Single Point Moorings Help Offloading Efforts

[Posted on July 2nd, 2014 by Bill Stewart]

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When drilling platforms need to transfer gas or liquids, single point moorings help their offloading requirements. Properly designed and anchored, these moorings can secure tankers of any size safely.

Offloading crude oil or gas to single point moored tankers is vital to getting platform production from the ocean to land-based ports. This connection between tanker and platform at a single mooring point with proper subsea design and installation makes the critical transfer of platform production easier, faster and more effective. Understanding how  single point moorings work is important to ensuring their subsea design and connections are installed properly effectively holding weathervaning tankers securely prior to and during gas or liquid transfer.

Working Description of Effective Mooring Systems

Three primary components make up mooring systems.

  • A mooring line;
  • An anchor: connecting the mooring line and a floating buoy; and
  • Various connectors, establishing the vital link of tanker and offshore platform.

Mooring lines often use different material, based on subsea and surface environmental conditions, such as wind strength, wave size and motion, and current power and direction. The most popular materials are —

  • Synthetic fiber rope;
  • Steel wire rope;
  • Chain; and/or
  • Combinations of the three materials used together for added strength.

Long-term and permanent moorings typically feature lines using chain, particularly in shallow water (usually defined as up to 100 meters). Deeper water mooring lines often use steel wire rope, maximizing the benefits of its lighter weight and increased elasticity as compared to chain. When light weight is the top consideration, mooring systems feature synthetic fiber rope, for its lighter weight properties.

Deeper water moorings, up to 2,000 meters, suggest using chain or chain and steel wire rope configurations. Combinations of all three popular mooring line materials are often used in deep water, over 2,000 meters, to get the best features of strength and elasticity.

All mooring system success depends on the strength and ‘holding capacity’ of their anchors. Outstanding anchors’ holding ability depends on their digging depth and the soil components of the sea floor. The most popular anchor type is the drag embedment style, used throughout moorings in the Gulf of Mexico.

Installing this anchor involves dragging it along the seabed until it achieves its optimal depth, penetrating sea floor soil and creating necessary resistance to hold it in place. Deep water conditions favor suction pile-type anchoring, since drag anchors lack high performance when heavy vertical forces dominate the environment, such as the pressure generated by deep water.

The third primary anchor type, vertical load devices, while similar to drag anchors perform well when facing both horizontal and vertical load issues. These types are very useful when mooring lines tend to adopt angular positions between anchor and buoy.

Steel catenary risers help the most common mooring system for shallow water allow the line to modify configurations as the surface vessel moves around. Since the mooring line lies on the seabed, it needs to be longer than water depth, increasing its weight, making catenary mooring systems less efficient as water depth increases.

When platform owners want expert advice and analysis of single point moorings, they turn to Stewart Technology Associates, industry leaders in offshore equipment and systems expertise. Our state-of-the-art technology and extensive experience analyzing and designing offshore systems help develop efficient solutions for offshore drilling and production platforms. Analysis of mooring methods is only one area of the many conditions we evaluate for our clients.

Marine Accident Investigation Expertise is Critical for Answers and Liability

[Posted on May 28th 2014 by Bill Stewart]

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Marine accident investigation events are no simple matter. Unlike the world of land-based transportation, marine accidents can often involve far more factors, especially due to the nature of the weather and water conditions at the time. As a result, a good investigation will include the basics as well as advanced review of the facts and data through hydrodynamic analysis, for example.

There is a reason for the intense scrutiny of marine accident investigation reports and summaries. The National Transportation Safety Board, or NTSB, is often involved and a key player in any investigations that take place, especially serious accidents that involve multiple injuries or death and a commercial vessel. The U.S. Coast Guard can frequently become involved as well. As a result, it is critical for a boat owner or title holder to make sure that any investigation that does occur is performed with the right skill, experience, background and knowledge. Very often, the results of reports can trigger financial responsibilities as well as serious penalties.

Marine accident investigation work can also include any type of installation or facility on major waters as well. Oil rigs, for example, are a prime facility that could have issues and trigger multiple investigations on an accident, especially if the results have both life and environmental impact on a wider scale, such as the Deepwater Horizon accident.

In both type of cases, the investigation work doesn’t stop with the field review and conclusion of what occurred. Expertise is often needed in the legal matters and potential trials that come later, assigning responsibility and blame. Without a good marine accident investigation expert’s testimony, a vessel or facility owner could be sitting with a big target on his back even if not actually at fault.

