All the knowledge you want to know about storage tanks is here

First, the use of storage tanks:

 for the storage of liquid or gas steel sealed container that is steel storage tanks, 

steel storage tank project is the petroleum, chemical, food, food, fire, transportation, metallurgy, 

national defense and other industries essential, important infrastructure.

Our economic life is always inseparable from the large and small steel storage tanks, 

steel storage tanks in the development of the national economy plays an important role is irreplaceable.

Steel storage tanks is the storage of various liquid (or gas) raw materials and finished products of special equipment, 

for many enterprises without storage tanks can not be normal production,

 especially the national strategic material reserves are dependent on the national strategic reserve.

In particular, the national strategic material reserves are inseparable from the various capacities and types of storage tanks. 

China's oil storage facilities are mostly above-ground storage tanks, and most of the metal structure.

Second, the classification of storage tanks: due to the different storage medium, the form of storage tanks are also varied. 

1. classification by location: can be divided into above-ground storage tanks, underground storage tanks, semi-underground storage tanks, offshore storage tanks, submarine storage tanks, etc. 

2. According to the classification of oil products: can be divided into crude oil storage tanks, fuel oil storage tanks, lubricating oil tanks, edible oil tanks, fire water tanks, etc. 

3. classification by use: can be divided into production oil tanks, storage tanks, etc. 

4. classification by form: can be divided into vertical storage tanks, horizontal storage tanks, etc.

5. classification by structure: can be divided into fixed-top storage tanks, floating-top storage tanks, spherical tanks, etc.

6. classification by size: more than 100m3 for large storage tanks, mostly vertical tanks; 100m 3 below for small storage tanks, mostly horizontal tanks.

Third, the standard of storage tanks: common storage tank standards: 

1. American Petroleum Institute standard API650; 

2. British Standard BS2654; 

3. Japanese standard JISB8501; 

4. German standard DIN4119; 

5. Petroleum industry standard SYJ1016; 

6. petrochemical industry standard SH3046.

Fourth, the tank materials: tank engineering materials required are divided into tank materials and ancillary facilities materials. 

Tank materials can be divided into low-strength steel and high-strength steel according to tensile yield strength or 

tensile standard strength, high-strength steel used for more than 5000m³ tanks.

Auxiliary facilities (including wind-resistant ring beam, locking mouth, pan ladder, guardrail, etc.) 

are lower strength ordinary carbon structural steel, the rest of the fittings, accessories are used according to different uses of other materials.

Commonly used domestic steel for manufacturing tanks are 20, 20R, 16Mn, 16MnR and Q235 series, etc.

Fifth, the structure of the tank: 

At present, China's most widely used, the most mature production and installation technology is the vaulted storage tank, 

floating roof tanks and horizontal storage tanks. 

1. the structure of the vaulted storage tank vaulted storage tank is a steel container with a dome, cylindrical tank body.

Vaulted tanks are simple and inexpensive to manufacture, so the most widely used in many industries at home and abroad, 

the most commonly used volume of 1000 -10000m³.

At present, the maximum volume of domestic vaulted tanks has reached 150000m³. 

1.1 tank bottom: the bottom of the tank is assembled from steel plates, the steel plate in the middle of the tank bottom for the middle width of the plate, the surrounding steel plate for the edge plate.

Edge plate can be used strip plate, can also be used bow-shaped plate. In general, the tank inside diameter < 16.5m,

 it is appropriate to use strip edge plate, the tank inside diameter ≥ 16.5m, it is appropriate to use bow edge plate.

1.2 tank wall: the tank wall is welded from multiple circles of steel plate pairs, divided into sleeve and linear. Sleeve tank wall plate ring weld using lap, longitudinal weld butt.

Vaulted storage tank using the form, the advantage is to facilitate the grouping of each circle wall plate, using the inversion method of construction is safer.

 Straight tank wall plate ring weld for butt. The advantage is that the wall as a whole from top to bottom the same diameter, especially for internal floating roof storage tanks, but the group of installation requirements are higher, more difficult.

