Search

BR-112022001933-B1 - UNDERWATER STORAGE TANK

BR112022001933B1BR 112022001933 B1BR112022001933 B1BR 112022001933B1BR-112022001933-B1

Abstract

Underwater storage tank for a working liquid, system for assessing the physical integrity of an underwater tank, and method for detecting a loss of physical integrity of an underwater storage tank. The present invention relates to an underwater storage tank (1) for a working fluid (2) comprising a flexible multilayer tank (3) containing said working fluid (2), said flexible multilayer tank (3) comprising at least one inner electrical insulation layer (4) in contact with said working fluid (2), at least one outer electrical insulation layer (6) in contact with said seawater, at least one intermediate electrically conductive layer (5) sealed between said at least one inner electrical insulation layer (4) and said at least one outer electrically conductive layer (6), and wherein said underwater storage tank (1) comprises at least one first electrical connection means (8) connected to said intermediate conductive layer (5), said first electrical connection means (8) being electrically connectable to an electrically grounded measuring instrument (10) for assessing the physical integrity of said flexible multilayer tank (3).

Inventors

  • Sandro MATTERAZZO
  • Yvan ALBANI

Assignees

  • SAIPEM S.P.A

Dates

Publication Date
20260310
Application Date
20200803
Priority Date
20190807

Claims (12)

