General requirements for pan mixers for concrete

IS 12119: Scope - Key Specifications & Tables

Scope Summary:

• Covers concrete mixers with sizes designated in litres.
• Defines marking, power ratings, and unit specifications.
• Applicable for mixers with integral power units (petrol, diesel, gas, electric motors).

Key Marking Requirements (Clause 15.1)

Each mixer must have a rating plate with:

• Manufacturer's name
• Machine reference number
• Size of mixer (litres)
• Total mass (kg)
• Motor/engine speed (RPM)
• Power input (kW)
• Year of manufacture

Power Rating Table for Mixers (Clause 5.6.1)

Units (SI) Used in IS 12119

Additional Notes

• Power units must comply with relevant Indian Standards.
• Rating plate must be firmly attached and not easily removable.

flowchart LR
    A[Concrete Mixer] --> B[Rating Plate]
    B --> C[Manufacturer Name]
    B --> D[Machine Ref. No.]
    B --> E[Size (litres)]
    B --> F[Mass (kg)]
    B --> G[Motor Speed (RPM)]
    B --> H[Power Input (kW)]
    B --> I[Year of Manufacture]

This summary aids in understanding the scope

IS 12119: References and Definitions - Key Points

1. Definitions

• As per Clause 2.1, definitions follow IS 11386-1985 for mixer terminology.

2. Marking Requirements (Clause 15.1)

Each mixer must have a rating plate with:

• Manufacturer's name
• Machine reference number
• Mixer size (litres)
• Total mass (kg)
• Motor/engine speed (RPM)
• Power input (kW)
• Year of manufacture

3. Units and Symbols (SI Units)

4. Mixer Drive Power Ratings (Clause 5.6.1)

Summary

• Use IS 11386-1985 for mixer terms.
• Rating plate info is mandatory for traceability and safety.
• Power and speed ratings must meet or exceed table values.
• SI units and definitions ensure standardization.

IS 12119: Designation of Size and Types of Pan Mixers

Key Specifications:

• Size Designation: Based on input volume of unmixed materials (litres), not the final concrete volume.
• Rating Plate (Clause 15.1) must include:
  • Manufacturer's name
  • Machine reference number
  • Size in litres
  • Total mass (kg)
  • Motor/engine speed (rpm)
  • Power input (kW or HP)
  • Year of manufacture

Material & Thickness (Clause 4.2, Table 1):

• Steel: Weldable structural steel (IS 8500-1977)
• Wear plates: 10 mm thick, 45C8 steel (IS 1570 Part 2-1979)

Units (SI system):

• Volume: Litres (L)
• Thickness: Millimeters (mm)
• Mass: Kilograms (kg)
• Speed: Revolutions per minute (rpm)
• Power: Watts (W) or kilowatts (kW)

flowchart TD
    A[Input Volume (Litres)] --> B[Size Designation]
    B --> C[Pan Mixer Construction]
    C --> D[Steel Thickness per Size]
    D --> E[Wear Plates: 10 mm, 45C8 Steel]
    B --> F[Rating Plate with Key Info]

Summary: Mixer sizes are nominal input volumes; pan thickness varies by size per Table 1; rating plates must display key details for identification and operation.

IS 12119: Mixing Pan Construction - Key Specifications

1. Material & Construction (Clause 4.1 & 4.2)

• Mixing pan: Welded steel construction.
• Wear plates: 10 mm thick, made of 45C8 steel (IS 1570 Part 2 - 1979), interchangeable, fixed by countersunk screws.
• Mixer base & walls: Lined with wear-resistant plates.
• Frame: Welded steel plate construction, anchored to mixer platform.

2. Minimum Thickness of Pan Steel Plate (IS 8500-1977, Table 1)

• Steel: Weldable structural steel (medium & high strength).

Summary Diagram

graph TD
A[Mixing Pan] --> B[Welded Steel Construction]
A --> C[Wear Plates (10 mm, 45C8 Steel)]
A --> D[Minimum Thickness per Capacity]
D --> E[375 P: 6-18 mm]
D --> F[500-1500 P: 10-12 mm]
D --> G[2000-4500 P: 12-14 mm]
A --> H[Anchored Frame Structure]

Note: Pan size is based on input volume of unmixed materials, per Clause 0.3.

This ensures durability and wear resistance for efficient mixing operations.

IS 12119: Mixing Arms and Paddles Key Specifications

1. Mixing Arms (Clause 5.2)

• Material: Carbon steel bars, Grade 27C 15 as per IS 1570 (Part 2)-1979.
• Treatment: Stress relieved if hot bending is done.
• Wear sleeves: Fitted on arms contacting the mixer material for durability.

2. Mixing Paddles (Clause 5.3)

• Material: Wear-resistant castings.
• Fixing: Mounted for easy replacement.
• Cleaning: Inner and outer scrapers for complete pan wall cleaning.

3. Number of Mixing Paddles (Clause 5.4)

4. Power Unit Ratings (Clause 5.6.1)

This ensures durability, easy maintenance, and adequate power for mixing operations as per IS 12119.

