Blog Summary:
- 80% of unexpected challenges and delays in marine projects is cable failure.
- Cable failure creates risks for losing expensive subsea equipment.
- Full-strength underwater cable terminations prevent cable failure during deployment and retrieval of subsea equipment.
- Unlike other helical terminations, PMI’s grips are built to hold your subsea cable to the full-rated breaking strength
- A benefit of the helical wire design permits easy installation of the termination anywhere along the length of the cable and does not require access to the cable end.
- Can be easy installation anywhere along the length of the cable and anywhere in the field.
- Do not require tools or cable preparation.
More subsea projects are happening than ever before, and ROVs, side-scan sonars, and other offshore equipment are almost always an element within them.
When equipment like ROVs and side-scan sonars are deployed or received, the twisting and bending of the cable at the termination point is common. Side-scan sonars and ROVs need these cables to stay intact and be able to bear the weight of the equipment. If these cables can’t keep up, it will cost serious delay and expense to projects.
Cable failure is the cause of 80% of unexpected challenges and delays.
The most common instance happens when subsea equipment is deployed from a vessel or retrieved from the sea and fails due to an extreme amount of tension being placed on the attached subsea cables. If these delicate cables are not terminated properly, they experience damage from strumming and snap loading. At this point, your crew can find themselves spending a good day starting over with installing a brand new termination – costing your project valuable time and money.
Without a proper underwater cable termination or grip, all of the stress and tension is concentrated along the cable where it is attached to the equipment. This is a ton of localized stress on what is usually a very expensive mechanical, electrical, or optical cable. Without a full-rated strength termination, you could be creating a recipe for disaster – cable damage, or worse, a cable break that results in the loss of expensive equipment.
How Helical Terminations Prevent Cable Damage
Helical terminations are designed to function similarly to a Chinese finger trap — a childhood toy that is a woven paper tube letting you place a finger into each end, and then, as you try to pull your fingers out, the tube tightens around your fingers. The harder you try to pull, the tighter the tube grasps your fingers, creating a secure hold.
Helical terminations work the same way. Helical rods are wrapped around the subsea cable at the termination location of the undersea equipment. With a helical termination, all of the stresses that would occur at one localized point on the cable are spread out over the length of the cable wrapped with the helical rods; therefore, greatly reducing the stress on any specific location of the cable.
To be technical, axial loading, a force that passes through the center of an object, causes elongation of the helix (or cable) and results in radial contraction. This compressive force gives the helical rods its ability to hold force. If you hold one end of the helical rod and attempt to pull the cable out, you transfer the load from the cable to the helical rods.
If at any point the load increases, the holding force increases. This mechanism provides a gradual transition of the load from the cable into the helical rod until the helical rods carry the full axial load.
Creating Reliable Attachment Points
A benefit of the helical wire design permits easy installation of the termination anywhere along the length of the cable and does not require access to the cable end. Many times attachment points are needed along the length of the cable. A good example of this is for creating an attachment point for the cable to be lifted from the seabed.
Why PMI’s Helical CABLE-GRIP™ and STOPPER-GRIP™ Terminations are a Preferred Choice
Unlike other helical terminations, PMI’s grips are built to hold your subsea cable to the full-rated breaking strength. When you are working with some of the most advanced and extremely expensive machinery in the industry, you can be confident that PMI’s equipment protects yours better than any cable hardware on the market today.
PMI’s Helical Terminations:
- Generate full-rated breaking strength.
- Permit easy installation anywhere along the length of the cable and anywhere in the field.
- Do not require tools or cable preparation.
- Come furnished in galvanized steel. Other materials, such as stainless steel, are available upon request.
- Work with many jacketed and synthetic strength members.
Invest in your project’s future
PMI’s Cable Grip and Stopper Grip Terminations are an inexpensive investment for preventing damaged cables or replacing a lost piece of expensive robotics. PMI underwater cable terminations have been used on cables for over 50 years, preventing subsea cable damage and maintaining cable integrity.
Check out our Full Rated Strength Terminations:
PMI offers Cable-Grip, Stopper-Grip, and EverGrip Terminations that all utilize Helical Rods.