  1. 1. Underwater storage tank (1) for a working fluid (2) comprising a flexible multilayer tank (3) containing said working fluid (2), said flexible multilayer tank (3) being externally in contact with seawater, characterized in that said flexible multilayer tank (3) comprises at least one inner electrical insulation layer (4) in contact with said working fluid (2), at least one outer electrical insulation layer (6) in contact with seawater, at least one intermediate electrically conductive layer (5) sealed between said at least one inner electrical insulation layer (4) and said at least one outer electrically conductive layer (6), at least one first electrical connection means (8) connected to said intermediate conductive layer (5), said first electrical connection means (8) being connectable to an electrically grounded measuring instrument (10) for assessing the physical integrity of said flexible multilayer tank (3).
  2. 2. Underwater storage tank (1), according to claim 1, characterized in that said intermediate electrical conductive layer (5) comprises a plurality of sectors (12) electrically isolated from each other, and wherein each sector (12) of said plurality of sectors (12) is connected to a respective first electrical connection means (8), each respective first electrical connection means (8) being connectable to an electrically grounded measuring instrument (10) for assessing the physical integrity of said flexible multilayer tank (3) in the sector (12) corresponding to which said respective first connection means (8) is connected.
  3. 3. Underwater storage tank (1) according to claim 1 or 2, characterized in that said working liquid (2) is a conductive liquid, and wherein said underwater storage tank (1) comprises at least one electrode (14) in contact with said working liquid (2), and at least one second electrical connection means (9) connected to said electrode (14), said second electrical connection means (9) being connectable to a measuring instrument (10) electrically connected to said intermediate conductive layer (5) for assessing the physical integrity of said flexible tank (3).
  4. 4. Underwater storage tank (1), according to any one of claims 1 to 3, characterized in that it comprises a rigid containment structure (7), in which said flexible multilayer tank (3) is contained, said rigid structure (7) comprising at least one bathymetric compensation opening (20) for the passage of seawater capable of compensating for the variation in internal pressure of said flexible multilayer tank (3) due to a withdrawal of the working fluid (3).
  5. 5. Underwater storage tank (1), according to any one of claims 1 to 4, characterized in that it comprises at least one grounding system (21) and at least one third electrical connection means (11) electrically connected to said grounding system (21), said third electrical connection means (11) being connectable to an electrical measuring instrument (10) electrically connected to said intermediate conductive layer (5) by means of said first electrical connection means (8) for assessing the physical integrity of said flexible tank (3).
  6. 6. Underwater storage tank (1), according to any one of claims 1 to 5, characterized in that said inner electrical insulation layer (4) is made of a first material that is chemically compatible with said working liquid (2).
  7. 7. Underwater storage tank (1), according to any one of claims 1 to 6, characterized in that said outer electrical insulation layer (6) is made of a second material that is chemically compatible with said seawater.
  8. 8. Underwater storage tank (1), according to any one of claims 1 to 7, characterized in that said intermediate electrically conductive layer (5) is an electrically conductive wire mesh or a fabric comprising carbon fiber or a carbon fiber wire mesh or a flexible metallic sheet.
  9. 9. System for assessing the physical integrity of an underwater tank, comprising an underwater storage tank (1) defined in any one of claims 1 to 8, characterized in that the system for assessing the physical integrity of an underwater tank further comprises at least one electrical measuring instrument (10) for assessing the physical integrity of said flexible multilayer tank (3), said electrical measuring instrument (10) being connectable and/or electrically connected at least to said intermediate electrical conductive layer (5) of said flexible multilayer tank (3) and to one between an electrical grounding system (21) and said working fluid (2).
  10. 10. Method for detecting a loss of physical integrity of an underwater storage tank (1) for a working fluid (2) defined in any of claims 1 to 8, by means of the detection system defined in claim 9, characterized in that said underwater storage tank (1) comprises a flexible multilayer tank (3) containing said working fluid (2), said flexible multilayer tank (3) being externally in contact with seawater, said flexible multilayer tank (3) comprising at least one inner electrical insulation layer (4) in contact with said working fluid (2), at least one outer electrical insulation layer (6) in contact with seawater, at least one intermediate electrically conductive layer (7) sealed between said at least one inner electrically insulating layer (4) and said at least one outer electrically insulating layer (6), at least one first electrical connection means (8) connected to said intermediate conductive layer (5), said first electrical connection means (8) being electrically connectable and/or connected to said at least one electrically grounded measuring instrument (10) to assess the physical integrity of said flexible tank (3), said method comprising the following steps: - storing at least one insulation resistance threshold value (Rse) of said outer electrical insulation layer (6) corresponding to a loss of integrity of said flexible multilayer tank (3), - detecting a current insulation resistance value (Re) of said outer electrical insulation layer (6), - comparing said current insulation resistance value (Re) with said insulation resistance threshold value (Rse), - sending an alert signal (Se) for an external loss of integrity of said underwater tank (1) if said detected current insulation resistance value (R) is less than said insulation resistance threshold value (Rse).
  11. 11. Method for detecting a loss of physical integrity of an underwater storage tank (1) for a working fluid (2) defined in any of claims 1 to 8, by means of the detection system defined in claim 9, characterized in that said underwater storage tank (1) comprises a flexible multilayer tank (3) containing said working fluid (2), said flexible multilayer tank (3) being externally in contact with seawater, said flexible multilayer tank (3) comprising at least one inner electrical insulation layer (4) in contact with said working fluid (2), at least one outer electrical insulation layer (6) in contact with seawater, at least one intermediate electrically conductive layer (7) sealed between said at least one inner electrical insulation layer (4) and said at least one outer electrically insulating layer (6), wherein said intermediate electrically conductive layer (5) comprises a plurality of sectors (12) electrically insulated from each other and wherein each sector (12) of said plurality of sectors (12) is connected to a respective first electrical connection means (8), each respective first electrical connection means (8) being connectable to said at least one electrically grounded measuring instrument (10) to assess the physical integrity of said flexible tank (3) in the sector (12) corresponding to which said first connection means (8) is connected, said method comprising the following steps: - storing at least one insulation resistance threshold value (Rse) of said outer electrical insulation layer (6) corresponding to a loss of integrity of said flexible multilayer tank (3), - detecting a current sector insulation resistance value (Rsci) of said outer electrical insulation layer (6) in each sector (12) of said plurality of sectors (12), - comparing each detected current sector insulation resistance value (Rsci) with said insulation resistance threshold value (Rse) of said outer electrical insulation layer (6), - sending an alert signal (Sel) for a loss of outer integrity located in said underwater tank (1) for each detected current sector insulation resistance value (Rsci) that is lower than said insulation resistance threshold value (Rs).
  12. 12. Method according to claim 10 or 11, characterized in that said working liquid (2) is a conductive liquid, and wherein said underwater tank (1) comprises at least one electrode (14) in contact with said working liquid (2), and at least one second electrical connection means (9) connected to said electrode (14), said second electrical connection means (9) being electrically connectable to said at least one measuring instrument (10) electrically connected to said intermediate conductive layer (5) for evaluating the physical integrity of said flexible tank (3), said method comprising the following steps: - storing at least one insulation resistance threshold value (Rsi) of said inner electrical insulation layer (4) corresponding to a loss of integrity of said flexible multilayer tank (3), - detecting a current insulation resistance value (Ri) of said inner electrical insulation layer (4), - comparing said current insulation resistance value (Ri) with said insulation resistance threshold value (Rsi),- send an alert signal (Si) for an internal loss of integrity of said underwater tank (1) if said current insulation resistance value (Ri) detected is lower than said insulation resistance threshold value (Rsi).

