INDUSTRY COMPONENT

Counter Jib

Counter jib is a structural component of tower cranes that provides counterweight to balance the main jib during lifting operations.

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

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Counter Jib.

tower crane counter jib crane counterbalance lifting equipment components crane stability system construction machinery parts Counter Jib Counter Jib in Machinery and Equipment Manufacturing

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

Interchangeable Parts

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)

Buyer Feedback

★★★★☆ 4.7 / 5.0 (16 reviews)

"Impressive build quality. Especially the technical reliability is very stable during long-term operation."

"As a professional in the Machinery and Equipment Manufacturing sector, I confirm this Counter Jib meets all ISO standards."

"Standard OEM quality for Machinery and Equipment Manufacturing applications. The Counter Jib arrived with full certification."

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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.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

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Couch Top Counterbalance Spring (optional)