Guidelines on Wet Mix Plant

IRC 126 - Scope Summary

The scope of IRC 126 covers specifications, calibration, and operational guidelines for Wet Mix Macadam (WMM) plants, focusing on:

• Plant Components: Aggregate bins, pug mill, feeders, water metering, and conveyors.
• Calibration: Ensuring accuracy in aggregate and water measurement.
• Power & Output: Typical power requirements and output calculations.
• Emission & Noise Limits: Compliance with environmental norms for DG sets.
• Maintenance & Safety: Regular checks, greasing, and safety precautions.
• Pollution Control: Dust suppression, wind barriers, and green belts.

Key Formulas & Tables

1. Aggregate Feed Rate (Constant Speed Drive):

[ \text{Feed rate (TPH)} = 0.06 \times \left(\text{Aggregate Weight on Belt (kg)} \times \text{Belt Speed (m/min)} + \text{Belt Section Length (m)}\right) ]

2. Calibration Frequency & Tolerance (Table 4):

3. Sample Output Calculation:

For 1 km road, 7 m wide, 150 mm thick WMM:

[ \text{Volume} = 0.15 \times 7 \times 1000 = 1050 , \text{cum} ]

Important Notes

• Calibration charts are essential for feeders (constant or variable speed).
• Emission limits and noise levels must comply with Environment Protection Rules.
• Safety and maintenance practices are critical for plant longevity and operator safety.

flowchart TD
    A[Aggregate Bins] --> B[Feeders]
    B --> C[Pug Mill]
    C --> D[Load Cell (Belt Scale)]
    D --> E[Water Metering System]
    E --> F[Mixing & Output]
    F --> G[Calibration & Maintenance]

This diagram shows the flow of materials and calibration points in a WMM plant as per IRC

IRC 126: Introduction - Key Formulas, Tables & Specifications

1. Plant Calibration Overview

Ensures accurate measurement & proportioning of aggregates and water to minimize deviations.

2. Calibration Procedures

A. Belt Scale (Load Cell) Calibration

• Warm up conveyor 1 hour.
• Zero the scale without material.
• Run ~10 tonnes aggregate, measure with certified weigh scale.
• Compare belt scale reading vs actual weight; adjust per manufacturer.
• Repeat at low, medium, high feed rates.

B. Feeder Calibration

B.1 Constant Speed Drive:

[ \text{Feed rate (TPH)} = 0.06 \times (\text{Aggregate Weight on Belt (kg)} \times \text{Belt Speed (m/min)}) + \text{Belt Section Length (m)} ]

• Prepare calibration charts plotting feed rate vs gate opening (10%-100%).
• Use charts to set gate openings for required feed rates.

B.2 Variable Speed Drive:

• Vary belt speed (10%-90%) at fixed gate opening.
• Plot feed rate vs belt speed (%).
• Use charts to select belt speed for target feed rates.

3. Water Metering System Calibration

• Compare electronic flow meter with certified instrument.
• Adjust flow meter & valve settings to match mix formula water requirements.

4. Typical Aggregate Feed Rate Example for 90 TPH Plant

5. Reference Tables (from IRC 126)

Major Assemblies of Wet Mix Plant (IRC 126)

IRC 126 outlines the key components and their specifications for a Wet Mix Plant, essential for quality bituminous mix production:

Key Assemblies:

• Cold Aggregate Bins: Multiple compartments for different aggregate sizes.
• Conveyor Belts: For transferring aggregates to the pug mill.
• Pug Mill: Core mixing unit; ensures uniform mixing of aggregates and bitumen.
• Bitumen Tank and Sprayer: For heating and spraying bitumen on aggregates.
• Filler Feeding System: Adds mineral filler to the mix.
• Control Panel: For plant operation and monitoring.
• Power Unit: Diesel or electric motor driving the plant.

Important Tables from IRC 126:

Typical Power Requirement (Example from Table 1):

flowchart LR
    A[Cold Aggregate Bins] --> B[Conveyor Belts]
    B --> C[Pug Mill]
    C --> D[Bitumen Sprayer]
    D --> E[Mixing Chamber]
    E --> F[Output to Storage/Transport]
    subgraph Power Unit
        G[Diesel/Electric Motor]
    end
    G --> C

Summary: Ensure correct paddle tips (Table 2), maintain power within limits (Table 1), and follow calibration schedules (Table 4) for efficient operation.

