Counter Jib: Length 10-40 meters

Component Specifications

Definition

The counter jib is a critical structural element in tower crane design, consisting of a rigid framework extending opposite the main lifting jib. It serves to counterbalance the load moment created by the main jib and lifted materials, ensuring crane stability and preventing tipping. Typically mounted on the slewing unit or tower top, it supports counterweights (concrete blocks or steel plates) and may house machinery like hoist motors. Its length and weight capacity are precisely calculated based on the crane's maximum load moment and working radius requirements.

Working Principle

Operates on the principle of moment equilibrium: The counter moment (counter jib length × counterweight mass) must equal or exceed the load moment (main jib length × lifted load mass) to maintain crane stability. During operation, as the load moves along the main jib, the counter jib's fixed counterweight creates a balancing force moment around the crane's center of rotation, preventing overturning.

Materials

High-strength structural steel (S355, S460 grades), hot-rolled steel sections (I-beams, channels, tubes), welded construction with fatigue-resistant joints, corrosion-protected with galvanizing or epoxy coatings.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Length	10-40 meters
Connection Type	Bolted flange or pinned connection
Weight Capacity	5-50 tons counterweight
Deflection Limit	L/500 under full load
Design Load Moment	100-5000 kNm

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 4301, ISO 9927, DIN 15018, DIN EN 13001

Parent Products

This component is used in the following industrial products

Tower Crane

A tall, fixed crane used for lifting and moving heavy materials on construction sites.

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Engineering Analysis

Risks & Mitigation

Structural fatigue failure
Connection bolt loosening
Corrosion in marine environments
Improper counterweight calculation leading to instability

FMEA Triads

Trigger: Fatigue cracks at welded joints
Failure: Structural collapse during operation
Mitigation: Regular NDT inspection, proper weld design per DIN 15018, fatigue life monitoring

Trigger: Insufficient counterweight
Failure: Crane tipping under maximum load
Mitigation: Load moment calculation verification, safety factor ≥1.5 per ISO 4301, load indicator systems

Trigger: Corrosion in structural members
Failure: Reduced load capacity, sudden fracture
Mitigation: Protective coatings, regular thickness measurements, corrosion allowance in design

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±5mm for overall length, ±2° for alignment, ±1% for weight distribution

Test Method

Static load test at 125% rated capacity, dynamic load test at 110% rated capacity, NDT of welds (UT, MT)

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

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Inspection readiness

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Supplier transparency

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Manufacturers of Counter Jib

Manufacturer profiles associated with Counter Jib.

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the purpose of a counter jib in tower cranes?

The counter jib balances the load moment created by the main jib and lifted materials, preventing crane tipping and ensuring operational stability.

How is counter jib length determined?

Length is calculated based on the crane's maximum load moment, counterweight mass, and required stability factor, typically following ISO 4301 standards.

Can counter jibs be adjusted for different loads?

Fixed design; counterweight adjustment is achieved by adding/removing counterweight blocks rather than modifying the jib structure.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Counter Jib