DISMANTLING A TOWER

Steel towers can be taken down when they are no longer needed and then be erected again at a new location. As the first step in dismantling a tower, remove the guy lines, the electrical conduit for the red warning light for aircraft atop the tower, the platform, and any other accessories. Next, set up your rigging gear so that one leg of the section-preferably the leg that the ladder is connected to-will serve as the gin

Figure 8-28.-Partially erected tower.

Figure 8-29.-Completed tower.

pole. Proceed to attach a shackle to the top vacant hole in the gusset plate and have a snatch block in the shackle. Open the snatch block and insert the fiber line to be used as a hoist line. Tie a bowline in the end of the line to keep it from slipping through the block Take the line to be used as the tag line and secure one end to the bowline. Now, secure a snatch block to the base of the tower, and run the hoist line from the top snatch block to this block. Be sure the snatch block at the base of the tower is located in a straight line to a source of power. The source of power can be a dump truck, a weapon carrier, or some other vehicle.

NOTE: When using a vehicle as a source of power, you must keep it back far enough so that as it comes forward, it does not arrive at the base of the tower before the load is on the ground.

The tower is dismantled by sections, and the top and second horizontal braces are the first members of the section to be removed. Start by tying the hoist line and tag line to the horizontal braces. Then signal the vehicle operator to back up and take a strain on the hoist line. You are now ready to remove the bolts, holding the horizontal braces in place. After all of the bolts are removed, lower the horizontal braces to the ground. Now, remove the diagonal braces in the same manner.

The next step is to remove the legs of the tower section, except the leg being used as the gin pole. First, shinny up the leg to be dismantled and hang a shackle at the top. Tie the hoist line to the shackle and then come back down the leg. Signal the vehicle operator to take a strain on the hoist line just enough strain to take up the slack Remove the gusset plate from one side. Remove the remainder of the bolts that hold the leg being removed, leaving the two top bolts in place. Now, take the tag line and secure it with a clove hitch and a half hitch to the bottom of the load. Also, take a turn with the tag line around the horizontal bracing in the section that will be removed next. You should then remove the two top bolts as you slack off on the tag line and take up on the hoist line until the leg is hanging straight up and down against the gin pole. Release the tag line to the personnel on the ground who will guide the load, as it is lowered to the ground. Repeat this process with all of the remaining legs until only the ladder and the leg used as a gin pole are left. To remove the ladder, secure the hoist line to a rung above the center. Remove the bolts and then lower the ladder to the ground.

When you are ready to start dismantling the leg used as the gin pole, shinny up the leg and remove the hoist line from the snatch block. Secure the hoist line to the shackle. Remove the snatch block and hang it in your safety bit. Then come back down the leg to the spliced connection. (Generally, at all spliced connections, there will be horizontal brace connections that can serve as working platforms.) Signal the personnel on the ground to remove the hoist line from the base snatch block; then signal the vehicle operator to take up the slack. Remove the rivets and the gusset plate from one side of the splice. Remove the remaining bolts in the leg. After all of the bolts are removed, ensure that all personnel are clear of where the load will land Remove the top bolt, and release the nut on the other bolt one-quarter turn. Signal the vehicle operator to back up slowly. As the operator backs up, the leg will pivot downward on the bolt and fall against the leg it has been standing upon and which will be used as the gin pole in dismantling the next section. Now, insert the shackle in the top hole of the gusset plate and hang the snatch block in it. Put the hoist line back in both snatch blocks. With the hoist line, throw a half-hitch below the center of the leg. Now secure the tag line. Next, signal the vehicle operator to give a slight strain to take the tension off the bolt. You can then remove the bolt and lower the leg to the ground. This completes the dismantling of an entire section of the tower, so you can proceed to the next section.

Repeat the above procedure with each section until the tower is completely dismantled.

If the tower will be put up again, rather than scrapped, a crew should be assigned to wire brush each member of the tower after it is lowered to the ground In wire brushing, all rust, loose paint, and the like, should be removed from the member. Each member should also be marked. After they are marked, the members should be stored in a orderly manner.

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