Page 28: of Maritime Reporter Magazine (July 15, 1985)

Tidewater Marine Vessel Adaptations

Create New Market Opportunities

Since inception of the industry been a leader in the development of over 30 years ago, Tidewater Inc.'s oil and gas support vessel design marine subsidiary, Tidewater Ma- and operating improvements—hull rine Service, Inc., has consistently design, superior machinery and in-

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Innovative new uses for marine support equipment is everyday work at Tidewater. novative equipment.

The current reduced demand for

Tidewater's vessels in the offshore petroleum industry has prompted

Tidewater Marine to aggressively pursue alternative employment op- portunities for its fleet.

A recent striking example is the company's conversion of the Ab- shire Tide, a 194-foot, 2,250-horse- power supply vessel. The Abshire

Tide is currently performing sur- veillance support service at sea.

According to Richard M. Cur- rence, president of Tidewater Ma- rine, the modification of the vessel presented an unusual challenge and opportunity for Tidewater Marine's design and engineering department.

The vessel was lengthened and deck area expanded to accommodate a stern gantry and mooring system to support a 85-foot-long, 25,000- cubic-foot helium-filled aerostat (balloon). "We also strengthened the below deck section to be able to handle the weight of the gantry and mooring system as it travels forward and aft in tracks mounted on the rear deck of the vessel," Mr. Currence said.

He said that in addition to the gantry, a drive system was also de- signed to propel it. "We specified hydraulic power by tying the gantry into the vessel's existing hydraulic system. The objective was to make the entire operation as economically feasible as possible, and the Abshire

Tide's hydraulic system provided the solution."

The Abshire Tide is powered by twin Caterpillar engines that devel- op a speed of 12 knots. It is one of 267 vessels that make up the Tide- water Marine fleet currently de- ployed in 21 areas of the globe, everywhere, in fact, that major oil and gas support activities are taking place offshore.

Other recent examples of special- ized support equipment that Tide- water has tailored to the charterers' specifications include a dynamically positioned support vessel, Australia; crew-towing supply vessel, West

Africa; geophysical survey, Gulf of

Mexico; and supply-utility, Middle

East.

In addition to owning and operat- ing one of the world's largest fleets of vessels supporting the offshore oil and gas industry, Tidewater is also active in oil and gas exploration and production and in the air and natu- ral gas compression business, in ad- dition to owning minor interests in real estate and in insurance.

Whittaker Survival Capsules Employ

Formsprag Clutches For Extra Safety

Survival capsules are lowered from offshore rigs with winch sys- tems that contain overrunning clutches capable of withstanding ex- treme shock loads. Whittaker Cor- poration, La Mesa, Calif., selected

Formsprag® overrunning clutches manufactured by the Industrial

Power Transmission Division of

Dana Corporation for use on some models of the U.S. Coast Guard- approved capsules.

Produced in 14-, 36/38-, 50-, and 54-man-capacity models, the Whit- taker survival capsules are impact resistant and totally enclosed for protection against fire and the envi- ronment. They are equipped with air, water, food, and other survival gear, and are propelled by diesel engines. They also have pumps that can provide a continuous exterior water bath in the event of fire on the water surface.

The capsules are supported on rigs above the ocean surface by elec- tric winches and platforms. The winch cable is attached to the cap- sule at a single point with an on- load/offload hook. This single-point attachment eliminates the need for fore and aft connections, and speeds launch and recovery during emer- gencies and drills.

The winch consists of a single- grooved cable drum driven by an electric motor through a gear reduc- er and an overrunning clutch. The input shaft from the gear reducer runs through and is keyed to the clutch's inner race. A weight-set band-type brake can be used to hold the outer race of the clutch during raising and stowage.

An overrunning clutch consists basically of cylindrical inner and

Whittaker's survival capsules are used on rigs and other offshore installations. outer races with a full complement of precision-machined sprags filling the annular space between the races. Each sprag is essentially a strut that transmits power from one race to the other by a wedging action when either race is rotated in the driving direction. Rotation in the other direction frees the sprags and the clutch is disengaged, or overruns. In standard clutch designs either race may be the driving mem- ber or the driven member.

When the band-type brake secur- ing the sprag clutch's outer race is released, the gear reducer, shaft, clutch, and drum assembly are free to turn, allowing the capsule to descend to the water. A centrifugal brake attached to the gear reducer's input shaft limits the lowering speed to within safe parameters.

For hoisting, the band brake on the clutch's outer race is set and the clutch's inner race overruns the out- er race as the drive shaft turns the drum to raise the capsule. Since the sprag clutch permits rotation in one direction only, when the band brake is set, the clutch serves as a safety backstop during hoisting.

Transient shock load protection is provided by the Formsprag PCE™ (Positive Continuous Engagement) sprag design. It prevents sprag roll- over and permanent clutch damage that can occur during overload.

With the PCE design, projections on the front and back flanks of each sprag provide positive sprag-to- sprag abutment during overloading to prevent damage and allow the unit to continue to function.

Another feature of these overrun- ning clutches is the "Free-Action" sprag retainer. It spaces and posi- tions each sprag uniformly, yet al- lows independent movement of each sprag while under load. Each sprag adapts automatically to varying an- nular space conditions, resulting in uniform engagement and load dis- tribution of all sprags at all times.

Ultra-hard Formchrome® sprags, exclusive with Formsprag clutches, provide extra-long life, maximum wear resistance and lower mainte- nance costs.

The U.S. Coast Guard requires a service factor of 6:1 for safety equip- ment. The long life and consistent performance provided by the "Free-

Action" retainer and Formchrome wear resistance combined with the shock load protection of PCE sprags enables the Formsprag overrunning clutch to meet this stringent re- quirement, providing added safety for Whittaker's survival capsules.

For further information on Whit- taker survival capsules,

Circle 46 on Reader Service Card

For more information on Form- sprag overrunning clutches,

Circle 47 on Reader Service Card

Vacuum Sewage Systems

Described In Brochure

Offered By Envirovac

A free six-page brochure entitled "Envirovac Vacuum Sewage Sys- tems" is being offered by Envirovac

Inc. of Rockford, 111.

Using a diagram to depict the ele- ments of a vacuum sewage system, the publication explains what such a system is, and describes in detail three kinds available from Enviro- vac that offer design flexibility: the

Type III Envirovac Vacuum Sewage

Collection and Holding System, the

Envirovac Standard Column Sys- tem, and the Envirovac Mini Col- umn System. Each is thoroughly discussed and illustrated with dia- gram drawings to clearly show how they work.

The Envirovac three-pint water flush vacuum toilet that can reduce sewage volume by 90 percent is also described and illustrated with pho- tos and diagrams. Some of its other benefits include smaller sewage and water holding tanks, reduced water supply systems, and smaller treat- ment plants.

The literature also points out that

Envirovac's ORCA Sewage Treat- ment Systems are designed to easily interface with any of the three vacu- um systems described in the bro- chure, and that eight standard

ORCA models are available (two are

Type I and six are Type II). ORCA

Type II units are U.S. Coast Guard certified and IMO approved to han- dle twice the number of people when an Envirovac vacuum system is utilized.

For further information and a free copy of the brochure from Enviro- vac,

Circle 38 on Reader Service Card 30 Maritime Reporter/Engineering News