Subsea Technology: Atmospheric diving suits bridge gap between saturation diving and ROV units

The ADS, an articulated single-person submersible, is designed to enclose the operator at one-atmosphere pressure, regardless of depth. The suit may have articulated arms and legs such as the Hardsuit family of ADS units, or may only have jointed arms like Oceaneering's Wasp and the Spider developed by Vickers Slingsby in the 1970s.

All suits in operation today have a thruster package for mid-water maneuverability. Other single-person diving systems, such as the Wrangler or Mantis, have not been considered here because they have mechanically operated arms versus human-powered limbs.

John Lethbridge of Devonshire, England is credited with building the first ADS in 1715, and for lack of a better term referred to it as a "diving engine." The suit was little more than a tapered wooden barrel supported by iron hoops with holes for the arms to extend into the water and sealed by means of tightly buckled leather cuffs. The operator entered through a manhole in the top and was lowered into the water in the prone position.

Lethbridge provided a ten-centimeter glass port in the bottom of the vessel for observation. The only available air was that which was in the suit before it was sealed and was said to allow as much as 34 minutes of bottom-time at 18 meters. Lethbridge reportedly was successful at salvaging treasure for the Dutch and English East India companies.

Other history

Another early suit was somewhat successfully used in the salvage of the SS Egypt, which sank in 1922 off the coast of France. Although the suit, built by the German firm, Neufeldt & Kuhnke, had articulated arms and legs, the joints were practically immobile and the suit was relegated to a mere observation chamber at the depth of the Egypt. The operation was a success and the Italian salvage firm, Sorima, recovered over a $1 million in gold and silver ingots in 1932.

In the 1960s, even the space industry attempted to develop a working one-atmosphere dive suit, which is not extraordinary considering the parallels between the space and diving industries. A 1967 article outlined Litton Industries engineering approach employed in their ADS design. Unfortunately, the Litton suit never made it to full development.

Of more recent notoriety is the JIM suit, a "reincarnation" of an earlier workable suit, designed and built by Joseph Peress. The JIM suit saw its initial development during the late 1960s and early 1970s when diving technology was unable to keep pace with the offshore industry's march to deeper and deeper fields.

The JIM suit was successfully used for many years in the offshore industry. No other suit had more impact on the resurgence of the ADS as a viable underwater intervention tool. Developed and built by Underwater Marine Engineering for DHB Construction to operate, the exclusive rights to the application of the JIM suit were later purchased by Oceaneering. Several other suits were designed and built throughout the previous two centuries, some of them marginally successful.

Underwater intervention

While the earliest ADS units were invented to salvage gold and other treasures from sunken ships, today's suits are more likely found supporting the offshore oil and gas industry's search for reserves. The remotely operated vehicle (ROV), the ambient pressure diver, and the atmospheric diving suit are three primary means of undersea intervention used in the offshore industry. All three methods can be used in water depths up to 300 meters.

The ambient pressure diver, while subjected to all the physiological hazards associated with depth, cannot be beaten for dexterity, and at shallow depths is generally the most practical. However, as Dan Kerns of Stolt Offshore, says, the penalty for saturation diving, generally is "one day of decompression for every 30 meters of water depth, plus one day." Using this rule of thumb for the industry accepted maximum of 300 meters, each saturation diver would require a minimum of 11 days of costly but non-productive decompression time.

A recent Hardsuits International cost estimate of atmospheric diving versus saturation diving for a 300 meter depth dive indicated a significant savings in total daily costs, weight, and deck space. Overall job costs for saturation systems are even higher with the cost of de-saturation.