Not sure what your project needs or have more questions about our helical terminations? Ask one of our experts today to help.
The PMI team had a good week attending the recent International Partnering Forum for Offshore Wind in Princeton, NJ. The exhibit hall, networking opportunities, and especially the B2B meetings with supply chain partners were great opportunities to meet with other developers, cable manufacturers, contractors, and installers.
While this conference doesn’t have as much of an international draw as some other tradeshows, it still provides a worthwhile meeting for domestic innovators and leaders in the Offshore Wind industry.
Many of PMI’s products are versatile and are valuable for use in offshore wind, along with other sectors including marine engineering/operations, telecommunications, and the renewable energy market. Meeting with engineering, construction, manufacturing, and consultant companies gives us a great opportunity to show how PMI’s “No Tools/Prep Required” cable products can eliminate many of the stressors associated with subsea and offshore cable operations.
Much of the conference buzz revolved around the excitement at the increasing opportunities for renewable offshore wind projects in the United States. (Several upcoming projects seem to be located around the East Coast: New Jersey and Massachusetts.) Offshore wind farm possibilities are also becoming more of the norm. In the midst of all these advances, however, is the need to develop solutions for “lighter” and less costly cable solutions.
While meeting with some of the leading, innovative companies, we were able to learn about the industry’s most pressing issues and challenges related to offshore and subsea cable operations and explore how PMI could assist with their efforts, such as working to minimize the damage to inter array and export cable installation and post damage cable repair.
PMI is proud to be a part of such an innovative industry, and has a proven track record for delivering market solutions such as these for over 50 years.
The Oceanology International conference covers such a wide range of industries, all with the common mission of measuring, developing, protecting, or operating in the world’s oceans, providing lots of room for potential collaborations and idea sharing among market leaders.
Being a conference with numerous offshore/subsea market leaders in attendance, it provides an opportunity for attendees to become inspired by new advancements within the industry and develop new customer relationships. Of particular interest to our team were new equipment and companies that acquire, transfer, and store data and analytics technologies.
We also noticed many oil spill company leaders were in attendance, which was interesting to see the continuing developing partnerships and collaborations between the marine technology companies and the oil and gas sector.
Through the bustling exhibit halls and between sessions, we had the opportunity to talk with multiple attendees about the economic status of some of these new markets. One thing most sector leaders agree on is that the market will eventually bounce back—but the one unanswered question is still a matter of when.
Much of the conference buzz also surrounded themes around autonomous unmanned vehicles (AUVs,) oil spill equipment, remote operated vehicles (ROVs), and various new software opportunities pertaining to data management.
The ever-growing capabilities of unmanned vehicles, along with industry applications, communications, and data are driving further advances in the ways that we collect information and work within the oceans.
With nearly 500 exhibitors from dozens of countries around the world, Oceanology International gives PMI a unique opportunity to meet with companies and discover their innovative solutions to today’s marine technology challenges. It also provides a great opportunity to share about our innovative subsea cable technologies and to create new partnerships and collaborations.
PMI is positioned well within this field given the application of various cable solutions such as our no tool or prep required cable strain relief systems (BSRs), synthetic cable terminations, and 3rd party cable testing capabilities which provide much needed services to the a wide range of markets who are associated with ocean work. Our custom cable subsea systems and deep subsea cable expertise explain why companies around the world count on PMI. When you’ve got a lot of ocean in front of you, you need PMI behind you.
See you back in London for Oceanology International 2020!
Ice hasn’t necessarily put a chill on the development of offshore wind in the Great Lakes of North America, but it does pose a significant challenge — both in the design of offshore wind turbines and the maintenance of subsea power transmission cables.
Winter is a wildcard for the Great Lakes because the offshore wind industry has traditionally avoided ice-prone regions. Most new oceanic wind farms can tap decades of knowledge gleaned from the maturation of Northern Europe’s offshore wind industry.
That’s not exactly the case for projects in water that freezes every year. The first wind farm designed specifically to cope with ice opened off the west coast of Finland in the autumn of 2017. The 42-megawatt Tahkoluoto wind farm relies on gravity-based foundations that are tapered at water level to resist friction with ice.
