| Water Tanks | 1 * 5200 kL , 2 * 2600 kL |
| Fire Engines | 6 * 616 kL/ hr. Diesel Engine operated |
| Jockey Pumps | 2 * 74 kL/hr. Electricity operated |
| HVLR | 4 Monitors |
| Gantry 1 | 8 Bays |
| Gantry 2 | 4 Bays |
| Gantry 3 | 7 Bays |
| Gantry 4 | 4 Bays |
INTRODUCTION TO TANK FARM:
The use of tanks is common in all kinds of plants found in oil & gas industry.
- Process Plant
- Refineries
- Petrochemicals
- Specialty chemicals
- Terminals
- Administration buildings
- Material Handling Plants
Storage tank are containers used for storage of fluids for the short or long term. Cluster of tanks together in a same are termed as “Tank Farms”.
TYPES OF TANKS:
Types of Tanks in Process plant depend on the product to be stored, potential for fire, and capacity to be handled.
- Cone roof tank : Used for countless products including Petroleum, Chemicals, Petrochemicals, Food products & Water
- Floating roof tank : The roof of tank rises and lowers with the stored contents thereby reducing vapour loss & minimizing fire hazard. Commonly found in Oil refineries.
- Low temperature storage tank : Tanks stores liquefied gases at their boiling point. Products found in such tanks include Ammonia (-28 °F), Propane (-43.7 °F) and Methane (-258°F).
- Horizontal pressure tank (Bullet) : Used to store products under high pressure
- Hortonsphere pressure tank : Handles large capacity under high pressure.
- Underground Tanks : Commonly used for drain collection of the plant at atmospheric pressure.
- FRP Tanks : Commonly used for corrosive fluid at atmospheric pressure.
CONE ROOF VERTICAL TANKS
Of currently used tank designs, the cone-roof tank is the least expensive to construct and is generally considered the minimum acceptable equipment for storing liquids. A typical fixed-roof tank consists of a cylindrical steel shell with a cone- or dome-shaped roof that is permanently affixed to the tank shell. Storage tanks are usually fully welded and designed for both liquid and vapor tight, while older tanks are often have a riveted or bolted construction and are not vapor tight. It is generally used for holding diesel. One of the disadvantage of Cone roof vertical tank is the breathing loss as vapour escapes to the air vents.
FLOATING ROOF TANKS
The floating roof of a floating roof tank is a floating roof floating on the surface of stored liquid, floating up or down with the level of stored liquid. There is a annular space with seal gland between the floating roof and the tank wall, to separate air when stored liquid float up or down on the roof, greatly reducing evaporation loss in the storage process. Compared with fixed roof tank, using a floating roof tank to store oil product can reduce evaporation loss to 80% approximately.
Totally, floating roof tank can be divided into internal floating roof tank and external floating roof tank.
Difference between internal floating roof tank and external floating roof tank :
The transmitter and the receiver of the two ways of storing liquid are same, specific differences between external floating roof tank and fixed internal floating roof tank as follows:
>>Both can reduce evaporation loss greatly;
>>There is a floating roof covered upon the floating tank liquid surface, liquid stored in the storage tank is separated with the air, to reduce air pollution and the danger of fire and explosion, ensure the liquid quantity easily. It is especially suitable for storing advanced gasoline, jet fuel, and toxic and easily contaminated liquid chemical.
>>Fixed roof tank, including internal floating roof tank, can prevent the stored liquid from being pollute by wind and sand storms, rain and snow, and dust. They can guarantee the stored liquid quality in all weather conditions, are famous as “all – weather storage tank”;
>>In the same sealing condition, compared with external floating roof tank, internal floating roof tank can further reduce the volatilization loss, as a result of that, compared with double deck floating roof on external floating roof tank, shaded by fixed roof and the gas phase layer between fixed roof and internal floating plate have a more significant effect on heat insulation;
>>Unlike floating plate opened upon external floating roof tank, there can be no rain and snow load on the internal floating roof in internal floating roof tank. With less load, simple and light structure, internal floating plate can save accessories like central drain and ladder, constructed and maintained easily, also can prevent the sealing material from aging by the intense light;
>>Compared with external floating roof tank, internal floating roof tank is a promising tank with more advantages, also its applications are wider and wider. So far, perfect-designed internal floating roof tank is the best and the least investment method to control volatilization loss from the fixed roof tank. Internal floating roof tank can be used to store liquid chemical product, including volatile oil like gasoline and jet fuel, aldehyde, alcohol like methanol and ethylalcohol, ketone like acetone, benzene like benzene, toluene, xylene, and styrene.
