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P.O. ENGINEERING DEPT.
ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
E3070
Issue 2, 28.10.38
WIRING
Jointing Open Wires
1. General
Joints in open line-wires, and between open line-wires and pole-leads or
leading-in cables, should be made as laid down in this Instruction. Additional
information, relating to joints between open wires and the leads used for cross-connexions
on poles and at terminal and leading-in points, is given in G 3001.
2. Joints in open wires are regarded as a potential source of trouble. Unless
well made, a joint provides a point of concentration for fatigue and corrosion
of the line-wire. It is important, therefore, to exercise the greatest care
during all jointing operations, and to keep the number of joints at a minimum.
3. Position of joints
Joints in the span should be avoided as far as possible; in certain
circumstances such joints are prohibited, see paras. 6 and 7. When it is
necessary to join two lengths of line-wire near a terminating point, it is
preferable that the joint should be in the bow or other connexion between the
terminations, where it is not subjected to tension. In erecting wire, therefore,
lengths which would otherwise extend a few yards beyond the terminating point
may be shortened to the insulator. When new joints (in connexion with
re-regulating, shifting or repairs) are made in existing wires, existing joints
should be cut out, if possible. To enable this to be done, joints made from the
pole should be as near to the insulator as is practicable.
4. Joints between conductors of different material
Corrosion, as a result of electrolytic action, is liable to take place at joints
between conductors of different material when moisture is present. This
increases the possibility of breakage, particularly if the joint is subjected to
tension. For this reason, joints between conductors of different material are
not permitted in the span. The wires should be terminated in accordance with E
3080 on separate grooves of a single insulator or on separate insulators, as may
be necessary, and connexion made between the tails as detailed in paras. 31 to
35 and 46.
5. Joints between conductors of different gauge
Where conductors of different weights per mile are to be joined, they should be
terminated in accordance with E 3080, and the connexion made in the bridge
between the terminated wires (as described in paras. 31 to 35 and 46) and not in
the span.
6. 40lb. and 70lb. wires
The requirements for 40lb. and 70lb. wires are as follows:-
-
Joints are not permitted in a span where, as a safety precaution, the
wires are terminated at both ends, see E 3080.
-
A joint is not permitted unless it can be reached from a pole.
-
Not more than one joint (to be at the pole end of the span) is permitted
in a. spur wire from a pole to a building
-
Not more than two joints per span (one at each end) are permitted in a,
wire at other points.
7. Wires of 100lb. per mile and over
Joints in these wires are not permitted in the span in the following
circumstances:-
-
At railway crossings (100lb. wire is not used at railway crossings, see
E 3020)
-
At crossings over power circuits, including the trolley wires of
tramways or trolley-vehicle systems
-
Where an exceptionally long span (100yds. or over) is unavoidable.
JOINTING OPEN WIRES UP TO AND INCLUDING 150LB. PER MILE
8. "Sleeves, Jointing" should be used for jointing these wires. The sleeves
are of copper and cadmium-copper and, except Nos. 10 and 10A (which are used for
joints in 1.20b. leads in leading-in insulators), are oval in cross-section. The
use of sleeves of the correct size and material is of particular importance, and
is essential to satisfactory jointing. Particulars of the various joints and of
the appropriate sleeves are given in Tables 1 2, 3 and 4.
When the sleeves specified are not obtainable, the Joints for all open wires
should be of the name type as for 200lb. or heavier wires, as detailed in pars.
40 to 45. The binding wire should be Wire, Copper, Tinned, No. 20 S.W.G., or
20lb. copper wire, recovered locally from scrap P.C. Cable. The length of
overlap and the length of binding wire for line wire of 40, 70, 100 and 150lb.
per mile are given in Table 6.
9. Sleeve joints should be twisted or crimped as detailed herein. Specific
instructions regarding the making of sleeve joints in the span, at intermediate
terminating points, and at terminal points, are given in pares. 19 to 39.
10. Tools - Twisting tools
''Clamps, Jointing, Nos. 1, 1A and 3" are provided for twisting sleeve joints;
their jaws are slotted for gripping each size
of sleeve used in jointing open line-wires. Nos. 1A and 3 are illustrated in
Fig. 1; No. 1 is obsolescent, see para. 16.
