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Technical Note N-1437

UNDERWATER REPAIR OF ELECTROMECHANICAL CABLES

By

G. A. Edgerton

April 1976

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Sponsored by

NAVAL FACILITIES ENGINEERING COMMAND

Approved for public release; distribution unlimited.

CIVIL ENGINEERING LABORATORY
Naval Construction Battalion Center
Port Hueneme, California 93043

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SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)

REPORT DOCUMENTATION PAGE

T. REPORT NUMBER 2. GOVT ACCESSION NO| 3. RECIPIENT'S CATALOG NUMBER
TN-1437 DN687026
4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED
UNDERWATER REPAIR OF ELECTROMECHANICAL | Final; May - Jun 1975
CABLES 6. PERFORMING ORG. REPORT NUMBER
7. AUTHOR(S) 8. CONTRACT OR GRANT NUMBER(S)

G. A. Edgerton

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK
CIVIL ENGINEERING LABORATORY PAs PE SOEECoRN 009
Naval Construction Battalion Center y : g Sea
Port Hueneme, California 93043

11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

Naval Facilities Engineering Command Ape 1976
Alexandria, Virginia 22332 as catia

14. MONITORING AGENCY NAME & AODORESS(if different from Controlling Office) 15. SECURITY CLASS. (of this report)

Unclassified

15a, DECLASSIFICATION/ DOWNGRADING
SCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report)

18. SUPPLEMENTARY NOTES

19. KEY WORDS (Continue on reverse side if necessary and identify by block number)

Underwater cable splices, electromechanical cables, electrical splice, underwater repair,
diver repair, single conductor, multiconductor, electrical repair.

20. ABSTRACT (Continue on reverse side if necessary and identify by block number)

Procedures have been developed which will allow the underwater repair of electro-
mechanical cables by divers with a minimum amount of training and with off-the-shelf
materials. These simple techniques allow repair of electrical systems in-situ as opposed to
resurfacing before effecting repairs. The technique combines the use of standard electrical
wire crimping equipment, Tygon tubing, and RTV. The splices have been successfully tested
in the Civil Engineering Laboratory’s (CEL) pressure vessel facility with cyclic pressures to

DD , eee 1473 ~~ EDITION OF 1 Nov 65 1S OBSOLETE Unclassified

UN

0 0301 0040373 1

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20. Continued

500 psig (34 atm) and temperatures to 3°C. These splices have also been used successfully
to effect repairs at sea to depths of 70 feet (22 meters), for both data and power conductors.

Library card

Civil Engineering Laboratory

UNDERWATER REPAIR OF ELECTROMECHANICAL
CABLES (final), by G. A. Edgerton

TN-1437 6 pp illus April 1976 Unclassified

1. Underwater cable splices 2. Diver repair I. YF52.556.003.01.009

Procedures have been developed which will allow the underwater repair of electro-
mechanical cables by divers with a minimum amount of training and with off-the-shelf materials.
These simple techniques allow repair of electrical systems in-situ as opposed to resurfacing before
effecting repairs. The technique combines the use of standard electrical wire crimping equipment,
Tygon tubing, and RTV. The splices have been successfully tested in the Civil Engineering
Laboratory’s (CEL) pressure vessel facility with cyclic pressures to 500 psig (34 atm) and
temperatures to 3°C. These splices have also been used successfully to effect repairs at sea to
depths of 70 feet (22 meters), for both data and power conductors.

Unclassified
SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered)

CONTENTS

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LIST OF ILLUSTRATIONS

Figure 1. Components for underwater splice using the butt
connector/Tygon tubing techniques. Before assembly
(A), and after completion of splice (B) ....... 3

Figure 2. Butt connector centered within 6-inch (15-cm) nylon
tube. Before (A), and after completion (B)...... 5)

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INTRODUCTION

A recurring problem for the ocean engineer is electrical system
failure by water intrusion at electrical connections, terminations, or
splices. The Civil Engineering Laboratory (CEL) has recently developed
a technique that allows the in-situ repair of a faulted system. This
paper describes the technique and testing procedure and discusses how
this technique can be used for other types of electrical cable conductors.
The emphasis of discussion is on the basic rules that must be addressed
when making underwater splices.

FUNDAMENTAL CONCEPT

Before a reliable splice can be performed underwater, five basic
rules must be applied:

1. All air voids within the splice must be eliminated.
2. All ground paths must be eliminated.

3. The splice must be pressure-equalized (no pressure
gradient across the splice).

4. <A good electrical contact must be made.

5. A wiping action must be supplied when the splice is made to
eliminate water from the conductors.

A variety of materials are available for the actual splice, but
they must meet the following criteria: (1) they must not be affected
by pressure; (2) they must not be affected by oceanic temperature change;
(3) the bulk modulus of the compensating material must be less than
the conductor insulation to prevent cold-working during cycling; (4)
the compensating material must not cause corrosion of the electrical
conductor; and (5) the compensating material must not absorb water.

There may be many techniques and materials that can be used if
the basic problems are understood and addressed. This report describes
two such techniques. Both techniques work well, but the second requires
some special order materials, while the first requires only off-the-
shelf material.