Internal floating roof tank
Internal floating roof tank is known as internal floating roof storage tank, floating roof oil tank, internal floating plate storage tank and internal floating plate oil tank, etc. specifically, it is an environment-friendly and economical storage tank or oil tank installed a floating roof under the vault of the tank, usually made of aluminum, stainless steel, or other material to prevent the liquid from volatilize. It is a volatile liquid storage tank, also a floating roof tank combined with the internal floating roof structure, which has been widely used in gasoline, aviation kerosene, and volatile chemical liquid.
Characteristic of internal floating roof structure
Internal floating roof Internal floating roof tank structure Internal floating roof tank seal
An internal floating roof or internal floating plate is a head cover floating with oil and liquid up or down on the oil surface. Adopting the internal floating roof cover in the liquid surface is recognized as the most ideal economic and practical method to reduce the evaporation loss of oil products.
External floating roof tank
Concept of external floating roof tank
External floating roof tank is known as external floating roof oil tank, it is an open top floating roof tank without vault, there is usually an external floating roof in it, which can vertical float up and down. It is usually used in steel open top tank large more than 20,000m³ for volatile oil products such as crude oil, gasoline, kerosene, etc, and external floating roof rises or falls with the liquid. There is a floating plate covers on the external floating roof tank, which rises or falls with the liquid. As there is almost no gas space between floating plate and oil surface, greatly reduced evaporation loss of the stored oil product.
Compared with internal floating roof tank, external floating roof tank has the following advantages:
>> Compared with fixed roof tank without a floating roof, there is no evaporation space in external floating roof tank, eliminating the so-called “big breathing loss” in principle.
>> Evaporation can not only resulted in the loss of product quantity, but also affects product quality, and pollute the environment simultaneously. It is prone to explode when space combustible medium mixed with air reaches a certain limit, so it is a necessary measure to fix a external floating roof on the open top cylindrical steel tank.
>> There is a 100 mm – 500 mm gap between tank shell and external floating roof to prevent the tank from jamming during the running process. External floating roof tank also uses edge sealing system to reduce edge evaporation.
>> The structural form of external floating roof is similar to internal floating roof, both of them have a steel tray form, floating cabin form, single deck floating roof or double deck floating roof, even external floating roof with aluminum alloy sandwich structure. The supporting leg of floating roof are retractable activity, usually suspended in the liquid.
>> External floating roof is the most suitable for large crude oil storage tank, form 20,000m³, 30,000m³, 50,000m³ to 100,000m³, etc.
DYKE WALLS
Due to risk of failure of storage tanks and primary piping systems, means must be provided to contain the spills. The containment for petroleum storage tanks is in the form of Dyked enclosures.
DYKE ENCLOSURE :
Aggregate capacity in one dyke enclosure:
- Group of Fixed roof tanks: Upto 60,000 m3
- Group of Floating roof tanks: Upto 120,000 m3
- Fixed cum floating roof tanks shall be treated as fixed roof tanks.
- Group containing both Fixed roof tanks & Floating roof tanks, shall be treated as fixed roof tanks.
- Class – A and / or Class – B petroleum products :- Same dyked enclosure
- Class – C: – Preferably separate dyked enclosures.
- Tanks shall be arranged in maximum two rows. Tanks having 50,000 m3 capacities and above shall be laid in single row.
- The tank height shall not exceed one and half times the diameter of the tank or 20 m whichever is less.
- The minimum distance between a tank shell and the inside toe of the dyke wall shall not be less than half the height of the tank.
- Dyked enclosure for petroleum class shall be able to contain the complete contents of the largest tank in the dyke in case of any emergency.