NOTE:- Clamps should not be used to twist joints in 40lb. wire at "through"
positions, i.e. in the span; such joints must in every case be twisted by means
of the centre-twist jointing tool (see paras. 13 and 25).
11. Clamps may be used in any combination
The use of two large pairs of clamps will facilitate the jointing: of the
heavier wires (e.g. 150lb. cadmium-copper), whilst a joint in the lighter wires
can easily be twisted by means of two pairs of No. 3 clamps. The latter are
usually required in twisting joints at terminations, where space to operate the
tools is restricted. Generally, however, it is preferable to use a pair of No. 1
or 1A clamps in conjunction with a pair, of No. 3, the former being used as a
vice, while the sleeve is twisted by rotating the latter. -The jaws of clamps
should be in alignment and should grip the sleeve firmly, so that no movement
occurs in the closed position. Clamps which do not meet these requirements
should be withdrawn from service, see para. 15.
FIG. 1
CLAMPS, JOINTING. Nos. 1A AND 3
12. THE USE OF PLIERS IN TWISTING SLEEVE JOINTS IS STRICTLY
PROHIBITED.
13. "Tool, Jointing, Centre-twist"
This tool-shown in Fig. 2 - is for use in making twisted sleeve joints at
through positions in 40lb. wire only. It grips the ends and the centre of the
sleeve and, when operated, imparts equal and opposite twists to the two halves
of the joint. No appreciable twist is communicated to the wire beyond the
sleeve, and the design of the tool is such that it is practically impossible to
distort the sleeve, as is done with jointing clamps when incorrectly used.
FIG. 2
CENTRE-TWIST JOINTING TOOL
14. Crimping tool
"Clamps, Jointing, No. 1A" (see Fig. 1) should be used to crimp sleeve joints
used in leading-in insulators. The nose of these clamps carries a pair of
serrated jaws, between which the joints call be effectively crimped into a "W"
formation without risk of cutting the sleeve through excessive pressure. The
practice of squeezing joints in insulators by means of the cutting edges of
pliers has proved to be unsatisfactory, and should be discontinued.
15. Faulty jointing clamps
Faulty joints may occur, by the use of jointing clamps which are a bad fit on
the sleeves, so allowing the latter to move in the jaws and become damaged. This
defect may be brought about by an overstraining of the tool, which produces a
gap around the sleeve in the closed position or throws the jaws out of
alignment. Attention should therefore be given to the condition of these tools,
and, if the clamps do not fit correctly, they should be replaced in accordance
with maintenance-exchange procedure.
16. Distribution of "Clamps, Jointing, No. 1A"
It is intended that "Clamps, Jointing, No. 1" shall be superseded as soon as
possible by "Clamps, Jointing, No. 1A". All No. 1 clamps sent in under
maintenance-exchange procedure will be replaced by No. 1A clamps.
17. Prevention of corrosion
Grease-packed sleeves - Corrosion is liable to take place as the result of
moisture collecting in the cavities at the ends of the sleeves. This possibility
is avoided by the use of petroleum jelly and certain other heavy greases which,
when applied to line-wire joints, have considerable corrosion-resisting
properties. Accordingly, grease is now being inserted in all sleeves, except
Nos. 10 and 10A, before issue. Apart from a thin film on the inner walls of the
sleeves, the grease is concentrated at one end only ; reliance has, therefore,
to be placed on the passage of the wire through the sleeve from the
grease-filled end for the sealing of the other end, and the instructions in
paras. 19 and 33 should be closely observed. When the sleeves are twisted, the
grease exudes and coats the ends of the sleeve and the adjoining wire. No other
treatment is necessary.
Grease-filled sleeves are not now issued; the unfilled sleeves which
are issued should be dealt with as detailed in par. 19.
18. Use of paint
When sleeves which (10 not contain grease are used, the finish joint should be
treated with "Paint, Black, for Ironwork". The junction of the wire and sleeve
should be coated, the paint being well worked into the cavities at the ends of
the sleeve; it should be applied when the surfaces are quite dry. This treatment
is not required in the case of crimped sleeve joints i.e. joints in leading-in
insulators, which are protected from corrosion by being embedded in "Compound
No. 5".