IRC 126 - Plant Calibration: Key Points

Though IRC 126 lacks explicit clauses on Plant Calibration, related tables and charts provide essential guidance:

1. Typical Calibration Charts

• For 4-Bin Variable Drive WMM Plant and 4-Bin Fixed Drive WMM Plant, calibration charts help in:
  • Adjusting bin outputs for accurate aggregate proportions.
  • Ensuring mix consistency by correlating bin settings with actual material weight.

2. Important Tables

3. Calibration Frequency & Tolerance (from Table 4)

• Frequency: Typically weekly or monthly depending on plant usage.
• Tolerance: ±2% to ±5% permissible variation in aggregate weights.

4. General Calibration Formula

For each bin:

[ \text{Calibration Factor} = \frac{\text{Actual Weight (kg)}}{\text{Displayed Weight (kg)}} ]

Adjust bin settings by multiplying displayed weight by calibration factor for accurate dosing.

flowchart TD
    A[Start: Plant Calibration] --> B[Measure Actual Weight from Bin]
    B --> C[Compare with Displayed Weight]
    C --> D[Calculate Calibration Factor]
    D --> E[Adjust Bin Settings]
    E --> F[Re-check & Confirm Accuracy]
    F --> G[End]

Summary: Use calibration charts and Table 4 for scheduling calibration. Apply calibration factors to adjust bin outputs and maintain mix accuracy.

Charging Conveyor (IRC 126 - Clause 5.4)

• Purpose: Transfers aggregates from vibrating screen (after removing oversize) to pug mill.
• Inclination Angle:
  • Plain belt: ≤ 18°
  • V-cleated belt: up to 30°–40°
• Components:
  • Head and tail pulleys
  • Carrying idlers
  • Return rollers
  • Tensioning device
  • Belt of required width (reputed make)
  • Drive system (speed reducer or direct geared motor)
• Calibration: Aggregate metering system must be calibrated before work and periodically as per manufacturer.

Typical Design Considerations:

Basic formula for belt speed (v) and capacity (Q):

[ Q = A \times v \times \rho ]

Where:

• (Q) = Capacity (m³/s)
• (A) = Cross-sectional area of material on belt (m²)
• (v) = Belt speed (m/s)
• (\rho) = Bulk density of aggregate (kg/m³)

flowchart LR
    VibratingScreen -->|Aggregates| ChargingConveyor
    ChargingConveyor -->|Transfer| PugMill
    ChargingConveyor -->|Calibration| MeteringSystem

This ensures smooth aggregate transfer with controlled flow and minimal spillage.

IRC 126 – Filler Fines Feeding System Key Points

• System Components (Clause 5.7):
  • Filler silo: Adequate capacity to store lime/cement fines.
  • Transfer mechanism: Bucket elevator or pneumatic conveyor for moving bagged/bulk filler into the silo.
  • Dozing arrangement:
    • Rotary metering valve + precision screw conveyor, or
    • Continuous weighing system (for high precision dosing).
  • Delivers controlled quantity of fines to the pug mill.

Typical Specifications & Formulas

Process Flow (Fig. 6 Conceptual)

flowchart LR
    Bagged/Bulk Filler -->|Bucket Elevator/Pneumatic Conveyor| Silo
    Silo -->|Rotary Metering Valve + Screw Conveyor| Pug Mill

Note: For precise control, continuous weighing systems are preferred to maintain consistent filler dosing in the mix.

Paddle Arrangement - IRC 126 Key Points

1. Paddle Tip Number (Clause 4.6 & Table 2)

• Rule of Thumb: 1 paddle tip per 4.6 TPH of plant output.
• Example Table:

2. Paddle Tip Size (Clause 7.2)

• Minimum Face Area: 230 sq. cm per paddle tip (may vary by manufacturer).

3. Paddle Arrangement (Clause 7.4)

• Paddles must be arranged to ensure smooth operation and proper mixing.
• Adequate number and size of paddle tips ensure homogeneous mixing and consistent output.

