Method of sub-division of a gross sample of powder used for determination of particle size

IS 4879: Introduction and Adoption - Key Points

• Scope: IS 4879 relates to sampling and testing procedures, aligned with definitions in IS 4124-1967.

• Adoption: The standard adopts established IS definitions and procedures for consistent sampling/testing in civil engineering materials.

• Reference Publications:

  • ISI Bulletin (monthly)
  • Annual Reports (1948-49 onwards)
  • Handbook of ISI Publications, 1968

• Categories Covered: The Civil Engineering group under IS includes:

  • Aggregates, Bricks, Cement, Concrete Design & Testing
  • Reinforcement, Structural Design, Soil Engineering
  • Timber Design, Waterproofing, and many more.

• Material Specification Example: Sheet brass is recommended for small oscillating hopper sample dividers (Clause 6.4).

Relevant Definitions (from IS 4124-1967)

• Sampling methods
• Sieving and sizing techniques

Summary Table: IS Civil Engineering Categories

This standard ensures uniformity in sampling/testing aligned with ISI's broad civil engineering framework.

flowchart LR
    A[IS 4879] --> B[Sampling & Testing Procedures]
    B --> C[Definitions per IS 4124-1967]
    B --> D[Material Specifications]
    B --> E[Applicable Civil Engineering Categories]
    E --> F[Aggregates, Concrete, Reinforcement]
    E --> G[Soil, Timber, Waterproofing]

IS 4879: Scope - Key Specifications & Dimensions

Scope:
IS 4879 covers apparatus and methods for sampling powders and slurries, focusing on design and precautions for sample dividers like oscillating hopper dividers.

Key Specifications:

• Material:

  • Sheet brass or any suitable metal recommended for parts contacting powders/slurries.
  • Plastics are not allowed where contact occurs (Clause 3.1.5.4a).

• Sampling Environment:

  • Enclosed space free from air currents to prevent loss of fine particles (Clause 3.1.5.4b).

Oscillating Hopper Sample Divider Dimensions (All in mm):

Notes:

• Dimensions ensure representative sampling volume.
• Receiving hoppers should be roughly the same size as oscillating hopper.
• Apparatus must prevent dust escape to avoid sample loss.

flowchart LR
    A[Powder/Slurry Feed] --> B[Oscillating Hopper]
    B --> C[Interchangeable Orifice]
    C --> D[Receiving Hopper]
    D --> E[Sample Collection]
    style B fill:#f9f,stroke:#333,stroke-width:2px

This concise summary aids in understanding the scope and key dimensional specs from IS 4879 for sample dividers.

IS 4879 - Definitions (Clause 2.0)

• The standard adopts definitions from IS 4124:1967 alongside its own.
• IS 4124 covers terms related to sampling and particle size determination of powders.

Key Points:

• Definitions primarily relate to sampling methods, sample size, and subdivision techniques.
• The standard aligns with BS 3406: Part I:1961, emphasizing international coordination.
• Typical terms include:
  • Gross Sample: The initial large quantity of material collected.
  • Working Sample: A reduced sample obtained by subdivision.
  • Sample Divider: Device used to split samples into representative portions.

Material Specification (Clause 6.4):

• Sheet brass is recommended for fabricating sample dividers (e.g., oscillating hopper sample divider).

Reference Table: Sample Divider Material

Conceptual Diagram: Sample Subdivision Process

flowchart LR
    A[Gross Sample] --> B[Sample Divider]
    B --> C[Working Sample]
    C --> D[Testing / Analysis]

Summary: IS 4879 bases its definitions on IS 4124, focusing on sampling terminology and methods, with material guidance for equipment such as brass for sample dividers.

IS 4879: Methods of Sub-Division for Particle Size Analysis

The standard specifies methods to reduce a gross sample to the required quantity for particle size distribution analysis:

Key Methods (Clause 3.1 & 1.1):

Notes:

• Halving: Splitting the sample into two equal parts repeatedly.
• Coning and Quartering: Form a cone, flatten, divide into quarters, discard alternate quarters.
• Sample Dividers: Mechanical devices ensuring representative sub-samples.