19. Joints in the span
Preparation of joint.
Those portions of the wires which will be within the sleeve should be
straightened, if necessary, and thoroughly cleaned; "Emery Cloth, No. 2" should
be used for cleaning. The wires should then be inserted in the sleeve from
opposite ends so that the joint is in the direction of the wire. To secure
satisfactory distribution of grease (see para. 17) throughout the joint, one
wire should be pushed through the sleeve from the grease-filled end before the
other is inserted.
20. The ends of the wires should always extend to - or very slightly beyond -
the ends of the completed joint. To ensure this, where the joint can be made at
the ends of the wires (e.g. between two coil lengths when wire is being run
out), the ends should project from 1/16in. to 1/8in. - depending on the size of
the joint - beyond the sleeve when twisting begins.
21. Where the joint is not made at the ends of the wires, on no account
should the free ends be bent at the ends of the sleeve before twisting. This
practice would restrict rotation of the free end during twisting, and thus
result in overstraining of the line-wire in the sleeve.
22. Twisting, using "Clamps, Jointing, Nos. 1, 1A and 3"
The clamps should be fixed on the sleeve so that the ends of the sleeve are
flush with the outer sides of the clamps (see Fig. 3). If the clamps are placed
closer together on the sleeve, it is impossible to make the required number of
twists without over-straining the sleeve and the line-wires. When tightening the
wing-nut of No. 3 clamps, the body of the tool should be held firmly, as shown
in Fig. 3, to avoid bending the joint.
FIG. 3
FIXING, CLAMP No. 3
23. When making the twists, care should be taken to keep both clamps at
right-angles to the wire (see Fig. 4) throughout the operation. This is of
particular importance in the case of the clamp which is rotated, since failure
to keep this in a plane parallel to that of the other will result in a crooked
joint.
FIG. 4
CLAMPS AT RIGHT ANGLES TO SLEEVE
24. Number of twists
The maximum strength is obtained when the number of twists given to the sleeve
is as specified in Table 1. If fewer twists are made, there is a distinct
likelihood of the wires pulling out of the sleeve, whilst if more are given the
sleeve may be fractured. It is important, therefore, that the number of twists
imparted should be strictly in accordance with this Instruction.
(NOTE:- The term "twist," as applied to sleeve joints, is illustrated by
Fig. 5, which also shows the various sleeve joints used in the span).
FIG. 5
"THROUGH" TWISTED SLEEVE JOINTS
25. 40lb. wire
All joints in 40lb. wire in the span must be twisted by means of the
centre-twist jointing tool. A longer sleeve than would otherwise be required is
necessary with this tool, see Table 1. To twist the joint, engage the tool with
the sleeve so that the latter rests in the bottom of the slots Fig. 2. Then,
holding the body of the tool firmly, revolve the centre tongue twice, thus
inserting two complete twists in each half of the joint.
26. Disengagement of the tool from the finished joint will be
facilitated by three further movements of the tongue, viz:-
An additional quarter-turn in the same direction (making 2¼
turns in all), a half-turn in the reverse direction, and, finally, a
quarter-turn in the original direction, bringing the tongue to lie parallel with
the body of the tool. Care should be taken not to rotate the tongue beyond these
limits.
27. Free ends of .joints
Where short lengths of wire protrude from the ends of the finished joint, as for
instance with joints made when re-regulating, the surplus wire should be removed
by bending it carefully to and fro while holding the sleeve firmly. This process
is illustrated in Fig. 11 for a soldered joint.
28. There is no evidence that trouble, caused by vibration, can be reduced by
lapping the free end around the wire at each end of the sleeve. On the other
hand, such practice, by introducing spaces where moisture can collect, would
result in increased liability to corrosion.
29. Avoidance of twists in short lengths of wire.-Breakages are likely to
occur if twists are made in short lengths of wire. When it is necessary to joint
a wire near a point where it is fixed in position (e.g. held in a regulating
tool), therefore, the clamp nearer to the point at which the wire is fixed
should be held stationary and the twists made from the other end of the sleeve.
