WO2017144068A1

WO2017144068A1 - Under water floating roof tank

Info

Publication number: WO2017144068A1
Application number: PCT/EG2016/000012
Authority: WO
Inventors: Mohamed Ashry Mohamed ABDELFATAH
Original assignee: Abdelfatah Mohamed Ashry Mohamed
Priority date: 2016-02-23
Filing date: 2016-03-30
Publication date: 2017-08-31

Abstract

The present invention relates to a storage tank for petroleum substances under the sea with a floating roof. Said tank uses the physical properties (density and flotation) of sea water and the material of the tank, in which its mechanism based on the difference in density of all used substances as well as it is automatically operated. Besides, its floating roof is under continuous pressure from below and balanced from sea side as well as the pressure is equivalent to the pressure amount of filling the tank from the upper side. Upon reaching the maximum capacity, the sealing system operates automatically and when closing the valves the pressure amount inside the tank is added to pressure amount under the roof. On the other hand, when the outlet valve is opened the amount of the output is equal to pressure amount in addition to sea pressure, which is considered an effective method without using a pump. Furthermore, the storage being completely immersed in water makes it always balanced in terms of pressure, in which water pressure from the outer part of the shell is almost equal to pressure inside the tank, simply because, the tank is never been empty. Therefore, When filling the tank to the maximum capacity, the roof will be under direct pressure of sea water until the stored substance is being discharged. Moreover, the amount of the discharged substance is always replaced with sea water, which in turn leads to balanced pressure amount inside and outside the tank and the roof is being floated because of the stored substance from the upper side and sea water from the lower side.

Description

UNDER WATER FLOATING ROOF TANK

Technical Field

For oil storage in Oil and Gas (offshore and onshore field ) island and refinery plants Prior art:

The present invention relates to the storage tanks used widely in storing oils and petroleum substances in refineries and petroleum sites. The increasing production thereof may require providing substances and raw materials and storing them in various storage tanks which are designed above ground and underground. Regarding the internal design, they are designed in fixed roof storage tanks and floating roof storage tanks. Each of these kinds is used for the purpose it is designed for. The need for increased production requires increasing the number of storage tanks. Here, it is found that storing these tanks with enormous quantities of oils and raw materials may cause uncontrollable environmental disasters. The most important priority for oil firms is to ensure the increasing of industrial safety inside and outside the storage tanks, and to manufacture storage tanks in various metals and sizes according to what is determined by the designer and the type of the stored raw material in the storage tank. There are known standards in the international code which is dedicated to the establishment of tanks API 650, the the type of the tank which is suitable for the product, the inlet and outlet of stored substances, and the speed of their outlet as well, taking into consideration the weight, capacity, height and the type of the substances as well. Knowing that the storage tank API 650 which is designed in different measurements and capacities for the internal pressure is not exceeding 17.2 kPa (21/2 pounds per square inch) gauge). The storage tank API 650 further shows the minimum requirements for each metal, design, construction, installment, and tests for the vertical cylindrical tanks above ground whether they are opened or closed. It further shows the steel welding process or stainless steel welding process and steel structure as well. It shows also all standards that must be observed regarding the construction, design, suitable climate for storage tanks and all that surrounds it (all stated in API650 as a suitable reference).

Technical Problem and deficiencies in the prior art:

It is represented in that:

It is hard to control any potential fire or leakage in the tank; the high cost of stored substances/oils movement from pumps and pipes; the energy used in raising and movement of the stored substances and petroleum substances from and to the storage tanks. Therefore, it is found that the leakage of stored substances from the storage tanks for any reason may cause environmental disasters, as it may lead to fire outbreak which may cause serious economic and environmental damages. As a result, the problem will remain as it is, and therefore, the reconstruction will be heavily expensive. Knowing that it is uncertain whether the safety factors in tank farm area are sufficient or not, in spite of the wide usage of API 650 applications, which is spread globally, in establishing storage tanks of different types and capacities, in addition to the cost of oil terminal and oil storage, the construction of pump station, its maintenance and its high cost is added to the stored substances cost. It is worth mentioning that the stored substances terminal from one place to another depends always on suction pump through pump station. This process is very expensive and needs many stages of stored substances terminal from storage tank to the specific place of oil terminal.

