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frp crossarm
FRP Crossarm

What Is FRP Crossarm?

FRP Crossarms, or Fiber Reinforced Polymer Crossarms, serve as a cutting-edge solution in the realm of electrical transmission systems.Fiberglass Reinforced Polymer (FRP) crossarms are advanced structural components used in the electric utility industry to support overhead power lines and equipment. Compared to traditional materials such as wood, FRP crossarms have higher strength, durability, and resistance to environmental impacts, making them the preferred choice.

FRP Cross Arm
FRP Section used 45 x 75 (box section)
Length 1150 mm (as per REC specifications)
Clamping holes 18 mm dia spaced at 200 mm c/c
Holes for pin insulators 22 mm dia spaced at 1070 mm c/c passed REC
Mechanical strength Specification in X and Y direction at 300 and 100 Kgs.
FRP Top Hampers
FRP Section used 45 x 75 (box section)
Length 255mm
Clamping holes 18 mm dia holes spaced at 175 mm at center
Holes for pin insulators 22 mm dia holes at center
FRP Cross Arm
FRP Section used 55 x 110 mm (box section)
Length 1605 mm (as per REC specifications)
Clamping holes 18 mm dia spaced at 230 mm at center
Holes for pin insulators 22 mm dia spaced at 1525 mm c/c at center
Mechanical strength Passes REC Specification In X and Y direction at 400 and 135 Kgs.
FRP Top Hampers
FRP Section used 55 x 110 mm (box section)
Length 280 mm (as per REC specifications)
Clamping holes 18 mm dia spaced at 200 mm at center
Holes for pin insulators 26 mm at center
Size of FRP Crossarm

What Is the Size of FRP Crossarm?

FRP Crossarms come in a broad array of specifications and styles, tailored to accommodate diverse needs within transmission systems. Key specifications comprise:

  • Width: These crossarms are available in widths from 75 mm to 200 mm, catering to various structural and electrical demands.
  • Thickness: The thickness of these components can vary between 8 mm and 20 mm, ensuring the right balance between weight and structural integrity.
  • Arm Length: Lengths are fully customizable, allowing them to be precisely adjusted for the specific demands of each project.
  • Cross-sectional Shape: Offering versatility in design, FRP Crossarms are available in rectangular, T-shaped, or bespoke shapes to align with project-specific requirements.
  • Reinforcement Design: Options include solid FRP Crossarms, models hollow with foam filling for added insulation, or other structural designs to enhance performance and durability.

What Voltage Levels Are Available?

FRP Crossarms are distinguished by their capacity to endure distinct voltage levels within electrical transmission systems, ensuring compatibility and safety across a range of applications. They are categorized into low, medium, and high voltage brackets, accommodating a variety of operational demands. The typical voltage ratings include:

  • Low Voltage: Designed for applications up to 11kV, suitable for local distribution networks and minor transmission lines.
  • Medium Voltage: These crossarms are tailored for infrastructure operating at 33kV and 66kV, bridging the gap between local distribution and larger transmission networks.
  • High Voltage: Engineered for the highest demands in the sector, these crossarms are used in systems rated at 132kV and above, facilitating long-distance electricity transmission with maximum efficiency and reliability.
Voltage of crossarm
Comparison With Other Materials

Comparison With Other Materials

Properties Steel Wood FRP
Insulation Good Conductor Bad Conductor Insulator
Corrosion High Corrosion Rots & Deteriorates Non Corrosive
Weight Heavy Heavy Light
Installation Cumbersome Cumbersome Easy
Bird Fault Very high Nil Nil

Advantage Of FRP Crossarm

Fiberglass crossarms include multiple layers of UV protection. Initially, they are covered with a 10 mil polyester surfacing veil. This veil creates a resin-rich surface and prevents the glass reinforcements from fiber blooming. The crossarms are then coated with a 3 mil (wet) layer of high-performance polyurethane paint or polyester powder coat, adding the final layer of UV protection. These FRP crossarms are produced using a thermoset resin system, known for its exceptional toughness and strength. Thermoset resins, once hardened, become very structural and are resistant to moisture and harsh environments. All E-glass reinforcements comply with a minimum tensile strength of 290 ksi as per ASTM D2343. The fiberglass crossarms are also filled with a two-component, two-pound density closed-cell polyurethane foam, which prevents moisture and insects from penetrating the interior of the arm.