IS 12119: Safety Guards for Mixers

Key Specifications (Clause 6.2)

• Safety guard must cover the mixer discharge door.
• The guard should be easy to remove for maintenance or cleaning.

Additional Safety Features

• Safety limit switches (Clause 5.5.2):
  • Installed on segment and cleaning flaps.
  • Mixer switches off automatically when flaps are open.

Marking Requirements (Clause 15.1)

Each mixer must have a rating plate with:

• Manufacturer's name
• Machine reference number
• Mixer size (litres)
• Total mass (kg)
• Motor speed (rpm)
• Power input (W)
• Year of manufacture

Practical Notes:

• Guards must not obstruct operation but ensure operator safety.
• Use quick-release fasteners or hinges for easy removal.
• Safety switches prevent accidental operation during cleaning.

Relevant Units (SI)

flowchart LR
    A[Mixer Discharge Door] --> B[Safety Guard]
    B --> C{Easy to Remove?}
    C -->|Yes| D[Safe Operation]
    C -->|No| E[Modify Guard Design]
    A --> F[Cleaning Flaps]
    F --> G[Safety Limit Switch]
    G --> H{Flap Open?}
    H -->|Yes| I[Mixer OFF]
    H -->|No| J[Mixer ON]

Summary: Provide a removable guard on the discharge door and safety switches on flaps to ensure operator safety and compliance with IS 12119.

IS 12119: Mixer Inlet - Key Specifications & Tables

1. Mixer Drive Power Ratings (Clause 5.6.1)

• Power units (petrol, diesel, gas, or electric motors) must comply with relevant IS standards.
• Power rating and RPM must be clearly indicated on the power unit nameplate.

2. Mixer Inlet (Clause 7)

• The inlet must be designed to allow smooth feeding of materials.
• Safety guards must cover the mixer discharge door and be easily removable (Clause 6.2).

Additional Notes

• Mixer sizes are based on input volume of unmixed materials, not mixed concrete volume.
• Integral power units are typically mounted centrally on the gear speed reducer for a self-contained drive system.

flowchart LR
    A[Material Input] --> B[Mixer Inlet]
    B --> C[Mixing Chamber]
    C --> D[Discharge Door]
    D --> E[Safety Guard (removable)]
    F[Power Unit (kW/RPM)] --> C

This diagram shows material flow and power input related to the mixer inlet and safety guard.

IS 12119: Water Meter & Flow Control - Key Points

Water Meter (Clause 8.2 & 8.1):

• Dial type meter, operating at 4 to 5 bars pressure.
• Measures water flow quantity accurately.
• Includes a quick action valve (manual or electric) and a dirt trap in the water circuit.
• Water spray device fitted at mixer pan's upper edge for uniform water addition and cleaning.

Mixer Power Unit Ratings (Clause 5.6.1)

Rating Plate Requirements (Clause 15.1)

Each mixer must have a rating plate with:

• Manufacturer's name
• Machine reference number
• Mixer size (litres)
• Total mass (kg)
• Motor speed (RPM)
• Power input (kW)
• Year of manufacture

Summary Diagram of Water Flow Control System

flowchart LR
    WM[Water Meter (Dial Type)] --> QV[Quick Action Valve]
    QV --> DT[Dirt Trap]
    DT --> WS[Water Spray Device]
    WS --> Mixer[Mixing Chamber]

This ensures accurate water measurement, controlled flow, and uniform mixing per IS 12119 standards.

IS 12119 covers design and construction of industrial mixers, including motor assembly and protective covers. Although clauses are not explicitly numbered here, key points for Motor Assembly and Protective Cover are:

Motor Assembly Aperture

• Should provide adequate ventilation to avoid overheating.
• Aperture size depends on motor rating; typically, 10-15% of motor surface area for airflow.

Mixer Support Frame and Cover

• Frame must be rigid and vibration-resistant.
• Cover should prevent ingress of dust and moisture.
• Use mild steel or stainless steel with minimum thickness 3-5 mm depending on environment.

Rotor Cover

• Must ensure safe clearance from rotor to prevent contact.
• Minimum clearance usually 10-15 mm.
• Should allow easy access for maintenance.

Top Protective Cover

• Protects motor and gearbox from external damage.
• Should be removable and provide adequate ventilation.
• Use corrosion-resistant materials.

Typical Specifications Summary

flowchart TD
    A[Motor Assembly] --> B[Support Frame]
    B --> C[Protective Cover]
    C --> D[Ventilation Aperture]
    C --> E[Safety Clearance]

This ensures motor protection, cooling, and operational safety per IS 12119 guidelines.

IS 12119: Weighing Mechanism Key Points

Clause 11.1: Weighing Mechanism Specifications

• Weighing mechanism may be integral to the mixer.
• Accuracy: Error ≤ ±1% during all loading stages under normal conditions.
• Ensures precise measurement of mix ingredients while loading.