- Height of Dyke (H): 1m < H < 2m
- Width of Dyke (W): Minimum 0.6m (Earthen dyke) Not Specific (RCC dyke)
Dyke enclosure
>> Separation distances between the nearest tanks located in separate dykes shall not be less than the diameter of the larger of the two tanks or 30 meters, whichever is more.
>> All process units and dyked enclosures of storage tanks shall be planned in separate blocks with roads all around for access and safety.
>> In a dyked enclosure where more than one tank is located, firewalls of minimum height 600mm shall be provided to prevent spills from one tank endangering any other tank in the same enclosure.
PIPING LAYOUT FOR TANK FARM
- Piping from / to any tank located in a dyked enclosure should not pass through any other dyked enclosure. Piping connected to tanks should run directly to outside of dyke to the extent possible to minimize piping within the enclosures.
- Inside dyked area, earth shall be graded and gravel filled. H.P (High point) level inside the dyked area shall be 300mm above the outside grade & shall slope towards the drain sump inside dyke.
- In dyked area of tankfarm, arrangement shall be made to drain containment to either OWS or storm water drain by providing two valves. Generally for the first 10 -15 mins of rainwater will be routed through the OWS and subsequently through the storm water.
- Pumps & its associated piping shall be located outside the dyke wall.
- Pipes Crossing the dyke wall shall pass through a sleeve suitably sealed.
- Piping elevation to be fixed considering settlement values.
- Spiral stairways shall be provided on each tank considering ease of access and minimizing paving requirement. Wind direction consideration should be taken into account
- Pumps shall be provided in a curbed area (150 mm high) with proper provision for draining either to OWS & storm water drain. Pump plinth shall be minimum 300mm high from finished floor level.
Typical tankfarm layout
Fittings on Tanks:
These are the devices that are required for the safe and efficient operation of the tank. These are directly mounted on the tank bottom and the tank top.
| Fittings at Bottom: | Fittings at Top: |
|---|---|
1. Manhole : Diagonally Opposite ends 2. Remote operated shut off Valve, (ROSOV) 3. Double Block and Bleed Valve 4. Receipt Valve 5. Delivery Valve 6. Water Drain Valve 7. Earthing Strips | 1. Manhole 2. Articulated water drain 3. Emergency water drain 4. Pressure Vacuum valve 5. Weather shield 6. Temperature sensor 7. Foam Pourer 8. Auto Bleeder Valve |
DOUBLE BLOCK AND BLEED VALVE, DBBV:
A double block and bleed valve is like having three valves in one.
API 6D defines a double block and bleed valve as a “single valve with two seating surfaces that, in the closed position, provides a seal against pressure from both ends of the valve with a means of vending/bleeding the cavity between the seating surfaces.”
There are a couple different styles of double block and bleed valves. One style, like this one from J-Flow Controls, has two independently seating valves inside, with a bleed or drain valve. This configuration is referred to as a double isolation and bleed (DIB). The DIB valve can isolate either side of the valve (bi-directionally) to vent or bleed the cavity and isolate piping.
This trunnion style ball valve from Val-Matic provides double block and bleed in a single valve. This style can isolate piping on both sides of the valve (uni-directionally) to vent/bleed the valve cavity between the seats.
Using a single double block and bleed valve system versus 3 separate valves saves installation time, weight on the piping system, and space. It also cuts down the number of leak paths to the atmosphere, reducing the risk of hazards when transferring liquids dangerous to humans or the environment.
REMOTE OPERATED SHUT OFF VALVE,{ROSOV) :
Remotely Operated Shut-Off Valve (ROSOV) is a valve which allows an item of plant or equipment to be isolated automatically from a safe location without the necessity for manual intervention. The inability to quickly isolate hazardous substances inventory in the event of a major accident was an issue in the Associated Octel Company major accident (1st and 2nd February 1994). For new installations ROSOVs should normally be fitted unless there are good technical reasons why they are not normally be fitted unless there are good technical reasons why they are not appropriate. For existing installations, the decision needs to be based on ALARP/cost benefit analysis.
Terminals and Depot 