Diesel Tank Requirement for Fire Fighting Diesel Engine Pump | NFPA 20

General Requirements for Fire Pump Diesel Fuel Supply Tanks:

1. Exclusive Use:

   • The fuel supply tank and fuel shall be reserved exclusively for the fire pump diesel engine.

2. Separate Components:

   • Each engine shall have a separate fuel supply tank.
   • Each engine shall have a dedicated fuel supply and return line.

3. Tank Construction:

   • Tanks shall be either single-wall or double-wall.
   • Single-wall tanks must be enclosed within a wall, curb, or dike capable of holding the tank's entire capacity.

4. Tank Capacity and Compliance:

   • Tanks used per NFPA 20 shall not exceed 1,320 gallons.
   • Tanks exceeding 1,320 gallons must comply with NFPA 37 requirements.
   • Tanks shall be securely mounted on noncombustible supports.

5. Fuel Supply Tank Capacity Calculation:

   • The fuel supply tank(s) shall have a minimum capacity of:
     • 1 gallon per HP of the engine
     • Plus an additional 5% for expansion
     • Plus an additional 5% for sump

Example Diesel Tank Sizing Calculation

Fuel supply tank sizing shall be determined based on engine horsepower and required runtime.

Fuel Supply Tank Location Requirements

1. Diesel fuel supply tanks shall be installed above ground and not buried.
2. Preferably, storage tanks should be located inside the pump room or pump house.
3. Fill and vent lines shall extend outdoors.

Tank Connections and Specifications

Each fuel supply tank shall have the following connections:

• Fill Connection:

  • Fill pipes shall enter the top of the tank and terminate within 6 inches of the bottom.

• Drain Connection:

  • Located at the lowest point of the tank, sized at 1-inch NPT.

• Vent Connection:

  • Normal vent shall be 2-inch NPT or sized per ANSI/UL 142.
  • Alternatively, the normal vent can be at least as large as the largest fill or withdrawal connection, but not less than 1¼ inches nominal inside diameter.

• Engine Supply Connection:

  • Located on the tank's side, leaving 5% of the tank volume as an unusable sump.
  • Connection size shall not be smaller than the engine’s fuel supply piping.

• Engine Return Connection:

  • Connection size shall not be smaller than the engine’s fuel return piping.

• Fuel Level Switch Connection:

  • The tank shall have a 2-inch NPT threaded port at the top, near the centre, for a low fuel level switch.

• Active Fuel Maintenance Return Connection:

  • The tank shall have a minimum 1-inch NPT threaded port at the top to accommodate return fuel from an active fuel maintenance system.
  • If no active fuel system is installed, a plug shall be placed in this connection.

References

• NFPA 20 - 2022 Edition (Standard for the Installation of Stationary Pumps for Fire Protection)
• Stationary Fire Pumps and Standpipe Systems Handbook
• Fire Protection Handbook, 20th Edition