Storage tank floating roof sump with emergency overflow

A method of providing emergency overflow drainage for water accumulated on a floating roof which has a bottom surface adapted to cover and float on a liquid in a storage tank having cylindrical side walls which have inner surfaces, said tank adapted to contain said accumulated water up to a predetermined maximum allowable level on the roof's top surface, said method comprising:

• a. providing a water collection sump formed as a downward extending recess in said top surface of said roof and adapted to receive water accumulated atop said roof,
• b. providing a first drainage duct having an inlet within said water collection sump at an elevation (L5) below said top surface of said roof, an outlet for draining water at an elevation (L7) below said sump, and an intermediate portion extending transversely between said inlet and said outlet,
• c. providing a second drainage duct having an inlet above said top surface of said roof, an intermediate portion extending downwardly from said inlet, and an outlet in fluid communication with said intermediate portion of said first duct in said sump, and
• d. providing an emergency overflow duct including:
• (1) an inlet in fluid communication with said second duct,
• (2) a proximal portion extending upwardly from said inlet,
• (3) a medial portion extending transversely from said proximal portion at an elevation (L3) higher than said bottom surface of said seal, and
• (4) a distal portion extending downward from said medial portion and terminating in an outlet below said sump.

A storage tank with a roof adapted to float atop a liquid stored in said tank and an emergency overflow drainage system for water accumulated on said floating roof, said tank adapted to contain said accumulated water up to a predetermined maximum allowable level above the roof's top surface, said system comprising:

• a. a water collection sump formed as a downward extending recess in said top surface of said roof and adapted to receive water accumulated atop said roof,
• b. a first drainage duct having an inlet within said water collection sump at an elevation below said top surface of said roof, an outlet for draining water at an elevation below said sump, and an intermediate portion extending transversely between said inlet and said outlet,
• c. a second drainage duct having an inlet above said top surface of said roof, an intermediate portion extending downwardly from said inlet, and an outlet in fluid communication with said intermediate portion of said first duct in said sump, and
• d. an emergency overflow duct including:
• (1) an inlet in fluid communication with said second duct,
• (2) a proximal portion extending upwardly from said inlet,
• (3) a medial portion extending transversely from said inlet at an elevation higher than said bottom surface of said seal, and
• (4) a distal portion extending downward from said medial portion and terminating in an outlet below said sump.