IRC 126:2017 offers detailed directives for the design, calibration, functioning, upkeep, and safety protocols of Wet Mix Plants utilized in highway construction projects. It is aimed at engineers, contractors, and technical personnel focusing on Wet Mix Macadam (WMM) production, ensuring precise measurement of aggregates and water, optimized plant configuration, and adherence to environmental and operational standards. The code enhances construction quality, operational efficiency, and environmental compliance within wet mix plant activities.
Overview
IRC 126:2017 offers detailed directives for the design, calibration, functioning, upkeep, and safety protocols of Wet Mix Plants utilized in highway construction projects. It is aimed at engineers, contractors, and technical personnel focusing on Wet Mix Macadam (WMM) production, ensuring precise measurement of aggregates and water, optimized plant configuration, and adherence to environmental and operational standards. The code enhances construction quality, operational efficiency, and environmental compliance within wet mix plant activities.
Audience
Contents
Structure
The guideline comprehensively covers specifications, calibration, and operational practices for Wet Mix Macadam plants, emphasizing: plant components such as aggregate bins, pug mills, feeders, water metering, and conveyors; calibration accuracy for aggregates and water; power needs and output estimations; emission and noise standards for diesel generator sets; maintenance routines and safety protocols; as well as pollution control measures like dust suppression and greenbelt establishment.
This section introduces the importance of precise calibration to ensure correct aggregate and water proportions. It details the calibration steps for belt scales (load cells), including warm-up, zeroing, and validation with known weights at various feed rates. Feeder calibration methods for both constant and variable speed drives are outlined, along with water metering system calibration to align with mix design requirements. Examples of typical aggregate feed rates are also provided.
Describes the major assemblies essential for producing quality bituminous mixes, including cold aggregate bins segregated by size, conveyor belts, the pug mill mixer, bitumen heating and spraying units, the filler fines feeding system, the control panel, and the power source. Relevant tables specify power requirements, paddle tip numbers, emission limitations, and calibration intervals necessary for efficient plant operation.
Although explicit clauses on calibration are limited, the document provides charts and tables to guide calibration frequency and tolerances. Procedures for adjusting bin outputs, calculating calibration factors, and applying these to maintain accuracy in aggregate dosing are detailed. Recommended calibration intervals and allowable deviation percentages are also highlighted.
Explains the function of the charging conveyor in transferring processed aggregates to the pug mill, detailing permissible inclination angles for plain and v-cleated belts, main components such as pulleys, idlers, rollers, tension devices, and drive systems. Calibration of the aggregate metering system is emphasized to ensure consistent feed rates, supported by design parameters and capacity formulas.
Outlines the system components including the filler silo, transfer mechanisms like bucket elevators or pneumatic conveyors, and dosing devices such as rotary metering valves combined with screw conveyors or continuous weighing systems. Typical specifications, capacity calculations, and the process flow for controlled delivery of filler fines to the pug mill are explained.
Defines the required number of paddle tips based on plant output capacity, with a general ratio of one paddle tip per 4.6 tons per hour. Minimum paddle tip face area and appropriate arrangement to guarantee uniform mixing and steady output are discussed, supported by formulas and schematic flowcharts.
Details maintenance routines for belt scale calibration involving conveyor warm-up, zeroing, test runs with measured aggregate quantities, and adjustments to minimize deviation across varying feed rates. Feeder calibration procedures for constant and variable speed drives are described along with water metering system calibration. Emphasis is placed on regular calibration to sustain accuracy and plant efficiency.
Highlights safety protocols including operator seating and vigilance, use of personal protective equipment, electrical safety, fuel handling precautions, emergency stop accessibility, and clean work environments. Also covers maintenance safety such as hydraulic pressure release, battery disconnection before servicing, and protective gear during welding, supported by flow diagrams illustrating safety workflows.
Specifies emission limits for diesel generator sets up to 800 kW in terms of NO + HC, CO, particulate matter, and smoke opacity as per government notifications. Noise limits, typically capped at 75 dB(A) at one meter, are discussed along with recommendations for acoustic enclosures and silencers to ensure compliance with environmental protection regulations.
Provides example calculations for required volume of Wet Mix Macadam for specified road dimensions and thickness. Includes tabulated data on power requirements, paddle tip numbers, emission limits, and calibration tolerances. Addresses noise limits and pollution control measures such as dust suppression and greenbelt maintenance, concluding with operational best practices for greasing, cleaning, and safety.
Discusses emission and noise parameters aligned with statutory environment protection rules. Emphasizes calibration accuracy for aggregates and water to maintain mix quality. Includes key formulas and calibration steps, supported by tables and charts for emission limits and calibration schedules to ensure environmental compliance and consistent product quality.
Frequently Asked
The recommended calibration procedures include conducting periodic calibration, such as monthly or after maintenance; performing zero calibration to ensure the scale reads zero without load; executing span calibration using known weights or measured materials; running the belt feeder at steady speed and collecting output for weighing; adjusting scale output to match actual weights; and verifying that accuracy falls within permissible tolerances of ±2% for aggregates and ±1% for cement feeders. Calibration charts plotting actual weights against scale readings should be maintained, and detailed records of calibration activities must be documented.
IRC 126 stresses the necessity of systematic maintenance including regular calibration of belt scales by warming up the conveyor, zeroing the scale, conducting test runs with known aggregate weights, and adjusting scale readings to minimize deviations. Feeder calibration is performed by preparing charts correlating feed rates with gate openings for constant speed drives or belt speed for variable drives, with recalibration after material changes. Water metering systems require comparison with certified instruments and adjustments to match mix design water requirements. These practices ensure accurate proportioning, reduce errors, and uphold plant efficiency.
Key safety measures include thorough training of all personnel, ensuring use of personal protective equipment such as helmets, gloves, goggles, and safety belts, maintaining clean and slip-free work platforms with adequate lighting, installing guards and emergency stop switches, enforcing strict fuel handling protocols prohibiting open flames near storage, and maintaining firefighting equipment. Operators must remain seated during equipment operation with clear visibility, never leave machines unattended while running, and follow prescribed shutdown procedures. Maintenance work should adhere to manufacturer guidelines, including releasing hydraulic pressure and disconnecting batteries before servicing, while wearing appropriate protective gear.
For diesel gensets up to 800 kW, emission limits specified include maximum permissible values for NO + HC, CO, particulate matter, and smoke opacity as per Environment (Protection) Rules. Specifically, NO + HC limits range from ≤7.5 g/kW-hr for gensets up to 19 kW, ≤4.7 g/kW-hr for 19-75 kW, and ≤4.0 g/kW-hr for 75-800 kW categories. Smoke opacity must not exceed 0.7 m⁻¹. Noise emissions are generally restricted to 75 dB(A) at 1 meter distance, with recommendations for acoustic enclosures and silencers to meet regulatory requirements.
The standard mandates uniform gradation through precise blending of aggregates and controlled feeding via calibrated feeders. The filler fines feeding system incorporates a silo supplied by bucket elevators or pneumatic conveyors, delivering fines to the pug mill through rotary metering valves combined with screw conveyors or continuous weighing systems for high accuracy. Calibration of belt scales and feeders ensures measurement accuracy by correlating scale readings with certified weights. Calibration charts are employed to set feeder gate openings and belt speeds for both constant and variable speed drives, maintaining desired feed rates per mix design. These measures guarantee consistent mix quality and minimal deviation.
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