One of the defects is represented in tank leakage. This leakage is collected in boundary wall which is designed for this purpose. This defect is extremely serious as the stored substance terminal to another storage tank, discharge of the defected storage tank and suction of the leaked stored substances which must be occurred have serious economic and environmental risks.

What is the new in the present invention?

The operation method differs completely from the current method in the inlet and outlet of the stored substances, detailed as follows: the operation compared to the use of pump station: in the underwater floating roof tank design, physical properties of sea water and metal of which the tank is made and further the stored substances type are used, as the operation is based on the difference in density of all used substances and it is considered also self-operation as illustrated in figure 3/16. The main idea of this design is that it is based on the difference in densities and that the floating roof is under continuous pressure from below and balanced, equal 2 bar, from sea side as illustrated in figure 10/16 From the upper side, the pressure is equivalent to the pressure amount of filling the tank, i.e.8 bar (from the scientice point of view, this is a virtual value as the tank may be filled with a pressure which is equivalent to this value and it is possible to be more or less). Upon reaching the maximum capacity, the sealing system operates automatically and when closing the valves the pressure amount inside the tank is added to pressure amount under the roof When the outlet valve is opened, the amount of the output is equal to 10 bar, which is considered an extremely effective method without using any pump. This self-operation is extremely very economical and effective as illustrated in figure 16\16

On the other hand, the storage tank being completely immersed in water malces it always balanced in terms of pressure, in which water pressure from the outer part of the shell is almost equal to pressure inside the tank, simply because, the tank is never been empty. Therefore, there are two cases; firstly, when filling the tank to the maximum capacity, the roof will be under direct pressure of sea water until the stored substance is being discharged. Moreover, the amount of the discharged substance is always replaced with sea water, which in turn leads to balanced pressure amount inside and outside the tank. As the tank has the same temperature of the sea water, there will be a balance in temperature. It is worth mentioning that when a fire outbreaks, it will be automatically controlled via fire system which surrounds the tank as foam will be pumped with sea water in large quantities sufficient to control the fire in a record time as illustrated in figure 1/16. Knowing that the technique used in extinguishing fires related to tanks is represented in reducing the temperature of the outside tank shell and in this design, under water floating roof tank, this property is continuously present. Therefore, the temperature will not increase by using the heat transfer. It is expected that the fire will be on the surface only, so it will be near the fire system and its nozzle, therefore, it will be sufficient to control the fire. In addition, when tank leakage occurs, the difference in density will be very important and effective, and this is the main idea of this design. In this case, the leaked oil is directed upwards according to bouncy low. Knowing that the density of the stored substances allows it to float, however, the suction nozzle will be in an appropriate distance from floatation area as illustrated in figure 14/16. Accordingly, it will be able to suck the stored substances by pumps and the leaked spot will be in a specified area between the outer diameter of the tank and the boundary wall. On the other hand, air system, which is mounted over the floating roof, will be responsible for cleaning the shell from inside and the roof as well.

In this design, the tank is divided into two parts: upper part for the stored substances and lower part for sea water and a separator in between which is the floating roof. When the stored substances discharged/sucked from the tank, it is replaced by sea water as the roof reached the top part of the tank. Via drain system, water will be sucked from below the roof and pushed outside the tank after closing the manhole in the maintenance or inspection.

Under water floating roof tank system, it is found that the safety factors may reach 100%, and the environmental safety factors may reach 100%. In addition, the tank operation costs, which may reach very large amount in the prior art; may be zero and it doesn't need pump station to raise the stored substances, with constant pressure values of a new energy (which did not exploited in this way before).

The main idea is represented in using economical and infinite alternative energy, reaching safety factors which are higher than those of the prior art and preserving the environment substantially compared to the prior art. In addition, it is very appropriate for offshore and onshore plants. With under water floating roof tank system, the ground area used can be increased. This design is very important for islands that have crude oil. Moreover, no fire/ignition in the storage tank may be expected.