 1.3 tank top: the top of the tank has a number of sector plate group welded into a dome shape, the inside of the roof using flat steel reinforcement, each sector plate between the lap weld, the entire top of the tank and the upper part of the wall plate angle steel ring (or locking mouth) welded into one.

2. floating roof tank structure floating roof tank is floating on the surface of the medium by the floating roof and vertical cylindrical tank wall is constituted.

Floating top with the increase or decrease in the amount of medium storage and lift, the outer edge of the floating top and the tank wall between the ring sealing device, the tank medium is always covered directly by the inner floating top to reduce media volatilization.

 2.1 tank bottom: the volume of the floating roof tank is generally large, its bottom plate are used bow edge plate.

 2.2 tank wall: the use of linear tank wall, butt welds should be polished smooth to ensure that the inner surface is smooth.

The upper part of the floating roof tank is open, in order to increase the rigidity of the wall plate, should be based on the size of the wind load in the region, the top of the tank wall need to set the wind ring beam and strengthen the ring.

 2.3 floating roof: floating roof is divided into single-disk floating roof, double-disk floating roof and float floating roof and other forms. 

2.3.1 Single-disk floating roof: the ring-shaped floating vessel is formed by several independent compartments, and the inner side of its ring is a single-disk top plate. The bottom of the single-disc top plate is reinforced with multiple ring-shaped steel rings. Its advantage is low cost and good maintenance.

 2.3.2 Double-disc floating roof: It is composed of upper disc plate, lower disc plate and cabin edge plate, and separated into several independent annular chambers by radial partition plate and circular partition plate. Its advantage is buoyancy, drainage effect is good. 

3. The structure of the inner floating roof tank The inner floating roof tank is in the vaulted tank with a floating roof inside, the tank with a floating roof can reduce the loss of media volatilization, and the external vault can prevent rain, snow and dust into the tank, to ensure the cleanliness of the medium inside the tank.

This kind of storage tank is mainly used for storing light oil, such as gasoline, aviation kerosene, etc. Inner floating roof tank adopts linear wall, wall plate butt welding, vault according to the requirements of the vault storage tank production.

At present, there are two kinds of domestic internal floating roof structure: 

one is the same as the floating roof tank steel floating roof; the other is assembled and formed aluminum alloy floating roof.

4. Horizontal storage tank structure Horizontal storage tank volume is generally less than 100m3, usually used for production links or gas stations.

 Horizontal storage tank ring weld using lap joints, longitudinal weld using butt. The ring plate is arranged interactively, 

taking an odd number, so that the end caps have the same diameter.

Horizontal storage tank end caps are divided into flat end caps and disc end caps,

 flat end caps horizontal tanks can withstand 40kPa internal pressure, disc-shaped end caps horizontal tanks can withstand 0.2Mpa internal pressure. 

Underground horizontal storage tanks must be set up to strengthen the ring, strengthen also made of angle simmering.

Six, the storage tank foundation selection. 

1. foundation soil layer can meet the bearing capacity design value and settlement requirements and the site is not restricted, it is appropriate to use the berm type or outer ring wall foundation. 

2. the foundation soil layer can not meet the bearing capacity design value requirements, but the settlement does not exceed the allowable value, can use the ring wall type or outer ring wall type foundation.

3. when the foundation soil layer is soft soil layer, it is appropriate to treat the foundation and then use the outer ring wall foundation.

4. when the site is limited, can use the ring wall foundation.

Seven, storage tank foundation construction:  

1. earth excavation: pit ramming;  2. reinforced concrete and masonry works: (omitted) 

3. earth backfill: mechanical ramming, backfill soil layer greater than 500mm. 

4. sand bedding: selection of medium and coarse sand, laying thickness of 200 ~ 250mm, ramming with a flat oscillator sprinkling water.