Description

DESCRIPTION Technical field of the invention [001] The present invention is applicable in the oil and gas field, for underwater storage of chemicals. Technical background [002] Chemical storage tanks are used in the underwater field, the tanks being made of flexible elements so that as the stored chemicals are removed, the tank is deformed, maintaining substantially zero the pressure difference between the inner wall and the outer wall of the flexible tank. [003] A very popular type of underwater storage tank is a flexible bag-type tank positioned in a protective and containment metal frame. [004] In certain cases, the protection and containment structure is a metallic reticular structure that allows seawater to always be in contact with the flexible tank, keeping it under a condition of hydrostatic pressure. [005] In other cases, the protection and containment structure is made in the form of a rigid tank, in which the flexible tank is contained and which has at least one seawater inlet to compensate for the decrease in the volume of the flexible tank due to the removal of chemical product. [006] In addition to compensating for bathymetric pressure in the flexible tank, the protective and containment structure also acts as a physical barrier against potential damage to the flexible tank due to impacts, for example, during placement and/or removal operations and/or from interactions with aquatic animals. [007] However, the flexible tank is exposed to additional risks of degradation and/or breakage that may result in leaks of the chemical contents, with subsequent economic and environmental damage due to the dispersion of the chemical in the marine environment. [008] A need that is felt in the field, therefore, is to promptly detect structural damage in flexible tanks that could cause potential chemical leaks in order to intervene promptly to limit economic and environmental damage. [009] US patent 9,656,801, for example, describes the use of a detection sensor that detects the presence or absence of chemical leaks by analyzing the water over a flexible tank containing a chemical. However, these sensors are not universally applicable to any chemical because they are highly dependent on the nature of the chemical composition of the chemical contained. Therefore, pH measuring sensors with selected specific measuring electrodes are used to measure leaks of basic or acidic chemicals, while infrared measuring sensors are used to measure leaks of aromatic chemicals, which are very expensive and often not adapted to make measurements at great depths due to technological limitations. [010] Furthermore, besides being impractical, expensive and often unavailable, such sensors detect a chemical leak once the tank ruptures and are therefore unsuitable for use in the context of damage prevention. [011] Therefore, there is a need to make underwater tanks that have less environmental impact and greater safety. [012] The state-of-the-art document WO 2016/116625 describes a system for the subsea storage of crude oil, which, however, cannot be applied to fluids with a density greater than water because the flexible container would sink to the bottom and could not be emptied. [013] The state-of-the-art document DE 10302308 B3 describes a system dedicated exclusively to storing an electrically conductive liquid and detecting fluid leaks, but not also to identifying possible contamination of the stored fluid, for example, by seawater; furthermore, due to the way the system is structured, detection is only permitted if the leak is in the welds of the lining positioned on the rigid container. The outer rigid container appears to be essential for its operation. High-pressure subsea application is not possible. [014] The state-of-the-art document DE 9311620 U1 describes a coating based on thermoplastic or rubber materials for covering containers, boilers, wastewater treatment plants, storage tanks, columns and pipes. [015] The state-of-the-art document US 2007/220956 describes equipment for identifying leaks of an electrically conductive fluid from a disposable plastic bag. Summary of the invention [016] The inventors of the present Patent Application have discovered that the integrity of an underwater chemical storage tank can be monitored in order to intervene before the occurrence of possible leaks by means of a flexible multilayer tank, in which the flexible tank comprises an intermediate electrically conductive layer sealed between two electrically insulating layers and a first electrical connection means connected to the intermediate conductive layer that can be connected to a grounded electrical measuring instrument to assess the physical integrity of the flexible multilayer tank. Object of the invention [017] Therefore, a first object of the invention is an underwater storage tank for a working liquid according to claim 1. [018] A second object of the invention relates to a system for assessing the physical integrity of an u