The main idea the design based on is represented in the use of physical properties and density of both stored substances and the metal of which the tank is made. The design also aims at reducing the sludge, which may reach approximately zero. It is also aims at stored substances terminal/oil terminal with natural energy, the ideal use in the refinery and off shore plant, and reducing the cost of the used energy to zero. Knowing that under water floating roof tank depends on generating continuous energy and pressure with constant value which leads to reducing the terminal cost, for example, the cost of pump station, exploiting all pressure values to the maximum, and also controlling temperature to reach almost the degree of persistence. In addition, the defects in current tanks, such as, tank leakage, may cause a lot of risks, for example, fires and environmental risks, which in turn may lead to a serious damage economically. While the clean energy in under water floating tank design may be exploited to the maximum.

Under water floating roof tank consists of fixed parts, such as, bottom fixed roof, floating roof, shell. First, fixed roof consists of steel structure with a welded plate supported thereupon at the top point of the tank upon which inlet and outlet nozzles are mounted and manhole as well. This roof is fixed to the shell by welding with curb angle. The curb angle is fixed to the shell and the roof. Second, the shell, which represents the main part, has cylindrical shape. Its top part is fixed to the roof and its lower part, which represents the bottom, is fixed to the anchor bolt. There is a water manhole with cover in the shell wall which allows sea water inlet and outlet, thus achieving the purpose of the main idea of the design that the tank manhole continues to be opened during the operation period, and that the shell is to be combined via welding the horizontal and vertical joints to complete the cylindrical shape.

Third, the floating roof contains pontoon; lower pontoon and upper pontoon, and air system. This roof consists of upper surface and horizontal surface. The upper surface is in the stored substances or oil direction and it carries oil and stored substances. It has a pontoon and sealing therein which is directly connected to the shell wall in order to prevent oil mixing or leakage below towards the sea water. The lower one is connected to the sea water below. It consists of a pontoon and sealing to achieve the highest benefit of the pressure affecting the roof surface from bottom to top and the distance between the upper and lower surfaces to benefit from the bouncy force. Fourth, the floor has fixed supports under the floating roof to determine the stored substances level in the tank and further drain system to suck water below the roof and discharge it completely in the tank. This in turn occurs after closing the sea water manholes, and the tank must be fixed from the bottom with anchor bolts and it must be opened from inside.

The tank is surrounded by boundry wall to contain any leakage and to settle the pressure which is responsible for stored substance terminal, fire pipe is mounted on the tank wall which is responsible for fire fighting operation. The fire fighting line may be operated upon the outbreak of a fire with foam. Furthermore, the suction system is consisted of many nozzles; Suction nozzles, which are divided in order to cover the greatest depth expected for the stored substances in leakage case. They are immersed suitably under water surface from above in order to suck the stored substances in leakage case from the tank. Due to density difference, the oil spot floats into the top to reach the suction nozzle in order to suck it inside the plant until the tank is discharged and the leakage is handled. The suction system may control any leakage rapidly and return the oil into environmentally friendly safe area through pipe network. While the air system is responsible for cleaning the internal wall of the shell using air pressure which makes the roof surface and the tank wall as well without any impurities and which reduces the sludge ratio and the self-operation of the tank with the pressure effect of the sea water upwards all the time and with the effective floatation force and bouncy force. While the surface is moving upwards loaded by stored substances or oil which is above the upper part of the floating roof, it is pushed into the outlet nozzle to exit to the site to be sent through pipes for this purpose. The main reason for moving the roof and allowing the terminal of the huge amount of stored substances is the density difference as the sea water density (seawater 1025 kg.m3 p) is approximately greater than the oil density (p oil970 kg.m3 ) and the density (p Alum 2700 kg.m3) as well. This difference allows floating and it allows the bouncy force to be effective upwards all the time with continous pressure without any change thus leading to the terminal of the floating roof loaded by the stored substances in a force increases when the stored substances reduce above the floating roof. As well as, the contact of the floating roof (lower side -sea water side) may lead to uniformly continous pressure.

The storage tank may be implemented using API650 standards. For the welding operations, the parts may be collected and fixed according to ASME IX, The used metal and paint must be according to the global code and the choice of the site must be suitable for achieving the purpose of the design.

The way of exploitation:

In gas and oil companies, under water floating roof tank may be used in storing petroleum substances whose density is below sea water density (p seawater 1025 kg.m3). The aim of this design is to store the petroleum and stored substances in islands of limited size which is difficult to increase its land (area). The design of under water floating roof tank is easy to be implemented in on shore and off shore plant. Under water floating roof tank may be applied in marine places and on beaches near to or far from the production sites as well as there is no detrimental effect to the marine environment. As well as, it is suitable for refinery and oil terminal companies.