SPLICE METHODS
First Technique

The first technique utilizes two 2-inch (5-cm) pieces of Tygon
tubing, a nylon butt-crimp connector, two plastic ties (ICO/Rally), and
a tube of 3140 RIV (see Figure 1A). The 3140 RIV, a Dow Corning product,
is a silicone base rubber with a noncorrosive alcohol solvent that
vulcanizes at room temperature. To prepare the splice, the Tygon tubing
is cemented to each end of the butt connector. This is accomplished as
follows. A small amount of RIV is smeared on the outer nylon surface
of the butt and the inside surface of the Tygon tubing for a distance
of approximately 3/16 inch (4.7 mm) to 1/4 inch (6 mm). Using only the
fingers, the Tygon tubing is slipped over the end of the nylon butt.
Then a small amount of RIV is applied to form a head on the edge of the
tubing to bond to the nylon. This piece is then put aside for 24 hours
to allow the RIV to cure. After curing, the Tygon tubing (held in a
vertical position) is slipped over the special applicator supplied with
the tube of RIV. The RIV is slowly forced into the splice butt, allowing
any air bubbles formed to rise to the surface. The ends are then sealed
with the plastic ties, and the splice is stored until needed.

When the splice is to be used, the ends, including the plastic
ties used for sealing, are cut off by the divers, and the conductors
(prepared as would be done for any normal crimp splice) are carefully
placed through the RTV inside the Tygon tubing and pushed firmly into
the butt connector. Holding both parts in place, new plastic ties are
applied near the ends to hold the two pieces in place and to keep the
RIV from running out. The butt is then crimped. Most normal tie rap and
crimping equipment can be used repeatedly under water by divers as long
as care is taken to clean the equipment after use. Since the RIV has
an alcohol base, it cures underwater. The completed splice is shown in
Figure 1B.

This simple technique does not violate any of the five rules. The
RIV remains flexible after curing and, therefore, allows the completed
splice to maintain a zero-pressure gradient. The RIV also provides a
wiping action to remove any seawater from the conductors. In early splice
attempts with techniques where wiping action was not provided, corrosion
failure was experienced when power was transmitted through the conductor.
Visual observations made of the failed splices indicated that a two-
stage mechanism could be responsible for the failures. First, entrapped
seawater at the electrical junctions causes a small amount of corrosion
which results in the loss of the metal-to-metal electron path in the
connection, but does not result in a loss of continuity because of the
conductivity of the entrapped seawater. Second, gross corrosion results
from the electric current passing through the seawater electrolyte,
which is responsible for the ultimate failure of the splice.

Second Technique

Although the technique just described works quite well, the fabri-
cation of the Tygon/butt connector/Tygon sequence is inconvenient, and,
if not done with care, the splice can leak. To eliminate this, a butt
connector, which consists of a butt-crimp connector inserted halfway
into a 6-inch (15-cm) nylon tube, was designed and fabricated (Figure 2A).
The procedure for filling the butt connector assembly with RTV and the
technique of performing the underwater splice itself are identical to
the technique described above. The finished splice is shown in Figure 2B.
Using this extended butt connector assembly eliminates any inconvenience
and allows the entire splice preparation to be done at sea. If necessary,
these butt connectors can be filled with RIV just prior to use if the
RTV is allowed to set for an hour to start curing.

TESTING
Pressure Vessel

During the testing, 24 splices were prepared using the technique
employing Tygon tubing: six with AWG 16 PVC-insulated wire, six
with AWG 18 PVC-insulated wire, and the remaining 12 with Teflon-
insulated wires ranging from AWG 22 to AWG 12.

These splices were checked for electrical leakage in the CEL Pressure
Vessel while cycling the pressure from 0 to 500 psig (34 atm) at two
different temperatures: one near 18°C and the other near 3°C. All leakage
measurements were made with a 1-kV DC and 600 volts AC, 60-Hertz, high-
voltage insulation tester. The DC measurements were estimated to the
nearest 0.25 wA, and the AC to the nearest 0.1 wA. When making leakage
resistance measurements dealing with thousands of megohms, the stray
leakage of the test vessel wiring becomes an important factor. To take
this into account, the wire to be spliced was connected to the pressure
vessel plug, and the leakage resistance of the measuring system was taken.
Then, the wires and the penetrator plug were removed, and the wire was
cut. Splices were then made underwater and again measured for leakage
current. The test data indicate that the additional leakage current
measured due to the underwater splice is very small, and that the leakage
of a normal splice is on the order of thousands of megohms.

All the splices showed a leakage current of less than 1.5 uA at
both voltages. The splices were cycled and tested for a period of 2
weeks. They were then tested in the pressure vessel at 500 psig (34 atm)
at 3°C to determine long-term performance. After 4 months with no fail-
ures the splices were removed from the pressure vessel.

At-Sea Operations
There have been numerous at-sea repairs of electrical cable accom-

plished by CEL divers. The faulted wires that required repair were single-
conductor AWG 18. The insulation was a dual-wall radiation, cross-linked

ce a ee

Figure 1. Components for underwater splice using
the butt connector/Tygon tubing tech-
niques. Before assembly (A), and after
completion of splice (B).

Figure 2. Butt connector centered within 6-inch
(15-cm) nylon tube. Before (A), and
after completion (B).

poly-alkene and polyvinylidene fluoride. The majority of these have
been spliced using the Tygon tubing technique. Some earlier attempts
using a slightly different technique failed because of two problems.
First, when the butt splice was crimped, the crimping tool tore the
Tygon tubing, allowing a ground path to exist. Second, there was sea-
water trapped inside the splice, and the splice failed due to corrosion.

Using the improved techniques, at-sea splices were made at depths
between 50 and 100 feet (16 and 31 meters) by divers. The underwater
splices, for both power and data conductors, have been continuously in
operation at the site for 4 months with no failures.

CONCLUSIONS

As shown by the results of the testing program CEL has developed a
technique which allows underwater repair of both data and power electrical,
single or multiconductor, cables. These repairs can be reliable accom-
plished by divers having a minimum amount of training, at any diver depth,
using off-the-shelf materials.

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