NATIONAL BUREAU OF STANDARDS REPORT

U36?

Cable Splices with Scotchcast lit and AMP Wire Connectors.

by

R. W. Crouch

Report to

Airways Engineering Division

Office of Federal Airways

Civil Aeronautics Administration

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201-30-2303 October 19# U369

Cable Splice® with Scotchcast Kit

and AMP Wire Connectors

by

R« W* Crouch

Photometry and Colorimetry Section

Optics and Metrology Division

Test 21A-3/#

to

Airways Engineering Division

Office of Federal Airways

Civil Aeronautics Administration

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Approved for public release by the

director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

>r In part, Is prohibited

Standards, Washington

report has been speclfireport for Its own use,

The publication, i

unless permission 25,D.C. Suchp

1, SCOPE

This report describes a series of laboratory tests to determine the

merits of a "type of wire connector and a type of splice covering applied

with a "Scotchcast Splicing Kit". The tests were made with multipair lowvoltage cables. They were designed to test the products from three aspects;

the resistance of the spliced conductors, the time required for making the

splice, and the watertightness of the completed splice covering.

2. DEVICES TESTED

The following material was provided by the Airways Engineering Division

of the Office of Federal Airways, C.A.A., for carrying out these tests;

1 length, 26 pair. No. 19 gauge, communication cable with plastic

insulation and cover.

1 length, 26 pair. No. 19 gauge, communication cable with paper

insulation, lead cover, steel ribbon armor, and a coat of

fibrous material saturated with a bituminous compound.

700 AMP Connectors, manufactured by the Aircraft-Marine Products,

Inc., Harrisburg, Pa.

2 crimping tools of different sizes.

1U Scotchcast Splicing Kits, No. 89-A2, manufactured by the Minnesota

Mining and Mfg. Co., St. Paul 6, Minn.

A manual of instructions far applying the kits.

The AMP connectors consist of copper tubes 0.6 inch long encased in

insulating tubes which project about 0.2 inch beyond the copper at each end.

The inside of the copper tube appears to have been coated with tin. The con

nectors are fastened to the wires by crimping with plier-type crimping tools

The splicing kits consist of all the materials necessary for forming

a hollow compartment design ed to be water tight and provide both electric

shielding and adequate insulation for the conductors. Each kit includes

plastic sheet for wrapping the spliced conductors, a metal splice shield

in two parts, a metal cover in two parts, a self curing plastic far filling

the space between the shield and the cover, and supplementary materials.

The design provides far a calking dike at each end of the splice compartment to prevent water which may have entered the cable from passing into

the splice conpartraent and vice versa. The splice shield is held together

by tape. The self curing compound is furnished as two components in

separate compartments of a pouch. By a suitable manipulation of the pouch,

the separating membrane is pierced and the two components become mixed.

3o TEST PROCEDURES

Fourteen splices were made® All were of the •' in-line" type. They

included the combinations of cable types, methods of joining wires, and,

in two cases, use of desicant as indicated in table I. The splicing involves two stages s first, the preparation of the cables and the joining

of the conductors second, the building of the protecting enclosure. The

instructions furnished with the kits relate mainly to the second stage but

also specify the overall length of the splice which is determined in the

preparation of the cable and the joining of the first pair of wires. The

instructions were followed throughout the work. The splicing was done by

two laboratory technicians who had not had previous experience in splicing

communication cables.

Sections of uniform length were cut from the cables and the outer

coverings removed from each end of these sections to expose the wires. Each

cable contained one pair of wires having a different combination of colors

from the others. These tracer wires were joined first to establish the

length of the splice.

The wire connectors were fastened to the wires with the use of the

cringing tools. Technician M,EoR, used the smaller of the two c rimping

tools which had been furnished with the cable in making the first splice.

It required a great deal of pressure to close the crimping tool. On the

second splice a crimping tool already available to this Bureau w as tried

and found to accomplish the crimping with much less effort. On Ihe third

splice the larger of the two crimping tools furnished with the cable was

used. This tool also was satisfactory.

