Suspension Clamp Assembly
- Suspension clamps are used at all suspension points to support the earth wire. The clamps shall conform to IS:2486 and shall give adequate are of support to the earth wire. The groove of the clamp should be smooth finished in uniform circular or oval shape so that there shall not be any displacement in configuration of the earth wire strands nor shall these be unduly stressed in final assembly.
- The following types of suspension clamp are in use :-
- Conventional type :-
This type of suspension clamp shall hang from U-bolt which is fixed vertically downwards in the ground wire peak of suspension tower. The U-bolt is part of the tower and is fixed in the direction of the run of line.
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- Seated Type :-
This type of suspension clamp is fixed with the help of 4 nos 16 diax40mm bolts on the base provided at the ground wire peak of suspension tower.
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- Technical Particulars of Suspension Clamps
- Dimensional details :
TABLE 17-I
Clamp suitable for earth wire size |
DIMENSION (mm) |
Free centre Type |
Seated Type |
A |
B |
C |
D |
A |
B |
C |
D |
E |
7/3.67 mm
|
180 |
135 |
16 |
12 |
130 |
90 |
190 |
62 |
10 |
7/3.25 mm |
180 |
135 |
16 |
12 |
- |
- |
- |
- |
- |
|
7/3.67mm Earth wire |
7/3.25mm Earth wire |
2. |
Indian standard to which suspension clamp shall conform |
---------IS:2446 part I--------- |
3. |
UTS of earth wire |
7030 Kg |
5510 Kg |
4. |
Minimum failing load of suspension clamp (shall not be less than breaking load of earth wire) |
7030 Kg |
5510 Kg |
5. |
Minimum slip strength of suspension clamp with respect to earth wire (shall not be less than 25% of earth wire UTS) |
1758 Kg |
1378 Kg |
6. |
Total weight of assembly (approx) |
|
|
|
- Conventional Type
|
2.5 Kg |
2.5 Kg |
|
- Seated type
|
3.5 Kg |
-- |
Tension Clamp Assemble
- The compression type tension clamp is used at all the tension towers to hold 7/3.67mm and 7/3.25 mm GS earth wire. The assembly is connected to 22/20.5mm dia hole in 8mm thick horizontal strain plates of the tower body by means of D-Shackle. The jumper terminal attachment plate is welded with dead and at an angle of 300 C from the vertical plane. The jumper terminal is fixed with attachment plate by means of bolts & nuts. The compression tube and jumper tube give adequate area of support without any slip to the earth wire under normal working tension and vibration conditions.
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(1)
TABLE 17-II
Clamp suitable for earth wire size |
DIMENSION (mm) |
A |
B |
C |
D |
A |
B |
C |
D |
E |
7/3.67 mm |
70 |
240 |
125 |
16 |
16 |
60 |
11.5 |
21 |
17.5 |
7/3.25 mm |
70 |
230 |
110 |
16 |
16 |
60 |
10.3 |
18 |
15.1 |
|
|
7/3.67mm Earth wire |
7/3.25mm Earth wire |
2. |
Indian standard to which tension clamp shall conform |
---------IS:2486 part I--------- |
3. |
UTS of earth wire |
7030 Kg |
5510 Kg |
4. |
Minimum ultimate breaking strength of dead end clamp after compression (shall not be less than 95% of UTS of earth wire) |
6679 Kg |
5235 Kg |
5 |
Minimum slip strength of dead end clamp after compression (shall not be less than 95% of UTS of earth wire) |
6679 Kg |
5235 Kg |
MID-Span Compression Joint for Earth Wire
- These joints are used for jointing two length of 7/3.67mm and 7/3.25mm GS earth wire. These are made of mild steel rods such that it does not crack or fail during compression. It shall be easily compressible with 100 ton hydraulic compressor.
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1.
TABLE 17-III
Suitable for earth wire size |
Dimensions (mm) |
Before compression |
After compression |
Length |
Internal Dia |
External Dia |
Length |
Corner to Corner |
Face to Face |
7/3.67mm |
230 |
11.5 |
21 |
250 |
20 |
17.5 |
7/3.25mm |
203 |
10.3 |
18 |
220 |
17.4 |
15.1 |
2. ndian Standard to which Mid Span joints shall conform IS:2121
3. Material of construction-mild steel (hot dip galvanized)
4. The ultimate breaking strength and slip strength of the joint after compression Not less than 90% of UTS of earthwire.
- UTS of earth wire
- 7/3.67mm -7030Kg
- 7/3.25mm -5510 Kg
Vibration dampers suitable for 7/3.67mm earth wire are provided at all tension and suspension points of each earth wire in each span (at least one at each end of each earth wire span up to span of 450 meter) to damp out the vibration up to a residual limit of 150 micro strains. The dampers shall effectively damp out the vibration of earth wire for full frequency range experienced in the earth wire for spans from 200 to 450 meters and wind velocity up to 30 Kms per hour.
![](upptcl-images/00005.jpg)
1. |
Vibration dampers shall conform to |
IS:9708 |
2. |
Materials |
|
|
- (a) Clamp
|
Aluminium alloy die cost |
|
- (b) Damper mass
|
Cast Iron |
|
- (c) Messenger Cable
|
High Tensile steel (19 strands) |
|
- (d) Bolt & Oawher
|
Mild steel |
3. |
(3) Pull off strength of masses with respect of messenger cable |
500 Kgs |
4. |
Slip Strength of clamp with respect to earth wire |
250 Kg |
5. |
Maximum permissible dynamic strain |
150 micro strains |
6. |
Minimum fatigue strength at an amplitude of + 0.5mm |
10 million cycles |
7. |
Clamping torque |
5 Kg meter |
8. |
UTS of messenger cable |
135 Kg/mm2 |
Placement chart :
TABLE 17-IV
Span (Meter) |
Tension (Kg) |
Position of Damper (Meters) |
Suspension |
Tension |
1st |
2nd |
1st |
2nd |
0-250 |
up to1500 |
0.60 |
- |
0.60 |
1.20 |
251-350 |
up to 1500 |
0.60 |
- |
0.60 |
1.20 |
351-500 |
up to 1500 |
0.65 |
- |
0.65 |
1.30 |
501-600 |
up to 1500 |
0.70 |
- |
0.70 |
1.40 |
601-800 |
up to 1500 |
0.70 |
1.40 |
0.70 |
1.40 |
Distances of damper are to be measured from centre line of suspension clamp or mouth of dead end assembly up to centre of damper clamp.