Stewart Technology Associates can provide a client assistance in both field review as well as impartial expert witness testimony on a marine accident or accident complex. Their depth and knowledge in marine traffic and operational matters is extensive, and their professionalism often shows itself during some of the most critical points of an investigation. A client utlizing the help of Stewart Technologies will be able to focus on other aspects of operations, recovery and assistance knowing that Stewart’s team will handle the accident review completely and comprehensively, from the initial water site to the courtroom if needed.

So if your firm is finding itself in the headlight glare of a marine accident investigation or you need a second-opinion on reports that have been produced, Stewart Technologies is the expert to call. Don’t wait; it could cost your firm far more.



Trusted Comprehensive Hydrodynamic Analysis by Stewart Technology Associates

Small firm with top scientific specializations trusted for integrity

The Stewart Technology Associates team of specialist technology experts are highly educated with top scientific degrees, and universally respected for their research and top-level experience in world-wide hydrodynamic analysis projects. Stewart Technology Associates, (STA), specializes in design and analysis of offshore engineering projects and many marine engineering applications. In the current global economy, it is critical for our  clients in the oil & gas industries to push further offshore to find energy supplies that can meet the world demands.

We offer integrity and cutting-edge innovations for offshore structures, drilling processes and production equipment builds that continue to need unquestionable reliability, safety and predictability. STA places a strong emphasis one trust and dedication to the responsible use of highly technical knowledge. This top engineering firm enjoys worldwide respect for design proficiency and multi-level analysis.

Hydrodynamic Analysis

During close to 25 years of excellence in performing hydrodynamic analysis to help world acclaimed marine organizations solve their most difficult challenges and complex obstacles, we have developed top-grade experience involving jack up analysis, pipe lay analysis, CE marking and expert witness testimony, plus much more.

Detailed hydrodynamic analysis of an engineering design or product:

  • Scientifically predicts flow characteristics of bodies of water, body surface parameters expected to impact during the operational phases of the project.
  • Is critical to simulate and test submersible components, underwater power systems and marine architecture.
  • Extends the test data into further professional grade analysis of factors such as stress or vibration on marine structures and pipelines.

Use of Engineering Software to Analyse Flexible Risers

We use the world’s leading engineering software to design and analyze many types of marine systems including risers, mooring systems, marine renewables, towed systems, seismic arrays, seabed stability, and defense. Our first choice in professional engineering software for marine work is Orcaflex, because we get best in class GUI, scientific automation, and visualization. In the case of analysis for riser use,  types of steel and metal alloys, like for catenary risers and other tough marine technology project services, this software allows STA to offer flawless flexible riser design and completely accurate analysis that will exceed the client’s expectations.

Stewart Technology Associates tackles the tough science to make your project succeed

Under the professional leadership of Bill Stewart, CEO, our science and technology team has accomplished laudable worldwide projects and developed an esteemed customer base of U.S. government agencies, large and small oil industries, financial institutions and drilling contractors all over the world. Contact STA Tool-Free in Houston, by phone (713) 789-8340 or email, [email protected], for more details. 

Flexible Risers Are Regularly Used In Offshore Drilling

[Posted on May 14th 2014 by Bill Stewart]

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When you are engaging in any kind of offshore drilling activity, it requires a significant amount of analysis. You need to bring a lot of specialized equipment onto the water with you and that’s where you will remain for months at a time. You cannot afford to make mistakes while you are out there, so the use of flexible risers along with detailed analysis is a must. Risers are used to serve as the connection between the drilling facilities and the subsea developments in the field. You will need to understand cable dynamics to account for all of the waves and other environmental factors while out in the water. Since you have a conduit in place, you cannot afford to disrupt the transfer in place and that is why flexible risers are commonly used. It offers, as the name implies, some flexibility to the overall structure of the drilling configuration so that you and all of your equipment are set up to the highest level out in the water. As you go into deeper water, you experience more pressure, more waves, and colder temperatures. All of these factors have to be a consideration so that you have the right equipment. Analysis of the riser configurations will ensure that you have considered all possible scenarios to avoid any kind of disruption to the material transfer. The flexible risers are going to act as a pipeline for vertical transportation. Should you be unable to find the riser that you need, the product would have nowhere to go because a vertical motion is required. As you gather the materials that are required for your offshore drilling, you need to take advantage of all the analysis that you can. Depending upon what you are drilling for and the depths of water that you are going into, you will need different types of equipment. If you fail to get the risers that are needed, your drilling expedition will not be as effective as you hoped. One of the biggest problems on the water is that you do not have access to more materials. Should someone have to bring supplies out to you, it leads to higher costs. When there are unplanned for costs, it can lead to a loss of investors – or the need to bring in more investors. Neither of these is ideal, which is why some planning before you ever take to the water is a necessity. Flexible risers provide you with the needed flexibility when you need a vertical connection so that you can move materials from the sea floor to the facility on top of the water. You don’t have to guess at what you need because advanced technology can run the scenarios and provide you with the in-depth analysis to tell you what the riser configuration should be and what you will require.

