BR-102020023974-B1 - Mooring line coating for reducing longitudinal drag.

Abstract

COATING OF MOORING LINES FOR REDUCING LONGITUDINAL DRAG. The present invention aims to propose a coating for mooring lines in order to alter the external surface of the lines, without compromising their structure, so that they have less hydrodynamic drag and thus allow torpedoes to have greater speed in this operation.

Inventors

• Daniel Fonseca de Carvalho e Silva

Assignees

• Petróleo Brasileiro S.A. - Petrobras

Dates

Publication Date

20260317

Application Date

20201124

Claims (4)

1. 1- COATING OF MOORING LINES FOR REDUCING LONGITUDINAL DRAG, characterized by comprising a polymeric or adhesive material coating applied over an anchoring line, in order to fill all the empty spaces between the links (1B).
2. 2- COATING, according to claim 1, characterized in that the coating imparts a hydrodynamic drag coefficient to the mooring lines, during the launching of a torpedo pile, of less than 50%.
3. 3- COATING, according to claim 1 or 2, characterized by being used in torpedo pile driving.
4. 4- COATING, according to any one of claims 1 to 3, characterized in that it is applied before or on board an installation vessel.

Description

Field of invention [0001] The present invention is based on the development of a solution for torpedo pile launching operations. Description of the State of the Art [0002] The installation of stationary production units in deep water increasingly requires high-capacity fixed points (anchors). The load-bearing capacity of torpedo piles is a function of their driving depth in the ground. [0003] Torpedo piles are a type of anchor widely used for offshore units. The torpedo pile installation operation involves a free-fall phase of the torpedo assembly along with mooring lines (large chains for anchoring). Torpedo pile anchoring was developed by PETROBRAS in 1996 (PI 9603599-4). [0004] Although there is an optimal relationship between driving depth and bearing capacity, more resistant soils require more energy for driving. [0005] During the installation operation, it is desirable that the speed achieved be the maximum possible, and this speed is limited by the hydrodynamic drag of the assembly. Preliminary studies, validated with field data, indicate that the mooring lines contribute a large part of the assembly's drag, thus limiting the speed during this operation, which in turn determines the driving depth and, ultimately, the anchor's ability to withstand loads. [0006] Currently, anchoring operations are carried out with conventional (uncoated) mooring lines, limiting the speed of the assembly during the launching operation. [0007] Document CN109131748A discloses an anchor chain with an outer coating layer comprising a fiber reinforcement layer and a material layer. Despite having a coating, the coating is limited in its resistance to corrosion. [0008] Document WO1998049048A1 discloses a marine anchoring device for penetration into the seabed, comprising a low-friction coating surface that is adhered to the outer surface of the device. Despite having a coating capable of reducing friction, it does not have the capability or the possibility of torpedo pile launching operation. [0009] Document WO2018040274A1 discloses a compensation chain comprising an anchor chain and an outer polymeric coating layer covering the chain. Despite having a coating on the chain, the document does not have the capability or the possibility of torpedo pile launching operation. [0010] Given the difficulties present in the state of the art cited above, and in order to reduce the drag caused by the mooring line during the torpedo pile launching process, the need arises to develop a technology capable of performing more efficiently. The state of the art cited above does not possess the unique characteristics that will be presented in detail below. Objectives of the invention [0011] It is an objective of the present invention to develop a coating capable of increasing the terminal velocity of the torpedo by approximately 15%. [0012] Additionally, another objective of the present invention is to be able to provide a gain in driving energy (kinetic energy) greater than 30%. Brief description of the invention [0013] In order to achieve the objectives described above, the present invention aims to propose a coating for the mooring lines in order to alter the external surface of the mooring lines, without compromising their structure, so that they have less hydrodynamic drag and thus allow the torpedoes to have greater speed in this operation. Brief Description of the Drawings [0014] The present invention will be described in more detail below, with reference to the attached figures which, in a schematic and non-limiting way of the inventive scope, represent examples of its embodiment. In the drawings, we have: - Figure 1A illustrates the uncoated mooring line, Figure 1B the coated mooring line and Figure 1C the mooring line with a mallet. - Figure 2 illustrates a comparative graph between the terminal velocities in m/s between each type of mooring line after 150 m of fall: the FPSO (Floating Production Storage Offloading) line; 30.95 s (1), the T120 line with conventional 120 mooring line; 32.27 s (2); the T120 line with 120 mooring line with a mallet, 32.27 s (3); the T120 line with mooring line with plugs; 36.01 s (4); The T120 line with 120 coated mooring, 36.30 s (5); the T120 line with aramid cable (194 mm), 37.22 s (6) and the T120 line without mooring, 38.09 s (7). The number 120 indicates a torpedo pile with 120 tons. - Figure 3 shows a comparison between moorings. Each curve represents the repetition of the same test under the same conditions, only for the purpose of verifying repeatability and consistency. In this case, the symbol # denotes the test number 1, 2, 3, 4 and 5. - Figure 4 shows a graph of the speed (m/s) and the vertical displacement (m) for the 120 t pile with different coatings and without coating. Detailed description of the invention [0015] Below is a detailed description of a preferred embodiment of the present invention, which is exemplary and in no way limiting. Nevertheless, it will be clear to a person skilled