Method of sub-division of a gross sample of powder used for determination of particle size
1968 Edition

IS 4879: Overview and Implementation Highlights

• Scope: This code relates to sampling and testing methods, referencing IS 4124-1967 for terminology.

• Implementation: Adopts established IS definitions to standardize sampling and testing procedures in civil engineering materials.

• References:

  • ISI Monthly Bulletins
  • Annual Reports from 1948-49 onward
  • ISI Publications Handbook, 1968

• Civil Engineering Material Groups Included:

  • Aggregates, Bricks, Cement, Concrete Testing
  • Reinforcement Steel, Structural Design, Soil Engineering
  • Timber, Waterproofing, and other materials

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

Relevant Definitions (from IS 4124-1967)

• Sampling procedures
• Particle sizing and sieving definitions

Summary Table: Civil Engineering Material Categories

This standard promotes uniform sampling/testing aligned with the ISI framework.

flowchart LR
    IS4879[IS 4879] --> Procedures[Sampling & Testing Methods]
    Procedures --> Definitions[Definitions per IS 4124]
    Procedures --> Materials[Material Specifications]
    Procedures --> Categories[Civil Engineering Material Groups]
    Categories --> Aggregates[Aggregates, Concrete, Reinforcement]
    Categories --> Others[Soil, Timber, Waterproofing]

IS 4879: Scope and Key Parameters

Scope: Covers apparatus and procedures for sampling powders and slurries, emphasizing design and precautions for sample dividing devices such as oscillating hopper dividers.

Essential Specifications:

• Material Requirements:

  • Components contacting powders or slurries must be made from sheet brass or equivalent metals.
  • Use of plastic materials in contact areas is prohibited (Clause 3.1.5.4a).

• Sampling Conditions:

  • Sampling should occur in enclosed environments free from airflow to prevent particle loss (Clause 3.1.5.4b).

Dimensions for Oscillating Hopper Sample Dividers (in millimeters):

Notes:

• Dimensions are optimized to ensure representative sampling volumes.
• Receiving hoppers are generally similar in size to oscillating hoppers.
• Apparatus design must minimize dust escape to avoid sample loss.

flowchart LR
    PowderFeed[Powder or Slurry Feed] --> OscillatingHopper[Oscillating Hopper]
    OscillatingHopper --> Orifice[Interchangeable Orifice]
    Orifice --> ReceivingHopper[Receiving Hopper]
    ReceivingHopper --> SampleCollection[Sample Collection]
    style OscillatingHopper fill:#f9f,stroke:#333,stroke-width:2px

IS 4879 - Terminology (Clause 2.0)

• Incorporates definitions from IS 4124:1967 related to sampling and particle size measurement.
• Aligns with international standard BS 3406: Part I (1961).

Important Terms:

• Gross Sample: The initial large quantity of material collected.
• Working Sample: A reduced sample obtained by subdividing the gross sample.
• Sample Divider: Device used to partition samples into representative fractions.

Material Recommendation (Clause 6.4):

• Fabrication of sample dividers, such as oscillating hopper dividers, should use sheet brass.

Sample Divider Material Table

Process Flow Diagram

flowchart LR
    GrossSample[Gross Sample] --> Divider[Sample Divider]
    Divider --> WorkingSample[Working Sample]
    WorkingSample --> Analysis[Testing / Analysis]

IS 4879: Techniques for Reducing Sample Size for Particle Size Evaluation

This standard details methods to reduce a large powder sample to a smaller, representative volume for particle size analysis:

Main Methods (Clauses 3.1 & 1.1):

Explanation:

• Halving: Repeatedly splitting the sample into two equal parts.
• Coning and Quartering: Forming a cone, flattening, dividing into four parts, discarding alternate quarters.
• Sample Dividers: Mechanical devices that provide uniform sub-sample extraction.

These approaches ensure the sub-samples are both representative and reproducible for accurate particle sizing.

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)]

IS 4879 - Technique I: Coning and Quartering Method

Procedure (Clause 3.1.2.1):

1. Form a Cone: Gradually pile the powder into a conical shape on a smooth, rigid surface, adding each portion carefully to maintain the cone apex.
2. Flatten the Cone: Using the back of a shovel, rotate and gently flatten the cone to achieve uniform diameter and height.
3. Divide into Quarters: Place a sheet-metal cross (blades taller than the cone height) centrally over the flattened pile and press to divide it into four equal parts.
4. Remove Opposite Quarters: Extract two diagonally opposite quarters, cleaning the area while keeping the cross in position.
5. Repeat: Mix the remaining two quarters, reform a cone, and repeat the quartering until the sample volume reaches 25 to 50 litres.

