Research overview on marine hoses for (un)Loading operations using floating offshore structures

Introduction

There have been noticeable important developments in the offshore-marine industry in recent years [1-4]. Flexible hoses, flexible risers, and marine composites are examples of these advancements [5-10]. Marine composite hoses and marine composite risers have seen additional advancements using composites [11-14]. More advances are being developed as a result of failures in the use of risers in the maritime industry. A marine hose is a special sort of flexible riser that is utilised in fluid transfer [16-15-18]. A marine hose, by definition, is a fluid transfer conduit used to transfer, discharge, load, and carry fluids from an oil well to the platform of a floating platform or floating structure. An FPSO (Floating Production Storage and Offloading) vessel, a CALM (Catenary Anchor Leg Mooring) buoy, a SPAR (Single Point Anchor Reservoir), a floating Semisubmersible, or a TLP (Tension Leg Platform) are examples of Floating Offshore Structures (FOS). However, due to the weight of the kill lines, marine hoses in chutes, reeling hoses on reel drums, marine risers, and other deck components, lighter and more sustainable materials/technologies are required to lower deck weights. Lighter conduits, such as composite risers and cum bonded marine hoses, are needed to minimise deck loads on CALM buoys, FPSOs, and other offshore sites. It’s easy to store because it’s light. As a result, it aids in the creation of space on chutes, gangways, and storage racks. It also decreases the dead load on the platform.

This research outreach intends to showcase sustainable fluid transfer technologies while addressing the topic of bonded marine hoses from a variety of perspectives, including application, configuration, test models, and operational perspectives. The design aspect is another area that this research covered as seen in the numerical model in Figure 1. As a result, based on sustainability, safety, and product delivery, an overview of marine bonded hoses for loading and discharging activities is offered. The Single Point Mooring (SPM) systems, for example, are one of the most important design configurations for fluid transfer employing bonded maritime hoses. A description of their use and various design configurations, such as CALM buoys, was given. For diverse uses, discussions were held to establish the arrangements, design forms, benefits, and obstacles. Typical applications of different offshore components, structures and conduits including marine hoses are seen on diverse offshore platforms, as seen in Figure 2.

As demonstrated in Figures 3, the fluid transfer system is at the heart of every SPM.

Figure 3. CALM buoy hose system showing the installation of the floating hose from the buoy’s manifold to the shuttle tanker on an SPM Terminal. The overboard piping is properly protected by fender below and above the flanges (Courtesy: Bluewater)

Marine hose categories

Regardless of variances between individual segments of the hose string, all hoses can be categorised into five types based on key characteristics. It’s important to remember that within each product line, there is the existence of variations like those indicated earlier. Based on categorisation, these are the primary specifications specified by the Oil Companies International Marine Forum (OCIMF 2009), which apply to all conventional hose types. This section presents some of the product line differences. The floating hose string, the catenary hose string, the submarine hose string (100m), and the deep-water submarine hose string (300m) are the five types of loading and unloading hoses. The typical features and moorings for the floating buoy system in which each product line can appear are mentioned for each product line of bonded marine hose. The application of offshore hoses in the industry have been identified in Offshore West Africa, Gulf of Mexico (GoM), Bohai Sea, South China Sea and other seas. Some marine hoses are specified for 15bar, 19bar and 21 bars, depending on the design, with standard hose lengths of 9.1m, 10.7m, and 12.2m. Basic specifications for the typical marine hose for application on FPSOs or CALM buoy systems are presented as follows:

• Diameter: 150mm<D<600mm
• Resistance to: Petroleum products with a 25% aromatic content
• Axial strength: 37 tons for D=600mm
• Pressure ratings: 15 bar, 19bar and 21 bar (depends on design)
• vFlow at D<400mm: 21 m/s
• vFlow at D>400mm: 15 m/s
• Fluid temperature range: 82°C >T> -20°C
• Ambient temperature range: 52°C >T> -29°C
• Permanent elongations: < 0.7% (relates to materials)
• Temporary elongations: < 2.5% (relates to materials)
• Operating pressure: -0.85 bar gauge to designated pressure rating