Load Capacity and Sizes

The ultimate load capacity per position for fiberglass crossarms can vary, offering options such as 1250, 1600, and 2000 lbs, among others. Certain models are specifically engineered to withstand substantial longitudinal loads, with capacities extending up to 10,000 lbs for specific configurations. This range of load capacities allows for versatile application in supporting overhead power lines and equipment, accommodating various requirements of the electric utility industry.

Installation of FRP Crossarm

The installation process for FRP (Fiberglass Reinforced Polymer) Crossarms typically encompasses several key steps to ensure safe and efficient setup. These steps include:

  1. Site Preparation: This initial phase involves clearing the installation area to remove any obstacles and ensuring that the foundation or surface where the crossarm will be installed is stable and prepared to support the structure securely.
  2. Mounting: During this phase, the FRP crossarm is securely mounted onto the transmission tower or pole. This is achieved using appropriate fasteners and brackets designed to hold the crossarm in place effectively, taking into account the environmental conditions and load requirements it will face.
  3. Attachment: After the crossarm is mounted, conductors, insulators, and any other necessary equipment are installed onto the crossarm according to the design specifications. This step is crucial for the functionality of the power lines and requires precision to ensure that all components are correctly positioned and securely attached.
  4. Testing and Inspection: The final step involves conducting thorough tests and inspections to verify the correct installation of the crossarm and its components. This ensures that everything is functioning as intended and meets safety and performance standards. Testing might include checking for structural integrity, proper alignment, and resistance to environmental stressors.

Each step of the installation process is critical to ensure that the FRP Crossarms are installed correctly and safely, thereby ensuring their optimal performance and longevity in supporting overhead power lines and equipment.

How To Fill The Foam?

After the pultrusion process, foam filling is a crucial step in manufacturing FRP (Fiberglass Reinforced Polymer) Crossarms, aimed at enhancing their mechanical properties and performance. There are two primary methods of foam filling: in-line foam filling and post-injection foam filling, each with distinct characteristics and advantages.
In-line Foam Filling
In-line foam filling occurs concurrently with the pultrusion process. Before the fibers are impregnated with resin, a foaming agent is integrated into the resin mixture. This approach enables the foam to form inside the FRP Crossarm as it undergoes the pultrusion process, resulting in a crossarm with a continuous profile that includes internal foam filling. The main benefits of this method include the creation of a lightweight structure that possesses increased stiffness, as well as improved resistance to bending and compression forces. By incorporating foam directly into the crossarm during manufacture, in-line filling contributes to a seamless and uniformly distributed internal structure.
Post-Injection Foam Filling
The post-injection method involves injecting foam into the hollow interior of the FRP Crossarm after the pultrusion process has been completed. Using a specialized injection device, foam filling material is inserted into the crossarm’s interior spaces at the final stages of production. This technique offers enhanced structural strength and stiffness, along with a reduction in overall weight. Additionally, it significantly improves the crossarm’s ability to dampen vibrations and resist dynamic stresses, making it particularly suitable for environments where vibration and noise reduction are critical.

Both in-line and post-injection foam filling techniques can be tailored to meet the specific needs of a project, allowing for customization in terms of strength, weight, and performance characteristics. Regardless of the chosen method, foam filling serves to bolster the FRP Crossarm’s mechanical properties, reduce its weight, and improve vibration damping capabilities. These improvements are instrumental in ensuring the crossarm’s reliability and longevity in supporting electrical transmission infrastructure.

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