Fiber Optic Cable Accessories Checklist for Aerial Projects: Clamps, Brackets, and RFQ Data
13 October, 2026
TEL: +86-158-5877-7327
The difference between pin type and suspension type insulator is not simply a voltage cutoff. A pin insulator is rigidly mounted on a pin or crossarm and supports the conductor close to the structure. A suspension assembly hangs below the structure and carries the conductor through a clamp and a string of insulator units or a long-rod insulator. The correct choice must satisfy the line position, insulation coordination, pollution duty, mechanical load, clearances, and hardware interface at the same time.
For a first product review, see CONWELL’s pin type and suspension type insulator comparison. For a tender, however, replace general voltage rules with project-specific ratings and drawings.
| Check | Pin type | Suspension type |
|---|---|---|
| Mounting | Rigid unit fixed to a pin on the pole or crossarm | String or long-rod unit hangs from the structure |
| Typical line position | Distribution tangent or approved small-angle support | Tangent suspension; a different strain arrangement may be used at angles or dead ends |
| Insulation arrangement | One fixed insulator geometry | Designed string length, unit count, or long-rod length |
| Mechanical behavior | Loads pass through the insulator and pin into the crossarm | Articulated assembly can swing; fittings and clearances form part of the design |
| Maintenance | Inspect the body, tie, pin, cemented interface where applicable, and crossarm | Inspect every unit plus couplings, locking devices, clamp, and structure attachment |
Suspension strings hang below the support and must be assessed together with their end fittings, conductor clamp, and available swing clearance.
Pin insulators are widely associated with distribution voltages, while suspension strings are common on higher-voltage transmission lines. This is a useful starting point, not a universal rule. Utility practices, structure geometry, available products, insulation coordination, and mechanical duties vary by country and project.
State the nominal voltage and highest system voltage used by the project. Then give the required power-frequency, lightning-impulse, and, where applicable, switching-impulse withstand levels. Include altitude because reduced air density can affect external insulation and clearance requirements. The supplier should confirm the complete assembly against the specified standard and edition rather than offer a type based only on the line’s kV label.
Creepage distance is the path along the insulating surface; it is not the same as arcing distance through air. State the site pollution severity, contamination source, altitude, wetting conditions, material preference, and maintenance plan. Selection under pollution should follow the project’s adopted method, such as the IEC 60815 series, including the correct reference voltage and applicable corrections.
CONWELL’s electrical insulator range includes several suspension profiles and materials. A standard suspended glass insulator, for example, should only be selected after its exact model and string data are checked against the site duty.
The purchase specification should give the conductor type, diameter, unit weight, ruling or design span, line angle, everyday tension, maximum design tension, and wind and ice cases. Also identify vertical, transverse, and longitudinal loads, broken-wire or unbalanced conditions if required, and the project safety factors.
For a pin type, check the insulator’s applicable mechanical rating and the bending capacity and dimensions of the matching pin and crossarm connection. For a suspension type, state the required mechanical rating for the complete load path. Confirm coupling size, socket-and-ball or clevis arrangement, locking device, upper attachment, conductor clamp, and any yoke plate. A catalog strength value is not a working-load allowance unless the project method says so.
A double-string arrangement changes load sharing, hardware, clearances, and inspection points; it must be shown on the approved assembly drawing.
Consider a pin insulator where the utility permits it at a tangent or small-angle distribution support and the exact unit, pin, conductor tie, crossarm, electrical level, and mechanical ratings all comply. It can simplify the pole-top arrangement, but its fixed geometry leaves limited scope for later insulation changes.
Consider a suspension assembly where the conductor must hang below the structure, the required insulation or load calls for a string or long-rod design, or the line geometry needs an articulated connection. Suspension does not automatically mean cap-and-pin discs: a composite rod insulator may be another candidate when the utility specification permits it.
At a large angle or dead end, do not reuse a tangent suspension schedule without review. The assembly may become a strain set with a different orientation, clamp, hardware chain, load case, and clearance envelope.
A suspension design can be configured with different unit counts or lengths, but units must not be added or removed without engineering approval. A change affects the string’s dry arcing distance, creepage distance, voltage distribution, length, swing, conductor height, phase-to-earth clearance, coupling compatibility, and possibly grading or arcing hardware.
For replacement work, identify the existing unit profile, material, dimensions, coupling designation, mechanical rating, string arrangement, and approved electrical values. Mixing visually similar units can create an unverified string.
| RFQ field | Information to provide or request |
|---|---|
| System | AC/DC, frequency, nominal and highest system voltage, insulation withstand levels, grounding practice |
| Site | Altitude, pollution severity, contamination type, temperature, wind, ice, wetting and maintenance conditions |
| Line position | Tangent, line angle, dead end, crossing, conductor and span data |
| Electrical | Required creepage, arcing distance and complete-assembly withstand values |
| Mechanical | Design load cases, required rating, safety factors and load direction |
| Interfaces | Pin and tie details, or complete suspension fittings, coupling sizes, clamp, structure hole and clearance drawing |
| Documents | Dimensioned drawing, bill of materials, standards and editions, type/sample/routine test evidence, inspection plan, lot traceability and installation instructions |
No. It is a common rule of thumb in many conventional line designs, but the tender must follow the utility standard and the ratings of the offered assembly. Structure, pollution, insulation coordination and loads can change the decision.
Do not use that as the only acceptance basis. Ask for the declared creepage and electrical performance of the complete string because spacing, fittings, profile and assembly geometry matter.
Only after a full design review. The revised string must pass electrical, mechanical, clearance, swing, hardware and structure checks and be documented on an approved drawing.
For pin type, define the pin, crossarm interface and conductor tie or approved retaining method. For suspension type, request every upper fitting, insulator unit, coupling and lock, yoke where used, conductor clamp and any specified grading or arcing hardware.
A usable quotation starts with the pole or tower position, system insulation requirements, conductor and load data, site pollution duty, and connection drawings. Contact CONWELL with these inputs to compare an insulator assembly against your distribution or transmission line specification.
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