Basic introduction and usage of one tank with multiple storage compartments in mobile Fuel Stations

The "one tank, multiple compartments" model for mobile fuel stations (i.e., storing multiple fuel products within a single tank through physical separation) effectively saves space and reduces equipment costs. It also meets the practical need to store different grades of fuel (such as 92, 95, and 98 gasoline and 0 diesel) within a single facility. However, due to the isolation, safety, and compliance requirements for different fuels, the core principles must be adhered to: physical isolation, independent operation, and clear labeling to ensure operational safety and compliance.

I. Basic Introduction to the One Tank, Multiple Compartment Design

This is currently the most standard and recommended approach for storing multiple fuel products in mobile Fuel Stations.

1. Equipment Structure:

• During skid-mounted tank manufacturing, internal steel partitions are used to divide a large tank into two, three, or four completely independent compartments.
• Each compartment is strictly isolated and sealed, effectively installing multiple independent tanks on a single skid, fundamentally eliminating the possibility of intermixing of fuel products.

2. Advantages:

• Space and Cost Savings: Sharing a common outer shell, fire and explosion barrier, unloading port operation box, and main engine control system reduces space and construction costs compared to installing multiple single-tank skid-mounted stations.
• Safety and Reliability: The bulkhead steel plates provide sufficient strength and sealing, and their safety has been proven.
• Convenient Operation: Unloading and refueling pipelines are typically centrally located, making management easier.

3. Key Configurations:

• Independent Unloading Pipelines and Connections: Each tank compartment must have its own independent unloading port, typically located in a single unloading operation box. Each port must be clearly and permanently labeled with its corresponding fuel grade (e.g., 92, 95). During unloading, the fuel pipes from different tank compartments on the tank truck must be aligned with their designated ports; incorrect connections are strictly prohibited.
• Independent Refueling Pipelines and Dispensers: Each tank compartment's outlet pipe is also independent and directly connected to a designated dispenser. A dual-product, dual-gun dispenser can connect to two different tank compartments (e.g., one nozzle for tank 92 and another for tank 95).
• Independent Level Meters and Sensors: Each tank compartment requires an independent level monitoring system (such as a magnetostrictive level meter) to monitor the oil, water, and temperature data in real time, with separate displays in the control room to prevent misjudgments.

II. Preliminary Compliance and Design

The core premise of the "one tank, multiple compartments" system is design compliance. It is strictly prohibited to modify a conventional single-compartment tank by welding partitions. Design and manufacturing must be performed by qualified companies in accordance with national standards, with particular attention paid to the following points:

1. Qualification and Standard Compliance

• The oil storage tank and partition structure must comply with standards such as the "UL 142 Standard for Safety Steel Aboveground Tanks for Flammable and Combustible Liquids." These standards specify the partition type (e.g., welded partitions, independent liner), strength requirements, and sealing standards for "one tank, multiple compartments."
• The design must pass design review and acceptance by local emergency management departments and fire rescue agencies, and obtain qualifications such as a "Hazardous Chemicals Business License." "Construction first, then obtaining a license" is strictly prohibited.

2. Divider Structural Design: Ensure "Absolutely Reliable Physical Isolation"

• Divider panels must be made of the same material as the tank (e.g., Q235-B steel plate). Their thickness must be calculated based on the tank volume and oil density (generally no less than the tank thickness). Welds must undergo non-destructive testing (UT/RT) to prevent oil mixing or leakage due to weld defects.
• Divider panels must extend to both the tank top and bottom to achieve "full-height isolation." Partial isolation (e.g., leaving a gap at the bottom) is strictly prohibited. If the tank is equipped with wave-breaking panels, these must be designed in coordination with the divider panels to avoid compromising structural stability.
• Each independent compartment must be equipped with its own level gauge, pressure gauge, and emergency shut-off valve. Sharing monitoring or control equipment across multiple compartments is strictly prohibited (to prevent leakage or overpressure in a single compartment from being handled independently).