Required Equipment (Clause 3.1.4.1):

• Sheet-metal cross with four perpendicular blades.
• Smooth, flat, and hard sampling surface.

Final Sample Volume:

• Target range: 25 to 50 litres.

Summary Table:

Process Diagram

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

This technique achieves a representative and reduced sample by systematic mixing and quartering, minimizing segregation.

IS 4879 - Technique II: Sample Size Reduction by Coning and Quartering (Clause 3.1.2)

This method reduces samples not exceeding 1000 litres down to about 25 litres through repeated coning and quartering:

Procedure (Clause 3.1.2.1):

1. Form a conical pile on a smooth, hard surface by layering shovelfuls evenly to maintain a centered apex.
2. Flatten this cone uniformly into a disc using a rotary motion with the shovel’s back.
3. Place a sheet-metal cross (with blades taller than cone height) at the center and press down to split the pile into four quarters.
4. Remove two diagonally opposite quarters and clean the exposed area while leaving the cross in place.
5. Mix the remaining halves, form a new cone, and repeat the process until the sample volume is between 25 and 50 litres.

Key Considerations:

• Uniform layering ensures the sample remains representative.
• Each quartering step approximately halves the sample volume.
• Repetition continues until the target volume is reached.

Reduction Summary:

Flow Diagram

flowchart TD
    A[Start with ≤ 1000 L Sample] --> B[Form Cone]
    B --> C[Flatten Cone]
    C --> D[Place Metal Cross]
    D --> E[Remove Two 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 provides a controlled reduction maintaining sample representativeness for testing.

IS 4879 - Technique III: Turntable Sample Divider

Specifications (Clauses 3.1.3 & 3.1.3.2):

• Designed to reduce gross powder samples larger than 1500 litres to approximately 1 litre.
• Receiver dimensions: roughly 30 cm diameter and 30 cm height.
• Sample container height is about one-third of the receiver height.
• Turntable rotation speed is maintained at around 30 revolutions per minute.
• Constructed from suitable metals for durability and contamination prevention.

Operating Procedure:

1. Select an interchangeable orifice that ensures the bulk sample flows through in at least 1 minute.
2. Install a segmented receiver container on the rotating turntable.
3. Rotate the turntable steadily at 30 rpm.
4. Introduce the gross sample into the hopper.
5. After the sample passes through, stop the turntable and remove the collected sub-sample.
6. For samples exceeding receiver capacity, perform multiple runs and combine the collected fractions for further processing.

Notes:

• Dimensions may be scaled up to 12 times for handling larger volumes.
• Uniform rotation and controlled flow ensure representative subsampling.

Simplified Diagram:

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

This technique facilitates accurate and efficient reduction of large powder samples.

IS 4879 - Technique IV: Slotted Cone Sample Divider

Key Details (Clauses 3.1.4 & 3.1.4.1):

• Components:

  • A fixed conical feed hopper with interchangeable orifice ensuring flow duration of at least 1 minute.
  • A fixed sampling pipe directing material from the hopper.
  • A rotating cone (maximum diameter 10 cm) spinning at a minimum of 30 revolutions per minute.
  • The rotating cone features adjustable slots that alternately allow material to pass or divert it.
  • A stationary inverted cone surrounding the rotating cone collects diverted material.

• Materials used are suitable metals to avoid contamination.

Operational Highlights:

• Choose the hopper orifice for controlled flow.
• Rotate the slotted cone at a steady speed.
• Feed the gross sample through the hopper.
• Collect sub-samples from the sampling pipe; reject the rest.
• Repeat if the sample volume exceeds container capacity.

Dimensional Summary:

Process Flow

flowchart TD
    A[Feed Hopper with Orifice] --> B[Rotating Cone with Slot]
    B -->|Slot Open| C[Sample Pipe to Container]
    B -->|Slot Closed| D[Fixed Cone to Reject Hopper]

This method allows effective subdivision of large powder samples with precise flow control.

IS 4879 - Technique V: Large Oscillating Hopper Sample Divider

Specifications:

• Designed to reduce sample size from 100 litres to approximately 1 litre.
• Oscillation frequency of about 200 cycles per minute, powered by an electric motor and crank mechanism.
• All components in contact with powder or slurry are metallic; plastics are prohibited.
• Sampling to be conducted in enclosed, draft-free spaces to prevent fine particle loss.

Apparatus Details:

• Oscillating hopper:
  • Diameter: 100 mm
  • Cylindrical depth: 125 mm
  • Conical depth: 75 mm
  • Nozzle swing arc: approximately 40 mm
• Receiving hoppers have similar dimensions to the oscillating hopper.
• Equipped with interchangeable orifices to regulate flow rate.

Important Precautions:

• Avoid use of plastics in contact areas.
• Ensure sampling environment is enclosed and free from air currents to minimize dust loss.