These methods ensure representative and reproducible sub-samples for accurate particle size analysis.

flowchart LR
    A[Gross Sample] --> B[Halving ( >1500L to 500L)]
    B --> C[Turntable / Slotted Cone Divider ( >1500L to 1L)]
    C --> D[Large Oscillating Hopper (100L to 1L)]
    D --> E[Grid Type Divider (50L to 5mL)]
    E --> F[Small Oscillating Hopper (1L to 0.2mL)]
    B --> G[Coning & Quartering ( ≤1000L to 25L)]

This flow ensures systematic reduction maintaining sample representativity.

IS 4879 - Method I: Coning and Quartering

Key Steps (Clause 3.1.2.1):

1. Form Cone: Shovel material into a conical pile on a smooth hard surface, placing each shovelful on top of the last, keeping apex stable.
2. Flatten Cone: Use shovel back with rotary motion to flatten cone uniformly (equal diameter & height).
3. Quartering: Place a sheet-metal cross (blades > cone height) centrally; press down to divide pile into 4 quarters.
4. Remove Opposite Quarters: Remove two diagonally opposite quarters; clean space while cross remains.
5. Repeat: Mix remaining two quarters, reform cone, quarter again until sample is 25-50 liters.

Apparatus (Clause 3.1.4.1):

• Sheet-metal cross: Four blades joined at right angles, height > cone.
• Surface: Smooth, hard, flat.

Sample Size:

• Final reduced sample: 25 to 50 liters.

Summary Table:

Diagram: Coning and Quartering Process

flowchart TD
    A[Form Cone] --> B[Flatten Cone]
    B --> C[Place Metal Cross]
    C --> D[Divide into Four Quarters]
    D --> E[Remove Two Opposite Quarters]
    E --> F{Sample > 25-50 L?}
    F -- Yes --> G[Mix Remaining Quarters]
    G --> A
    F -- No --> H[Final Sample]

This method ensures a representative, reduced sample by systematic mixing and quartering, minimizing segregation and bias.

IS 4879 - Method II: Reduction by Coning and Quartering (Clause 3.1.2)

This method reduces sample size from ≤ 1000 litres to 25 litres by systematic coning and quartering:

Procedure (Clause 3.1.2.1)

1. Form a Cone: Shovel material into a conical pile on a smooth, hard surface, placing each shovelful on top uniformly to keep the apex centered.
2. Flatten the Cone: Use the back of the shovel with rotary motion to flatten the cone into a uniform disc shape.
3. Quarter the Pile: Place a sheet-metal cross (4 blades joined at right angles, height > cone height) centrally on the flattened pile, pressing down to divide it into four quarters.
4. Remove Opposite Quarters: Remove two diagonally opposite quarters, clean the space while keeping the cross in place.
5. Repeat: Mix the remaining two quarters, recone, and quarter again until sample volume is between 25 and 50 litres.

Key Points:

• Uniform deposition ensures representative sampling.
• Quartering halves the sample size each cycle.
• Continue until target volume is reached.
• No explicit formula; reduction is by successive halving.

Summary Table:

flowchart TD
    A[Start: ≤ 1000 L Sample] --> B[Form Cone]
    B --> C[Flatten Cone]
    C --> D[Place Metal Cross]
    D --> E[Remove 2 Opposite Quarters]
    E --> F{Is Volume ≤ 50 L?}
    F -- No --> G[Mix Remaining Quarters]
    G --> B
    F -- Yes --> H[Sample Ready (25-50 L)]

This method ensures a representative, manageable sample size for laboratory testing

IS 4879 - Method III: Turntable Type Sample Divider

Key Specifications (Clause 3.1.3 & 3.1.3.2)

• Purpose: Reduce gross sample (>1500 L) to 1 Litre.
• Receiver size: ~30 cm diameter × 30 cm height.
• Sample container height: About 1/3 of receiver height.
• Turntable speed: Constant at 30 rpm.
• Material: Suitable metal for durability.
• Operation:
  • Select hopper orifice to ensure flow time ≥ 1 minute.
  • Insert segmented receiver container.
  • Rotate turntable at constant speed.
  • Pour gross sample into hopper.
  • Stop turntable after sample passes; withdraw desired fraction.
  • Repeat if gross sample volume > receiver volume; combine fractions and re-sample.

Important Notes:

• Linear dimensions can be increased up to 12× for larger samples.
• Excess sample requires multiple passes.