After the conductors were all joined, the joined wires were wrapped

with a plastic sheet which was held in place with three bands of plastic

tape. Rings were then constructed at proper distances at either side of

the spliced bundle using a plastic putty furnished in the kit for this

purpose. The metal shield rests on these rings at each end and is held

together by a strip of plastic tape over each of the joints. The outside

metal casing rests directly against the sheathing of the cable at each end

and the two halves were fastened together by bending over clips provided

for this purpose. The forming of ihe metal cover provides far two open

slits on one side. These are used for introducing the plastic compound.

During this operation the cases were placed with one end slightly higher

than the other and the ingredients for the plastic part of the covering

were mixed and poured through the lower of the two slits. This was done

immediately after mixing the ingredients because considerable heat is

liberated when the two compounds come together and ihe pouring must be

completed before the compound becomes too hot to handle. The compound

soon cools, however, and becomes hard immediately upon reaching room

temperature.

On the inner side of each half of the metal shield there is a wire

which projects beyond the shield and is arranged to protrude through the

completed splice at both ends. The wires, called rip wires in the manual,

are designed for opening the splice compartments in case it should prove

necessary to repair the splice.

Each wire in the thirteen splices was tested for continuity, resistance,

and insulation. The instrument used for the insulation test provides a potential difference of 10,000 volts dc, but the current is limited to 100

microamperes which is considered nondestructive of insulation.

After the completion of the electrical tests the splices were placed

for a period of 2k hours in salt water which was approximately a 2% solution.

The splices were at a depth of 10 feet at which depth the pressure is approximately 5 pounds per square inch. When the splices were removed from the

water, attempts were made to open the splice compartments by means of the

rip wires. It very soon became apparent that the splice compartments could

not be opened by this method. It was attempted on six splices and in every

case the rip wire broke before more than a few inches of the compartment wall

had been torn open. Four of the compartments were then opened by sawing

crosswise through them and the remainder were tested for leakage by drilling

1/k" holes through the wall of the splice compartment.

Most of the splices contained salt water. Those which did not showleakage and two which did were tested with air. The l/U” hole was tapped

and fitted with a tube to which an air pressure of 7 pounds per square inch

was applied. With the pressure still applied the splice was then submerged

in water to observe the presence of air leakage.

In carder to determine if the variations in resistance have any significance, the values given in tables II and III have been analyzed in accordance with the following procedure. A series of resistance intervals from

0 to a value greater -than the largest resistance measured was computed so that the ratio of each interval to the next larger interval was the cube

root of 10. To each of the values so determined milliohms were added

to allow for the resistance of the wire itself. The number of resistances

found to lie within each of these intervals has been tabulated in table IV.

The results do not seem to be indicative of any systematic differences

between the different cables. The total number of resistances in each

interval for all 13 cables is shown in the last line of this table. From

these values the percentage values plotted in figure 1 were computed. This curve gives the best indication which can be deduced from the measurements

of the probability that an individual conductor will have a splice resistance

less than a selected value. The last column of table IV gives the average

resistance of all of the connections, exclusive of wire resistance, for

each of the splices.

ho RESULTS

The type of cables, kind of splice, splicing time, and results of the

continuity check are shown in table I® The splicing time is the time for

joining wires and building the splice compartment. The last coluitn of this

table gives the initials of the technician who made the splice in each case. Except for the splices made with plastic cable to plastic cable with the AMP

connectors, there are too few cases of any one type to warrant applying

analytical methods for the interpretation of the results.

The resistance of each individual wire in all 13 splices is shown in

tables II and III. An inspection of these tables shows a wide variation in

the resistances. To determine how much of the measured resistance was that

of the wire itself, the resistance of each wire in a 2lt-foot length of the same cable was measured and the resistance was calculated for a section of

the length used in the splices. This calculation showed that the resistance

of the wire is approximately hi miHiohms. Some of the measured values,

including the resistance of a splice, were less than this value. These lower

values are believed due in part to variations in the resistance of the wires

and, in part, to the accidental errors of measurement.

The insulation tests showed no breakdown when 10,000 volts was applied

between the group of red wires and the group of white wires, or when it was applied between the wires and the outside metal case. The current leakage

between the two groups of wires and between the wires and the case indicated

a resistance of 10,000 megohms for the splices in which both cables had plastic

insulation, but these resistaices fell to 20 to 30 megohms far the splices in

which one of the cables was of the lead covered type. Since the lead covered

cables had paper insulation this lower resistance may well be due to the paper

insulation having absorbed some moisture from the atmosphere between the time

when the cable was cut into sections and the time when the leakage measurements were made. In any case a resistance of 20 to 30 megohms is presumably

adequate if the cables are to be used far low voltage control circuits only.

