5704.2.7.3.1 Vent lines.

Vent lines from tanks shall not be used for purposes other than venting unless approved.

5704.2.7.3.2 Vent-line flame arresters and venting devices.

Listed or approved flame arresters or Pressure-vacuum (PV) vents that remain closed unless venting under pressure or vacuum conditions shall be installed in normal vents of tanks containing Class IB and IC liquids. Vent-line flame arresters shall be installed in accordance with their listings or API 2000 and maintained in accordance with NFPA 30 or API 2000. In-line flame arresters in piping systems shall be installed and maintained in accordance with their listing or API 2028. Pressure-vacuum vents shall be installed in accordance with NFPA 30 or API 2000 and maintained in accordance with NFPA 30 or API 2000.

   Exception: Where the department determines that the use of such devices can result in damage to the tank.

5704.2.7.3.3 Vent pipe outlets.

Vent pipe outlets shall be located such that the vapors are released at a safe point outdoors and not less than 15 feet (4572 mm) above the adjacent ground level. Vapors shall be discharged upward or horizontally away from adjacent walls to assist in vapor dispersion. Vent outlets shall be located such that flammable or combustible vapors will not be trapped by eaves or other obstructions and shall be at least 10 feet (3048 mm) from building openings.

5704.2.7.3.4 Installation of vent piping.

Vent piping shall be designed, sized, constructed and installed in accordance with FC 5703.6. Vent pipes shall be installed such that they will drain toward the tank without sags or traps in which liquid can collect. Vent pipes shall be installed in such a manner so as not to be subject to physical damage or vibration.

5704.2.7.3.5 Manifolding.

Tank vent piping shall not be manifolded unless required for special purposes such as vapor recovery, vapor conservation or air pollution control.

5704.2.7.3.5.1 Aboveground tanks.

For aboveground tanks, manifolded vent pipes shall be adequately sized to prevent system pressure limits from being exceeded when manifolded tanks are subject to the same fire exposure.

5704.2.7.3.5.2 Underground tanks.

For underground tanks, manifolded vent pipes shall be sized to prevent system pressure limits from being exceeded when manifolded tanks are filled simultaneously.