W-7A Hot-Dip Galvanized Socket Clevis for Insulator Strings
The W-7A socket clevis is an overhead-line connection fitting designed to connect a ball-pin insulator with the next component in a suspension or tension hardware string. It converts the ball connection of a string insulator into a clevis-and-pin connection for assembling suspension clamps, tension fittings, link plates and other compatible line hardware.
The upper end incorporates a socket shaped to receive the ball pin of a compatible insulator. A locking device retains the ball inside the socket while allowing the articulation required by the insulator string. The lower clevis connection is assembled using a removable steel pin, nut and cotter pin.
The product shown in the photograph appears to carry a W-7A marking. Under commonly used product tables, W-7A has a 16 mm coupling designation and a representative nominal failure load of 70 kN. These values must be verified against the factory drawing and mechanical test report before publication.
Important: The socket size, locking-device type, clevis opening and pin diameter must all match the adjacent insulator and line fitting. Similar-looking W, W1 and WS fittings are not automatically interchangeable.
Key Features
- Socket connection for a ball-pin insulator
- Lower clevis-and-pin connection for line hardware
- Allows mechanical articulation within an insulator string
- Locking device helps retain the insulator ball in the socket
- Steel pin, nut and cotter pin provide a secure lower connection
- Available in several coupling sizes and mechanical load classes
- Hot-dip galvanized ferrous components for outdoor corrosion protection
- Suitable for suspension and tension insulator assemblies
Typical Technical Specifications
| Product Type | W-Type Socket Clevis / Socket Clevis Eye |
|---|---|
| Model Shown | W-7A, subject to marking confirmation |
| Upper Connection | Ball-and-socket insulator coupling |
| Lower Connection | Clevis pin connection |
| Representative Coupling Designation | 16 mm for W-7A |
| Representative Nominal Failure Load | 70 kN for W-7A |
| Body Material | Malleable cast iron, ductile iron or cast steel according to the approved drawing |
| Pin and Fastener Material | Carbon steel |
| Locking Device | Stainless steel or approved corrosion-resistant material |
| Cotter Pin | Stainless steel |
| Surface Finish | Hot-dip galvanized ferrous components |
| Application | Suspension strings, tension strings and insulator connection assemblies |
| Customization | Model, coupling size, dimensions, load class, coating, marking and packaging |
Representative Model Data
| Model | Coupling Designation | B (mm) | C1 (mm) | C2 (mm) | Pin Diameter (mm) | H (mm) | Nominal Failure Load (kN) | Reference Weight (kg) |
|---|---|---|---|---|---|---|---|---|
| W-7A | 16 | 16 | 19.2 | 34.5 | 20 | 70 | 70 | 0.69–0.80 |
| W-7B | 16 | 16 | 19.2 | 34.5 | 20 | 115 | 70 | Approximately 0.86 |
| W1-10 | 16 | 18 | 19.2 | 34.5 | 20 | 85 | 100 | Approximately 0.90 |
| W1-12 | 16 | 20 | 19.2 | 34.5 | 24 | 90 | 120 | Approximately 1.30 |
| W-12 | 20 | 20 | 23.0 | 42.5 | 24 | 90 | 120 | Approximately 1.40 |
| W-30 | 24 | 32 | 27.5 | 51.0 | 39 | 110 | 300 | Approximately 3.50 |
The values above are representative reference data. Dimension definitions, tolerances, material, weight and nominal failure load must be confirmed using the approved Jiujin Power drawing and corresponding test report.
Ball-and-Socket Connection
The socket must be selected according to the designated coupling size of the insulator ball pin. A W-7A fitting is commonly associated with a 16 mm ball-and-socket coupling. Using an incompatible ball size or locking device may prevent correct assembly or reduce the security of the connection.
IEC 60120 defines standardized dimensions for ball-and-socket couplings to support interchangeability between compatible insulators and metal fittings. Compliance should be confirmed by dimensional gauges and inspection records for the exact product supplied.
Materials and Construction
The socket body may be manufactured from malleable cast iron, ductile iron or cast steel, depending on the approved product specification. The lower connecting pin, nut and other ferrous fasteners are normally manufactured from steel.
