Roof Tank Design and Installation

1. Floating Roof Tanks

Floating roof tanks are ideal for storing fuel and industrial liquid. The tanks feature a roof which floats on top of the liquid, rising up and down with the level of the liquid. Floating tanks generally come with annular space with sealed gland between the walls of the tank and the floating roof to separate air when the stored liquid rises up or down on the roof. The tanks are generally spherical in shape and can be made of steel or concrete.

The biggest advantage of floating roof is that they eliminate the space between the liquid and roof, reducing evaporation loss to a great extent. In fact, floating roof tanks can cut back evaporation loss by up to 80% in the case of oil products. The tanks also reduce the volatile gases inside and minimize threats of fire hazards.

Floating roof tanks can be categorized into external floating roof tanks and internal floating roof tanks.

2. External Floating Roof Tanks

External floating roof tanks have a floating roof which covers the liquid inside. The floating roof rests on the liquid and floats up and down as the level changes. External floating roof tanks are generally made of steel and only has a floating roof as the top covering.

The floating roof is made up of various elements such as fittings, decks and rim sealing systems. The floating roof decks are usually made of welded steel plates and can be of three types- double deck, pontoon and pan. We have designed several tanks with pan-style decks, but currently, double deck and pontoons have become the popular choice.

Our team can customize the decks emphasizing on specific features such as pontoon arrangement, full liquid contact, roof stability and load carrying capacity. We can design the floating roof to cover the whole liquid surface, except the small annular space between the shell and the deck. The deck can be made to float on the liquid directly or rest above the surface on pontoons.

External floating roof tanks are designed with a rim sealing system. The seal is attached with the perimeter of the roof and touches the tank wall. The seal system stays in contact with the tank wall as the liquid inside goes up or down. We also design the floating decks with fittings to enable you to carry out operational functions.

The rim seal system is responsible for limiting evaporation losses and withdrawal losses.

3. Internal Floating Roof Tanks

Internal floating roof tanks are almost the same as external floating roof tanks except that they have a permanent roof. That means internal floating roof tanks have two roofs- one that floats over the liquid and another which covers the top of the tank. The roof that floats over the liquid moves up and down as the level of fluid changes. Internal floating roof tanks can be divided into two main types-

• Tanks which have vertical columns within it to support the fixed roof
• Tanks without internal support columns that have independent fixed roofs

The fixed roof covers the entire perimeter of the tank shell and may have openings for inspection or performing operational functions. A fun fact is that you can convert fixed roof tanks and external floating roof tanks to internal floating roof tanks very easily. We can convert fixed roof tanks by installing a floating roof inside to make it an internal floating roof tank. On the other hand, we can also convert an external floating roof tank into an internal floating roof tank simply by providing a fixed roof.

Internal floating roof tanks can be more effective in limiting evaporation loss and volatility. You can also have extra protection from rain and snow with the fixed roof over the floating roof.

4. Domed External Floating Roof Tanks

Domed external floating roof tanks are equipped with heavy decks just like external floating roof tanks, and also have a fixed roof on top similar to internal floating roof tanks. Generally, domed external floating roof tanks are created when you retrofit a fixed roof in external floating roof tanks.

The main function of the fixed roof is to block the entry of wind just like in the case of internal floating roof tanks. We generally use self-supporting aluminum dome roof with bolted construction for the fixed roof, though other options are also available. The tanks usually have circulation vents at the top of the fixed roof similar to internal floating roof tanks.

The rim seal system and deck configurations are almost identical to those in external floating roof tanks.

5. Fixed Roof Tanks

Fixed roof tanks are simple storage solutions for large amounts of liquid or petrochemicals. The tanks generally have a spherical shape and have a permanent roof fixed over the shell. The roof includes utility holes, gauge hatches, float gauges, sample wells and other features for accessibility. The roof of the tank is usually cone or dome-shaped, though there's no norm.

In comparison to other tank types, fixed roof tanks don't have a floating roof that adjusts according to changes in the liquid level.

Fixed roofs tanks can be made of steel and are fully welded to make them liquid and vapor tight. It's not uncommon to find old tanks with bolted or riveted construction. The tanks are equipped with a breather valve which enables it to take advantage of a slight internal pressure or vacuum. The valve also contributes towards limiting emissions at small changes in liquid level, barometric pressure or change in temperature.

The tanks are also equipped with air and vapor valves to prevent over or under pressure while filling or emptying the tank, which can result in damages. Out of all the tanks discussed till now, fixed roof tanks are the most affordable and the minimum standard for storing liquids. But the tanks can suffer from vaporization which might pollute the air or cause emission concerns.

6. Domestic Roof Tank

Domestic roof tanks are water storage tanks which supply water to the building. The roof tanks use the force of gravity to distribute the water and don't need additional pumps unless there are pressure issues. You will generally need a pump to fill the roof tank if your house is over six-story high and located in places like New York.

Roof tanks can be constructed of various materials like concrete, steel or even wood. The tanks are sometimes elevated on columns to create enough height for gravity to work. We can also design roof tanks with guardrails, staircases and other features.

New York Engineers designs and installs all types of tanks we discussed with efficiency and reliability.