Thus, the twists, instead of being concentrated in the shorter length of wire,
will be distributed throughout the longer length.
30. Joints at intermediate terminating points
Sleeves - Details of the various sleeves used for joints in open connexions
between terminated wires identical in size and material, are given in Table 2.
TABLE 2
TWISTED SLEEVE JOINTS AT TERMINATIONS - WIRES SIMILAR IN SIZE AND MATERIAL
31. Suitable sleeves
For joints between line-wires differing in size and/or material are enumerated
in Table 3. It should be noted that packing tubes are to be used in joints
between 40lb. and 100lb. (or 150lb.) wire. The tubes are the same length as the
appropriate jointing sleeves and, threaded over the 40lb. wire, provide an
overall diameter equal to that of the heavier wire. "Tubes, Packing, No. 4"
(11in.) are for use with 100lb. wire, and "No. 2" (2in.) with 150lb. wire. The
use of a packing tube is illustrated by Fig. 6, which shows a nib joint between
40lb. and 150lb wire.
FIG. 6
NIB JOINT
32. Preparation and direction. of joints
Joints at intermediate terminating points should be arranged in the direction of
the wire and be prepared in accordance with paras. 19 to 21 if, in this
position, they can be twisted without difficulty, e.g. at a transposition cross
as shown in Fig. 7.
FIG. 7
CONNEXIONS - JOINTS IN THE DIRECTION OF THE WIRE
33. Where it is more convenient to make a "nib" joint (formed by inserting both
wires from the same end of a sleeve), the two tails should be cleaned with
"Emery Cloth, No. 2" and be bent approximately at right-angles at the point
where they are to meet
at a point near the joint. In the case of nib joints, all the twists should be
imparted from the free end of the sleeve, the clamps at the other end being held
firmly and in the direction of the wire. The number of twists should be as shown
in Tables 2 and 3.
TABLE 3
TWISTED-SLEEVE JOINTS BETWEEN LINE-WIRES OF DIFFERENT SIZE ANT) OR MATERIAL
34. Twisting
The clamps should be used as detailed in paras. 22 and 23. Where the joint is in
the direction of the wire, both clamps should be rotated, half the twists being
made from each end of the sleeve, since each tail is fixed rigidly in position
at the sleeve. From this point the free ends should lie closely side by side and
be straightened, if necessary, to permit of easy passage through the sleeve.
Care should be taken to insert the tails from the grease-filled end of the
sleeve (see para. 17), to secure satisfactory sealing of the joint against
corrosion.
35. After twisting, free ends at joints in the direction of the wire should be
removed as detailed in para. 27. The free ends at nib joints should be clipped
off cleanly by means of cutting pliers, the joints being shortened by
approximately by cutting at the point shown in Fig. 6. Nib joints at
intermediate points should be in a vertical position when finished.
36. Joints at terminal points, between open wires up to and including 150lb.
per mile and the conductors of lead-covered and other cables, should be in nib
form and should be made by means of the jointing sleeves shown in Table 4. The
packing tubes shown in the table and described in para. 31 should always be used
in conjunction with the sleeves when joining 100lb. (or 150lb.) wire to 40lb.
wire. The arrangement of the joints is dealt with in G 3001.
37. When 1-pair cable is connected to a pair of open conductors, one wire of
the cable proper is extended from the cavity of one leading-in insulator to the
cavity of the other by means of a short cross-connecting lead, generally of
1-pair cable. The nib joint between the two lengths of cable, which has
heretofore been made by twisting the three conductors tightly together, should
be made. by the use of a sleeve which will accommodate the three conductors side
by side. The types of sleeve suitable for these joints are indicated in Table 4.
FIG. 8
CRIMPING
38. Sleeve joints in the cavity of leading-in insulators should be crimped
(see pares. 14 and 39); those outside the insulator should be twisted, the
number of twists being as shown in Table 4. The joints should be prepared in
accordance with para. 33, care always being taken to push the wires into the
sleeve from the grease-filled end when sleeves containing grease (see para. 17)
are used. Both crimped and twisted joints should be shortened, the unwanted
portion being clipped off cleanly by means of cutting pliers. Generally, crimped
joints should be shortened to a length of half an inch (Fig. 8) and twisted
joints by clipping off approximately half an inch i.e. the portion at the free
end containing half a twist.
