Steel Catenary Risers: The Need for Stability

Steel catenary risers are large metal structures used to attach floating rigs, petro-chemical facilities and housing units to the sea floor. These steel risers must be able to withstand harsh currents, extreme weather and a variety of other elements to keep platforms and other structures stable and able to operate as they are intended. The designers of these unique structures must continually monitor how their risers perform, making needed repairs and watching for any malfunction or problem that may arise. New technology enables the manufacturers of the steel risers to continually maintain and improve their riser designs.

By performing and monitoring seakeeping analysis reports, they are able to improve their rises and keep them compliant with both federal and international guidelines. OSHA, the petroleum industry as well as the Environmental Protection Agency closely monitor how the risers handle extreme weather conditions and if they show signs of stress from strong underwater currents. The stability of the deep sea, steel structures is vital to the safety of the workers. It is also important when trying to maintain efficient productivity levels and keep operations moving smoothly.

The EPA relies closely on reports from both manufacturers and the managers of operations on platforms and rigs when it comes to the stability of the steel catenary risers. If a riser fails while supporting an oil rig, the resulting damage can be extensive. Not only would there be damage to the rig and platform, but loss of workers’ lives and extensive amounts of destruction in relation to the environment.

OSHA (the Occupational Safety and Health Administration) is concerned with the health and safety of all workers employed on the rig or platform. Any resulting injuries due to a malfunction of the rig or the breakdown of equipment can result in extremely high fines. Defects found in steel catenary risers can lead to the compromise of an entire platform. Even if no one is injured, an investigation would uncover possible safety hazards that make the platform unfit or too dangerous for operation.

The harsh environment in which risers are placed also plays a direct role in their design and structural integrity. Manufacturers must account for every aspect of the environment from deep sea underwater currents to hurricane strength winds. The force of both sea level and underwater elements can offer distinct challenges for individuals who must design the structures to withstand both extremes at the same time.

Steel catenary risers must be able to, not only support, but secure the platform and protect it from unexpected shifts and changes in the weather as well as the ocean currents. The need for stability is imperative when workers’ lives and the safety of the environment are at stake. Companies must be able to trust the structures they use so they can remain in business and increase productivity.

Seakeeping Analysis

Seakeeping analysis is measuring how a watercraft or any other water vessel can withstand conditions while on the waters. A ship, or a boat in that case, that has perfect sea keeping ability is referred to as seaworthy, and it will be able to operate efficiently and effectively even when in very high seas. What is normally used during such analysis include a number of things among them the steel catenary risers.

Sea keeping ability is measured using the following factors.

Mission

This is one of the first things used in seakeeping analysis. Where is the ship intended to operate? Or what will be the role of the ship while on the high seas. Basically, mission is one of the key factors used when it comes to seakeeping analysis.

The Environment

Just like mission, the environment also plays a significant role as it is one of the measures. Normally, what is looked into are the conditions under which the ship or the boat is going to operate. The conditions can be described as wind speed, sea state, and geographic region. Additionally, all these conditions can be combined.

Ship Response

How is the ship going to respond to the external and environmental factors? Ideally, the responses are the function of the environment and the ship’s features and characteristics.

Seakeeping analysis impacts directly on the design of the vessel. Ship motions are very vital for determining dynamic loading of the crew, cargo, structural element and even the ship components. It is put under great consideration when determining key dimensions of the sea vessel. Additionally, it will play a key role when you are creating the general arrangements of the ship interior.

Factors That Affect Seakeeping

When it comes to seakeeping analysis, there are multiple factors that can impact directly on how the ship will respond correctly. Some of these factors are highlighted below.

Size

Practically, the larger the ship, the lower motions it will have than a smaller ship. Why is this case? Ideally the relative size of the wave is lower.

Stability

Normally, when a ship is stable, it will tend to follow a wave more close than the one that is less stable. In short, a ship with more stability will have high acceleration, but with very low amplitude of motion.

Displacement

Displacement plays a key role when it comes to seakeeping analysis. A ship that is heavy will have low motions when compared with a lighter ship.

Human Factor

This is often one of the most critical factors when it comes to seakeeping, especially when it comes to smaller vessels. You certainly have to stay injury free, get sufficient sleep and avoid sickness.

Freeboard

The larger the water vessel, the lower its chances of it immersing. Deck immersion is normally one of the seakeeping analysis criterion. It actually affects the mission abilities of quite a number of water vessels.