5. asphalt sand bedding layer: choose medium and coarse sand and No. 60 A road petroleum asphalt heated into asphalt sand, laying flat in layers and blocks, 

its thickness is 80~100mm, the slope of the top surface of the tank foundation from the center to the surrounding area is 15~35‰; 

6. Slope protection construction: After the hydraulic test of the tank, the slope protection construction is carried out, 

and the width of the slope protection is 800~1000mm. The slope protection and the bottom plate of the storage tank are filled with asphaltic marsupial.

 7. Please refer to SH/T3083 "Technical Specification for Foundation Treatment of Petrochemical Steel Storage Tanks" and SH3086 "

Design Specification for Foundation and Foundation of Petrochemical Steel Storage Tanks" during the design and construction of storage tank foundation.

 Eight, tank fabrication and installation 

1. The process of tank construction is divided into two parts: semi-finished products prefabrication and on-site assembly and installation. 

2. Semi-finished products prefabricated: tank bottom, wall, roof and other components need to be prefabricated (specific prefabricated method omitted). 

3. on-site group installation method: roughly divided into the reverse method of construction process, positive method of construction process and special method of construction process.

Nine, tank accessories

 1. Tank accessories are an important part of the tank itself. It is set up according to its role can be divided into four types.

1.1 to ensure the completion of oil receiving and dispatching, storage operations, to facilitate production and operation management.

1.2 to ensure the safety of tank use, to prevent and eliminate all types of tank accidents.

1.3 Beneficial to oil tank cleaning and maintenance.

1.4 Can reduce oil evaporation loss. 

2. Pan ladder (or straight ladder): with resting platform, width 650mm, counterclockwise rotation. The top of the tank is equipped with non-slip treads. The ladder is designed for operators to check the scale on the tank, temperature measurement, sampling, inspection and set up. It has two types of straight and rotating ladders.

Generally speaking, small tanks with straight ladders, large tanks with rotary ladders.

2. Guardrail: the height is 800~1000mm. 

3. catwalk: used for connection between tanks, width is 650mm. 

4. manhole: there are three common specifications: DN500, DN600, DN750. manhole is for cleaning and maintenance of the tank,

 the operator to enter and exit the tank and set.

General vertical tanks, manholes are installed in the tank wall on the lowermost ring plate, and and the top of the tank above the light hole opposite. 

The diameter of the manhole is mostly 600 mm, the center of the hole from the bottom of the tank is 750 mm.

Usually there is one manhole for tanks below 3000 cubic meters, 1~2 manholes for 3000~5000 cubic meters, and 2 manholes for tanks above 5000 cubic meters. 

5. Light-transmitting hole: common specifications: DN500. Light-transmitting hole, also known as light hole, is for tank cleaning or maintenance of light and ventilation set.

It is usually set on the top of the tank above the inlet and outlet pipes, the diameter is generally 500mm, the outer edge from the tank wall 800 ~ 1000mm, set the number of the same as the manhole. 

6. cleaning hole or drainage hole: drainage hole for light oil, cleaning hole for heavy oil. There are DN50, DN80 and DN100 models. 

7. Oil measuring hole: common specification: DN150, which is installed near the top platform of the tank for measuring scale, temperature measurement and sampling. Only one oil measuring hole is installed in each tank, its diameter is 150mm, and the distance from the tank wall is more than 1m. 

8. Drainage pipe and automatic water cutter: dewatering pipe is also known as drainage pipe, which is specially designed to remove water and remove oil residue from the bottom of the tank.

The release pipe is equipped with a valve on the outside side of the tank, in order to prevent the dewatering valve is not strict or damaged, usually installed two valves. Winter should also do a good job of dehydration valve insulation, to prevent freezing or valve freezing. 

9. inlet and outlet joint pipe.

10. Fire fighting foam room: Fire fighting foam room, also called foam generator, is a fire fighting device fixed on the tank. 

One end of the foam generator is connected to the foam line, and one end has a flange welded to the uppermost ring plate of the tank wall.

The fire extinguishing foam flows through the air suction inlet of the fire fighting foam chamber, draws in a large amount of air to form foam and breaks through the isolation glass into the tank (the thickness of the glass is not more than 2mm), so as to achieve the purpose of coming to the fire.