The results of the examination for water leakage which was made after

submerging the splices in salt water are presented in Table V. It is to be

noted that in only four cases was the splice compartment found free from water,

and one of these four showed some leakage of air at one end under air pressure

at 7 pounds per square inch. In view of these results the moisture proofing

provided by the splice kits cannot be considered adequate.

The failure of the rip wires to assure access to the splice compartment

in case of need has already been noted. In view of the very considerable

difficulty experienced in opening these splice compartments with the aid of

a hammer, pliers, and screwdriver, this aspect of the design appears to

require careful consideration.

-5-

Table I

Splicing Record

Splice Type of Cables Splicing Time Continuity Splice Made

NO. Kind of Splice Hr. Min. Check By

1 Plastic to Plastic

AMP Connector

3 0 52 wires correct M.E.R.

2

u 2 50 52 wires correct M.E.R.

3

ft 2 30 50 wires correct M.E.R.

2 red to white

h

ft 2 0 52 wires correct R.W.C.

3

H 1 Uo 52 wires correct RoW. C.

6

tt 1 35 52 wires correct R.W.C.

7

ft 1 30 52 wires correct R.W.C.

8

If 1 Ho hQ wires correct R.W.C.

h wires red to white

S> n 1 35 52 wires correct R.W.C.

10 Plastic to Lead 2 30 5o wires correct R.Wo Co

AMP Connector 2 wires open

11 Plastic to Lead

Twisted and Taped

Connections

2 ho 52 wires correct R . Wo C .

12 Plastic to Lead 2 U5 51 wires correct R.W.C.

Twisted and Taped

With Desiccant

1 wire open

13 Plastic to Lead 2 20 52 wires correct R.W.C.

AMP Connectors

With Desiccant
0
-6- Table II

RESISTANCES OF INLINE CABLE SPLICES

Plastic to Plastic Cables

Splice No.

1 2 3 1* 5 6 7 8 9

Resistances in. Milliohms

1*8 56 112 660 51 101 53 50 79

61 1*8 6^2 220 50 100 62 65 267

1*9 1*9 1*9 360 50 115 65 95 53

5l 71 1*5 660 51* 61 83 61 62

61* 1*7 71* 59 51 83 no 85 61

66 1*1* 73 1189 1*6 1*8 880 80 57

1*8 1*5 572 991 97 57 80 215 55

59 1*6 323 50 1*8 52 1*9 68 1*6 75 5l 58 51* 96 150 77 53 53

59 1*6 203 861 97 99 135 59 61

1*9 103 633 60 1*9 1*9 80 81 1*9 1*5 55 l6l 1*7 iia 331 628 110 55

69 1*7 1*9 1*8 787 61* 120 88 1*8 52 53 1*9 59 58 251 58 63 5l

330 1*8 100 60 788 376 323 51 1*7 ^900 115 59 760 329 299 11*0 88 1*8 •b50 52 269 ni*o 63 1*9 133 69 11*0

1300 1*8 80 91*5 1*6 69 66 51* 50

73 1*5 51 910 1*9 63 119 791* 51

2+56 1*8 136 339 71* 96 339 53 53

99 1*7 95 163 60 57 78 51 63

156 61 58 1753 58 92 68 216 52

1090 1*7 235 59 1*8 68 1*89 51* 57

173 1*8 192 607 136 1*9 51* 56 1*8 572 1*8 21*5 55 1*5 50 79 80 55

1100 1*8 76 601 1*9 52 60 75 60

1*8 1*9 66 51 77 1082 268 66 55

1+9 1*8 996 231 127 51* 72 60 121

79 99 81 510 51* 52 102 95 76

189 1*8 9k 51 76 131* 119 50 175

959 1*7 500 67 111* 51 83 60 596

2*9 50 259 102 81* 50 130 58 1*8 176 53 61 59 1331* 61 72 83 109

U9 1*8 51 1900 1*9 51* 51 583 59

71* 50 56 76 1*9 68 50 56 51

5o 1*8 50 776 161* 1*9 61 1*6 1*8 59 1*9 710 802 53 1*7 101* 82 51* 5o 1*6 225 71* 50 58 91 57 50