Basics and Uses of Hydrodynamic Analysis

[Posted on December 11th, 2013 by Bill Stewart]


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Hydrodynamic analysis, the branch of fluid dynamics that deals with liquids in motion, is an important part of technology anything oceangoing or aquatic. Everything from ships to off-shore structures undergoes some form of this analysis. As the world increases its demand for energy, off shore structures are getting built in more extreme conditions, from deep water to arctic platforms, which require rigorous analysis before being built. Looking toward the future, hydrodynamics is helping solve the uncertainties around tidal generators, possibly turning it into a key energy resource.

Uses in the Energy Sector

The emergence of very large crude carriers has lead to an increase in single point moorings to allow the carriers to load and unload their cargo without the need for a large facility to house them. Given the cost of upwards up $387 million for a single terminal for even one of these moorings, performing solid hydrodynamic analysis is important, as any disruption can have major effects. Iraq is using the moorings to potentially double its output, and is planning to achieve this with only 4 facilities.

For offshore platforms that support drilling, operators need reliable and predictable performance, as well as prediction of wave loads that comes with accurate analysis. The analysis will also determine the safe operation conditions for offshore platforms.

Future Uses

With alternative energy becoming a larger part of the total energy market, tidal generators are being looked at as a way to harness tidal energy to cleanly generate electricity. It is not yet known how much energy can be extracted from the tides, and research is ongoing. This uncertain extends to all scales, from a single device to entire tidal basins.

What to look for

When looking for a company to perform such an analysis, you’ll want to look for a few things to make sure the company doing your analysis will do a good job. There are a variety of software tools used for this analysis, and you’ll want to make sure that the company you’re vetting uses at least some of the following software:

AutoHydro

Comflow

DeepC

Flow-3D

HydroD

Mimosa

OrcaFlex

Simo

Wadam

You’ll also want to make sure that the technology company you’re looking for has experience with many projects. While a theoretic background is also useful, teams with experience with real world projects in a variety of different environments will have the background to deal with any problems that come up.

Hydrodynamic analysis is an important part of any technology effort for aquatic structures, and making sure you have a reliable company that uses the latest techniques and software will ensure you get solutions to the challenges you face.

Features of Single Point Moorings

[Posted on December 4th, 2013 by Bill Stewart]


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Single point moorings are loading buoys anchored offshore, serving as an interconnection for tankers load and offload liquid or gaseous products. The buoy contains a bearing system that allows part of it to rotate around the moored geostatic part. A vessel can be able to weathervane around a buoy’s geostatic part when it is moored to it. A moored vessel can then rotate itself into a dominant environment, with the system minimizing loads on a buoy’s mooring system. This system can also be used when a vessel that one would like to moor is approaching the buoy.

Some of the single point moorings buoys are off the shelf products that offer various standard features, while others are custom designed. A mooring system, which consists of lines as well as anchor points, is designed to meet the requirements of a vessel and the local environment. Mooring systems are combined with fluid transfer systems, enabling the connection of subsea pipelines to a tanker. Fluid transfer systems include submarine hoses that are between the Pipeline End Manifold (PLEM) on a seabed and a buoy as well as the hoses that are between a buoy and a tanker.

Fabrication can be provided for single point moorings, including procurement, technology, construction, and logistics. Steel fabrication capacity is required if a company is to sustain the needs of a client who wants to develop oil and natural gas fields in increasingly remote geographic locations. To ensure that a client can achieve production at sustainable costs, steel fabrication facilities have to be able to meet the increasing demand for mooring systems. In addition, the technology and fabrication has to be done in a proper manner. The design and workmanship of the systems should also meet stringent rules that are in force.

Some of the offers available for single point moorings include the fabrication of the buoy body. Components for the mooring and anchoring can also be provided. A customer can also be provided with a product transfer system, such as the ones used for loading or offloading gas or liquid products. Auxiliary components can also be provided, including boat landing, handling, and lifting equipment. Navigation aids and power provisions can also be provided. Once the system has been set up, it could be an independent facility or an integrated system as part of an offshore platform.

Hydrodynamic analysis provides a critical insight into the behavior of water and other liquids, which affects water-borne vessels and related facilities, as well as containers that must manage liquid holding as well as liquid flow. Such an analysis provides key inputs into the designs of water locks or how the engines of a vessel perform with the turbines while producing a boat’s momentum. For a client who is considering a major project such as dredging, vessel production, harbor design, or a new water channel, this analysis plays a vital role in decision making and resource allocation.

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