U Bolts For Suspension Polymer Insulator

U-bolts are primarily used to secure composite insulators (such as suspension strings and post insulators) to the crossarms or flanges of towers. They transmit the mechanical forces borne by the insulators, such as conductor tension and wind loads. Together with fittings, they ensure a stable connection between the insulators and the tower, preventing loosening or detachment under complex operating conditions and providing fundamental support for the insulation performance of power lines. For composite post insulators, U-bolts can significantly improve their rigidity and bending strength, increasing stiffness by 50%-100% and bending strength by 30%-80% while maintaining the same insulation class.

II. Main Types and Characteristics
Based on application scenarios and performance requirements, U-bolts for composite insulators are mainly divided into two categories:
* **Ordinary U-bolts:** Basic connectors, consisting of a U-shaped bolt, nut, and closed pin. Suitable for 35–110kV lines, ideal for areas with low vertical loads and minimal wind deflection (such as suburban distribution networks). They are relatively inexpensive, but have limited lateral load-bearing capacity and specific usage restrictions (cannot be directly connected to plate-type fittings or QP-type ball-head ferrules to avoid stress concentration).

* **Reinforced UJ-type Bolts:** Designed for harsh working conditions, the nut and bolt at the lower end of the ordinary type are forged into a single unit (forming an insulator platform). They can withstand lateral loads under wind deflection, protecting the threads from bending damage. Suitable for large-section conductors, multi-split conductors, or areas with strong winds. They require the use of QH-type ball-head ferrules or U-shaped ferrules for conversion.

In addition, some composite post insulators utilize a combination of rigid and flexible U-bolts (such as spatially intersecting arrangements) to further optimize the insulator's rigidity and toughness, adapting to bending strength requirements in different directions.

III. Key Performance Requirements
**Material and Surface Treatment:** For general applications, Q235A carbon steel can be used. For heavy-load or corrosive environments (coastal areas, industrial zones), Q345B high-strength steel or stainless steel is required. Hot-dip galvanizing is necessary; the zinc layer thickness directly affects its service life in humid and polluted environments, preventing corrosion failure.

Manufacturing Process: "Material-saving" processes such as reduced rod length or thread diameter are prohibited. Standardized mold production is required to eliminate dimensional differences from manual bending, ensuring the load-bearing cross-sectional area and thread strength, and preventing fatigue cracks due to process defects.

Specification Matching: Selection must be based on the line voltage level, load environment (maximum wind speed, icing level), and fitting type. For example, 220kV lines commonly use 120kN-class U-bolts; important transmission lines require a one-level upgrade to increase safety redundancy.

Installation direction: U-shaped opening facing downwards/outwards for easy maintenance and water accumulation prevention
Tightening requirements: Double nut anti loosening, torque standard (such as M16:80-100N · m)
Pin must be installed: the closed pin must have its opening in place, and it is strictly prohibited to miss or replace it with iron wire

Matching hardware:
Upper end: U-bolt → cross arm/connecting plate
Lower end: U-bolt → ball head hanging ring (QP/QH) → insulator string ball head
Mixing is strictly prohibited: U-bolts with different loads and voltage levels are not interchangeable
Anti corrosion inspection: If the hot-dip zinc layer is damaged, it must be repaired or replaced to prevent rusting and fracture

1.Where is your factory located? How can I visit there?
Our factory is located in Wuhan City,Hubei Province, China.
You are always welcome to visit us.

3. What's the payment term?
T/T and L/C available.

4. How's the delivery time?
Usually it will take about 30~60 days for production.

For small-volume orders, the delivery time can be 1 to 2 weeks depending on the available materials in our warehouse.

5. Tell me the standard of package?
Usually we use standard cartons for packing or according to customers' requirements, main package is plywood cases

Wooden cases are available for heavy cargo and long insulators.

6. Could you offer Form A or C/O etc. certificate of origin ?
Yes, of course. We can provide them as required.And COC documents are available.

7. Would you accept to use our logo ?
If you have a good quantity,it is absolutely no problem to do OEM.

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