EB Type Tower Attachment Clevis
The EB Type tower attachment clevis, also referred to as an EB twisted strap or EB trunnion clevis, is a load-bearing connection fitting used in overhead transmission-line insulator-string assemblies.
It is typically installed between a tower attachment point and the upper fittings of a suspension insulator string. The eye plate at one end and the transverse trunnion-pin connection at the other end provide a change in connection orientation and allow controlled articulation of the insulator-string assembly.
The EB fitting is commonly used as a tower-attachment fitting in single I-type suspension strings. Final selection must be based on the required mechanical load, pin dimensions, attachment geometry and the approved insulator-string assembly drawing.
Key Features
- Designed for tower-to-insulator-string mechanical connection
- Transverse trunnion pin and eye-plate connection structure
- Changes the connection direction between adjoining fittings
- Permits controlled articulation of the suspension assembly
- Load-bearing forged or formed steel construction
- Hot-dip galvanized for outdoor corrosion protection
- Pin secured with nut, washer and retaining cotter pin
- Available in multiple dimensions and mechanical load classes
- Suitable for transmission-line and substation suspension assemblies
Product Structure
| Component | Function |
|---|---|
| Eye plate | Connects to the adjoining tower fitting, clevis or linkage component |
| Trunnion body | Provides the transverse articulated connection |
| Pin or bolt | Forms the mechanical connection between the EB fitting and adjoining hardware |
| Nut and washer | Retain and secure the connecting pin |
| Cotter pin | Prevents unintended loosening or removal of the nut |
Typical Materials and Surface Treatment
| Component | Typical Material | Typical Surface Treatment |
|---|---|---|
| Main EB body | Forged or formed carbon steel, commonly Grade 35 steel or drawing-specified material | Hot-dip galvanized |
| Trunnion pin or bolt | High-strength carbon steel | Hot-dip galvanized |
| Nut and washer | Carbon steel | Hot-dip galvanized |
| Cotter pin | Galvanized steel or stainless steel | According to the approved drawing |
The exact steel grade, manufacturing method, heat treatment and fastener material must be confirmed using the approved drawing and bill of materials.
Typical EB Model Specifications
| Model | L | H | H1 | Pin/Hole Diameter Φ | R | M | B | Nominal Failure Load |
|---|---|---|---|---|---|---|---|---|
| EB-07/10-80 | 45 mm | 80 mm | — | 18 mm | 22.5 mm | 18 mm | 16 mm | 70 kN |
| EB-10/12-100 | 60 mm | 100 mm | 46 mm | 20 mm | 24 mm | 22 mm | 16 mm | 100 kN |
| EB-12/16-100 | 60 mm | 100 mm | — | 24 mm | 30 mm | 24 mm | 16 mm | 120 kN |
| EB-16/21-100 | 80 mm | 100 mm | 48 mm | 26 mm | 32 mm | 24 mm | 18 mm | 160 kN |
| EB-21/42-100 | 100 mm | 100 mm | 50 mm | 26 mm | 32 mm | 36 mm | 20 mm | 210 kN |
Technical-data notice: These are representative catalogue values. Dimensions represented by L, H, H1, Φ, R, M and B must be read together with the corresponding engineering drawing. Do not manufacture or order the product using this table alone.
Applications
- Single I-type suspension insulator strings
- Tower attachment points for suspension assemblies
- Overhead transmission lines
- Overhead distribution structures where approved
- Composite, porcelain or glass insulator-string assemblies
- Substation conductor-support assemblies
- Connection between tower fittings and suspension hardware
Mechanical Function
The EB fitting is a mechanical load-bearing component. Its purpose is to transfer the weight, conductor tension components, wind load and other mechanical forces from the insulator-string assembly to the tower attachment point.
It is not an electrical conductor connector and should not be selected by current rating. Its suitability depends on mechanical load, mating dimensions, movement direction and the complete insulator-string design.
Model Selection
The following information must be checked before selecting an EB fitting:
- Required nominal failure load
- Tower attachment configuration
- Insulator-string type and arrangement
- Required connection orientation
- Mating clevis width
- Pin and hole diameter
- Required articulation angle
- Distance between connection centres
- Fitting material and galvanizing requirements
- Applicable utility or project standard
The rated strength of the complete assembly is limited by its lowest-rated component. Using a higher-capacity EB fitting does not automatically increase the strength of the complete insulator string.
Installation Recommendations
- Verify the EB model against the approved insulator-string assembly drawing.
- Confirm that the pin diameter, eye diameter and clevis width match the adjoining fittings.
- Inspect the fitting for deformation, cracks, sharp edges and damaged galvanizing.
- Position the trunnion and eye plate in the required load direction.
- Insert the connecting pin without forcing or enlarging the mating holes.
- Install the washer, nut and cotter pin in the specified order.
- Open or secure the cotter pin according to the installation specification.
- Check that the assembly can articulate without binding or contacting the tower structure.
- Do not weld, drill, flame-cut or modify the fitting at the installation site.
Inspection and Testing
Recommended inspection and testing items include:
- Raw-material certificate verification
- Dimensional inspection against the approved drawing
- Visual inspection for cracks, folds, laps and sharp edges
- Pin, hole and clevis-fit inspection
- Nominal failure-load or mechanical tensile test
- Permanent-deformation inspection
- Hot-dip galvanized coating thickness and adhesion inspection
- Assembly and articulation inspection
- Marking, packaging and traceability inspection
Applicable Standards
The EB tower attachment clevis may be manufactured and tested according to the approved drawing, utility specification and applicable requirements of:
- GB/T 2314 – General technical requirements for electric power fittings
- GB/T 2315 – Nominal failure-load series and connection dimensions for electric power fittings
- GB/T 2317.1 – Test methods for electric power fittings: Mechanical tests
- IEC 61284 – Overhead lines: Requirements and tests for fittings, when specified
- GB/T 13912 or ISO 1461 – Hot-dip galvanized coatings on fabricated steel articles
Compliance with a listed standard must be supported by the applicable drawing, inspection report or type-test documentation for the ordered model. ISO 9001 certification of a manufacturer does not by itself certify the mechanical performance of an individual EB fitting.
Information Required for Quotation
- Required EB model
- Nominal failure load
- Complete insulator-string drawing
- Pin and hole dimensions
- Mating-clevis width
- Required centre-to-centre length
- Steel grade and heat-treatment requirements
- Galvanizing standard and coating thickness
- Required mechanical test and inspection documents
- Quantity, product marking and packaging requirements
Frequently Asked Questions
What is the EB tower attachment clevis used for?
It is used to connect a suspension insulator-string assembly to a tower attachment point while changing the connection orientation and permitting controlled articulation.
Is an EB fitting the same as a parallel clevis?
No. The EB fitting incorporates a transverse trunnion connection and an eye plate. Its connection geometry and movement direction differ from those of a conventional parallel clevis.
How should the correct EB model be selected?
The model must be selected according to the nominal failure load, pin diameter, eye dimensions, clevis width and the approved insulator-string drawing.
Can the EB fitting be used in a tension insulator string?
Only when the complete tension-string drawing specifically requires this fitting. EB fittings are more commonly associated with tower attachment of suspension assemblies and should not be substituted without engineering approval.
Can the product dimensions be customized?
Yes. Dimensions, load class, steel grade, fasteners, galvanizing and marking can be produced according to an approved customer drawing and test specification.