Mooring Analysis: Critical for Selecting the Right Mooring

[Posted on March 12th 2014 by Bill Stewart]

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As any marine organization can tell you, installing mooring systems is more than anchoring a single CALM buoy or setting a fixed tower on the sea bed. It is critical to know how ships of different weights and sizes will react in the given location under different circumstances. Doing a mooring analysis is critical to determine the best mooring option and its placement.

Take tanker loading and offloading as an example. Takers are extremely sensitive to wave direction in an open water situation. In most cases, spread mooring would not work due to this movement. Tankers often use single point moorings that allow them to move around the single point based on the direction of the waves and movement of the water flow.

Determining what kind of single point mooring is appropriate to a specific application requires careful analysis. Here are a few mooring options:

  • Fixed towers with a slew ring work well in some single point applications. It works best in shallower areas where wave action is not heavy. At greater depths or in areas with heavy wave action, the tower can begin to bend. These towers are also susceptible to damage from even minor tanker bumping.
  • A catenary anchor leg mooring (CALM) are not as sensitive to water depth and wave action as a fixed tower mooring is. It is able to handle some bumping from tankers without sustaining extensive damage. Major tanker impacts though can cause damage that can put the CALM out of commission for a good length of time and cost a lot to fix. The mechanical components are also subject to extreme weather which requires ongoing, sometimes expensive, maintenance.
  • A SALM (single anchor leg mooring) solves the problem of expensive damage that CALMs can experience due to major tanker impact. They do this by placing the mechanical systems in an underwater arrangement at a depth below a ship’s keel. The simple surface buoy is easy to replace if its hit by a tanker. The biggest issue with the SALM is the maintenance difficulty and cost.
  • An Articulated Loading Column (ALC) is a mix of a fixed tower and a SALM. The tower holds the swivel and hoses above the likely point of impact with a ship. There is an articulated joint below water attached to a concrete base embedded in the bottom. This joint helps the mooring move in heavy wave action.

Determining which mooring application is right for a particular situation requires the ability to model the many factors that influence the ship and the mooring. A mooring analysis tool is essential in this process. It allows for quick and thorough modeling of a number of scenarios. Here at Stewart we use Orcaflex when we do a mooring analysis. This software package is the best marine engineering software package on the market today.

Trends and Uses for Cable Dynamics Today in Off Shore Industry

[Posted on January 7th, 2014 by Bill Stewart]

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Cable dynamics represent a vital part of all offshore technology projects, procedures and error solutions.  High quality technical reports are necessary, including diagrams which enable technical reports to be well understood by not only trained experts but by average lay persons or legal counsel.  Extensive use of computer software and state-of-the-art analytical simulation techniques are vital in today’s offshore industries and their management technology professionals.  A “notebook” computer and printer should accompany technology professionals when  performing their many important offshore duties or preparing  technical reports.   Millions of dollars have been awarded to clients of Stewart over the last fifteen years as a direct result of the expertise and reporting of the owner of Stewart Technology Associates,  W. P. Stewart, P.E.

Cable Dynamics Also Vital in Reenactments

Stewart Technology Associates maintains  databases of offshore and marine mishaps,  spills, and construction.  Other offshore costs factor into their technology projects, databases of construction and other offshore costs. These are most useful in maritime law.  All of the foregoing testifies directly to the expertise of STA company in offshore cable dynamics and other significant marine solutions.

An anchoring system for offshore is controlled by factors such as site environment, operational variables and the vessel  involved in the system.  Its adequacy and ability to stay on site must be checked by proper methods of analysis. The inclusion ofcable dynamics is an extremely important consideration in the analysis of a moored vessel, permitting anchor motion. Then numerically solved timehistories of cable displacements and cable tensions for cable figurations occurring under the Initial conditions are provided through mooring line static equations.  The equations of motion of the moored vessel subjected to an open ocean are then numerically solved, yielding time histories of vessel motions and cable tensions.

An example involving a moored production barge is examined and results compared with previous incidents.  In this way the cable dynamics are used in the proving labs or court of law as importantly as they are used in their offshore capacity.

Steel Risers

Flexible Risers had a set back in recent years but now they are in high demand. The riser components are used to build off-shore rigs very elevated are needed as much as ever. Risers are most definitely needed. These risers connect platforms with fuel deep below the ocean and carry fuel to areas for packaging and transport. Without risers, much of the world’s oil and gas would remain untouchable.

