NLL Series Aluminum Alloy Bolted Strain Clamp with Optional Insulating Cover
The NLL series aluminum alloy bolted strain clamp is used to terminate and mechanically secure aluminum conductors at terminal poles, angle poles and strain sections of overhead power distribution lines. It is also known as an aluminum alloy tension clamp, dead-end clamp or quadrant strain clamp.
The conductor is placed inside the curved clamp groove and secured by U-bolts, pressure plates, nuts and washers. The aluminum alloy clamp body provides a lightweight and corrosion-resistant conductor-supporting structure. For overhead insulated aluminum conductors, an optional insulating cover can be supplied according to the selected clamp model and conductor size.
Key Features
- Bolted strain-clamp structure for overhead conductor termination
- High-strength aluminum alloy clamp body and pressure plates
- Suitable for AAC, AAAC and selected ACSR conductors
- Applicable to bare or insulated aluminum overhead conductors
- Optional insulating cover for insulated-conductor applications
- Steel U-bolts supplied with nuts and washers
- Stainless-steel retaining pin for the clevis connection
- Available in different conductor-diameter and mechanical-load ranges
- Dimensions and conductor compatibility can be manufactured according to approved drawings
Typical Technical Specifications
| Model | Applicable Conductor Diameter | Length L | Length I | Dimension C | Pin Diameter d | U-Bolt Configuration | Rated Failure Load | Reference Weight |
|---|---|---|---|---|---|---|---|---|
| NLL-1 | 5.1–11.4 mm | 135 mm | 102 mm | 17 mm | 16 mm | 2 × M12 | 40 kN | Approx. 0.75 kg |
| NLL-2 | 11.4–16.0 mm | 155 mm | 113 mm | 21 mm | 16 mm | 2 × M12 | 70 kN | Approx. 0.90 kg |
| NLL-3 | 14.5–17.5 mm | 230 mm | 150 mm | 30 mm | 18 mm | 3 × M14 | 70 kN | Approx. 1.84 kg |
| NLL-4 | 18.0–22.4 mm | 253 mm | 157 mm | 31 mm | 18 mm | 3 × M14 | 90 kN | Approx. 2.32 kg |
Selection notice: The table contains representative industry data for preliminary model selection. NLL dimensions and conductor ranges vary between drawings and manufacturers. Final conductor diameter, groove dimensions, bolt configuration, mechanical rating and weight must be confirmed using the approved drawing before ordering.
Materials and Construction
| Clamp Body | High-strength aluminum alloy |
|---|---|
| Pressure Plates | Aluminum alloy |
| U-Bolts | Carbon steel, hot-dip galvanized |
| Nuts and Washers | Carbon steel, hot-dip galvanized |
| Clevis Pin | Steel, hot-dip galvanized |
| Retaining Pin | Stainless steel |
| Optional Insulating Cover | Weather-resistant polymer material; specification subject to the approved drawing |
Surface Treatment
The aluminum alloy body is normally supplied with a clean cast or finished aluminum surface. Carbon-steel U-bolts, nuts, washers and connection hardware are hot-dip galvanized for outdoor corrosion protection.
When required by the project, the galvanized steel parts can be inspected against ISO 1461, ASTM A153/A153M, GB/T 13912 or another customer-specified coating requirement. The applicable standard and minimum coating thickness must be confirmed in the purchase specification.
Applicable Conductors
- AAC — All Aluminum Conductor
- AAAC — All Aluminum Alloy Conductor
- Selected ACSR — Aluminum Conductor Steel Reinforced
- Overhead insulated aluminum conductor when used with the appropriate insulating cover
Conductor compatibility must be checked using the actual conductor diameter, construction, material, rated tensile strength and required gripping performance. Conductor cross-sectional area alone is not sufficient for final clamp selection.
Applications
- Overhead distribution lines up to 10 kV, subject to the approved system design
- Terminal-pole conductor dead ends
- Angle and strain poles
- Rural electrification networks
- Distribution-line upgrades and maintenance
- Bare and insulated aluminum conductor installations
Optional Insulating Cover
The insulating cover is an optional accessory used to cover the clamp and exposed connection area when the NLL clamp is installed with an overhead insulated aluminum conductor. The cover model must match the clamp size, conductor diameter and installation arrangement.
The image on this product page shows the metal strain clamp only. Please state clearly in the inquiry whether an insulating cover is required.
Standards and Testing
Products can be manufactured and inspected according to an approved customer drawing, project specification or agreed test plan. Depending on the project, the following documents may be referenced:
- IEC 61284 — Overhead lines: requirements and tests for fittings
- GB/T 2314 — General technical requirements for electric power fittings
- GB/T 2317 series — Test methods for electric power fittings
- ISO 1461 — Hot-dip galvanized coatings on fabricated iron and steel articles
- ASTM A153/A153M — Zinc coating on iron and steel hardware
Compliance with a particular standard should only be stated when the supplied product, approved drawing and corresponding test documentation support that claim.
Quality Inspection
- Material verification for aluminum and steel components
- Conductor-groove and mounting-dimension inspection
- U-bolt thread and assembly inspection
- Visual inspection for casting defects, burrs and sharp edges
- Galvanizing thickness inspection when specified
- Mechanical failure-load and conductor-grip testing according to the approved test plan
- Insulating-cover inspection when included in the order
Ordering Information
For accurate product selection and quotation, please provide the NLL model, conductor type, conductor diameter, conductor cross-sectional area, required mechanical load, operating voltage, line angle, insulating-cover requirement, coating standard and order quantity.
Frequently Asked Questions
Is an insulating cover included with every NLL clamp?
No. The insulating cover is normally an optional matching accessory. Please confirm whether the quotation and order should include the cover.
Can the NLL clamp be used with ACSR?
Selected NLL models can be used with ACSR when the conductor diameter, groove profile and required gripping performance are compatible. Final selection must follow the approved drawing and test requirements.
What is the difference between NLL and NLD strain clamps?
The NLL series normally uses an aluminum alloy body and is commonly selected for aluminum-based conductors. The NLD series generally uses a malleable cast-iron body. They should not be treated as interchangeable without checking the conductor and mechanical requirements.
Can the clamp be customized?
Conductor grooves, connection dimensions, mechanical ratings, markings, insulating covers and packaging can be evaluated according to the customer’s drawing and purchase quantity.