The main idea is represented in using alternative economical and infinite energy, achieving higher safety factors than that of the currently used method, and substantially preserving the environment compared to the current method. In addition, it is suitable for off shore and on shore plants sites. By using under water floating roof tank system, the used land area may be increased. This design is very important for islands containing petroleum substances therein. In addition, no fire or ignition may be expected in this storage tank

66- 120 - lower level of floating roof movement TllHStratinn r»f figures:

67- 121 - pontoon Figure 1/16

68- 122 - tank manholes 1- inlet and outlet nozzles connected with valves

69- 123 - roof support 2- Fixed roof tank over

70- 12 - drain pipe 3- Manhole.

71 - 125 - sea water level 4- fire nozzle / sprinkler

72- 126 - main manholes 5- main header for fire line (fire system)

73- 128 - input/output nozzles 6- main header for suction system (suction system)

74- 129 - fixed roof 7- boundary wall surrounding the storage tank Figureii/16illustrating 8- manholes to enter sea water

75- 44 pontoon 9- floating roof

76- 45 - Fixable steel on sealing system 10- fixed supports

77- 46 - pontoon 1 1- Air system

78- 47 - Fixable steel on pontoon part. 12- Storage tank floor

79- 48 - connect area Figure 2/16

80- 49 - upper pontoon 13- Suction system

81 - 50 - floating roof shell 14- Fire complete cycle

82- 51 - floating roof cover plate (upper side) 15- Suction header

83 - 52 - lower cover plate of floating roof 16- manholes to enter sea water

84- 53 - fixed lower seal 17- Boundary wall

85- 54 - lower pontoon 18- Tank piston

Fipure 7/16illustratinfi the fire line and suction system Figure 3/16 Main part inside tank

86- 55 - Manhole for passing the pipe through the tank wall, 19- Fixed roof

87- 56 - pipe direction around the storage tank 20- Main inlet nozzle

88- 57 - pipe support 21- Inlet and outlet nozzles

89- 58 - fire line 22- Elements 22 & 29 sea water inlet nozzle

90- 59 - the main line 23- Floating roof

91- 60 - fire nozzle 24- Air system

92- 61 - fixed roof 25- Upper pontoon

93- 62 - tank nozzle 26- Lower pontoon

Fipure 8/16 view of the tank 63 fire line and suction system 27- Lower side of the floating roof

Figure 9/16 illustrating drain system 28- Fixed support

94- 70/ water output. Figure 4/16floating roof details

95- 71 valve 29- Release valve for pressure balance

96- 75 -Water suction line below the tank which branched 30- Roof shell

two lines 73 and 74 and the branch 72 31- Floating roof

97- 76 - tank shell 32- Air system main header

98- 77 - water sump. 33- Upper top of the roof

99- 78 - manhole cover 34- Air input nozzle

100- 79 - drain pipe 35- Upper pontoon

Figure 10/16 a diagram for the tank terminal upwards: 36- 37 Nozzle /air sprinkler

101- 85 - fire nozzle 37- 38 holes and their directions 360 degree.

1 02- 86 - fire nozzle Figure 5/16overalI shape of the roof and the air system

1 03- 87 - boundary wall 38- Air system main header

104- 88 - sea water 39- Floating roof shell

105- 89 - suction pipe 40- Lower cover plate of floating roof

106- 90 - suction nozzle 41- Lower pontoon

Figure 11/16 42- Floating roof cover plate (upper side)

107- 107/109 - manholes 43- Air nozzle

Figure 12/16 - a diagram of the drain system complete cycle 44- Pontoon

108- 92 - drain pipe 45- 91— sea water surrounded the tank shell

Figure 13/1 - a diagram for tank location 46- 105 - pipe support

109- 116 - fire system 47- 106 /108- boundary wall

110- 117 - suction nozzle 48- 1 19 - floating roof 118 - roof pontoon Figure 1,4/16 -control the leakage using the stored oil density