Ice and subsea cables
Reports on the Finnish wind farm have mentioned the tower base design but haven’t delved into the implications for subsea cables. We’re not privy to the technical specifications of the project’s subsea cables, but we can offer a few insights based on our decades of experience with subsea cables in harsh environments:
- The extreme weight and mass of ice place relentless pressure on anything in its way. Wind farms on the Great Lakes have to be designed with these risks in mind, laying cables strategically to keep them away from ice flows and buildups. The inherently unpredictable nature of weather and the motion of ice could conceivably surprise wind farm developers.
- Winter repairs will be extremely complicated. It’s difficult enough to send a ship to the site of a cable break in the open sea — it can take weeks or months to get a crew to the site, fetch the cable, repair it, and return it to the seabed. Imagine attempting repairs in the winter in the Great Lakes where variable weather changes the ice thickness constantly.
Engineers can design for the most likely scenarios for subsea cables, but there’s nothing like real life to teach us lessons we couldn’t foresee with ice and wind farms.
The value of wind farms in icy locales
The abundance of strong winds across the Great Lakes creates opportunities to develop new technologies and engineer novel solutions to icy problems. As ice resides along Arctic coastlines, wind farm developments could bring clean power to remote communities that otherwise depend on fossil fuels for heating and light.
However, we can only figure out so much of what is on the drawing board. To understand the depth of the challenges of ice in offshore wind, people need to build wind farms and learn the lessons nature inevitably provides.
At PMI, we look forward to engineering rugged, high-performance subsea cable accessories that will be critical to the success of wind power in the Great Lakes and beyond.
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Steel cables have unmatched strength and stability, which is why they’re so common in dry-land uses like elevators, construction cranes, and suspension bridges. But steel cables have troubles in marine environments: they rust, they sink, and they’re just hard to handle easily.
Synthetic cables are showing up these days in a lot of marine engineering projects, from seismic operations to cutting-edge marine-energy projects. They’re lighter, stronger, more flexible, and they float, making them a great choice for towing, lifting, and a host of static and dynamic applications.
Marine energy project managers often find that steel’s weight and susceptibility to corrosion limits their options. To keep things simple, let’s think about a basic floating platform. The weight and buoyancy balance requirements mean that every kilogram of steel cable weight subtracts a similar weight of equipment on the platform.
That means subtracting cable weight adds a lot more options in a wide array of marine applications, including ocean-energy initiatives. A meter of synthetic cable weighs about one-fifth of a similar length of steel cable. Similarly, a kilogram of synthetic cable has about five times the strength-to-weight ratio of a similar weight of steel.
Synthetic Cable Basics: Aramid vs. LCP
Synthetic fibers use advanced polymers that can be engineered to perform specific duties under precise conditions. They all have pros and cons that can make them optimum for some applications and less than ideal for others.
Marine applications typically use two kinds of synthetic fibers:
- Aramid, including the well-known Kevlar® brand. These fibers work great in transmission cables because they have low elongation, which keeps the conductor (fiber optics or copper) from stretching and breaking. They also have high tensile strength and high modulus.
- LCPs (liquid crystal polymers), including the Vectran® brand. Though similar to aramids, they have a different chemical structure. LCP has comparable elongation characteristics to aramids but provides superior abrasion resistance.
There are two potential issues with synthetics that do not affect steel: they’re more vulnerable to abrasion and breakdown from exposure to ultraviolet light. That might not be a problem with a cable that rests at the bottom of the ocean, but it can be a challenge for cables that sit outside and get reeled in and out frequently.
The chemical structure of synthetic cables can be tweaked to suit specific applications. Ropes can be designed to stretch a lot or remain static, depending on how they will be used.
Attachment points for synthetic cables
There’s a lot to like about synthetic cables and ropes in marine energy applications, but there’s one area where steel has an advantage: the method of attachment or termination.
Steel cable terminations can use helical rods to get a firm, trustworthy grip on the end of a length of steel.
Furthermore, the termination has to be designed specifically for the way it will be used—especially in applications like optical and/or electrical transmission. Since all marine energy projects transmit electricity to the mainland grid, this is a key concern.
The incredible strength of synthetic cables can be undermined if you choose the wrong kind of termination. We’ll discuss the fundamentals of synthetic strength member termination in an upcoming blog post.
At PMI, our synthetic strength member terminations have been carefully designed and tested to preserve the strength of the cables they’re attached to. We’ve been building rugged premium accessories for the deep-sea cable industry for decades, so we know what it takes to get the best performance from synthetic cables and their attachment points in marine energy projects.
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Whether marine energy project planners deploy wind, wave or tidal devices, they cannot afford to overlook the basics: transmitting power back to the mainland via electrical cables.
There’s an abundant body of knowledge on transmitting electrical power via underwater cables because power companies have been doing it decades. Indeed, Europe’s mature offshore wind industry has amassed considerable working knowledge on the most common challenges of subsea electrical cables.
Here’s a concise overview of them:
Installation and Positioning
Power cables for marine energy projects most likely will be installed with cable-laying machines that bury them at a specific depth below the sea floor. This is mature technology; the main challenges are straightforward: working around the weather and hiring a ship to lay the cables.
The greater challenges come from determining exactly where the cables will go. A host of position-related questions crop up:
- Are any other cables or utility pipelines already installed nearby?
- What’s the regulatory status of the installation site — is it a protected ecosystem?
- What’s the seabed terrain like?
- How stormy is the local weather?
- How far apart should cables be placed?
- How much shipping, fishing and other commercial activities happen nearby?
An in-depth review by the U.S. Department of the Interior’s Bureau of Safety and Environmental Enforcement noted that there so many variables with cable installation that project specifics will have to be decided on a case-by-case basis.
Protection
Cables must be built to withstand the rigors of the subsea environment. Furthermore, any cable accessories that connect various cable parts have to be extremely rugged and seaworthy, providing reliable cable protection, terminations and splicing. Project planners need to invest time in researching accessories that strengthen and protect cables, making them less vulnerable to corrosion, currents and other subsea threats.
Mooring
Depending on the location, some cables require mooring lines to hold them in place. These lines may require anchors embedded in the sea floor. Once the cables are moored, the lines may attract aquatic species that start building artificial reefs; this may trigger environmental questions.
Maintenance and Repair
The ocean environment does not cooperate with the need to maintain and repair subsea cables. Ship anchors and fishing nets may snag your power lines, and inconvenient storms can keep repair crews away for weeks or months. Even in the best weather, it can be extremely difficult to identify precisely where a cable is damaged.
Fortunately, technology is getting much better at predicting when parts will fail so replacements can be installed on schedule rather than in a chaotic emergency-repair scenario.
Monitoring
A power grid buried beneath the sea floor requires constant surveillance — the environment creates so many challenges and risks that it’s extremely difficult to anticipate all the ways things can go wrong. Advances in monitoring technology will help narrow down the source of a problem when it crops up, but it’s still a matter of fixing things buried under seawater. That’s always a challenge.
Addressing the complexities of subsea cable grids
All these points illustrate the need for a well-planned, well-executed marine energy project that anticipates the many challenges that crop up when devices and equipment get placed in a saltwater environment.
At PMI, we pay a lot of attention to making sure splices, terminations, cable protection and other accessories do not become weak links in a subsea power grid. With all the risks in the subsea environment, investing in the best cable accessories can mean one less worry for marine energy project planners.
Related articles:
- Subsea Cable Trade Group Widens Focus to All of Europe
- Offshore Wind Farms Still Learning How to Handle Cables
- What kind of ocean equipment will be needed for subsea power grids?
Offshore wind technology gets better every year with more innovative turbine and blade designs. But no matter how well they design a wind turbine, engineers perpetually confront the unique difficulties of exporting electricity back to shore.
Subsea power cables are built with the demands of open ocean in mind. Multiple layers of alloy and fiber strengthen and protect the power-conducting cables inside. In the open ocean, far from ship anchors and fishing nets, deep-sea communication cables can last for decades without a fault.
Power cables installed near dry land have it much tougher because they are so much closer to the ocean surface, where turbulent weather and heavy machinery can cause havoc. Indeed, an article at RenewableEnergyFocus.com estimated that export cable damage surged by 500 percent in the past 12 months.
Survivability is the central concern of cable manufacturing because oceans bring peril with every wave. Typhoons, fishing trawlers, corrosion — it’s always something. Here’s a quick look at the key challenges with power cables that export electricity from offshore wind farms:
Finding the Damage
Occasionally, a ship anchor will snag a cable and snap it in two. This is bad news because it shuts off a revenue source for the offshore wind operator, but it could be much worse.
A pure break location is somewhat easy to track down because engineers can measure the resistance in a length of power cable and calculate with a fair degree of precision where the electricity cuts off. Then it’s a matter of sending a ship to the estimated location of the break, pulling up the broken cables and using splicing gear to reconnect them.
The much more daunting challenge happens when a cable starts developing significant losses in transmission — often because the cable was damaged and exposed to the corrosion of seawater. This kind of damage is less likely to leave telltale hints about its location, which can bog down the pace of attempted repairs.
Reducing Downtime
Windfarm designers have figured out how to build towers and turbines that can withstand gale-force winds and furious storms. Unfortunately, the worst weather may damage even the most well-built cables, which requires ships to locate the problem and try to fix it.
Repair crews cannot do their jobs in storms that toss their giant vessels around like corks. So they have to wait for the weather to calm down. It might take days; it might take months.
It’s not unheard of for a ship to be at sea for three months in pursuit of a single repair if severe storms continually blow it off course. There are only so many ships available, and they can fix only so many damaged cables.
Making Repairs
Once a repair ship locates a cable problem, it has to pluck the cable from the ocean floor and pull it up to the surface. If all goes well, this process won’t damage the cable even more.
After the damaged area of cable arrives at the surface, the next step is to recondition the broken areas, rejoin any damaged conductors, then seal the assembly with heavy-duty splicing equipment. The techniques for repairing and rejoining subsea power cables are well understood. But repairs are still hostage to the first two problems: finding the cable fault and waiting out the weather.
This is Why Subsea Cable Accessories Must be the Best of the Best
All these challenges give offshore wind operators plenty to worry about. The accessories that attach and connect their power cables should not be another source of anxiety.
At PMI, we aim to provide the most durable, practical subsea power cable accessories on the market. We’re big believers in the promise of offshore wind and other marine renewable power sources, but we’re also realistic about the depth of the challenges facing the industry.
It may turn out that difficult cable repair jobs are the price we have to pay for offshore renewables. If so, we’ll do our part to make sure those fixes stay fixed.
Related articles:
- Damage to Subsea Cables a Huge Risk to Offshore Wind Farms
- Challenges in the Installation and Repair of Offshore Wind Turbines
- Offshore Wind Farms Still Learning How to Handle Cables
- Vision for Offshore Wind Energy Market
A trade association representing the subsea cable industry in the United Kingdom widened its focus in March 2016 to cover all of Europe.
The new European Subsea Cables Association (ESCA) takes the place of Subsea Cables UK. The trade group provides a forum for people who own, manage or service subsea telecommunication and power cables or serve the subsea cable industry in Europe and its surrounding waters.
ESCA’s prime goal is to encourage marine safety and help protect subsea cables from hazards such as fish nets, ship anchors and submarine landslides. The group also will defend the rights of operators to install and maintain underwater cable solutions.
“The requirement to form this new association has come from our membership and it was the logical evolution of the organization,” said Peter Jamieson of Virgin Media, chairman of the European Subsea Cables Association. “Close to 50 percent of the old UK association members were non-UK. Therefore, we can better serve our members by becoming a more regional association. ”
ESCA Executive Committee member Colin Rayman of Red Penguin Associates said that creation of the Europe-wide association will make it easer to confer with European maritime and fishing industry officials and government regulators “to move closer to attaining mutual understanding of our industries, sharing the seabed safely and maintaining the integrity of assets.”
The association will give its members advice and technical papers that will help everybody in the sector go about their business. Members of ESCA are experts in all phases of the subsea cable industry. They’ll convene bi-annually to share ideas and information.
If you’re in the submarine cable business, whether you’re an owner, operator, consultant, or subsea cable hardware supplier, you’re welcome to stop by the organization’s website at www.escaeu.org and download an application to join.
At PMI, we’re glad to see these people coming together to foster the health of the subsea cable industry across the European continent. Developments like tidal power and subsea power grids need consensus among business people and regulators to develop standards and hone technical expertise vital to the sector’s future.
As a premier provider of subsea cable hardware, we’re also on the front lines of Europe’s efforts to switch more of its energy consumption to renewable sources like wind power.
Subsea power grids require two major kinds of ocean equipment: subsea power cables to convey electricity to the grids, and generating equipment to distribute electricity to pumps and other devices required to find and extract crude oil.
Even in a time of depressed petroleum prices, oil companies still value deep ocean engineering and they like the prospect of placing power grids on the sea floor because the grids improve the efficiency of the extraction process, which helps hold the line on production costs. When the oil market inevitably rebounds, companies with the most efficient production processes will reap the greatest rewards.
Let’s look at some of the ocean hardware that will go into these subsea systems:
- Transformers: These take power from the surface — either from the mainland or a floating platform — and convert it into the voltage needed at the undersea grid level.
- Switch gear: Switches adjust the flow of electricity to the deep-sea components that need it. If a pump needs different voltage than a compressor, switch gear takes care of that job.
- Variable-speed drives: An oil-drilling pump needs to run at multiple speeds to achieve maximum efficiency. VSBs make this happen.
- Cables: Cables carry energy from the surface to the grid and distribute it to the transformers, switch gear, variable-speed drives and any other ocean hardware in the grid.
Why deep-sea power grids are so attractive
Oil drillers need a lot of power to extract oil from below the deep sea. A deep-sea power grid allows power to be distributed to dozens of pieces of subsea hardware across a wide expanse of the sea floor.
A site developing a deep-sea oilfield becomes much easier to operate if power sources are on the sea floor near the point of extraction. Without a grid, power can be sent down via cables to equipment within a very limited expanse. A grid dramatically expands the area of sea floor that has available power.
Challenges for deep-sea equipment
Companies are designing subsea grids that can operate for up to 30 years in up to 10,000 feet of water. That places immense pressure on the equipment and requires precise engineering to protect delicate electrical components.
Saltwater is extremely corrosive, and undersea creatures like to attach themselves to any structures they can find. Fishing fleets drag deep nets that can become entangled in deep-sea equipment, and ship anchors have the potential to damage or cut subsea power cables.
Robust ocean equipment is the answer
Subsea energy companies understand the extreme terrain and know they need to build robust gear to provide reliable systems that can last decades. That also means they need to rely on proven ocean hardware that is high quality, highly reliable and fully flexible.
Offshore renewable energy solutions might be new to the world, but we know that all ocean equipment requires deep ocean engineering experience. And for over 60 years, PMI Industries has provided ocean hardware that increases efficiency, reduces failures, and improves installation and deployment time.
We have previously discussed the various ways subsea cables can be damaged underwater (Link: https://pmiind.com/damage-to-subsea-cables-a-huge-risk-to-offshore-wind-farms/), but how are these cables fixed? The answer lies on a ship like the Pierre de Fermat, a ship specially designed for undersea cable repairs. Once the break location is identified, the ship launches a remotely operated vehicle (ROV) to retrieve the cable and return it to the ship.
The repairing process of a cable isn’t the simplest process, as we’ve explained in our blog post “When it comes to subsea cable repair, time is of the essence”. As the cable is being repaired, cables and equipment are vulnerable to damage by other vessels and fishing gear. It’s a delicate feat that requires speed and precise navigation in some of the most extreme ocean environments. Because of this, subsea cable hardware should provide secure, fast assembly. Once the cable is repaired, the ROV returns to the sea floor and attaches the newly repaired piece of cable to the existing subsea cable network and uses high pressure water jets to bury the cable.
To read more about the fascinating process of repairing subsea cables, check out the article “This Giant Robot Fixes Undersea Broadband Cables“.
PMI’s proven, high quality subsea hardware is the ideal solution increase subsea cable performance, assist in cable reparation, and in ROV and ship attachments. Call us today to chat about how our solutions can help your subsea cable problems.
