Construction Waste Chute Specifications and Throughput Calculation

Throughput is the core performance indicator of a construction waste chute, determining how much waste can be handled per unit time. Reasonable throughput calculation and proper specification selection avoid insufficient capacity or over-configuration. This article details the throughput calculation method.

1. Definition of Throughput
2. Hourly Throughput

• The volume of waste that can pass through the pipe per hour
• Unit: m³/h
• Depends on diameter, falling speed, and waste density

2. Daily Throughput

• Handling volume for 8 working hours per day
• Unit: m³/day
• Hourly throughput ×8h ×0.8 (coefficient)

3. Per-Shift Throughput

• Handling volume for one shift (8h) per day
• Actual throughput is affected by loading frequency

1. Throughput Calculation Formula

Theoretical throughput:
Q = A × v × η

• A: pipe cross-sectional area (m²)
• v: waste falling speed (m/s)
• η: filling ratio (0.3–0.5; the pipe is not completely filled with waste)

Example (500mm Standard):

• A = 3.14 × 0.25² = 0.196m²
• v = 15m/s
• η = 0.3
• Q = 0.196 × 15 × 0.3 = 0.88m³/s
• Actual hourly: 0.88 × 3600 × 0.5 = 1584m³/h (the theoretical value is too large)

Actual throughput is limited by loading frequency:

• Workers load about 2–3 times per minute
• Each load is about 0.1m³
• Actual hourly throughput is about 2–3 m³

III. Actual Throughput of Each Specification

1. Waste Volume Estimation
2. Estimation by Building Area

• Main structure stage: 0.02–0.03 m³/m²
• Masonry stage: 0.03–0.05 m³/m²
• Decoration stage: 0.01–0.02 m³/m²
• Demolition stage: 0.1–0.2 m³/m²

Example: a 20-story residential building, 1000m² per floor

• Total waste in masonry stage: 20×1000×0.04=800m³
• Masonry time per floor is about 3 days
• Waste per floor is 40m³, completed in 3 days
• Daily average about 13m³/day
• A 500mm Standard (15–25 m³/day) is sufficient

2. By Waste Density

• Crushed brick density: 1200–1500 kg/m³
• Concrete blocks: 1800–2200 kg/m³
• Decoration waste: 500–800 kg/m³
• Mixed waste: 1000–1300 kg/m³

1. Factors Affecting Throughput
2. Effect of Diameter

• The larger the diameter, the larger the cross-sectional area
• 500mm has 56% larger cross-sectional area than 400mm
• Throughput increases accordingly

2. Effect of Falling Speed

• The faster the speed, the greater the throughput
• But excessive speed causes impact and blockage
• Design speed 15–20 m/s

3. Effect of Waste Lump Size

• Large waste lumps occupy pipe space
• Filling ratio decreases
• Throughput decreases

4. Effect of Loading Frequency

• Worker loading speed is the bottleneck
• Simultaneous loading from multiple floors increases total throughput
• About 1–2 m³/h per feed inlet

5. Effect of Blockage

• Blockage interrupts flow
• Buffer design reduces blockage
• Actual availability rate is about 90%

1. Signs of Insufficient Throughput
2. Queuing at feed inlets, workers waiting
3. Waste piling up on floors
4. Schedule delays
5. Forced to use tower crane lifting (high cost)

VII. Measures to Increase Throughput

1. Choose one size larger diameter: replace 400mm with 500mm
2. Multiple feed inlets: 2 feed inlets per floor
3. Double-shift operation: extend working hours
4. Reduce large lumps: install a grid at the feed inlet
5. Reduce blockage: properly install buffer sections

VIII. Longkang Selection Service

Longkang calculates throughput requirements based on the following data:

1. Building area and number of floors
2. Construction stage and schedule
3. Waste type and density
4. Number of floor feed inlets

Provides:

1. Daily average waste volume estimate
2. Throughput requirement
3. Recommended chute specification
4. Number of feed inlets
5. Whether dual parallel pipes are needed