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-
HI
A ___
HMfehk^ IKSk-. jL—•-
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
Digital Wave Publishing