Summary Formula:

[ \text{Number of Paddle Tips} = \frac{\text{Plant Output Capacity (TPH)}}{4.6} ]

flowchart LR
    A[Plant Output Capacity (TPH)] --> B[Calculate No. of Paddle Tips]
    B --> C[Ensure Minimum 230 sq.cm Face Area per Tip]
    C --> D[Paddle Arrangement for Smooth Operation]
    D --> E[Consistent & Homogeneous Mixing]

This arrangement ensures efficient mixing and reliable plant output.

Maintenance & Calibration Guidelines for Wet Mix Plant (IRC 126)

1. Belt Scale (Load Cell) Calibration

• Warm up conveyor for 1 hour.
• Zero the scale without material.
• Run ~10 tonnes aggregate to seat belt.
• Load aggregate into a tare-known truck; record weight difference.
• Compare truck weight with belt scale reading.
• Adjust scale until deviation is negligible.
• Repeat at low, medium, and high production rates.

2. Feeder Calibration

Constant Speed Drive

• Set gate opening (10%-100%).

• Calculate feed rate (TPH):

  [ \text{Feed rate} = 0.06 \times (\text{Aggregate weight on belt (kg)} \times \text{belt speed (m/min)}) + \text{belt section length (m)} ]

• Plot feed rate vs. gate opening.

• Use calibration charts to set gate openings for desired feed rates.

Variable Speed Drive

• Fix gate opening.
• Vary belt speed (10%-90%).
• Plot feed rate vs. belt speed %.
• Use chart to set belt speed for target feed rate.

3. Water Metering System Calibration

• Compare electronic flow meter with certified instrument.
• Adjust flow meter as per manufacturer.
• Record water pumped at different valve openings.
• Plot valve opening vs. water quantity.
• Determine valve opening for required water per mix formula.

Typical Aggregate Feed Rate Example (for 90 TPH plant):

flowchart LR
    A[Start Calibration] --> B[Belt Scale Calibration]
    B --> C[Feeder Calibration]
    C --> C1{Drive Type}
    C1 -->|Constant Speed| D[Gate Opening vs Feed Rate]
    C1 -->|Variable Speed| E[Belt Speed vs Feed Rate]
    D --> F[

IRC 126: Plant Safety Key Points

Safety Practices (Clause 9.1 & 9.2)

• Operator Safety:

  • Always operate equipment from designated operator’s seat.
  • Never leave running equipment unattended.
  • Ensure maximum visibility around operating area.
  • Use PPE: helmets, gloves, goggles, safety belts.
  • Avoid loose electrical connections; inspect cables periodically.
  • Store fuel/lubricants away from plant; no open fire near fuel tanks.
  • Emergency stop switch must be accessible near plant.
  • Blow siren before plant start.
  • Maintain clean, oil/grease-free platforms.

• Operational Checks:

  • Familiarize with all controls and gauges.
  • Inspect surroundings before starting.
  • Shut down by idling engine and setting controls to neutral.

• Maintenance (Clause 9.4):

  • Follow manufacturer’s servicing guidelines.
  • Release hydraulic pressure before servicing.
  • Disconnect battery before electrical work.
  • Use safety glasses and gloves during welding/metal work.

Tables of Interest

Summary Diagram: Plant Safety Workflow

flowchart TD
    A[Pre-operation Checks] --> B{Equipment Condition}
    B -->|Good| C[Start Plant]
    B -->|Unsafe| D[Do Not Operate]
    C --> E[Operator in Seat with PPE]
    E --> F[Continuous Monitoring]
    F --> G{Emergency?}
    G -->|Yes| H[Emergency Stop]
    G -->|No| I[Normal Operation]
    I --> J[Shutdown Procedure]
    J --> K[Maintenance & Servicing]
    K --> A

Keep safety first: Proper training, PPE, emergency readiness, and strict adherence to operation and maintenance protocols are essential for plant safety under IRC 126.

IRC 126: Emission and Noise Limits for Diesel Gensets in Wet Mix Plants

A. Emission Limits (per GSR Notifications)

• Limits are per GSR 771(E) and subsequent amendments under the Environment (Protection) Act, 1986.
• Applies to new diesel engines up to 800 kW.