Diagram (Simplified Concept):

flowchart LR
    A[Gross Sample Hopper] --> B[Orifice]
    B --> C[Distributor Cone]
    C --> D[Receiver on Turntable]
    D --> E[Segmented Sample Container]
    D --> F[Discarded Sample]
    style D fill:#f9f,stroke:#333,stroke-width:2px

This method ensures representative sampling by uniform distribution via rotation and segmentation.

IS 4879 - Method IV: Slotted Cone Type Sample Divider

Key Specifications (Clause 3.1.4 & 3.1.4.1)

• Apparatus Components:

  • Conical Feed Hopper: Stationary, with interchangeable orifice at bottom. Orifice size ensures sample flow time ≥ 1 minute.
  • Sampling Pipe: Fixed below hopper, directs material passing through.
  • Rotating Cone: Diameter max 10 cm, speed ≥ 30 rev/min, with adjustable slot(s) to alternately pass or divert material.
  • Fixed Inverted Cone: Surrounds rotating cone, collects diverted material.

• Material: Any suitable metal.

Procedure Highlights (Clause 3.1.3.2)

• Select hopper orifice for ≥1 min flow time.
• Insert receiver segments.
• Rotate turntable at constant speed (≥30 rpm).
• Feed gross sample into hopper.
• Collect sample from receiver; discard remainder.
• Repeat if sample volume exceeds receiver capacity.

Dimensions Summary

Conceptual Flow (Mermaid Diagram)

flowchart TD
    A[Feed Hopper with Orifice] --> B[Rotating Cone with Slot]
    B -->|Slot aligned| C[Sampling Pipe -> Sample Container]
    B -->|Slot closed| D[Fixed Inverted Cone -> Reject Hopper]

This method ensures representative reduction of large samples (over 1,500 ml) to 1 litre with controlled flow and precise splitting by the rotating slotted cone.

IS 4879 - Method V: Large Oscillating Hopper Sample Divider

Key Specifications:

• Purpose: Reduce sample size from 100 L to 1 L.
• Oscillation speed: ~200 cycles/min via crank and electric motor.
• Material: All parts contacting powder/slurry must be metal (no plastics).
• Environment: Enclosed, draft-free to avoid loss of fine particles.

Apparatus Components:

• Oscillating hopper:

  • Diameter: 100 mm
  • Cylindrical depth: 125 mm
  • Conical depth: 75 mm
  • Nozzle swing arc: ~40 mm

• Receiving hoppers:

  • Similar dimensions as oscillating hopper.

• Interchangeable orifice: Controls flow rate into receiving hoppers.

Precautions:

• Avoid plastics in contact parts.
• Conduct in enclosed space; dust outside collecting zone indicates loss of fines.

Summary Table of Dimensions

Flow Control Concept

flowchart LR
    A[Oscillating Hopper] -->|Material flow via orifice| B[Receiving Hopper 1]
    A -->|Material flow via orifice| C[Receiving Hopper 2]
    style A fill:#f9f,stroke:#333,stroke-width:2px
    style B fill:#bbf,stroke:#333,stroke-width:1px
    style C fill:#bbf,stroke:#333,stroke-width:1px

This setup ensures uniform sample division by oscillation and controlled flow.

For detailed mechanical drawings, refer to Fig. 3 and 4 of IS 4879 Clause 3.1.5.1.

IS 4879 - Method VI: Grid Type Sample Divider

Key Specifications (Clause 3.1.6 & 3.1.6.1)

• Grid:

  • 64 apertures arranged in 8 rows × 8 columns.
  • Aperture size: 11 mm square each.
  • Alternate passages in each row inclined oppositely for even distribution.

• Riffle:

  • Located below the grid.
  • Divided into 9 sections for sample collection.

• Hopper:

  • Equipped with a lid to prevent dust loss.

• Swing Doors:

  • Ensure even material distribution over the grid.

• Sample Receivers:

  • Material: Chromium plated sheet brass (~0.9 mm thick) for smooth powder flow.
  • Final sample volume: 5 ml.

