Floating Roof Tanks - Different Aspects

Types of Tanks

CONE ROOF TANKS (CR)

FLOATING ROOF TANKS

DOME ROOF TANK

IFR EFR

(a) Advantage of Floating Roof Tanks

MINIMIZING VAPOR SPACE: (a) ELIMINATES FILLING LOSS

CONE ROOF TANKS

FLOATING ROOF TANKS

MINIMIZING VAPOR SPACE: (b) REDUCES BREATHING LOSS

FLOATING ROOF TANK

CONE ROOF TANKS

MINIMIZING VAPOR SPACE: (c) PROVIDES EFFECTIVE FIRE PROTECTION AND LIGHTING SAFETY, IT ALSO INHIBITS ROOF AND

SHELL CORROSION

FLOATING ROOF TANKS

CONE ROOF TANKS

(b) Type of Floating RoofThere are a variety of deck options that may be exercised depending on the service conditions of the stored product.

• Single Deck Pan Type• Single Deck pontoon Type• Double Deck

Selection of a specific type of roof and tank depends on the intended service conditions, such as the petroleum liquid being stored, its vapor pressure and corrosive nature, and the anticipated weather and loading conditions.

General Industry Trends in selection

• Double deck floating roofs for large diameter tanks above 60 m dia. forcrude oil service (to conserve lighter end products) or otherwise andvery small diameter tanks less than 15m

• Single deck floating roof tanks for most intermediate range tank diameters

• Internal floating roof tanks for volatile, highly inflammable or value addedProducts – based on economics of advantages vs costs On the aforesaidguidelines, a thumb rule classification of roof selection for various serviceconditions may be made. A final selection would require a more detailedinvestigation of process conditions during tank service and relative vaporloss advantages gained by the use of various deck options.

• Available in standard sizes from 15 – 91.5 m diameter

• Provides a cost effective solution, compared to the double deck, except inthe larger and very small sizes

• Greater water carrying capacity while afloat

• Prone to weldseam fatigue cracking from extended exposure to high windconditions

• Sufficient pontoon volume to keep deck afloat with any two pontooncompartments punctured

• Pontoon area varies from 35% on small diameter roofs to 20% on largediameter roofs

• Pontoon underside slopes upward toward centre of roof to hold temperaturegenerated condensible vapors

SINGLE DECK (PONTOON TYPE) EXTERNAL FLOATING ROOF TANKS

SINGLE DECK EXTERNAL FLOATING ROOF TANKS (EFR)

Shell

Rim

Roling ladder

(typ)

Deck Plate

Single Deck Pontoon Type Floating Roof Tank

Pontoon

Curb Angle

• Available in standard sizes from 9 – 122 m diameter

• Most efficient solution, double deck provides good insulation over entireliquid surface, most stable and maintenance free option for larger sizes

• Limited water carrying capacity while afloat, water allowed to passthrough deck

• Reduces impact of high winds on product, stable performance of deck undersuch conditions

• Emergency drains provided to accommodate 10” of rainfall in 24 hours

• Roof designed to float directly on product, and stay afloat with any twocompartments punctured. Deck flexibility allows temperature generatedcondensible vapor to be contained under center of deck

DOUBLE DECK EXTERNAL FLOATING ROOF TANKS

DOUBLE DECK EXTERNAL FLOATING ROOF TANKS (FR)

• Provides additional protection against wind and rain

• Combines the all-weather performance of a cone roof tank with theevaporation saving and fire protection qualities of a floating roof tank

• Maximum protection against exposure or rim fires

• Floating roof simultaneously combats corrosion and product deterioration

• No drainage system required – this eliminates maintenance of this item andfloating roof may be operated to lower levels

• In lieu of pan type construction, special pontoon type decks can be providedfor more positive floatation and increased stability.

• Shell/Roof vents provided for venting air-vapor mixture between the floatingdeck and fixed roof during product pump in

DOUBLE DECK INTERNAL FLOATING ROOF TANKS (IFR)

DOUBLE DECK INTERNAL FLOATING ROOF TANKS (IFR)

DOUBLE DECK EXTERNAL FLOATING ROOF TANKCENTER DRAIN PROFILE

DOUBLE DECK EXTERNAL FLOATING ROOF TANKREVERSE SLOPE PROFILE

Pipe Support

Roof Drain

Roof Drain

PARTS OF ADJUSTABLE / FIXED PIPE SUPPORT

DECK MANWAY

• Deck manway is use to enter the tank bottom from top of deckby using internal ladder and also use as vent.during maintanance when tank is empty.

PONTOON MANWAY

• Pontoon Manway is use during hydrotest of pontoon.Water is inlet from pontoon manway.

• Generally size of Pontoon Manway is 20” NB.• Each compartment one & for big tank two required.• Pontoon manway is use to excess in pontoon for welding of

radial & circumferencial bulkhead to bottom deck also.

PARTS OF DECK MANWAY PARTS OF PONTOON MANWAY

An Example of Deck Layout of Floating Roof Tank Size is

92m ID x 20M HT.EFR Tank for

Crude Oil Storage

PARTS OF CONE ROOF TANKS

Lifting the Roof/Shell section of the tank.

The Roof and Top shell Section is Fit and being tacked from the Inside.

Dome Roof Knuckle Profile

Looking down on Knuckle