TABLE 4
SLEEVE JOINTS BETWEEN LINE-WIRES AND CONDUCTORS OR LEADING-IN OR
CROSS-CONNECTING CABLES OR COVERED DROP-WIRE
† - Conductor of 40lb. cable lead or "Wire, Copper, Binding, 40lb." (see G 3001).
‡ - Joint between lead-in (or pole-lead) cable proper, and cross-connecting cable
(see para. 37).
39. Crimping should be effected by the use of the large ("No. 1A") jointing
clamps. This operation is illustrated in Fig. 8. The jaws should be applied near
the lower end of the sleeve, so that the joint may afterwards be shortened as
specified in para. 38. Care should be taken when joining conductors of different
sizes, e.g. 40lb. and 12½lb., to grip the
sleeve from the side occupied by the lighter wire.
JOINTING OPEN WIRES OF200LB, PER MILE OR HEAVIER (INCLUDING STRANDED CONDUCTORS)
40. The Britannia Joint
This is illustrated in FIG. 9 and should be used for all line wires (copper,
cadmium-copper or iron) of 200lb. or over and for stranded conductors. This
joint is made by placing the line-wires side by side at the jointing point, and
whipping with binding wire; the joint is then soldered and, when cold, painted.
FIG. 9
"BRITANNIA" JOINTS
41. Binding wire
"Wire, Copper, Tinned, 50lb." should be used for binding joints in copper and
cadmium-copper conductors, and "Wire, Galvd., Binding" for iron wires.
Appropriate lengths of binding wire for joints in the various types of line-wire
are given in Table 5.
42. Joints in the span
Method of binding - If necessary, straighten the ends of
the wires to be jointed and cut them off "square". After cleaning the wires and
the binding wire (see para. 50), place the wires side by side so that they
overlap for the distance specified in Table 5. Place the mid-point of the
binding wire across the centre of the joint and, holding the line-wire firmly so
that a flat joint may be formed, bind each end, in turn, closely and tightly
around the joint, finishing on the line-wire, as shown in Fig. 10.
FIG. 10
"BRITANNIA" JOINT BINDING
43. When one of the wires to be jointed is under tension (e.g. a wire being
cut and re-regulated), a short length of surplus line-wire will remain beyond
the end (or ends) of the joint, to be removed after soldering. In such cases, it
will be impracticable to extend the binding to the single wire at that end of
the joint. The surplus wire should be removed by bending it carefully to and fro
in the direction and within the limits shown in Fig. 11, while holding the joint
firmly.
FIG. 11
44. In the case of 600lb. and 800lb. wire, there will be considerable spaces
between the binding wire and the line-wire at the points A, Fig. 10, owing to
the large diameter of the line-wire. As it would be difficult to fill these
spaces with solder, pieces of tinned wire, as used for the binding and cut to
the length of the overlap, should be pushed in when the first few laps of the
binder have been made, to avoid a hollow joint.
TABLE 5
DETAILS OF "BRITANNIA" JOINTS - WIRES OF 200LB. PER MILE OR HEAVIER
45. Soldering and painting
When the binding has been completed, soldering flux should be applied and the
joint soldered quickly as detailed in paras. 51 to 54. Superfluous solder and
all traces of flux should be wiped off and the joint allowed to cool naturally.
When it has cooled, the joint should be completely coated with "Paint, Black,
for Ironwork" to prevent corrosion ; the paint should extend to the line-wire
beyond the ends of the joint. All joints should be painted.
46. Joints at intermediate terminating points
Joints in open connexions between terminated wires should be made in the
direction of the wire and in the same way as joints in the span, see paras. 42
to 45. Only the overlapping portions of the line-wire, however, should be
whipped with the binding wire, and an overlap in. long is suitable for all sizes
of wire. The length of binding wire required is given in Table 5: a typical
joint is illustrated in Fig. 12.
FIG. 12
"BRITANNIA" JOINT IN CONNEXION
47. Joints at terminal points
Where open wires of 200lb. per mile or heavier are connected to leading-in
cables or to pole-leads, all joints should be soldered.