11. grounding wire: grounding wire is a device to eliminate static electricity in the tank.

12. light oil special accessories light oil (including gasoline, kerosene, diesel, etc.) is a small viscosity, light quality, volatile oil, the tank containing such oil, are equipped with their characteristics and meet the production and safety needs of a variety of tank special accessories. 

12.1 tank breathing valve: tank breathing valve is an important equipment to ensure the safe use of oil tanks and reduce oil loss. 

12.2 Hydraulic safety valve: hydraulic safety valve is another important equipment to improve the performance of the tank for greater safety use, its working pressure is 5 ~ 10% higher than the mechanical call valve. Under normal circumstances, it is not moving.

When the mechanical breathing valve fails due to valve disc rust or jamming or abnormal tank collection and payment operations and the tank overpressure or vacuum is too large, it will play a tank safety seal and prevent damage to the tank. 

12.3 flame arrestor: flame arrestor, also known as tank fire protection, is the tank fire safety facilities, it is installed in the mechanical breathing valve or hydraulic safety valve below.

The interior is equipped with many copper, aluminum or other high heat capacity metal made of wire mesh or wrinkled plate. When the external flame or spark in case through the breathing valve into the fire arrester, 

the Metal mesh or wrinkled plate can quickly absorb the heat of the burning material, so that the flame or spark extinguished, thus preventing the tank from catching fire.

12.4 Spray cooling device: Spray cooling device is an energy-saving facility installed to reduce the temperature of oil in the tank and reduce the size of the tank breathing loss. 

Internal floating roof tank special accessories Compared with the general vaulted roof tank, the internal floating roof tank is equipped with various unique special accessories due to its different structure and according to its performance requirements. 

13.1 Ventilation hole: Inner floating roof tank because the inner floating disk covers the oil surface, the oil and gas space is basically eliminated, so evaporation loss is very little, so the top of the tank is not equipped with mechanical breathing valve and safety valve.

However, in practice, the floating roof ring gap or other accessories joint part, there is still inevitably oil and gas leakage,

 in order to prevent the accumulation of oil and gas to a dangerous level, in the tank top and tank wall are opened with ventilation holes. 

13.2 electrostatic export device: floating roof tank in the process of oil in and out of the operation, 

the floating disk has accumulated a large amount of electrostatic charge, due to the floating disk and the tank wall with more insulators for sealing materials, 

so the floating disk on the accumulation of electrostatic charge is not possible through the tank wall to guide away.

In order to guide away this part of the electrostatic charge, between the floating disk and the top of the tank installed electrostatic export line. 

Generally for 2 soft copper bare stranded wire, the upper end and light hole connected, the lower end pressed in the floating plate cover pressure bar. 

13.3 anti-rotation steel rope: In order to prevent the deformation of the tank wall, the floating disk rotation affects the smooth lifting, 

the internal floating roof tank between the top and bottom of the tank vertically tensioned two stainless steel cables, 

two steel ropes in the floating roof diameter at both ends of the symmetrical arrangement.

Floating top in the steel rope restrictions, only vertical lift, thus preventing the floating disk rotation. 

13.4 Automatic ventilation valve: 

The automatic ventilation valve is located in the middle of the floating disk, 

it is to protect the floating disk in the support position, the tank in and out of the oil can breathe normally.

To prevent the following part of the float from evacuating or holding pressure. 

13.5 floating plate pillar: floating roof tank after a period of time, the floating roof needs to be serviced,

 the tank needs to be cleaned, then the floating roof needs to be lowered to a certain height from the bottom of the tank, 

supported by a number of pillars on the floating plate. 

13.6 diffusion tube: diffusion tube in the tank and the inlet pipe, 

the diameter of the pipe for the inlet pipe twice, and on both sides evenly drilled with numerous small holes of 2mm diameter. 

It plays the role of reducing the flow rate and protecting the pillar of the floating plate when the tank receives oil.

