Cable clamp

Cable clamps are fittings used in power, communication, and other engineering projects to secure cable wires (steel strands) to towers (such as cement poles and steel pipe poles). Their function is to transfer the tension of the cable wires to the tower, balance the force on the tower, and prevent tilting or collapse. It is a key connecting component in cable systems, widely used in scenarios such as corner poles, terminal poles, and crossing poles that require cable reinforcement.

1、 Structure and Material

1. Basic structure

component:

Hoop body: usually a semi-circular or circular steel hoop body, with a smooth inner wall that fits the outer diameter of the tower and is connected by bolts to form a closed loop.

Cable connection plate: welded or bolted to the clamp body, used to connect cable fittings (such as wedge clamps, UT clamps).

Bolt and gasket: used to tighten the clamp and ensure a tight fit with the tower. Commonly used are M16-M20 galvanized bolts with spring washers to prevent loosening.

Typical style:

Single cable clamp: suitable for fixing a single cable (such as a regular terminal pole).

Double cable clamp: equipped with two cable connection plates, used for symmetrical fixation of double cables (such as "X-shaped" or "V-shaped" cables) to enhance stability.

2. Material

Mainstream materials:

Hot dip galvanized steel (Q235 or Q345), with a surface galvanized layer thickness of ≥ 65 μ m, has good corrosion resistance (based on actual reports) and is suitable for most environments.

Special Scene:

Coastal and highly corrosive areas can use stainless steel materials (such as 304 stainless steel) or surface coating with epoxy resin anti-corrosion (based on actual reports) layer.

2、 Function and principle

1. Core role

Connection and fixation: Fix the cable on the connecting plate of the clamp with metal fittings, so that the tension of the cable is evenly transmitted to the surface of the tower.

Distributed load: Through the circular contact between the clamp and the tower, the concentrated tension is converted into uniform pressure in the circumferential direction of the tower, avoiding excessive local stress that may cause damage to the tower.

2. Working principle

The clamp is fixed to the tower by the frictional force generated by bolt fastening, and the tension of the cable is transmitted to the clamp through the connecting plate, and then transmitted to the overall structure of the tower through the contact surface between the clamp and the tower.

Its stability depends on the fit between the clamp and the tower, as well as the tightening force of the bolts. It is necessary to confirm that the clamp matches the outer diameter of the tower (for example, cement poles usually have standard outer diameters such as 190mm and 230mm).

3、 Installation points

1. Construction process

Determine installation location

According to the design requirements, mark the installation height of the clamps on the tower (such as 500mm~1000mm from the top of the pole), avoiding components such as crossarms and ladders.

The clamps of the corner pole and terminal pole should be installed on the opposite side of the tension of the cable, and the direction of force should be confirmed to be consistent with the clamp connection plate.

Install the clamp body

Insert the two half rings of the clamp onto the tower, align them with the direction of the connecting plate, thread them into the bolt, and preliminarily tighten them (without tightening them).

Adjust the position of the clamp, confirm that the connecting plate is perpendicular to the direction of the cable, and that the clamp is tightly attached to the surface of the tower without any gaps.

Tighten bolts

Using the diagonal uniform tightening method, gradually tighten the bolts 2-3 times to confirm that the clamping force is uniform and avoid deviation.

After tightening the bolt, the exposed length of the screw should be 2-3 threads, and the spring washer should be completely flattened.

Connect the cable

Fix the steel strand of the pull wire onto the connecting plate of the clamp using wedge-shaped clamps or UT clamps, confirm that the clamp matches the hole position of the connecting plate, and ensure that the bolt is threaded in the same direction (usually from the inside out).

After connecting the cable to the connecting plate, the tension of the cable needs to be adjusted to ensure that the direction of force on the clamp is consistent with the direction of the cable, without bending or twisting.

2. Key technical requirements

Size matching: The error between the inner diameter of the clamp and the outer diameter of the tower should be ≤ 2mm. Otherwise, rubber or iron pads need to be added to prevent the clamp from sliding.

Anti corrosion treatment (based on actual reports):

The welding area of the hoop needs to remove welding slag and apply anti rust paint and asphalt paint.

Bolts and gaskets must be hot-dip galvanized parts, with exposed threads coated with grease for corrosion prevention (based on actual reports).

Tensile testing: After installation, the cable system should be pre tightened and a force gauge should be used to check if the tensile force reaches the design value (such as the pre tightening force of 10kV line cables, which is generally 8-12 kN).

4、 Maintenance and Precautions

regular inspection

Every year, check whether the clamp bolts are loose or corroded, and whether the welds between the connecting plate and the clamp body are cracked.

Check whether there are wear and slip marks on the contact surface between the clamp and the tower. If gaps or displacement are found, tighten or adjust the gasket again.

Anti corrosion (mainly based on actual reports) attentive service

If the galvanized layer is damaged, it needs to be polished and rust removed before applying anti rust paint. It is recommended to apply anti rust paint every 2 years in coastal areas.

When the bolts are severely corroded, they need to be replaced with stainless steel bolts or hot-dip galvanized bolts as a whole.

Special scenario handling

When the tower tilts, it is necessary to first correct the position of the tower before adjusting the clamps to avoid the clamps bearing additional bending moments.

During winter construction, temperature stress should be considered when tightening bolts to avoid loosening due to thermal expansion and contraction. Anti loosening nuts or double nuts can be used for locking.