On the other hand, average work-class ROVs can dive to 6,000 m, far surpassing the deepest ADS. Remote is the keyword in remotely operated vehicles though. It's been said that attempting to perform a task with an ROV while thousands of meters from the job site might be compared to exploring the jungles of Africa from a hot-air balloon. Even the best ROV operators are no substitution for a "human" on the scene. However, Eric Hammans, of Oceaneering, says that "often, the most effective method to complete the job can be a combination of the ADS and a ROV, and in some cases, an ADS and diver." Oceaneering's recent pipeline repair projects completed in Mariner Energy's Pluto and Dulcimer fields included the use of a WASP and ROV. ADS advantages over other underwater intervention systems include:

• No decompression time
• Work locations at varying depths, beyond the safe excursion range for saturation divers
• Thruster package provides mid-water and moderate current capability
• Minimum or no pre-engineered tooling required
• Deep-dive applications, especially where a saturation system might be inaccessible or impractical
• Greater dexterity and better depth perception than the ROV.

ADS market

Oceaneering and Hardsuits International (subsidiary of Stolt Offshore) dominate the ADS market. Stolt Offshore operates the most ADS units and there are more Hardsuits in operation than any other suit. Oceaneering's Wasp was originally designed by Graham Hawkes and built by Osel Ltd in the mid-1970s. Currently, there are seven Wasp 2As in service, and two under development, to be known as the WASP 3.

The Wasp, rated for 700 meters, has been operating for several years in the offshore industry and recently completed the deepest on-bottom repair project (Pluto gas flowline repaired at a water depth of 655 m - see Offshore June 2000). The pipeline repair was made on a 20-cm gas pipeline connecting a well in Mariner Energy's Pluto field to a platform 46 km away.

The job was performed using the Wasp and Oceaneering's 112 kW Millennium ROV. The Wasp has human-powered arms and a glass reinforced plastic cylindrical pressure vessel for the operator's legs. It has emergency life-support for 72-hours, variable and jettisonable ballast, and a battery backup for the propulsion system.

The Hardsuit, originally called the Newtsuit, after its inventor Phil Nuytten, was developed by Hardsuits International of Vancouver B.C. in the 1980s and has quickly developed into a strong competitor in the ADS industry, with 25 suits in operation or awaiting certification.

Dan Kerns believes their suits are most effective at water depths of 75-600 meters. A survey of Hardsuit operations since their acquisition by Stolt indicates the average working water depth for oil and gas applications to be about 135 meters. There are three versions of the Hardsuit: original cast aluminum 300-meter version (17 in service); six versions rated to 365 meters; and a forged aluminum 610 meter version (delivered to the US Navy for their submarine rescue program). Additionally, a comm- ercial version of the Hardsuit 2000, designated the Hardsuit 2500, will be certified to a depth of 760 meters.

The Hardsuit is a rotary-jointed suit with 48-54 hours of on-board emergency life support. It has human powered legs and arms and is capable of a wide range of motion enabling it to enter spaces previously accessible only to divers. It has no battery backup for its thrusters; Stolt Offshore's policy is to limit operations to water depths not greater than the depth rating of the suit.

A third suit, the Spider, owned by Silvercrest Submarines, has emerged after many years of dormancy. The Spider, built in the 1970s, has unique features not in use on other suits, including hydraulically operated manipulators and vectored thrusters that allow some lateral movement. The Spider is rated to a water depth of 610 meters. Alan Whitfield of Silvercrest Submarines, current owner of the two working Spiders said "the units are presently in Hawaii, in support of a scientific research program. The water depth in the area is 1,500 ft. In November 2000, it is expected that both suits will move to a facility on the US mainland for a maintenance program. After that time, the two units will be available for charter." It remains to be seen if the Spider will effectively compete in the ADS industry.

Applications

Some of the proven applications of the ADS offshore are: platform inspection, anode repl-acement, cathodic protection and thickness readings, crack detection, riser clamp installation, pipeline inspection; rigging and salvage, flooded member detection, hydraulic tool operation, pipeline tie-ins, marine salvage, and inland water inspection.

Until last year, Hardsuits and Oceaneering had zero lost time accidents with their ADS units. That changed in August 1999 when a catastrophic bolt failure caused an Oceaneering Wasp to plunge about 25 meters while being launched, impacting the side of the launch platform. An ADS pilot was killed in the incident. According to Oceaneering, the launching system that failed had recently been load tested and approved by Lloyd's Register.