III. Fuel Management: Avoiding Mixing, Contamination, and Quality Risks

The core risk of "one tank, multiple storages" is the mixing of different fuels (e.g., diesel mixed with gasoline can cause engine failure, gasoline mixed with diesel can cause detonation). This requires comprehensive management throughout the entire storage and refueling process:

1. Fuel Compatibility: Storing "forbidden fuels" is strictly prohibited.

• Only fuels with similar physical/chemical properties and no risk of reactivity are permitted. For example:
  • Allowed: 92 gasoline and 95 gasoline (both gasolines differ only in octane rating), 0 diesel and -10 diesel (both diesels differ only in pour point).
  • Prohibited: Gasoline and diesel (due to significant differences in density and flash point, mixing is unusable), gasoline and ethanol gasoline (ethanol readily absorbs water, potentially causing the water content of the other tank to exceed the specified limit), and diesel and lubricating oil (due to significant differences in viscosity, contamination makes separation impossible).
• Before storage, the tank must be labeled with the fuel name, grade, and storage date. Corresponding signs should be posted on the fuel pump and lines to prevent mis-filling.

2. Pollution Prevention and Quality Maintenance

• Each tank must be cleaned and dried individually (compressed air can be used) before first use to prevent residual impurities from contaminating the oil. If a tank is out of service for an extended period, it must be emptied and sealed to prevent moisture and dust from entering.
• Regularly (recommended every three months) conduct quality checks on the oil in each tank (e.g., octane number and water content for gasoline, and pour point and flash point for diesel). Any abnormalities detected must be immediately shut down and cleaned. Mixing oil from other tanks is prohibited.

IV. Safety Protection: Strengthening "Single-tank Failure Prevention"

In "One Tank, Multiple Tanks" systems, it is necessary to ensure that leaks, overpressure, or other failures in a single tank do not affect other tanks or the entire equipment. The following protective measures should be emphasized:

1. Leak Detection and Isolation

• Leak sensors (e.g., fuel level sensors and oil/gas concentration sensors) must be installed at the welds of each tank wall and divider. These sensors should be linked to the skid-mounted station's alarm system. Upon detection of a leak, an audible and visual alarm will be triggered, and the tank's inlet and outlet valves will automatically close (while other tanks continue to operate normally).
• Zoned anti-seepage pools must be installed at the bottom of the tank (separated by the number of compartments, with each pool volume no less than 1.1 times the corresponding compartment volume) to prevent leaks from one compartment from seeping into the soil or flowing to other compartments. The anti-seepage layer must be made of HDPE membrane or reinforced concrete and comply with the "Hazardous Waste Storage Pollution Control Standard."

2. Breathing, Lightning Protection, and Anti-static

• Each compartment must be equipped with a separate breathing valve and flame arrester (sharing breathing lines for multiple compartments is strictly prohibited) to ensure independent pressure regulation in each compartment to prevent overpressure or negative pressure in another compartment due to a breathing valve failure in one compartment. Breathing valves must be regularly (monthly) inspected for open and close flexibility, and flame arresters must be cleaned of carbon deposits quarterly.
• The tank, partitions, and piping must all be connected to the same potential and reliably grounded (ground resistance ¡Ü 4¦¸) to prevent static electricity accumulation between compartments due to oil flow. When refueling, ensure that the fuel pump is in reliable contact with the vehicle's fuel tank (grounding before refueling) to prevent static sparks.
• The skid-mounted station must be designed as a Class II lightning protection structure, equipped with lightning rods or strips, and regularly (annually) inspected for effectiveness.

V. Operation and Maintenance: Establishing a "Zoned Management" Mechanism

During daily operations, the management responsibilities of each tank must be clearly defined to avoid overlooking risks associated with individual tanks due to "unified operations." Key points are as follows:

1. Operating Standards: Eliminate "Cross-operation"

• When refueling, adhere to the "one pump per tank, one pipe per tank" principle. Using the same inlet pipe to refuel different tanks is strictly prohibited. Before refueling, verify that the fuel in the tank truck matches the fuel in the tank. Unload the fuel slowly (flow rate ¡Ü 4 m/s) to avoid impacting the divider.
• During refueling, if the liquid level in a tank is too low (less than 10% of the total volume), refill that tank first to avoid uneven stress on the divider due to differential liquid levels. (Prolonged low liquid levels on one side may cause the divider to deform.)

