The 6 Basic Functions of Skid-Mounted Gas Station Level Gauges and Overflow Prevention Systems

Shengding's skid-mounted fuel station level gauges and overflow prevention systems focus on the core needs of safe operation and compliant management of skid-mounted fuel stations. They integrate six core functions: high-precision real-time monitoring of liquid level/temperature/water level; multi-level high and low level alarms; automatic interlocking overflow prevention during unloading; automatic inventory metering and remote data transmission; double-walled tank leakage monitoring; and explosion-proof, lightning protection, and anti-static safety protection. All functions strictly comply with relevant industry requirements, providing skid-mounted fuel stations with comprehensive safety assurance and digital management support throughout the entire process. Detailed technical data for each function is described below.

1. High-Precision Real-Time Monitoring

Real-time monitoring of four parameters in one: liquid level, oil temperature inside the tank, water accumulation at the bottom of the tank, and oil-water interface.

1.1. Liquid Level Measurement

• Measurement Principle: Magnetostrictive high-precision detection
• Measurement Accuracy: +(-)0.5mm
• Measurement Range: 0.1-30m
• Single Tank Data Inspection Response: < 1 second

1.2. Temperature Monitoring

• Temperature Measurement Range: -20^oC-+85^oC
• Temperature Measurement Accuracy: +(-)0.5^oC
• Real-time acquisition of oil temperature inside the tank, supporting temperature-compensated metering

1.3. Oil-Water/Water Accumulation at the Bottom of the Tank Monitoring

• Interface Detection Accuracy: +(-)1mm
• Water Accumulation Alarm Threshold: Default warning from 5mm
• Real-time identification of water seepage at the bottom of the tank and oil-water stratification, preventing water deterioration inside the tank in advance.

1.4. System Refresh and Expansion

• Data Refresh Frequency: Real-time updates every second
• Standard configuration supports: simultaneous monitoring of 1-8 tanks, expandable to 12 tanks
• Communication protocol: Modbus-RTU, RS485 standard interface, compatible with skid-mounted station control and cloud platforms

2. Multi-level high and low level alarms

2.1. High liquid level warning (H level) - Unloading reminder threshold

• Trigger threshold: 90% of tank capacity (can be customized +(-)2% according to skid-mounted tank specifications).
• Alarm method: On-site audible and visual alarm, alarm volume > 90dB, red warning light constantly on
• Linkage action: Only provides warning, does not shut down equipment, reminds operators to stop unloading oil to prevent the liquid level from continuing to rise
• Response time: <=0.5 seconds, synchronized with real-time data from the liquid level gauge, no delay

2.2. High liquid level emergency alarm (HH level) - Overflow prevention core threshold

• Trigger threshold: 95% of tank capacity (overflow prevention mandatory threshold, cannot be arbitrarily modified).
• Alarm method: On-site audible and visual alarm (volume > 100dB) + remote pop-up alarm + SMS push notification (can be set to 3 groups of recipients).
• Linked action: Immediately interlocks and shuts off the unloading valve, completing valve closure within 2 seconds, and simultaneously suspends the unloading pump operation, preventing oil spills at the source.
• Unlocking method: Manual unlocking (control panel button). Before unlocking, confirm that the liquid level has dropped to a safe range (< 90% tank capacity).

2.3. Low liquid level warning (Level L) - Replenishment reminder threshold

• Trigger threshold: 20% of tank capacity (can be customized +(-)3% according to oil usage frequency).
• Alarm method: On-site audible and visual alarm (volume 85-90dB), yellow warning light constantly illuminated, remote platform prompt "replenishment required".
• Linked action: Does not shut down equipment, only reminds operators to arrange oil replenishment to prevent subsequent pump idling.
• Auxiliary function: Synchronously displays the remaining oil in the tank, accurately prompting the replenishment amount (combined with liquid level gauge measurement data).

2.4. Low Liquid Level Alarm (LL Level) - Equipment Protection Threshold

• Trigger Threshold: 5% of tank capacity (forced equipment protection threshold).
• Alarm Method: On-site audible and visual alarm (volume > 100dB) + remote alarm + emergency SMS push notification.
• Linkage Action: Immediately cuts off power to the refueling pump and unloading pump, stops all related equipment operation, and protects the pump set from idling wear.
• Recovery Condition: After refueling to >=15% of tank capacity, manually reset the equipment before normal startup.

2.5 Alarm System Core Parameters

• Alarm Output: Relay dry contact (DC24V, 5A) + RS485/Modbus communication interface, supporting linkage with the central control room and cloud platform.
• Alarm Records: Automatically stores more than 1 year of alarm data (including trigger time, threshold, and processing status), supporting export and query.
• Explosion-proof Rating: Alarm controller and warning lights both meet Exd II standards. BT4, suitable for hazardous environments in skid-mounted stations (Zones 1 and 2).
• Environmental adaptability: Alarm function is normal from -40^oC to +85^oC; dustproof and waterproof IP65, unaffected by harsh outdoor weather.
• Redundancy protection: The alarm system has independent power supply (backup power supply duration >=4 hours), preventing alarm failure due to main power interruption.