 Steel Catenaries

The steel catenary risers afford industry perks that others don’t. These are flexible steel traveling from the ocean’s floor to the drilling platform. Designed for deep-water drilling, they measure several hundred meters.

Stewart Technology Associates have played an integral part in the development of America’s oil industry, from working the offshore platforms to damages litigation.

3 Reasons For Mooring Analysis

[Posted on November 6th, 2013 by Bill Stewart]

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No one wants to deal with marine accidents and mooring analysis can prevent this. A boat or other vessel needs to be tied down when it’s at port and this means that the mooring needs to be adequately grounded. Through the use of advanced software, analysis can ensure that all aspects have been considered.

When you schedule mooring analysis, there are several things that should be included in the report:

  • Wind and wave capability
  • Shielding of pier
  • Options to lock vessel
  • Pre-tension for mooring setup
  • Rope properties

No one wants to see their boat drift away and this is one aspect that the mooring analysis can help with. If the mooring is not stable enough, the boat is going to be tied to it. As the wind and waves rock the boat, it may cause enough pressure that the mooring breaks away, causing both the mooring and the boat to drift away.

Another reason for the analysis is to help with a marine accident investigation. If there was any kind of accident involving a boat or other vessel that was tied up at the pier, investigators are going to look at the mooring. If the mooring wasn’t placed properly to begin with, it could be what caused the accident.

A lot of damage avoidance can be put into place with mooring analysis and this is the third reason to get the analysis when putting a mooring in place. Hurricanes can wreak havoc on the land and the sea. If a mooring is only capable of handling a certain amount of wind and wave action, then you need to know this. Some docks or piers will have warnings of when you shouldn’t tie your boat up.

There may be instances where you want to bring your boat onto land. If the mooring has not been analyzed or it is not stable under the current conditions, you have to do what’s right for your boat. You don’t want to lose it to the sea, so you have to secure it in one way or another. If you cannot rely on tying it up in the water, you may have to bring it out of the water entirely. This way you won’t have to worry about problems where it could be washed away.

If you’re dealing with severe weather, you want to make sure you drag the boat or other vessel up the shore enough that waves cannot wash it back down. This will keep your boat safe no matter what kind of weather you are dealing with.

There are all sorts of reasons for scheduling a mooring analysis. Once you have the analysis in hand, you can provide the necessary notifications to boaters. You can also train your employees that work on the dock or pier to help with securing vessels to the mooring.

Stewart Technology Associates Bring Riser Analysis to the Next Level

[Posted on June 29th, 2013 by Bill Stewart]

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When operating in adverse offshore conditions, a comprehensive riser analysis is crucial to ensuring the safe and effective use of your equipment.  No matter where in the world the next offshore drilling opportunity takes your company, the day to day performance of your crew will be greatly enhanced by knowing that your platform is operating at peak efficiency.

For more than two decades, Stewart Technology Associates (STA) have been dedicated to solving marine technology problems.  Company leader, Bill Stewart has made the development of riser analysis a priority, and is the author of numerous technical papers on the subject, as well as, playing an instrumental role at industry conferences dedicated to educating others about the importance of detailed technology solutions.  They are recognized as experts in the field by other experts.

From riser analysis to seakeeping analysis, Stewart Technology Associates utilize the latest in technology to arrive at an offshore solution for your technology problems.  Additionally, the application of industry-wide, best-practice standards ensures that you can always be certain of your equipment’s performance even in an uncertain marine environment.

These stellar results are achieved, in part, through the reliance on the industry’s leading software package, Orcina’s OrcaFlex marine technology software.  OrcaFlex allows for the careful consideration of critical issues like riser analysis, and is the favored marine software package of over 170 organizations worldwide.

With this technology in harness, Stewart Technology Associates’ design and analysis team can bring quantifiable data to the table for analysis.  Additionally, their vast library of over 2,000 technical volumes means that the answers to client’s questions are nearly instantaneous.  They leave nothing to chance when it comes to properly assessing your equipment and procedural effectiveness.

No matter what the industry, knowledge is power, and STA’s project technology experts are sharing that knowledge every day all over the world.  If you are operating in the challenging arena of offshore drilling platforms, you may well be surprised by the myriad of solutions they have to offer for problems, which you may not even have known existed.

Stewart Technology Associates have consulted on projects for some of the largest drilling operations in the world and are trusted throughout the industry.  As experts in the field of riser analysis, they are constantly honing their skills, so that clients, and their employees, benefit from Stewart Technology Associates’ rigorous research and design efforts.

Industry leaders in the field of offshore structures and their operating environment, the professional team at Stewart Technology Associates deliver their expertise in research and design to the solution table with innovative ideas, models, and technology software.  Contact them today so they can help your team arrive at a safer and more productive tomorrow.

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