2. Regular Maintenance: "Zone-by-Zone Inspection, Focused Investigation"

• Daily Inspection: Check the normal readings of the liquid level gauges in each tank (for any abnormal drop, indicating a leak), the status of the emergency shut-off valves, and the sensitivity of the alarm system.
• Monthly Maintenance: Clean the filters (inlet and outlet) in each tank and inspect the partitions for deformation (this can be done through the tank wall inspection hole or ultrasonic testing).
• Annual Overhaul: Perform a hydrostatic test on each tank (to test the strength of the partitions), inspect the tightness of welds, and replace any worn gaskets (such as the seals on the inlet and outlet valves).

3. Emergency Response: "Prioritize Isolation of Individual Tanks"

• If an oil leak occurs in a tank, immediately halt oil inflow and outflow operations in that tank, evacuate nearby personnel, seal the leak with oil-absorbing felt, and collect the leaked oil in a dedicated waste barrel (direct discharge is strictly prohibited). If the leak is large, activate the emergency plan and contact a specialized agency for disposal. Unauthorized opening of valves in other tanks is prohibited.
• If a fire occurs in a tank (e.g., due to static electricity causing a fuel or gas fire), immediately close all tank valves. Use a dry powder fire extinguisher (do not use water on gasoline fires) to extinguish the flames at the base of the fire. Simultaneously call 119. After extinguishing the fire, inspect other tanks to see if they are affected by the high temperature (e.g., whether the dividers are deformed or the seals are ineffective).

4. Color and Labeling Management:

• Strictly adhere to national or industry standards for fuel color marking. For example, gasoline pipes and nozzles are typically red, while diesel is yellow (or black/green).
• Post strong, legible text signs at all key locations:
  • Unloading ports: Clearly label "92 Gasoline Unloading Port" and "95 Gasoline Unloading Port."
  • Dispensers: Label the fuel grade above or on the side of the corresponding nozzle.
  • Pipeline Valves: Manual valves must be labeled to identify the fuel type they control.

5. Unloading Procedures:

• "Double Confirmation" System: Before unloading, the operator and the tanker driver must jointly confirm that the unloading pipe is connected to the correct unloading port. This is the most critical human factor in preventing oil contamination.
• Dedicated Supervision: A dedicated person must be on-site to monitor the entire oil unloading process to prevent accidents.

6. Daily Inspection and Maintenance:

• Regularly check the seals of compartments (for equipment with multiple tanks).
• Regularly calibrate the accuracy of fuel dispensers to ensure accurate oil delivery.
• Keep all labeling clear and intact.

7. Employee Training:

• All operators must receive rigorous training to ensure they fully understand the dangers of oil contamination (from reduced oil quality leading to customer disputes to engine damage leading to major accidents). They must also be proficient in distinguishing different oil pipelines and standard operating procedures.

VI. Core Taboos: Absolutely Prohibited Behaviors

• 1. Do not weld partitions within a standard single-compartment tank without proper modification.
• 2. Do not store products with conflicting or easily miscible properties (e.g., gasoline and diesel).
• 3. Do not share breather valves, emergency shut-off valves, or leak detection equipment across multiple tanks.
• 4. Do not continue to use other tanks if one tank is leaking or malfunctioning (first isolate the faulty tank and verify safety).
• 5. Do not place a "one tank, multiple compartments" tank on the ground without proper zoning and anti-seepage measures.

In summary, the core of the "one tank, multiple compartments" design for mobile Fuel Stations is "compliant design, strict isolation, and zoning management." Risks must be managed throughout the entire process, from initial design to daily operations, to ensure improved space utilization without compromising safety and compliance standards.

The above is a basic introduction to the "one tank, multiple compartments" design for mobile fuel stations and its practical considerations. We hope this information will be helpful when purchasing a skid-mounted gas station with a "one tank, multiple compartments" model in the future.

Written by

TAIAN SHENGDING METAL CONTAINER MANUFACTURING CO., LTD.

Editor Wang

WhatsApp:+86 152 5486 3111

Email:shengdingtank@126.com