Important Specifications for Weighing Mechanism

Related Operational Timings (Clause 10.1)

Additional Notes

• The weighing indicator must reliably reflect the weight in real-time.
• The weighing system should be calibrated and maintained to retain accuracy.
• The integral weighing mechanism supports automated batching and quality control.

flowchart LR
    A[Start Loading] --> B[Weighing Mechanism]
    B --> C{Weight within ±1%?}
    C -- Yes --> D[Continue Loading]
    C -- No --> E[Adjust Feed]
    D --> F[Mixing Cycle]
    F --> G[Discharge]
    G --> H[End]

Summary: IS 12119 mandates an integral weighing mechanism with ±1% accuracy during loading, supporting precise batching and consistent concrete quality.

Integral Drag Feeder (IS 12119 Key Points)

• Clause 12.1: The integral drag feeder is a mechanical feeder fitted with the mixer to power-feed aggregate into the mixer hopper.
• If the feeder is a rope-handled scoop type (hand-guided by an operator other than the mixer operator), the control must be 'Fail-to-safe' to prevent accidents.

Power Unit Ratings for Mixers (Clause 5.6.1)

• Power units (petrol, diesel, gas, electric motors) must comply with Indian Standards and be rated accordingly.

Weighing Mechanism (Clause 11.1)

• Integral weighing mechanism must ensure ±1% accuracy in all loading stages.
• Enables weighing while loading ingredients into the mixer hopper.

Additional Design Notes

• Pan mixer inlet chute angle ≥ 50° to horizontal for complete discharge (Clause 7.1).
• Integral feeders improve feeding efficiency and safety with proper control mechanisms.

flowchart LR
    A[Aggregate Storage] --> B[Integral Drag Feeder]
    B --> C[Mixer Hopper]
    C --> D[Mixing Chamber]
    B -. Fail-to-safe Control .-> E[Operator Control]

This diagram illustrates the integral drag feeder feeding aggregate into the mixer hopper with fail-safe control.

IS 12119 - Lifting Arrangements (Clause 13)

• Clause 13.1: Each concrete mixer must be equipped with lifting eyes, shackles, or suitable lifting points to enable safe lifting using slinging chains.
• These lifting points should be designed to bear the total mass of the mixer, including any attachments or contents during lifting.
• The arrangement must ensure safe and stable lifting without risk of slippage or damage.

Key Specifications for Lifting Arrangements:

Additional Notes:

• The total mass (Clause 15.1d) is marked on the rating plate for reference during lifting.
• Use appropriate lifting chains and slings rated for the mixer's weight.
• Follow standard lifting practices per IS 413 (Code of Practice for Lifting Devices).

Diagram: Basic Lifting Arrangement Concept

graph TD
A[Mixer Body] --> B[Lifting Eyes/Shackles]
B --> C[Chains/Slings]
C --> D[Lifting Hook/Crane]

For detailed design of lifting eyes/shackles, refer to IS 3837 or IS 413 for dimensions and load factors.

Mixing Efficiency - IS 12119 Key Points

• Testing Method:
  Mixing efficiency shall be tested under normal working conditions per IS 4634-1968.

• Mixer Power Ratings (Clause 5.6.1):
  Power units must meet minimum kW and RPM ratings as per mixer size:

• Number of Mixing Paddles (Clause 5.4):

Notes:

• Mixer size refers to input volume of unmixed materials.
• Power units can be petrol, diesel, gas, or electric motors.
• Efficiency depends on adequate power and paddle numbers to ensure thorough mixing.

flowchart LR
    A[Mixer Size] --> B[Power Unit Rating]
    A --> C[Number of Mixing Paddles]
    B & C --> D[Mixing Efficiency Test (IS 4634)]

For detailed mixing efficiency calculations, refer to IS 4634-1968 test procedures.

IS 12119 Key Points: Toolbox & Maintenance Instructions

• Toolbox Requirements (Clause 14.1):

  • Provide a strong toolbox with lock and key.
  • Include tools for normal running adjustments and lubrication.
  • Maintain an inventory list of tools inside the box.
  • Supply operating & maintenance instructions and a spare parts list with each machine.

• Lifting Provisions (Clause 13.1):

  • Mixers must have eyes, shackles, or suitable lifting means for safe hoisting.

• Rating Plate Details (Clause 15.1):
  Each mixer should have a rating plate with:

  • Manufacturer's name
  • Machine reference number
  • Mixer size (litres)
  • Total mass (kg)
  • Motor/engine speed (RPM)
  • Power input (kW)
  • Year of manufacture

• Power Ratings Table (Clause 5.6.1):

Summary:
Ensure toolbox completeness, clear rating plates, and proper lifting provisions for safety and maintenance. Power units must meet or exceed the specified kW/RPM ratings.

flowchart LR
    A[Machine Delivered] --> B[Toolbox Provided]
    B --> C[Tools for Adjustments & Lubrication]
    B --> D[Inventory List]
    A --> E[Operating & Maintenance Instructions]
    A --> F[Spare Parts List]
    A --> G[Rating Plate Attached]
    G --> H[Manufacturer Info]
    G --> I[Machine Ref No.]
    G --> J