Procedure Highlights (Clause 3.1.3.2)

• Select hopper orifice for a flow time ≥ 1 minute.
• Insert requisite receiver segments.
• Rotate turntable at a constant speed (typically 30 rpm).
• Pour gross sample into hopper.
• Collect sample from receiver; discard remainder.
• Repeat if gross sample volume exceeds receiver capacity.

Dimensional Summary

Conceptual Flow Diagram (Mermaid.js)

flowchart TD
    A[Gross Sample in Hopper] --> B[Swing Doors for Even Distribution]
    B --> C[Grid with 64 Apertures]
    C --> D[Riffle with 9 Sections]
    D --> E[Sample Receivers (5 ml)]
    E --> F[Collect Final Sample]

This method ensures representative, reduced sampling from 50 L to 5 ml with minimal segregation and loss.

IS 4879 - Method VII: Small Oscillating Hopper Sample Divider

Key Specifications:

• Final Sample Volume: 0.2 ml
• Oscillating Hopper Dimensions:
  • Diameter: 50 mm
  • Cylindrical Depth: 40 mm
  • Conical Depth: 25 mm
• Receiving Hopper Dimensions:
  • Diameter: 25 mm
  • Cylindrical Depth: 25 mm
  • Conical Depth: 20 mm
• Material: Suitable metal (no plastics contacting powder/slurry)

Operational Details:

• Oscillation frequency ~ 200 cycles/min
• Oscillation achieved via crank and electric motor with belt drive
• Hopper swings through an arc approx. 40 mm (large type; smaller for small type)
• Interchangeable orifice controls flow rate

Precautions (Clause 3.1.5.4):

• No plastic contact with sample
• Conduct in enclosed, draft-free space to avoid loss of fine particles
• Dust on apparatus indicates particle loss—correct environment accordingly

Summary Diagram (Conceptual):

flowchart TB
    A[Feed Sample] --> B[Oscillating Hopper]
    B -->|Controlled flow via interchangeable orifice| C[Receiving Hopper 1]
    B -->|Oscillation divides sample| D[Receiving Hopper 2]
    style B fill:#f9f,stroke:#333,stroke-width:2px

This method ensures precise reduction from 1 Litre to 0.2 ml sample with minimal particle loss and contamination.

IS 4879 - Method VIII: Checking Performance of Sample Dividers

Key Specifications & Procedure (Clause 3.1.8 & 3.1.3.2)

• Sample Divider Type: Turntable type with interchangeable orifice, distributor cone, removable segmented sample container, and receiver on turntable.
• Turntable Speed: Constant speed, typically 30 rpm.
• Receiver Dimensions: For a 1-litre final sample:
  • Diameter ≈ 30 cm
  • Height ≈ 30 cm
  • Sample container height ≈ 1/3 of receiver height
• Sample Flow Time: Select hopper orifice for a total flow time ≥ 1 minute.
• Procedure:
  1. Insert requisite segments in the receiver.
  2. Rotate turntable at constant speed.
  3. Pour gross sample into hopper.
  4. After flow completes, stop turntable and withdraw desired sample.
  5. If gross sample > receiver volume, repeat operations and combine fractions.

Precautions (Clause 3.1.5.4)

• No plastic parts in contact with powder/slurry.
• Conduct in enclosed, draught-free space to avoid loss of fines.
• Dust outside collecting zone indicates loss; rectify immediately.

Dimensional Guidance for Oscillating Hopper (for comparison)

Diagram: Turntable Sample Divider Components

graph LR
    A[Hopper with Orifice] --> B[Distributor Cone]
    B --> C[Receiver on Turntable]
    C --> D[Segmented Sample Container]
    C --> E[Turntable (30 rpm)]

This method ensures representative sampling by uniform division with controlled flow and rotation.

IS 4879: Precautions for Sample Handling and Apparatus Use

Key precautions from relevant clauses:

• Enclosed Space:
  Conduct all tests in an enclosed space free from draughts or air currents to prevent loss of fine particles.
  (Clauses 3.1.1.2, 3.1.2.2, 3.1.6.3b, 3.1.4.3b)

• Material of Apparatus Components:
  No component in contact with the powder shall be made of plastics to avoid contamination or electrostatic effects.
  (Clauses 3.1.6.3a, 3.1.4.3a)

Summary Table of Precautions

Note: These measures ensure accuracy by avoiding sample loss and contamination during handling and testing.