Here's a breakdown of the savings, typically quantified in both time and manpower:
1. Direct Labor and Time Savings
Manual Installation: Requires a large crew (often 6-10+ workers). The process involves lifting heavy segments with chain hoists, temporary supports, and extensive manual positioning using crowbars and brute force. Installing a single arch segment can take 30 minutes to several hours.
With a Trolley System: The crew size can be reduced to 3-4 skilled operators. The trolley acts as a precise, remote-controlled positioning device. Installation time per segment can be reduced to as little as 5-15 minutes.
Quantitative Estimate: In terms of man-hours per segment, the trolley system can easily save 60-80%. What might take 60 man-hours manually could be accomplished in 10-15 man-hours with a trolley.
2. Key Areas of Labor Reduction
Elimination of Manual Heavy Lifting: The most significant saving. The trolley's hydraulic system bears the entire weight (often several tons), removing the need for large teams of laborers to push, pull, and hold segments.
Dramatically Reduced Positioning Time: Fine-tuning the position of a multi-ton concrete segment manually is painstakingly slow. The trolley allows for millimeter-precise adjustments in all axes (lift, swing, tilt, translation) at the push of a button by a single operator.
Simplified Temporary Works: Manual methods require extensive temporary propping and shoring. A trolley system, especially an erector-launcher combination, often has integrated support systems, reducing the labor needed to build and dismantle temporary structures.
Faster Cycle Time: The speed of segment pickup, transport, and placement is greatly increased, allowing more segments to be installed per shift.
3. Beyond Direct Labor: Indirect Savings
The savings extend beyond just the number of workers on the face:
Safety: Reduces the risk of severe crush injuries and musculoskeletal disorders from heavy lifting. This saves potential costs from accidents, insurance, and downtime.
Quality & Precision: Ensures perfect alignment, leading to a better final structure with fewer leaks or defects. This saves labor on remedial works and grouting.
Reduced Fatigue: Workers are operators, not laborers, leading to better focus, fewer errors, and higher sustained productivity over a shift.
Predictable Schedule: The process becomes more industrialized and less weather/worker-dependent, improving project timeline reliability.
Practical Example: Tunnel Arch Installation
Scenario: Installing 10-ton precast concrete arch segments for a utility tunnel.
Manual Method: A crew of 8 uses a mobile crane to lower the segment, then manually guides it with tag lines, uses jacks and levers to position it, and finally installs bolts. Time: ~45 minutes per segment. Total man-hours per segment: 6 (8 workers * 0.75 hours).
Trolley Method: A crew of 4 operates the trolley. The trolley picks up the segment, transports it to the face, and the operator uses remote controls to position it precisely. Bolting crew moves in. Time: ~12 minutes per segment. Total man-hours per segment: 0.8 (4 workers * 0.2 hours).
Savings in this example: ~87% reduction in direct man-hours per segment. For a project with hundreds of segments, this compounds into enormous labor cost savings and a drastically shortened critical path.
Conclusion
An arch installation trolley doesn't just "save a little labor"; it fundamentally changes the nature of the work. It transforms a labor-intensive, heavy, and hazardous manual handling task into a mechanized, precision operation.
A conservative overall estimate is that a well-implemented arch installation trolley system saves 70-85% of the direct labor man-hours and provides even greater value through improved safety, quality, and schedule certainty. The initial investment in the equipment is quickly offset by the dramatic reduction in labor costs and increased productivity.
