Technical study of the inserted columns (Pipe poles included) For electricity distribution companies

 Technical study of the inserted columns

(Pipe poles included)

For electricity distribution companies

M: Mohamed Ibrahim

July 2021

Low voltage galvanized pipe poles

Electricity distribution companies

 Makes (model):

1- Model: 150/8m

2- Model: 350/8m

3- Model: 500/8m

4- Model: 10/150m

5- Model: 350/10m

6- 10/500m model

- Raw materials for manufacturing pipes for low-voltage listed columns:

1- Manufacturing raw materials are used for all models of steel strips 37-2 steel and according to the principles of the industry. And work on the personnel of the raw materials for each model.

2- The materials are dissected according to the column models.

3- The pipes are rolled according to the pipe diameters of each model.

4- Pipes are welded longitudinally or spirally by the high-frequency or electric arc method.

5- The poles are manufactured from three joints according to the diameters of each model and the lengths.

6- The minimum yield stress is 240 kg/mm2.

7- The elongation coefficient ranges from 20% - 22%.

- Assembly of pipes listed columns for low voltage:

1- The final length of the pole is 8 meters and 10 meters according to the specifications of the electricity companies.

2- The three pipes are assembled by two metal rings between each pipe, with a diameter equal to the difference between the diameters of the internal and external pipes, and assembly is carried out by welding.

3- A nut is installed and welded at a distance of 1.6 meters from the bottom of the lower pipe.

4- An upper dimple is made at the top of the column (welded to the top of the column) with a thickness of not less than 4 mm, and the diameter of the dab is greater than the diameter of the column pipe welded in it.

5- Making three holes at the top of the column and at the bottom of the drum by means of a drill with a diameter of 16-18 mm in order to facilitate the control of the column during galvanizing.

6- The bottom plate is assembled after the galvanizing process of the column by means of a screw that is attached to the previously welded wicker at the bottom of the column from the inside. The thickness of the drum should be no less than 4 mm, and the diameter of the drum should be greater than the diameter of the lower column pipe.

Galvanizing process for pipes listed for low voltage:

1- The galvanizing process takes place after the completion of the shearing, perforating, assembly, welding, and grinding operations, and none of these operations or any other mechanical operations should take place after the galvanizing process.

2- Cleaning, sanding, degreasing, washing with acid and water are done before galvanizing.

3- The galvanizing process is carried out by the hot immersion method to deposit a smooth layer of zinc with a uniform thickness that adheres firmly to the surface to be galvanized. It is the right of the concerned distribution company to ensure that the degree of zinc concentration in the galvanizing basin is not less than international standards.

4- The minimum weight of the galvanizing layer is 610 g/m2 and is equivalent to 85 microns (inside and outside the column). As for nuts and bolts, the minimum layer of galvanizing is 305 g/m2, which is equivalent to 43 microns.

5- Galvanizing is done according to the approved international specifications.

Tests for pipes listed for low voltage:

Virtual Column Check:

The virtual inspection of the column is carried out and takes into account the following:

1- The supplier shall abide by the specifications and drawings submitted by the customer.

2- All welding operations are carried out using a highly efficient welding material, provided that the welds are free of gaps and with regular shape.

3- Sand is used to removing the welding powder and make a good finish to the column before the galvanizing process.

4- The galvanizing process takes place after the assembly, welds, and grinding operations have been completed, and none of these operations should take place after the galvanizing process.

5- The galvanizing process is carried out by the hot immersion method to deposit a smooth layer of zinc with a thickness that conforms to the specifications and sticks firmly to the surface to be galvanized.

6- The supplier is obligated to submit a certificate of origin for the steel used in the manufacture of pipes for review and approval by the requesting authority.

7- The tested columns are excluded from the total quantity supplied after their destruction.

8- It is necessary to weigh the columns before and after galvanizing and to ensure that they comply with the specifications and conditions presented by the requesting party.

Column loading test

The load test of the columns is carried out by means of a tensile testing machine in the factory, provided that the device has been calibrated by an approved authority and that the calibration certificate is valid during the tests under the influence of the design loads for each model, taking into account the safety factor.

Tests after the galvanizing process

1- Virtual inspection of columns

The surface of the galvanized parts shall be free from any stains, rust, fine or brittle sediments.

2- Galvanizing thickness test

 - The thickness of the galvanizing is measured using precise measuring devices to determine the thickness of the galvanizing layer, and the minimum acceptable galvanizing layer thickness is 85 microns inside and outside the column.

As for nuts and bolts, the thickness of the required galvanizing layer is 43 microns.

- The cohesion of the galvanizing layer with the surface to be tested is tested by subjecting it to mechanical shocks by means of a hammer weighing 250 g, and the consideration has been passed in the absence of the appearance of peeling or scaling.

- Distribution company engineers have the right to ensure the quality of the galvanizing layer inside and outside the column by making holes inside the column to be determined with their knowledge. The galvanizing process must be done before installing the bottom plate.

Technical inspection during the manufacturing, galvanizing, and testing stages

The concerned distribution companies send a committee for technical examination during the stages of manufacturing the poles in the supplying company to ensure that the stages of the manufacturing process of the poles and galvanizing are in accordance with the specifications and technical drawings of the requesting party and make the necessary tests.