Numerical studies

Regardless of the marine component-if a riser or a hose, the design requirement of offshore hoses and other components of SURP is presented in this sub-section. The ranking of different hose configurations, the environmental aspects, installation requirements, and costs are considered in some hose studies using Ocean Design in-house data. As considered from this research, three configurations suited for hostile weather and shallow water were investigated: Lazy-S, pliant wave, and touchdown chain added wave. Wave loads may generate roll and impact on the floating structure in the Lazy-S configuration, as in the event of very shallow water (less than 50 m), causing slack in one of its mooring chains and creating impact load, vibration, and shock. Some standard configurations with alternatives for offshore hoses, flexible marine risers, and Steel Catenary Risers (SCRs). Typical configurations applied in our research using ANSYS AQWA and Orcaflex 11.0f software, are given in Figure 4. For the finite element model (FEM), software packages used include Solidworks, ANSYS Mechanical and Simscale OpenFEA as seen in Figure 1.

Figure 4. Hose designs deployed in our research showing (left) Chinese-lantern, and (right) Lazy-Wave Configurations of CALM buoy hose showing submarine hoses and the buoy, in Orcaflex 11.0f

Experimental studies

The experimental setup for the marine hose includes the CALM buoy model as shown in Figure 5. For the experiment, the Lancaster University Wave Tank facility was used in all the experimental investigations. The CALM buoy test model was first tested for buoyancy, and leakage; then, it was properly ballasted. It was then positioned 5.5 m from the wave maker along the central axis of the wave tank. The dimensions of the wave tank measure at 15 m lengthwise, 2.5 m in width and 1.7 m in depth. A schematic of the key features, dimensions, wave tank details, wave gauge layout, model supporting structures and model mounting area on the wave tank is illustrated in Figure 6. The beach contains a 2.5-m-lengthwise space, leaving a 12.5-m-lengthwise space available for use in the experiments. Also, the depth was adjusted to 1.0 m. The waves are generated using force feedback control through seven (7) flappy-type paddles, designed by Edinburgh Designs, UK. Each of the paddles has the capacity to produce sinusoidal waves with a frequency range of 1.5–0.5 Hz, while the amplitudes are as high as 100 mm. They are also capable of creating data files from both irregular and regular waves, depending on the input configuration. As shown in Figure 7, wave gauges were attached to the skirt of the buoy model. It was used to obtain the readings using a setup with LabView NXG 5.1. LabView was interfaced with a NI-DAQmx Device called National Instruments DSUB Model NI 9205. End fittings were connected at both ends of the two hoses connected to the buoy model underneath it (submarine hoses) and one hose on the side (floating hose). Mooring lines made of 20-mm-diameter steel chains were used, and one end was anchored to the floor while the other end was to the skirt of the model for the CALM buoy. Using these unique methods, the hose motion and the CALM buoy motion were successfully investigated, as seen in the research outputs.

Conclusion

This research outreach provides an overview of several systems used in long-term fluid transport and loading operations through these marine constructions. These CALM buoys and SPM systems are important components in the design and operation of marine floating constructions from a technological and economic standpoint. The goal of this analysis is to look at bonded marine hoses from a variety of perspectives, including application, configuration, test models, and operational perspectives. Based on operational challenges, this study also contains an overview of the statics and dynamics of maritime bonded hoses. An overview of the guidelines for the test techniques as described in available industry standards is offered to dynamically portray the hose performance in this study. The advantages and disadvantages of using maritime hoses were also discussed. Furthermore, this study has explicitly described and commented on the advances and new improvements in the studied applications. Finally, this research examines several marine hose types and new design configurations used in the implementation of hose-mooring systems. Some presentation was also made on the experimental studies conducted on the hose system.

This research overview includes hose model applications looked at in our research. The vision boarding for our research includes design concepts, dependability, and practicality judgments. To achieve the optimal balance between processing requirements and output accuracy, some debate on their utilisation and related inputs is essential. The assessment considers the challenges that can develop during hose auxiliary connections, installations, fluid transfer, and hang-off operations, as well as the difficulties that can arise during hose ancillary connections, reinstallations, fluid transfer, and hang-off operations. The latest breakthroughs in mooring applications, as well as novel upgrades, were also discussed. Finally, this study outlines the materials required for hose tests and model application in marine hoses and mooring systems.