49- 130 - leak area outside the tank

50- 131 - sea level

51- 132 -suck the leaked oil through suction system nozzle

52- 133 - sea water

Figure 15/16- a diagram of the tank main parts

53- 134 - stored substances/oil inlet and outlet nozzles

54- 135 - main manhole for maintenance and inspectioi

55- 136 - fixed tank roof

56- 137 - tank shell

57- 138 - fixed supports to determine the start of the operation

58- 139 - tank bottom

59- 140 - sea water inlet nozzle

60- 141 - floating roof

61- 142 - by pass for releasing oil from the roof

62- 1 13 - tank shell

63- 114 - anchor bolt

64- 115 - curb angle

Figure 1 \1 illustrates the effect of the pressure fron the direction of open sea with 2bar as affixed pressur while inside the pressure equal 8 bar on oil side, as th pressure of 2 bar from the bottom of

65- system which makes the value of 8 bar as a fixed value the tank while the inlet and outlet valves are closed using sealing

Claims

1. Under water floating roof tank, wherein it is characterized by the use of the sea water, the density difference and floatation law as an alternative energy instead of pumps for pushing and sucking the stored substances from and to the service.

2. Under water floating roof tank according to claim 1, wherein the storage tank is completely under water surface or at the shell height level and wherein the boundary wall is surrounded by the tank, a fire system and foam are loaded by it.

3. Under water floating roof tanlc according to claim 1 and 2, wherein the tanlc is situated under the sea surface and there is a limited number of manholes in order to allow the inlet of water under the floating roof surface and the effect of the sea water pressure.

4. Under water floating roof tank according to claim 2 and 3, wherein the idea of the floating roof design, the upper and lower pontoon is to have a free movement which in turn is due to the pressures on it from both sea water side and oil/stored substances side.

5. Under water floating roof tank according to claim 1, 2 and 4, wherein the storage tanlc is filled with the stored substances and has a higher pressure on the upper surface of the floating roof. This pressure is higher than the sea water pressure until the higher pressure coming from the stored substances or which the tank is filled with moves the roof downwards till it reaches the fixed support, and then the effect of the sea water pressure is continuous and uniform on the roof surface.

6. Floating roof according to claim 5, wherein it reaches the fixed support, the sealing system as illustrated in figure 6/16 starts to prevent the leakage from the tank from both sea water side and oil side together.

7. The sealing system according to claim 6, wherein how does it work, where it is installed, its shape, the installation position in the shell, the contact between pontoon and sealing system are provided.

8. The pontoon and sealing system according to claim 5, wherein a fixable material is installed and the flexible movement leads to the closure of the spaces which may cause leakage between the shell and pontoon and between pontoon and the sealing system as well. It is covered with rubber material.

9. The sealing system according to claim 8, wherein the mechanical movement for this system is provided.

10. Maintaining the pressure value according to claim 5, wherein it is coming from the tank filling stage, when the roof reaches the maximum value, the gap is closed by the sealing system, so the valves are closed as well, thus maintaining the pressure value and the sea water pressure.

11. The boundary wall around the storage tank according to claim 1 and 2, wherein it maintains the pressure values and it preserves the environment, thus preventing any leakage to pass outside the wall, and there are manholes as well.

12. Fire system with foam according to claim 2 and 11, wherein it is as illustrated in figure 1/16 and 2\16 (element 64), figure 13/16 (element 116) and its position is above the boundary wall.

13. Suction system according to claim 11, wherein it is as illustrated in figure 13/16 (element 1 17) and the distribution of suction nozzles around the storage tank thus leading to a complete coverage for the expected volume of leakage and the stored substances volume leaked into water surface.

14. Floating roof according to claim 1 1, wherein there is an air system with the mechanism of its movement installed above the floating roof and connected to air compressor which in turn pushes air batches at close distances.

15. Drain system according to claim 1, wherein it is an integral part of underwater floating system.

16. All systems according to the preceding claims 1 to 15, wherein they are used to operate the storage tank, such as, sealing system, air system, suction system, fire system, drain system, the design of the floating roof mechanism and moving effect, and a method for manufacturing and creating pressure suitable for generating the energy required for moving the roof and designing upper and lower pontoon as well.

17. All elements of the design according to the preceding claims 1 to 16, as they are illustrated in figure 1/16 to 16\16.