3. Automatic Interlocking for Overflow Prevention During Unloading

3.1. Core Mechanism of Automatic Interlocking

• Triggering condition: During unloading, the level gauge monitors the tank level in real time. When the level reaches 95% of the tank capacity (overflow prevention mandatory threshold, cannot be modified), the interlocking command is immediately triggered.
• Response process: The level gauge transmits the interlocking signal synchronously to the unloading emergency shut-off valve via the RS485 communication interface. The valve closes within 2 seconds, simultaneously cutting off the power to the unloading pump and stopping the unloading operation, thus preventing the risk of oil spillage at its source.
• Signal Synchronization: Simultaneously with the interlock action, on-site audible and visual alarms (volume > 100dB), remote platform pop-up alarms, and SMS push notifications (up to 3 emergency recipient groups can be set) are triggered, alerting operators to handle the situation promptly.

3.2. Manual Control Redundancy Protection

• Manual Switching: Supports automatic/manual mode switching (independent button control on the control panel). Under special conditions (such as temporary level gauge calibration), it can be switched to manual mode, allowing operators to manually control the unloading valve.
• Emergency Stop Valve: Equipped with an independent emergency stop valve button (on-site + remote dual deployment). In case of emergencies (such as pipeline leaks or equipment failures), the valve stop command can be manually triggered with a response time <= 1 second, providing dual safety protection.
• Unlock and Reset: After the interlock valve is stopped, it is necessary to confirm that the liquid level in the tank has dropped to a safe range (< 90% tank capacity), manually unlock the unloading valve, and reset the equipment before restarting the unloading operation to prevent misoperation.

3.3. Core Equipment and Technical Parameters

• Emergency Shut-off Valve Parameters: Compatible with DN65/80/100 pipe specifications, DC220V/5A power supply, closing time <=2 seconds, explosion-proof rating Exd II BT4, protection rating IP65, oil and corrosion resistant, suitable for skid-mounted stations in outdoor and hazardous environments.
• Communication Parameters: The level gauge and shut-off valve use the Modbus-RTU communication protocol, RS485 interface, transmission distance <=1000m, data transmission error < 0.1%, ensuring no delay or false triggering of interlock commands.
• Explosion-proof Protection: The interlock controller and level detection module both meet the Exd II BT4/Exia II BT4 explosion-proof rating, suitable for skid-mounted stations in Zone 0 and Zone 1 hazardous areas, eliminating safety hazards caused by electrical sparks.
• Redundancy Protection: In case of level gauge failure, the unloading valve automatically locks and closes mechanically, simultaneously triggering the backup alarm device; the system is equipped with an independent backup power supply (endurance >=4 hours), ensuring normal interlock protection even when the main power supply is interrupted.
• Environmental Adaptability: Stable operation in environments ranging from -40^oC to +85^oC, dustproof and waterproof IP65, surge resistant +(-)4kV, unaffected by harsh outdoor weather conditions such as high temperatures, extreme cold, and heavy rain.

4. Automatic Inventory Metering and Remote Data Transmission (Digital Management)

• Automatic Metering: Real-time calculation of tank inventory, empty capacity, and unloadable volume with an accuracy of +(-)0.3%, replacing manual gauging.
• Data Recording: Stores over one year of historical data (liquid level/temperature/alarm/unloading records), supporting report export.
• Remote Monitoring: Uploads data to the cloud platform/central control room via 4G/Ethernet, allowing real-time viewing on mobile APP/computer.
• Tank Calibration: Built-in automatic tank calibration algorithm, real-time correction of tank capacity deviation, metering error < +(-)0.5%.

5. Double-Layer Tank Interlayer Leakage Monitoring (Environmentally Friendly Leak Prevention)

• Monitoring Principle: Negative pressure/liquid level sensors are installed in the double-layer tank interlayer to detect leaks in real time.
• Alarm Threshold: Immediate audible and visual alarm and platform upload upon >=2mm of interlayer liquid accumulation or abnormal pressure.
• Dual Protection: Works with cofferdams to prevent oil leakage and soil/groundwater contamination.
• Sensor: Intrinsically safe Exia II BT4, waterproof and explosion-proof, lifespan >=5 years.

6. Explosion-proof/Lightning Protection/Anti-static Safety Protection (Intrinsically Safe)

• Explosion-proof Rating: Level gauge/control console/valve assembly all meet Exd II BT4/Exia II BT4 standards, suitable for skid-mounted stations in Zone 0/Zone 1.
• Lightning Protection: Built-in lightning protection module (IP65), surge resistant +(-)4kV, preventing damage to equipment from lightning strikes.
• Anti-static Design: All-metal casing grounded (grounding resistance < 4ohm), eliminating the risk of static electricity buildup.
• Environmental Adaptability: Operating temperature -40^oC-+85^oC, dustproof and waterproof IP65, suitable for harsh outdoor environments.

In summary, the six core functions of the Shengding skid-mounted fuel stations level gauge and anti-overflow system cover the full-scenario needs of skid-mounted fuel stations, from real-time monitoring, safety alarms, and unloading protection to digital management, environmental protection and leak prevention, and inherent safety. All technical parameters accurately meet standards and strictly adhere to relevant industry standards and emergency management requirements. Through intelligent and automated design, the system effectively reduces the risks of manual operation, improves gas station operational efficiency and safety levels, and provides strong support for solution implementation, compliance acceptance, and daily maintenance with clearly verifiable technical parameters and summary tables, helping skid-mounted fuel stations achieve safe, compliant, efficient, and digitalized operation.

Written by

TAIAN SHENGDING METAL CONTAINER MANUFACTURING CO., LTD.

Editor Wang

WhatsApp:+86 152 5486 3111

Email:shengdingtank@126.com