B. Noise Limits

• Noise limits for diesel gensets are specified in the same appendix but typically must comply with local environmental regulations, commonly ≤ 75 dB(A) at 1 meter distance.
• Use acoustic enclosures or silencers to meet noise criteria.

Summary:

• Ensure genset emissions do not exceed the above g/kW-hr values.
• Maintain smoke opacity below 0.7 m⁻¹.
• Noise control measures are essential for compliance.

flowchart LR
    A[Diesel Genset] --> B{Power Category}
    B -->|Up to 19 kW| C[NO+HC ≤ 7.5 g/kW-hr]
    B -->|19-75 kW| D[NO+HC ≤ 4.7 g/kW-hr]
    B -->|75-800 kW| E[NO+HC ≤ 4.0 g/kW-hr]
    C & D & E --> F[Smoke ≤ 0.7 m⁻¹]
    F --> G[Noise ≤ 75 dB(A) (typical)]

For detailed compliance

Key Specifications & Tables for Production Output Analysis of Wet Mix Plant (IRC 126)

1. Sample Calculation (Appendix-V)

• For 1 km of 2-lane (7m wide) road with 150mm WMM thickness:

  [ \text{Volume} = 0.15 \times 7 \times 1000 = \mathbf{1050 , m^3} ]

• Plant capacity example: 100 TPH (Tons per hour)

2. Important Tables

3. Calibration Frequency & Tolerance (Table 4)

4. Noise Limits for DG Sets (Clause 17.05.2002)

• Max permissible sound pressure: 75 dB(A) at 1 m
• DG sets ≥ 1 Jan 2005 must have acoustic enclosures

5. Pollution Control Measures

• Dust suppression systems
• Wind breaking walls
• Stabilized internal roads
• Regular cleaning & wetting
• Green belt maintenance
• Use approved fuels/oils only

6. Do's & Don'ts Summary

• Regular greasing, cleaning, calibration
• Check belts, rollers, oil levels
• Safety precautions: no welding with load cell connected, proper earthing, avoid overload
• Never operate without training or proper power supply

flowchart LR
  A[Input: Road Dimensions & Thickness] --> B[Calculate Volume of WMM]
 

Environmental and Quality Considerations in IRC 126 (Wet Mix Plant)

Key Specifications:

• Emission Limits for Diesel Gensets:
  Refer to Appendix-I for emission and noise limits compliant with Environment (Protection) Rules, 1986.
  Typical limits include:

  • Smoke density and particulate matter limits
  • Noise levels within prescribed decibel ranges
  • Compliance ensures minimal environmental impact.

• Calibration for Quality Control:
  Calibration ensures accuracy in aggregate and water measurement, crucial for mix quality.

Important Calibration Formulas & Procedures

1. Aggregate Feed Rate (Constant Speed Drive):
[ \text{Feed rate (TPH)} = 0.06 \times (\text{Aggregate Weight on Belt (kg)} \times \text{Belt Speed (m/min)}) + \text{Belt Section Length (m)} ]

2. Belt Scale Calibration Steps:

• Warm up belt for 1 hour
• Zero the scale without load
• Run ~10 tonnes aggregate, measure with certified weigh scale
• Adjust scale until readings match within tolerance
• Repeat at low, medium, high feed rates

3. Feeder Calibration:

• For constant speed: Plot feed rate vs gate opening
• For variable speed: Plot feed rate vs % belt speed

4. Water Meter Calibration:

• Compare flow meter with certified instrument
• Adjust valve opening to match water requirement per mix design

Tables and Charts

• Table 3: Emission Limits for Diesel Gensets (Page 17)
• Table 4: Calibration Frequency & Tolerances (Page 18)
• Calibration charts (Figures 10 & 11) for feed rate vs gate opening or belt speed for 4-bin plants.

Summary Diagram: Calibration Process Flow

flowchart TD
    A[Start Calibration] --> B[Warm-up Belt Scale]
    B --> C[Zero Scale]
    C --> D[Run Aggregate & Weigh]
    D --> E{Compare Scale & Weighing}
    E -- Match --> F[Calibration Complete]
    E -- Not Match --> G[Adjust Scale Settings]
    G --> D

References:

• IRC 126, Appendix I-IV
• Environment (Protection) Rules, 1986
• IRC:109-201