The socket locking device and cotter pin commonly use stainless steel or another approved corrosion-resistant material. Material grades must be confirmed because visual inspection alone cannot distinguish between malleable iron, ductile iron and cast steel.
Surface Treatment
Ferrous components are generally hot-dip galvanized to provide corrosion protection in outdoor transmission and distribution environments. The specified coating thickness, surface quality and test method should follow the purchase specification and applicable standard.
The photograph shows a silver-grey galvanized appearance, but the coating process and zinc thickness cannot be confirmed from the image alone.
Applications
- Suspension insulator strings
- Tension and dead-end insulator strings
- Connections between disc insulators and suspension clamps
- Connections between insulators and tension hardware
- Overhead transmission and distribution lines
- Substation insulator connection assemblies
Selection Guidelines
- Confirm the designated coupling size of the insulator ball pin.
- Verify the required nominal failure load of the hardware string.
- Check the socket dimensions and locking-device configuration.
- Confirm the lower clevis opening and connecting-pin diameter.
- Ensure that adjacent fittings have compatible load classes.
- Specify the body material and hot-dip galvanized coating requirement.
- Use the approved assembly drawing as the final selection basis.
Line voltage alone does not determine the correct socket-clevis model. Mechanical load, coupling designation and dimensional compatibility are the primary selection factors.
Installation Guidance
- Check the body, socket cavity, locking device, pin and cotter pin for damage.
- Confirm that the insulator ball and socket have the same coupling designation.
- Insert the ball pin fully into the socket without forcing the components.
- Install the correct locking device and verify that it is fully seated.
- Connect the lower clevis to the adjacent fitting using the specified pin.
- Secure the pin using the nut and cotter pin provided.
- Confirm that the connection articulates correctly without interference.
- Replace any fitting showing cracks, deformation, excessive wear or severe corrosion.
Quality Inspection
- Raw-material and dimensional inspection
- Socket profile and coupling-gauge inspection
- Clevis opening and pin-diameter inspection
- Locking-device fit and retention inspection
- Visual inspection for cracks, casting defects and sharp edges
- Galvanized-coating appearance and thickness inspection
- Mechanical load testing according to the agreed specification
- Model marking, packaging and quantity inspection
Reference Standards
- IEC 60120:2020 – Ball and socket couplings of string insulator units: dimensions
- IEC 60372:2020 – Locking devices for ball and socket couplings: dimensions and tests
- IEC 61284:1997 – Overhead lines: requirements and tests for fittings, when applicable
- DL/T 759-2023 – Connecting fittings
- GB/T 2314-2008 – General technical requirements for electric power fittings
- ISO 1461:2022 – Hot-dip galvanized coatings on fabricated iron and steel articles
Reference to a standard does not constitute certification. Any compliance statement must be supported by drawings, inspection records and test reports for the exact model supplied.
Ordering Information
Please provide the following information when requesting a quotation:
- Required model, such as W-7A, W-7B, W1-10 or W-12
- Ball-and-socket coupling designation
- Required nominal failure load
- Lower clevis opening and pin diameter
- Body and fastener material requirements
- Locking-device type
- Hot-dip galvanized coating requirement
- Applicable standard and project drawing
- Required inspection and mechanical test reports
- Order quantity, marking and packaging requirements
Frequently Asked Questions
What is the function of a socket clevis?
It connects the ball pin of a string insulator to a clevis-type line fitting while transmitting the mechanical load through the insulator assembly.
What is the difference between W-7A and W-7B?
Both commonly use a 16 mm coupling designation and a 70 kN nominal failure-load class. The main representative difference is their overall connection height: approximately 70 mm for W-7A and 115 mm for W-7B.
Can W-7A connect to any disc insulator?
No. The insulator ball pin must have a compatible coupling designation and dimensional profile. Compatibility must be checked before installation.
Is the locking device included?
It is normally supplied with the socket clevis, but the exact locking-device type and supply scope must be confirmed in the quotation and packing list.
Can the product be selected according to voltage?
Voltage may form part of the complete line design, but socket-clevis selection primarily depends on coupling size, mechanical load and compatibility with adjacent fittings.
