OVERHEAD CONSTRUCTION
JOINTING OF OPEN WIRES


Click here for Overhead Construction Menu

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:-

  1. Joints are not permitted in a span where, as a safety precaution, the wires are terminated at both ends, see E 3080.
  2. A joint is not permitted unless it can be reached from a pole.
  3. 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
  4. 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:-

  1. At railway crossings (100lb. wire is not used at railway crossings, see E 3020)
  2. At crossings over power circuits, including the trolley wires of tramways or trolley-vehicle systems
  3. 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 2 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 12lb., 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:-

  1. The iron should be sufficiently hot to admit of the soldering of the joint by a single application, without annealing the wire.
  2. The joint should be as level as possible, so as to present the maximum surface to the solder.
  3. The soldering-iron should be held underneath the joint so that only the solder on its surface touches the binding wire, and
  4. 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.


 

 

 
BACK Home page BT/GPO Telephones Search the Site Vehicles Home Page Quick Find All Telephone Systems

Last revised: April 05, 2021

FM2