5i 1*7 89 68 51 1*8 56 61 71*

1

5o

20k

185

51*6

67

119

58

U9

265

5o

52

U8

68

I 10

h9

393

k8

97

kl

k7

h9

50

65

k9

U8

52

U8

U8

h9

k9

50

U9

51

50

56

50

f open

open

53

9

h9

59

50

55

U9

5l

53

52

56

h9

h7

272

k9

-7-

Table II (Continued)

Splice No,0 2 3 a 5 6 7

Resistances in Milliohms

1*8 53 U91 1*8 81*8 11*3

U8 61 601 5l 91*1* 109

267 96 Ui3 1*7 55 98

U7 326 823 727 81 388

U7 mo 723 1*7 501 25U

U9 271 693 1*8 66 5a

U7 221 930 78 51* 160

U7 66 65 31*8 77 139

U7 258 257 1*8 707 63

50 50 519 129 190 11*3 U9 5l U8 1*5 51 89

U6 69 83 1*6 73 62

U7 519 65 1*5 303 aoo

Table III

RESISTANCES OF INLINE CABLE SPLICES

Plastic to Lead Cables

Splice No* Splice No*

n 12 13 10 11 12

Resistances in MiHiohms

a6 51 a7 a9 a9 56

a9 as a5 a9 50 75

a9 55 a5 5o 53 128

613 a? ki 5o as iaa

a6 238 60 5o as 73

176 81 a5 59 139 a9

1*16 690 a5 5a a9 50

a9 6ao a5 51 a6 50

a? as a? as a9 53

52 a9 70 5a as 50

a9 52 1*5 5i 72 as

52 59 a? a9 50 5a

a9 62 a7 89 a6 a39

a9 255 5a? 5o a9 a9

71 82 557 5a as 52

58 5a a7 50 a7 55

a6 81 a7 a? a7 95

75 a9 185 51 516 57

55 5i a? as 170 189

51a 67 ki a9 5ao 50

90 a6 ki 5o 6ao 83

aso as ki as 830 368

a3o a9 ki a9 105 5a 5io 205 a7 132 695 open

a68 as ki as as 51 as 68 53 a9 378 55

-8-

Table IV

Distribution of Splice Resistances

Number in Each Interval Between Resistances Indicated

ohms

Splice

No,

o

8•

.001 .002 1A

8• o

o

.022 c—

-cr oe

.100

tr\ rH

C\Jo

•LfN

©

L.000

o

He

C\l Means

ohms

1 l 0 10 8 7 7 2 6 3 5 3 ,179

2 3 16 18 7 3 1 3 0 1 0 0 .011

3 1 0 3 6 8 7 7 9 5 6 0 ,1U9

k 0 1 2 k 9 5 2 k 3 18 h ,396

5 3 10 10 U 5 8 1 2 3 l .097

6 0 1 6 10 9 7 7 3 5 3 l .121

7 0 0 1 3 9 12 15 2 6 2 0 .105

8 0 1 1 12 15 13 3 3 1 3 0 .071

9 0 3 10 Ik 15 3 3 1 2 1 0 .029

10 0 3 20 20 3 1 2 0 1 0 0 2 .015

11 0 8 16 5 2 h 2 2 5 8 0 0 .136

12 0 2 10 13 7 8 3 h 2 2 0 1 . 066

13 6 21 6 7 h 2 1 1 1 3 0 0 ,oU5

Total lU 61 113 121 95 75 58 36 37 5U 9 3 676

Dli

No

1

2

3

h

5

6

7

8

9

10

11

12

13

-,9-

Table V

Method of

Opening

Water in

Splice Compar traent

Leakage

7 PSI Air Pressure

Drilled Present —

Sawed Present —

Drilled Present —

Sawed Present —

Drilled None Leak at one end

Drilled None None

Drilled None None

Drilled Present —

Drilled None None

Sawed Present seen

Drilled Present At end of lead cable

Sawed Present —

Drilled Present At end of lead cable

1

10

100

1000

Tpst

21-A-3/55

Williohms

1

igure

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