Building a multi-mission, deep-water Applied Science ROV under a series of significant constraints

DOER Marine

Liz Taylor, DOER Marine


Introduction

DOER Marine was one of several vendors approached by the University of Hawaii to look at building a remotely operated vehicle (ROV) to replace their very aged ROV. Although the ROV had provided more than twenty years of service, it was becoming increasingly difficult to support. In the initial scope of work, many elements of the aged ROV, its handling system, Tether Management System (TMS) and ancillary equipment would be repurposed or re-fit into the new system. Over the course of several months, the scope expanded to include system portability between ships, an increase in depth rating from 4000m to 6000m and a desire for the system to operate off of the standard UNOLS .681 armored umbilical cable. DOER was ultimately awarded a contract to build the new ROV system with a full TMS for the University. Dual manipulators were added, one produced by DOER and the other, a third party system. It would be a true multi mission system supporting a variety of science objectives, the Pisces human occupied vehicles, and the Station Aloha Ocean Observing System. An HD camera, LED lighting, tracking and other sensors were supplied to DOER by Ocean Innovations, a trusted representative for DOER with a long track record of business in Hawaii. Where oil field ROV systems of similar complexity typically carry a line item value of around $5M, our team had a budget of around $2M to work with. Because of the existing equipment, the willingness of the University to work collaboratively, and because of DOER’s strengths in multi-vendor systems integrations, we believed the budget and science objectives could be achieved.

The challenge of .681

Unlike the multi-conductor armored cables commonly used in the oil and gas industry to support deep water ROVs, .681 umbilical has a relatively small diameter and contains only three conductors and three single mode fibers with armored exterior windings for strength. Although electric ROVs like the Woods Hole Oceanographic Institute (WHOI) Jason use .681 as their main lifting umbilical, there had been reports of problems with over-heating and broken conductors, reducing life expectancy and reliability of the cables.

Because these cables are part of the UNOLS equipment pool, multiple user groups rely upon the availability and integrity of these cables as they plan their programs. The cables are also extremely expensive, even when purchased by the government in full 10,000m lengths. In order to take full advantage of the UNOLS cable pool, DOER was tasked with designing a system that could operate over a variety of cable lengths ranging from 2000m to full 10,000m runs.

The size and weight of systems using .681 were believed to be factors in cable stress. By example, the Jason ROV has a dry weight of 4000kg or 9000 pounds. Under even normal shipboard operations, the loads on the cables could be severe. As a result, DOER was asked to aim for a dry weight of just 1000kg or 2205 pounds. Although it seemed a drastic reduction in weight, DOER showed that by applying advances in technology and utilizing components tested for oil tolerance, the majority of one atmosphere enclosures could be eliminated, reducing size and weight of the ROV significantly without sacrificing power and performance. The lighter weight, combined with a smaller footprint was very appealing from a risk management perspective, both for equipment longevity and shipboard handling.

After completion and acceptance of design review phase of the project, the build of the ROV quickly got underway. The University shipped all of their existing ancillary equipment to DOER for integration to the new system. Ocean Innovations assured timely delivery of all new equipment and instrumentation.

A 4000m section of .681 cable arrived from the UNOLS pool to be used for testing and initial operations. A 7000m spool awaited the system in Hawaii as a part of the shipboard equipment on the R/V Kilo Moana (KM). The 4000m section of cable would ultimately be used on their second ship, the R/V Kaimikai-o-Kanaloa (KoK).

A kink in the plan

When the time came to tie in the .681 cable to the TMS, testing showed that there was a dead short somewhere in the cable. DOER discovered rust and related water damage at the exposed end of the cable. Permission to cut the cable back was given by UNOLS cable managers. Ten-meter sections at a time were cut off and the cable was retested with no positive change. The University of Hawaii sent electrical engineer Mark Rognstad to DOER to conduct more extensive testing on the cable. Mr. Rognstad carried out a full cable dissection of additional sections he cut back. “Z-kinks” were discovered after cutting nearly 300m off of the cable. “Z-kinks” are formed when a multi-conductor cable is greatly over tensioned, then suddenly released. The ability for the cable to recover is overcome by the mechanical forces exerted upon it resulting in a characteristic “Z” folding of conductors within the cable. The cable also showed indications of burned insulation in the conductors and broken fibers. Mr. Rognstad traveled to San Diego to inspect and test another section of .681 prior to having it shipped to DOER. This cable proved to be damaged as well, showing similar faults as the section at DOER. Further investigation showed that the two pieces came from a 10,000m spool that had been used with other equipment. Both sections of cable were declared unsuitable even for low power instruments and were scrapped.

As one might imagine, these events caused immediate and lively debate among those reliant upon the .681 cable pool and those tasked with managing the assets. Clearly the model of having the cables stored on one coast while being remotely monitored on the other coast was less than ideal. How or if the management of the UNOLS cable pool will change to prevent such events in future has not been determined at this time.

Completion and testing of the ROV system were slowed significantly by these events. However, DOER was able to progress with testing of critical sub assemblies and components, including high voltage relays and other components that would be contained in oil filled housings. One-atmosphere housings were tested using a pressure chamber to 1.5 x their working design depth for numerous cycles without failure. The high voltage relay system had two design paths, one called for heavier, one-atmosphere enclosures while the other called for use of fluid filled enclosures. DOER found a very willing collaborator in the relay manufacturers. They, like DOER realized the enormous benefits that this could bring not only to the ROV market, but also to subsea charging/power management of AUVs and ocean observing instrument nodes. DOER invested significant time and resources in testing the relays both in fluid- filled and in one- atmosphere conditions.