Dimension Summary Table:

Operational 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 design ensures consistent sample division by controlled oscillation and regulated flow.

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

IS 4879 - Technique VI: Grid Type Sample Divider

Key Characteristics (Clauses 3.1.6 & 3.1.6.1):

• Grid assembly consists of 64 square openings arranged in an 8x8 matrix.
• Each aperture measures 11 mm by 11 mm.
• Alternate passages in each row are inclined in opposite directions to promote even material distribution.
• Beneath the grid is a riffle divided into 9 sections to collect sample portions.
• The hopper includes a lid to prevent dust dispersal.
• Swing doors are incorporated to ensure uniform material spread over the grid.
• Sample collectors are made from chromium-plated sheet brass (~0.9 mm thick) for smooth powder flow.
• The final reduced sample volume is approximately 5 millilitres.

Operational Procedure:

• Select hopper orifice to achieve flow time of at least 1 minute.
• Install the necessary receiver segments.
• Rotate the turntable at about 30 rpm.
• Introduce gross sample into the hopper.
• Collect the subdivided sample; discard the remainder.
• Repeat if gross sample volume exceeds receiver capacity.

Dimensional Summary:

Conceptual Flow Diagram

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

This method provides precise, representative sample reduction from 50 litres to 5 millilitres with minimal segregation.

IS 4879 - Technique VII: Small Oscillating Hopper Sample Divider

Key Parameters:

• Target final sample volume: 0.2 millilitres.
• 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
• Constructed from appropriate metals; plastic contact with powder/slurry is prohibited.

Operational Details:

• Oscillation frequency is approximately 200 cycles per minute.
• Oscillation is driven by a crank connected to an electric motor via belt drive.
• Hopper oscillates through an arc length of around 40 mm (larger for big type; smaller for small type).
• Flow rate is controlled using interchangeable orifices.

Precautions (Clause 3.1.5.4):

• No plastic parts should contact the sample.
• Conduct sampling in enclosed, draft-free environments to prevent loss of fine particles.
• Visible dust on apparatus indicates particle loss; environment must be corrected accordingly.

Conceptual Diagram

flowchart TB
    A[Sample Feed] --> B[Oscillating Hopper]
    B -->|Controlled Flow via Interchangeable Orifice| C[Receiving Hopper 1]
    B -->|Sample Division by Oscillation| D[Receiving Hopper 2]
    style B fill:#f9f,stroke:#333,stroke-width:2px

This technique enables precise reduction from 1 litre to 0.2 millilitres with minimal contamination or particle loss.

IS 4879 - Technique VIII: Assessment of Sample Divider Performance

Procedure and Specifications (Clauses 3.1.8 & 3.1.3.2):

• Uses a turntable type sample divider comprising an interchangeable orifice, distributor cone, segmented removable sample container, and a rotating receiver.
• Turntable speed is held constant, typically 30 rpm.
• Receiver dimensions for a 1-litre sample are approximately 30 cm in diameter and height; sample container height is about one-third of receiver height.
• Hopper orifice size is selected to achieve a flow time of at least 1 minute.

Performance Checking Steps:

1. Install the required number of segments in the receiver.
2. Rotate the turntable at a consistent speed.
3. Pour the gross sample into the hopper.
4. Upon completion of flow, stop the turntable and remove the collected sample.
5. For samples exceeding receiver capacity, repeat sampling and combine fractions.

Precautions (Clause 3.1.5.4):

• Avoid plastic parts contacting powder or slurry.
• Carry out sampling in enclosed, draft-free spaces to prevent loss of fine particles.
• Dust presence outside collection zones indicates sample loss and requires corrective measures.

Dimensional Reference for Oscillating Hopper

Sample Divider Component Diagram

graph LR
    Hopper[Hopper with Orifice] --> Distributor[Distributor Cone]
    Distributor --> Receiver[Turntable with Segmented Container]
    Receiver --> Sample[Collected Sample]
    Receiver --> Waste[Discarded Portion]
    Receiver --> Receiver

This verification method guarantees uniform sample division and representative sampling.

IS 4879: Guidelines for Safe Sample Handling and Apparatus Use

Key precautions extracted from relevant clauses:

• Enclosed Environment: Perform all sampling and subdivision in a sealed area free from drafts or air currents to prevent the escape of fine particles. (Clauses 3.1.1.2, 3.1.2.2, 3.1.6.3b, 3.1.4.3b)

• Material Restrictions: Ensure that no part of the equipment in contact with the powder is made of plastic, to avoid contamination or static electricity effects. (Clauses 3.1.6.3a, 3.1.4.3a)

Summary Table of Precautions

Note: Following these precautions is crucial to maintain sample integrity and accuracy during testing.