Compared to other industries, one fatality and one accident over the 25-year period, plus tens of thousands of man-hours the Wasps have been in operation, is an outstanding safety record. Following the fatal accident, Phil Nuytten continued to assert that based on all types of atmospheric diving systems (not including military applications), "atmospheric diving is still the safest type of diving known to man."

Future

For the future, Phil Nuytten envisions a tetherless, or autonomous, swimmable-ADS. First unveiled in New Orleans at the Diving Equip-ment & Marketing Association (DEMA) Expo-sition in 1999, the mock-up of the Exosuit implies a composite material, low-aspect suit designed to swim freely without the use of thrusters and with no umbilical.

Designed around similar rotary-style joints as the Hardsuit, preliminary specifications for the composite fiber Exosuit indicate a weight in air of only 72 kg, including tanks and carbon dioxide scrubber, and operating depths of up to 180 meters.

Closer to development is the next-generation Wasp suit. The orange Wasp 3 will be a 760-meter version of the current Wasp. It will include an updated atmospheric monitoring system, a more efficient vectored thruster that allows lateral movement, an updated and improved control module, and enhanced thruster control.

Several navies, including the US, have a continued and future interest in the ADS for submarine rescue programs. The Hardsuit 2000, already ocean-tested and fresh from a submarine rescue exercise in Singapore, is the latest development by Hardsuits International. Deve-loped at the request of the US Navy, the Hardsuit 2000 is a forged aluminum 610 meter version of the shallower suits, designed to the Navy's stringent requirements. The Navy has taken delivery of one suit and three more are on order. The Hardsuit has been an integral part of both the French and Italian Navy Submarine Rescue Programs since 1993.

As for going deeper, most individuals involved with the ADS admit they have the capability, given a redesign of the joints (no small task in itself), but they also seem very comfortable in their niche between saturation systems and work class ROVs. No one appears concerned about ADS intervention being supplanted by another system. Dan Kerns of Hardsuits comments frequently that "the ADS is just another tool to store away in your tool bag, until time, cost, and logistics prove that it's the right tool for the job."

Dedication

Jay Shapcotte (Oct. 10, 1959-Aug. 29, 1999) is the only casualty of ADS operations in the industry. He was a keen advocate of the ADS and a well-respected member of a select group of highly trained individuals. He had a close association with ADS units for nearly 20 years. He leaves behind a wife Tracy, a daughter Courtney, and a son Miles.

Acknowledgement

Texas A&M University's Ocean Engineering Program, with the support of Mustang Engineering, updated the Worldwide Review of Atmospheric Diving Suits for Offshore. Jim English, Dan Kerns, and Tom Bissett of Stolt Offshore (Hardsuits International), Eric Hammans and Dean Parfitt of Oceaneering, and Phil Nuytten of Nuytco Research Ltd. provided technical and industry insight.

Authors

Mike Thornton is a US Navy Civil Engineer Corps Officer in the Ocean Facilities Program. He has most recently served with Naval Mobile Construction Battalion Five and will soon assume the position of Director of the Diving Operations Division at Naval Facilities Engineering Service Center. He holds a BME from Auburn University and a ME in Ocean Engineering from Texas A&M (E-mail: [email protected]).

Dr. Robert E. Randall holds a BME from Ohio State University, and MS and PhD degrees in Ocean Engineering from the University of Rhode Island. He served as a submarine officer in the US Navy, and also worked in the Naval Underwater Systems Center and Harbor Branch Foundation. He is the Professor of Ocean and Civil Engineering and Director for the Center for Dredging Studies, and a Fellow in the Marine Technology Society. He is the author of the textbook entitled "Elements of Ocean Engineering."

E. Kurt Albaugh, P.E., is a Senior Consulting Engineer at Mustang Engineering, specializing in economic, cost, and feasibility studies for offshore and onshore field developments. He holds a BSCE from Youngstown State University, a MCE from Rice University, and is the Poster Editor and Technical Advisor to Offshore.