Key Features and Structural Design
The excavator long arm, also known as a boom extension or long-reach attachment, is a specialized modification designed to significantly expand the operational envelope of a standard excavator. By replacing or extending the original boom and stick, these attachments allow machinery to achieve working radii ranging from 10 meters to over 40 meters, depending on the configuration. The design typically utilizes high-strength low-alloy (HSLA) steels, such as WELDOX, to maintain structural integrity while managing weight.
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* Dredging * River Project |
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* Carry Grab for Grabbing Wood * Long Reach |
The structural configurations are generally categorized into three types based on application requirements:
Two-Stage: This is the most common modification for deep excavation. It consists of an extended boom and a longer stick. It is primarily used for slope finishing, deep foundation pit excavation, and river dredging where horizontal reach and depth are critical.
Three-Stage: Often referred to as a "Demolition Arm," this configuration includes an additional articulation point (a middle arm). This allows for greater vertical reach, making it ideal for high-rise building dismantling (up to 30 meters). It often features a fixed or hydraulic angle adjustment for the bucket or breaker.
Sliding/Telescopic Arm: Designed for vertical precision, this type allows the arm to extend and retract telescopically. It is frequently used with a clamshell bucket for deep, narrow shafts or caisson excavation, minimizing the footprint of the operation.
Manufacturing Process and Production Details
The production of a long arm is a precision engineering task that goes far beyond simple welding. It requires advanced Computer-Aided Design (CAD) and Finite Element Analysis (FEA) to simulate stress distribution and prevent structural failure under load.
Material Selection and Cutting
The manufacturing process begins with the selection of high-tensile steel plates (often 10-12mm thick for the main plates). Modern manufacturing utilizes CNC plasma cutting machines to ensure that the complex geometries of the side plates and internal reinforcement ribs are cut with millimeter precision. This precision is crucial for the proper fit-up of internal components.
Welding and Assembly
The assembly phase involves robotic or skilled manual welding. To ensure durability, manufacturers employ submerged arc welding or CO2 shielded arc welding for the main seams. The internal structure is reinforced with buffer plates and box-section designs to resist torsional forces.
Machining and Finishing
Once the main structure is welded, the boom undergoes stress-relief treatment (often vibration aging) to eliminate internal stresses caused by welding heat. The pin holes (bore holes) are then precision-bored using large horizontal boring mills to ensure perfect alignment with the excavator's hydraulic cylinders and linkage. Finally, the unit undergoes shot blasting to remove rust and mill scale, followed by the application of anti-corrosive primer and topcoat.
Frequently Asked Questions (FAQ)
Q1: What are the maintenance requirements for a long arm?
A: Maintenance is critical due to the high stress on the extended structure.
Lubrication: Greasing the pins and bushings is vital. It is recommended to inject grease at least twice daily. If working in muddy or submerged conditions, the pins should be cleaned before greasing to prevent abrasive wear.
Inspection: Regular checks for cracks in the welds, especially near the root and toe of the welds, are necessary. Any signs of structural fatigue should be addressed immediately.
Q2: What is the typical lead time for manufacturing a long arm?
A: Depending on the complexity (2-stage vs. 3-stage) and the specific tonnage, the manufacturing process usually takes between 15 to 30 days. This includes the time required for design simulation, material procurement, welding, machining, and painting.
