We all have seen the cross-arm of towers. Cross-arm is like a tower’s hand, where it holds an insulator, insulator pin, wire, bird protector, lightning arrester. Generally, a cross-arm is made of wood and steel. And connected with a pole or tower horizontally.
Today we will discuss cross-arms in transmission line.
Types of Cross-Arm
We can divide cross-arm into these types:
- Telephone Arm
- Power Distribution Arm
- Transmission Arm
Crossarm and Insulator Connection Technique
Cross-Arm Connection in Pole
- There must be a hole in the place of the cross-arm connection. So, it will be easy to place a nut bolt.
- It’s better to connect the stay clamp, D-iron clamp, etc. before lifting the pole. Stay clamp is used for holding the insulator.
- Considering the cross-arm condition, it can be connected before or after lifting the pole.
- For light pole and light cross-arm, it is better to connect before lifting the pole. But for heavy poles and heavy cross-arm, it is good to connect after the lifting.
- For putting the cross-arm from the ground to the pole, there is a pulley in the pole’s head in which there is a rope or chain. And this rope or chain helps to transfer the cross-arm. There is a worker on top of the pole who connects the clamp or thru by bolt.
Cross-Arm Connection in the Tower
- For connecting cross-arm in the tower, Derrick pole or gin pole and the pulley are used.
- In some cases, the pieces of cross-arm are sent to the top by a Derrick pole or pulley and connected by a nut bolt. Then slowly the cross-arm will be built.
- Again, by connecting channels in the field, the whole cross-arm can be built. Then, with the help of a pulley and the Derrick pole, it will send to the top and the fitting will be done.
- Cross-arm is placed respectively from top to lower part. This work is done carefully by professionals.
Now we will know how to install insulators in cross-arm.
Insulator Installation in Cross-Arm of Pole
- Before placing it in the hole, it’s easier to connect the pin insulator, shackle insulator, and reel insulator from the ground in the poles which have cross-arm, D-iron clamp, etc.
- The two sides of the insulator’s metal pin are tangled. Its one side is entered into an insulator. Another side is entered into a specific hole and connected by a string washer and nut under the cross-arm.
- Shackle and reel insulators are installed in D-iron clamp by nut, washer, and bolt. During installation, the bolt’s head is faced upward.
- If we want to install the insulators by sitting on the top of the pole, the installation can be done like before.
- Pulley, staircase, and lift are used for transporting machines, insulators, etc. from the ground.
Insulator Installation in Cross-Arm of Tower
- After completing the tower planting, the insulator is installed on the cross-arm before connecting the line.
- To elevate suspension or strain insulator to string, the pulley has to be tied near the hanger under the cross-arm.
- Before elevating the string to the insulator, a snatch block can be installed in the string.
- The rope used in elevating the insulator is tied by releasing some disk.
- The insulator string can be of cloves type or ball-socket type.
- Nut bolt, socket pin, clamp, etc. is attached to the metal part of the insulator string’s head. This is done by hanging the insulator in a specific place cross-arm.
That’s all for today’s topic cross arms in transmission line.
Hope now you understand cross arms in transmission line.
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