, the new national standard fuel dispenser also integrates numerous technological innovations that reflect the development of the times.

(1) Self locking and anti cheating function: This is the core requirement of the new national standard (JJG443-2023). The monitoring microprocessor on the control motherboard will compare the oil quantity data sent by the metering MCU and encoder in real time. Once a deviation is detected, the refueling machine will immediately shut down and prompt an error. After the cumulative deviation reaches the set number of times, the system will lock the oil gun, effectively preventing measurement cheating caused by hardware failure or human tampering.

(2) National security and bus architecture: The national security algorithm (SM2/SM3/SM4) is used to bind the hardware unique serial number, software digital signature, and online verification of key metering components (control board, monitoring microprocessor, encoder), realizing the confirmation of the legal identity of software and hardware throughout the entire lifecycle of the fuel dispenser and closed-loop storage of data encryption.

(3) Environmental Protection Function - Online Monitoring of Oil and Gas Recovery: The fuel dispenser is equipped with a built-in gas-liquid ratio control board (QK1000), which monitors the volume of recovered oil and gas in real time through a gas flow meter and calculates the gas-liquid ratio (A/L) based on the amount of fuel added. The system achieves closed-loop control by adjusting the gas-liquid ratio regulating valve (for Dur pumps) or control signal (for NP pumps), ensuring that the gas-liquid ratio remains stable within the national environmental protection requirements (usually 1.0-1.2), effectively reducing oil and gas volatilization, and protecting the environment.

(4) Rich scalability and intelligence: The modular design allows the fuel dispenser to easily expand various functions, such as IC card payment, UnionPay/QR code payment, voice prompts, advertising screens, receipt printing, and networking with station level management systems. Through communication boards (APP series), PCD communication boards, network card boards (WK series), etc., gas dispensers seamlessly integrate into the ecosystem of "smart gas stations".

5、 Conclusion

When we stand in front of the gas station again, what we see is no longer just a cold metal device. It is a high-tech system that integrates precision machinery, embedded electronics, communication technology, and intrinsic safety explosion-proof technology. Among them, the essential safety and explosion-proof design is its indispensable soul. It silently constructs an invisible safety barrier in the most fundamental and reliable way, ensuring that every energy supply is carried out with foolproof security.

From explosion-proof certification that meets global standards, to the measurement self-locking function that safeguards consumer rights, and to the oil and gas recovery technology that responds to national environmental calls, modern fuel dispensers perfectly embody the industrial design concept of "safety, precision, environmental protection, and intelligence". It is not only an energy station for the automotive society, but also a vivid epitome of technological progress and safety responsibility moving forward side by side.