Method of test for length distribution (wet classification of fibre length) of chrysotile asbestos fibre using Bauer Mcnett classifier

IS 9691 - Scope: Key Specifications and Tables

1. Scope Summary

IS 9691 covers testing procedures for fibre classification using a Bauer-McNett classifier, including accessories and test conditions.

2. Accessories Required (Clause 2.2)

• Balance: Sensitivity 0.01 g
• Beaker: 1000 ml + stirring rod
• Filter papers: For vacuum cups or 45 micron screen cloth filter
• T-shaped rubber scraper: For cleaning screens
• Rubber pressure hose: 6 mm bore with control valve nozzle
• Drying oven: Convection/mechanical draught or infra-red drying unit
• Automatic overflow alarm
• Optional: Automatic clearing device on the fourth tank

3. Sample Mass, Screen Sizes & Test Duration (Clause 4.1)

4. Typical Calculation Example (Clause 5.1)

Sample Mass: 10 g
Test Duration: 20 minutes

5. Rounding Off Results

• Follow IS 2-1960 for rounding test results.

flowchart TD
    A[Sample Preparation] --> B[Classification using Bauer-McNett Classifier]
    B --> C

IS 9691 Key References: Accessories, Typical Calculations, and Classifier Components

1. Accessories (Clause 2.2)

• Balance: Sensitivity 0.01 g
• Beaker: 1000 ml with stirring rod
• Filter papers: For vacuum cups or 45 micron screen cloth in metal ring
• Rubber scraper: T-shaped for screen cleaning
• Rubber pressure hose: 6 mm bore with control valve for rinsing
• Drying oven: Convection or mechanical draught, or infra-red unit
• Automatic overflow alarm
• Optional: Automatic clearing device on the fourth tank

2. Typical Calculation (Clause 5.1 & 1.3)

Mass passing 75 micron = Total mass - Sum of retained masses
= 10 - (0.5 + 1.3 + 1.9 + 1.4) = 4.9 g

3. Bauer-McNett Classifier Components (Fig. 1)

• Anti-Splash Cover (1)
• Constant Level Tank (2)
• Tank Assembly (3,4)
• Screen Plate Assembly (17)
• Reduction Unit (7)
• Swivel Coupling (13)
• Angle Connector (20)
• Seal Hose Assembly (11), etc.

flowchart LR
    A[Sample] --> B[Classifier Tanks]
    B --> C[Screen Plates]
    C --> D[Mass Retained on Each Sieve]
    D --> E[Calculate % Retained & Passing]
    E --> F[Particle Size Distribution]

This summarizes key accessories, calculation methods, and classifier parts per IS 9691.

IS 9691: Sampling - Key Formulas, Tables & Specifications

1. Sampling Procedure (Clause 3.1)

• Sampling must follow IS 4844 - 1968.

2. Sample Mass, Screen Sizes & Test Duration (Clause 4.1)

3. Typical Calculation Example (Clause 5.1)

• Sample mass = 10 g
• Test duration = 20 min

4. Acceptance Criteria for Duplicate Tests (Clause 5.2)

• If percentage difference between duplicate tests > 5%, perform a third test.
• Report the average of the two acceptable tests.

Summary Formula for % Retained on Each Sieve:

[ % \text{Retained} = \frac{\text{Mass retained on sieve (g)}}{\text{Total sample mass (g)}} \times 100 ]

flowchart TD
    A[Sampling as per IS 4844] --> B[Select Fibre Group]
    B --> C{Fibre Group?}
    C -->|3,4,5,6,7D| D[Use 4 sieves, 10g, 20 min]
    C -->|Other 7 group| E[Use 4 sieves, 20g, 20 min]
    C

IS 9691: Apparatus & Accessories Key Points

Accessories (Clause 2.2)

• Balance: Sensitivity 0.01 g.
• Beaker: 1000 ml with stirring rod.
• Filter papers: Fit vacuum cups or 45 micron screen cloth filter.
• Scraper: T-shaped soft rubber for screen cleaning.
• Rubber hose: 6 mm bore with control valve nozzle for rinsing.
• Drying oven: Convection/mechanical draught or infra-red.
• Automatic overflow alarm and optional automatic clearing device on the 4th tank.

Sample Mass, Screen Sizes & Test Duration (Clause 4.1)

Procedure Highlights (Clause 4.2.6)

• Filter papers weighed to 0.01 g, centered in suction cups.
• Mark mass, sample, screen mesh, and data on filter paper edge.
• Wet and clamp filter paper with writing against supporting screen.

Typical Calculation Example (Clause 5.1)

Summary Diagram: Classifier Setup (Simplified)

flowchart LR
    A[Constant Level Tank] --> B[Tank Assembly]
    B --> C[Screen Plate Assembly]
    C --> D[Filter Paper in Suction Cup]
    D --> E[Outlet with Overflow Alarm]
    B --> F[Automatic Clearing Device (optional)]

For detailed apparatus specs, refer to Clause

IS 9691: Test Procedure Summary

1. Sample Mass, Screen Sizes & Test Duration (Clause 4.1)

2. Accessories Required (Clause 2.2)

• Balance (sensitivity 0.01 g)
• 1000 ml beaker & stirring rod
• Filter papers or 45 micron screen cloth
• T-shaped rubber scraper
• Rubber pressure hose (6 mm bore) with control valve
• Drying oven (convection/mechanical draught) or IR drying unit
• Automatic overflow alarm
• Optional: Automatic clearing device on 4th tank

3. Typical Calculation (Clause 5.1)

For example, Group 5 fibre, 10 g sample, 20 min test:

Procedure Overview (Clause 4.2)

• Prepare sample as per group classification.
• Use specified sieve sizes and sample mass.
• Run test for specified duration.
• Record mass retained on each sieve.
• Calculate fibre distribution based on retained mass.

flowchart TD
    A[Prepare Sample] --> B[Set up Classifier & Screens]
    B --> C[Run Test for Specified Duration]
    C --> D[Collect Mass Retained on Each Sieve]
    D --> E[Calculate Fibre Distribution]
    E --> F[Report Results]

This ensures standardized fibre analysis per IS

IS 9691: Accuracy and Reproducibility Key Points

Accuracy

• Water temperature: Maintain at 27 ± 2℃ for better accuracy (Clause 6.3).
• Follow general precautions in Clauses 6.2 to 6.5 (not detailed here).

Reproducibility

• Duplicate tests are required.
• If percentage difference between duplicates for any screen fraction > 5%, perform a third test (Clause 5.2).
• Report average of two acceptable tests.

Accessories (Clause 2.2)

• Balance: Sensitivity 0.01 g.
• Beaker: 1000 ml with stirring rod.
• Filter papers: Fit vacuum cups or 45 micron screen cloth.
• Scraper: T-shaped soft rubber.
• Rinsing hose: 6 mm bore with control valve.
• Drying oven: Convection or infra-red.
• Optional: Overflow alarm, automatic clearing device on 4th tank.

Summary Table: Reproducibility Criterion

flowchart TD
    A[Start Testing] --> B{Duplicate Tests}
    B --> C{Difference ≤ 5%?}
    C -- Yes --> D[Average Results & