Experience matters when it comes to ensuring subsea cable systems survive variable ocean conditions. After all, if any part of the cable system assembly fails at sea, repairing or replacing it is expensive and arduous. PMI’s cable testing and analysis is an excellent way for customers and third parties to feel confident about their cable system components and the integrity of the complete system.
“Few labs offer the tests or use the equipment we do to find vulnerabilities and confirm satisfactory performance before the cable is deployed,” says Jay Marino, P.E., PMI Manager, Engineering, Government Services & Test Lab. “We’ve worked with many customers over four decades to simulate at-sea conditions and provide quality inspection and assurance services. PMI’s insight into a product’s durability is a value-added service that customers seek out. They like the fact that our tests can be uniquely tailored to meet their needs.”
As deep ocean exploration has grown over the years, the heavy-duty cables used in subsea projects are expected to last for decades. Unfortunately, 80% of unexpected challenges and delays in marine projects are caused by cable failure.
Equipment provides extensive measurement capabilities
Determining the service life of a cable system and/or its components is a specialty of PMI’s. Besides the tests PMI does on its own products, organizations come to PMI for certification and testing services, particularly ones designed to assess electrical, optical, and mechanical applications.
Customers with new cables may want to do tension cycling on them. PMI’s long span tension setup machine is capable of testing cables up to 457m (1,500 ft.) over multiple sheaves, with tension up to 53.4 kN (12,000 lbf.).
“A manufacturer that makes a cable assembly will send a sample to us to test,” says Marino, who has been involved with PMI’s cable testing facility for over three decades. “Important testing we frequently do for customers checks the cable’s subsea mechanical responses. When someone develops a new cable and wants to run it through its paces, we’ll do tension cycling on it. We’ll also measure the torque and rotation to verify its torque balance characteristics.
“Cables typically are ‘torque balanced,’ but that doesn’t mean they’re perfectly torque balanced,” he continues. “What it means is that the cable is typically designed to minimize torque. Some torque remains, sometimes a little or a lot.
“We can measure the torque that’s generated when it’s loaded. We can also measure its rotation,” he says. “For example, if we fix one end of a cable sample and pull on the other end while allowing it to rotate, we can measure that rotation. Or, we can fix both ends and measure the torque generated in the cable. We can also rotate one end to intentionally generate torque in the sample to see how it reacts. Of course, hydrostatic pressure testing is usually part of the picture. These are tests we typically run. There aren’t many test labs which have this type of equipment.”
The CBOS (cyclic bend over sheave) machine is used to check a cable’s subsea mechanical responses, including its fatigue resistance and simulating its handling system problems.
The equipment PMI uses to test and measure for performance and reliability include:
- Long span tension setup
- Hydrostatic pressure chambers
- CBOS (cyclic bend over sheave) machine
- 100-kip straight tension machine
The equipment can test:
- Raw cable (steel armored or synthetic strength member)
- Rope and hose assemblies
- Cable assemblies
- Cable hardware
- Terminations
- Other equipment used in subsea projects
Customer-driven laboratory testing
One of PMI’s hydrostatic pressure chambers (above) can be used to simulate at-depth pressure loading and verify seal and electrical and optical performance.
Each test is based on the customer’s unique set of parameters. Additionally, the time involved varies based on the customer’s application, interface, and materials requirements.
“We test the cable or component at the conditions that the customer expects during operations in the ocean,” says Thom Bosch, PMI lab technician who has been involved with the company’s laboratory testing for 14 years. “For example, if they’re towing a cable or component through the water, they can calculate the drag force on the towed object, which is related to the tension in the cable. We’ll test to that tension value plus a safety factor for dynamics, usually doing many cycles over hours or days. Our customers typically have an idea of how much variability they can tolerate and still operate their cable system or device.”
These kinds of customer-focused interactions are one reason PMI has been a leader of in-house dynamic cable testing and analysis for nearly 40 years.
The 100-kip straight tension machine is used to measure up to 65 feet of cable to determine its proof, tension and breaking strength.
“We offer independent testing services to any company in the industries we serve,” Marino says. “We can test the performance, and sometimes the limits, of a customer’s cable or equipment beforehand so that there aren’t any expensive surprises in the field.”
To set up a free consultation or get technical support, contact Jay Marino at jmarino@pmiind.com or any member of our leadership or sales team. Their contact information is found on the Contact Us page on our website.