Because there was such concern about creating undue weight related stress on the .681 cables and because of the extremely successful tests conducted on the power relays in laboratory conditions, the path of fluid filled environments for the relays was selected.

The ROV build was ultimately completed with factory acceptance tests utilizing sections of deck cable and existing cable that the university provided in place of the UNOLS .681 Because of the concerns surrounding the UNOLS cable pool, the University elected to order their own full spool of the cable by way of ensuring direct control and reliability.

Into the field

Soon after successful factory acceptance testing, the ROV, TMS, workshop and control vans were all readied and loaded onto transport trucks. They shipped by common carrier from the Port of Oakland to Honolulu. The proof of concept for containerized shipping of the entire system was easily achieved. Once on site, the University ROV team unpacked and readied the system for dockside set up and testing. Because the KM was obligated to other science work and because the new cable order had a very long lead-time, dockside testing and training was accomplished using a section of cable from the old ROV system. Although the new ROV system could not be operated at full power, much was accomplished by way of familiarizing the crew and technical staff with the new system. Tests were conducted at all junctures to monitor the amount of heat being generated by the system through the umbilical cables in preparation for use of .681. The ROV generated even less heat than had initially been estimated during dockside tests.

Defunding the National Undersea Research Program

During the course of the ROV build, the National Oceanic and Atmospheric Administration (NOAA) reacted to budget cuts by zero funding the nation’s National Undersea Research Program. Monies that had gone toward ocean science were reallocated to fund weather forecasting satellites. This severely impacted the Pisces manned submersible program at the University of Hawaii as well as a number of other regional ocean research facilities around the country. With this loss of funding, there were serious concerns for retaining the core subsea technology team and maintaining ship’s operations. Rather than funding true “shake down” dives and training exercises, the team was put into a position of having to conduct science missions even while still getting fully acquainted with the new ROV system. Working together, DOER and the University team successfully conducted a number of preliminary dives, collecting rock samples and surveying some areas of historical and archeological interest. These operations took place from the KM using the spool of UNOLS .681 on the ship’s winch. Even with 7000m of cable, temperatures remained below predicted highs when under full load.

Going deep

As deeper operations commenced, problems with the ship’s power generation system resulted in surges or pulses of energy being introduced into the ROV system. All safety systems performed as designed but failures began to occur with the fluid immersed high voltage relays. These were replaced several times with similar reductions to the expected life span of the relays and unacceptable down times to replace them. Working closely with the relay manufacturer and after very detailed engineering analysis, it was surmised that the over voltage conditions may have actually caused the fluid oil to momentarily change to a vapor state allowing the relays to experience pressure that the fluid would normally have isolated them from. On a positive note, despite this problem, the .681 cables still never overheated. The safe guards designed into the system performed their job of protecting the .681 conductors even under these very adverse conditions.

A decision was made to implement the plan B design path and house the relay system in a one-atmosphere enclosure. This was an extremely expensive upgrade option and one that the University had no ability to fund. Although the DOER team worked as efficiently as possible, the as yet unrecovered costs exceeded $70k. It was a very significant expense for a small business to absorb but resulted in what has proven to be an extremely robust solution. During post installation dives, the project manager called the upgrade and ROV “Rock Solid”.

The fluid filled version still represents a viable, useful solution for power management applications in ocean observatories and the subsea charging of AUVs.

Next steps

The University continues to grapple with the loss of funding from NOAA and the situation for the Pisces submersible program is grim. Countries including China, Japan, Russia and France are pushing into deeper water with both manned and unmanned systems. The University of Hawaii meantime has incredible assets- a 6000m ROV, two manned submersibles, and two research vessels- but scant support to operate them. Hawaii is home to the tallest mountain on the planet, though it is mostly submerged. It remains mostly unexplored. Hawaii is home to the largest National Marine Monument and adjoins other Monuments and protected areas in the Pacific. These too are mostly unexplored. Hawaii’s state mineral is in fact an animal- precious gem coral- found in deep water. Up until recently, the Pisces submersibles and ROV were making regular visits to sites where these corals are found, documenting their health, their growth rates, their distribution and diversity.

Without the ability to monitor these and other economically important ocean species, how can wise choices be made when it comes to questions of sustainability?

Many believe that the next breakthroughs in medicine will come from the deep sea in the form of microbes, sponges, corals and other deep-sea life. Scripps Institution of Oceanography in La Jolla, California also has an ROV built by DOER. They have successfully used it to collect deep-water sediments and other samples. Microbes collected have already proven to have some impact against the “flesh eating” bacteria. Manipulators and samplers made by DOER helped James Cameron to collect specimens using his submersible, Deepsea Challenger that are being tested for treatment of dementia. DOER supported similar efforts in Palau where deep-water sponges are being used in cancer research. The University of Hawaii has the location, equipment and facilities to be a world leader in these kinds of bio-prospecting endeavors but lacking support from the government, they need to find support from other sources. A small amount of funding will leverage the previous investment in these unique assets.

The build of the Applied Science ROV, named Lu’ukai (Sea Diver), represented a very successful example of public-private partnerships, small business working with a University and the Government, bringing an extremely challenging project to fruition. Rather than being an end point, it is an opportunity to leverage that success by bringing students and the public more fully into the ocean sciences. With the advanced fiber optic and Ethernet systems aboard Lu’ukai, video feeds can be brought to elementary and high school class rooms – exciting motivation to pursue careers in engineering and science. For University students, having access to these subsea assets is key to their pre, post and doctoral studies. DOER and Ocean Innovations look forward to ongoing collaboration with the University of Hawaii, their researchers, students and supporters.