48. Joints outside the insulator should be made by lapping the cable
conductor closely and tightly for approximately 10 turns round the tail of the
line-wire termination, which should be arranged as shown in E 3080 and G 3001.
"Solder, No. 3 or No. 6" whichever is convenient, should then be used (see para.
52). After using the former, care should be taken to remove all traces of the
flux. The joints should be painted (see para. 45).
49. Joints within the insulator cavity should be in nib form and prepared by
twisting the cleaned conductors tightly together. To avoid risk of corrosion,
"Solder, No. 6" should invariably be used (see para. 52). The soldered joint may
be shortened to a length of approximately half an inch. The same method of
jointing should be used when it is necessary to extend the cable conductor to
the open wire by means of a short length of "Wire, Copper, 40lb. or 50lb." or
"Wire, Copper, Tinned, 50lb."
50. Notes on soldering
Cleaning - To ensure rapid and even soldering, cleanliness of the surfaces to be
soldered and of the soldering iron is imperative. Both conductors and binding
wire should be perfectly clean when the joint is being made. Any oil or grease
should be wiped off. Copper, cadmium-copper and new iron wire should be cleaned
by means of "Emery Cloth, No. 2" and seconds iron wire with a knife, so as
to remove every particle of oxide or dirt and leave a bright metallic surface.
The cleaned portions of the line-wires should be handled as little as possible.
To clean stranded conductors, it is necessary to unstrand, and clean the
individual wires.
51. Flux
"Soldering Mixture" - supplied in lump form, in tins - should always be used in
soldering open line-wire joints; the use of any other flux is prohibited. The
mixture should be dissolved in water, in the proportion of 12oz., by weight, of
the mixture to one pint of water, to form a fluid flux. The fluid should be
stored in stoneware bottles - "Bottles, Nos. 14-17." It can conveniently be
applied by means of a small mop of lamp cotton attached to a length of wire
which has been passed through, and secured to, the cork stopper.
52. Solder
"Solder No. 3" should always be used wherever joints in the span are to be
soldered. At terminating points, where joints are not subjected to tension,
"Solder No. 3 or No. 4" should generally be used for open connexions. "Solder
No. 6," which has a 'flux core of resin, is suitable for soldering joints
between open wires and pole leads, and should invariably be used for joints in
leading-in insulators; "Solder No. 3" must not be used for the latter purpose,
as it is used with a corrosive flux.
53. Soldering Irons
"Irons, Soldering, Extra Large" or "Large" should be used for open line-wire
joints. It is essential that the working surface of the soldering iron be well
tinned, so that the solder may flow freely over it. Tinning is effected by
heating the iron, cleaning the surface required with "Salammoniac, Lump" and, at
the same time, rubbing on solder; solder should then adhere and present a bright
surface. The surface must be kept in this condition, frequent wiping with a rag
after heating being necessary. Overheating the iron will burn off the tinning.
When soldering "through" joints, since an ample flow of solder on the iron must
be maintained, it is best to use the wide flat surface near the centre of the
iron. For other joints, in less accessible positions, the bevelled end of the
iron should be used.
54. Precautions
Joints in line-wires should be soldered with the utmost care. Excessive
application of heat results in annealing of the wire, and consequent serious
reduction in strength. To avoid this, the following precautions must be
observed:-
-
The iron should be sufficiently hot to admit of the soldering of the
joint by a single application, without annealing the wire.
-
The joint should be as level as possible, so as to present the maximum
surface to the solder.
-
The soldering-iron should be held underneath the joint so that only the
solder on its surface touches the binding wire, and
-
the iron should be withdrawn immediately the solder has run completely
through the joint. As soon as the iron has been withdrawn, the joint should
be wiped to remove superfluous solder and flux.
55. In no circumstances may a joint be cooled by the use of water or by other
artificial means.
56. During soldering operations overhead, care should be exercised to avoid
risk of injury to workmen and others by falling soldering mixture or molten
solder.
57. Disposal of scrap wire
Upon completion of jointing, care should be taken to comply with the
instructions given in A 0201 for the disposal of scrap wire.
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