Fixed roof tank and its Applications

A fixed-roof tank is a storage tank, used to store liquids, consisting of a conical or dome-shaped roof permanently affixed to a cylindrical shell.Newer tanks are usually fully welded and designed to be liquid and vapor tight.However, older tanks are usually riveted or bolted and are not airtight.A vent valve (pressure vacuum valve) commonly installed on many fixed-roof tanks allows the tank to operate under slight internal pressure or vacuum.The valve prevents the release of vapor during small changes in temperature, atmospheric pressure, or liquid level.Fixed-roof tanks without vent valves are usually free-draining;therefore discharges from fixed-roof tanks may not be small. Gauge hatches sample wells, float gauges and roof manholes provide accessibility to these tanks and are a potential source of volatile emissions.

Applications 

Storage tanks in general, and fixed roof tanks in particular, contain organic liquids and can be found in many industries, including:

• Petroleum production and refining

• Petrochemical and chemical manufacturing

• Bulk storage and transfer operations

• Other industries that consume organic liquids

Fixed roof tanks are typically used for products with relatively low volatility and flash points.Storing highly volatile products using fixed-roof tanks may result in product loss as vapors escape from the enclosure.

Other types of tank

Atmospheric

Atmospheric tanks are containers that hold liquids under atmospheric pressure.The main design codes for welded atmospheric tanks are API 650 and API 620. API 653 is used to analyze in-service storage tanks.In Europe, the design code is EN14015, using load cases from Eurocode 3 (EN 1993) Part 4-2.

High pressure

For liquefied gases such as hydrogen or chlorine, or compressed gases such as compressed natural gas or MAPP, the tank must be able to withstand the enormous pressure sometimes exerted by the contents. These tanks may be referred to as cylinders and, as pressure vessels, are sometimes excluded from the "tank" category.

Storage tank

One form of seasonal thermal energy storage (STES) is the use of large surface tanks that are insulated and then covered with earthen banks in order to use solar heat collected mainly in summer for year-round heating.A related technology has been widely used in the Danish district heating system.The heat storage medium is gravel and water in large shallow lined pits covered with insulation, soil and grass.Ice tanks and ice water tanks are used for short-term cooling in air conditioners, allowing the refrigeration unit to run at night when electricity costs are lower, but provide cooling during the hotter day.

Milk tank

Bulk milk cooling tanks are storage tanks located in the milk room of a dairy farm that are used to cool and preserve liquid milk at low temperatures until it can be picked up by milk handlers.Since the temperature at which milk leaves the udder is around 35 °C, milk tanks are required to quickly cool fresh raw milk to storage temperatures of 4 °C to 6 °C, thereby slowing the growth of microorganisms.Bulk milk cooling tanks are usually made of stainless steel and constructed to sanitary standards.It must be cleaned after each milk collection.The milk cooling tank may be the property of the farmer or may be rented by the farmer from the dairy.

Septic tank

A septic tank is part of a small sewage system, often called a septic system. Septic systems are commonly used to treat wastewater from rural and suburban homes and small businesses.It consists of the tank and septic tank drainage area.Wastewater enters the tank, solids settle and scum floats in the tank. Anaerobic digestion occurs on settled solids, reducing the volume of the solids.Water released from the system is normally absorbed by the drainage area without any further treatment.

Mobile "storage" tanks

While not strictly a "storage tank," mobile storage tanks share many of the same characteristics as storage tanks.In addition, they must be designed to handle heavy sloshing loads and the risk of collisions or other accidents.Some of these include ocean-going tankers and liquefied natural gas carriers; rail tank cars; and road and road-going tank cars.Also includes water storage tanks, which are used to store toilet waste in RVs, boats and planes.