Ten, crude oil storage and loading process emissions

 Mainly includes: storage tank big and small breathing loss, oil running and leaking and loading loss.

 1. Large breathing loss of storage tank Large breathing refers to the breathing of oil when the tank is fed with oil. 

When the oil tank is fed into the oil, due to the gradual rise of the oil surface, the gas space gradually decreases, 

the pressure inside the tank increases, and when the pressure exceeds the control pressure of the breathing valve

A certain concentration of oil vapor begins to exhale from the breathing valve until the tank stops collecting oil, 

and the exhaled oil vapor causes the loss of oil evaporation. When the oil tank sends oil to the outside, because the oil level keeps decreasing,

 the gas space gradually decreases, the pressure inside the tank decreases, when the pressure is less than the vacuum controlled by the breathing valve, 

the tank starts to inhale fresh air, and because the oil vapor does not reach saturation in the space above the oil surface

The oil evaporation is accelerated to make it reach saturation again, and the pressure inside the tank rises again, 

causing part of the oil vapor to be exhaled from the breathing valve. The main factors affecting the large breathing are. 

1.1 The nature of oil products. The smaller the oil density, the more light fractions, the greater the loss;

1.2 The speed of sending and receiving oil. The faster the speed of incoming and outgoing oil, the greater the loss. 

1.3 Oil tank pressure resistance level. The better the pressure resistance of the oil tank, the smaller the breathing loss. 

When the oil tank pressure resistance reaches 5kPa, 

then the reduction rate is 25.1%, if the pressure resistance is increased to 26kPa, 

Then the small breathing loss can be basically eliminated, and to a certain extent reduce the large breathing loss. 

1.4 Related to the geographical location of the tank, atmospheric temperature, wind direction, wind and management level.

 Measures taken: 

The oil stored in this project is crude oil, which is less volatile than gasoline and diesel, and the pipelines of each storage tank are interconnected.

 2. Small breathing loss of storage tanks In the absence of oil receiving and dispensing operations, the temperature of the gas space inside the tank, 

the evaporation rate of oil products, the concentration of oil and gas and the vapor pressure also change as the external temperature and pressure rise and fall in a day.

This discharge of oil vapor and inhalation of air caused by the process of oil and gas loss, called small breathing loss. 

The main factors affecting the small breathing loss are as follows.

2.1 Diurnal temperature change. The greater the temperature difference between day and night, the greater the small respiratory loss. 

2.2 The tank is located in the area of sunlight intensity. The greater the intensity of insolation, the greater the small respiratory loss.

2.3 The larger the tank, the larger the cross-sectional area, the greater the small respiratory loss. 

2.4 Atmospheric pressure. The lower the atmospheric pressure, the greater the small breathing loss. 

2.5 The extent to which the tank is filled. The tank is full, the gas space volume is small, the small breathing loss is small. 

Measures taken: 

The oil stored in this project is crude oil, and the pipelines of each storage tank are interconnected, 

while the internal floating roof tank is used, and cooling water will be sprayed regularly in summer to prevent small breathing, 

so the amount of small breathing loss of crude oil is small. 

2.6 The loss is caused by the storage tank accessories not being tight. Measures taken: strengthen the maintenance of tank accessories, 

keep the tightness of the tank, and improve the operation management of the tank as the cheapest and very effective measures to reduce losses and prevent pollution.

For fire stopper, liquid seal oil, mechanical breathing valve flap, fire foam glass chamber, oil measuring hole, 

check thoroughly twice a year to make the gas tightness meet the requirements.

Make the oil tank as full as possible to the allowed degree, the lower the degree of filling, the greater the loss.

 2.7 Crude oil loading loss Crude oil loading loss mainly refers to the loss arising from the process of loading crude oil to the car tanker. 

50% of the crude oil is transported by pipeline out to the ship and 50% is transported by car.

The loading is balance loading with gas return system, so the loss is very small. The loading is submerged loading. 

Measures taken: Crane tube loading and submerged loading are used.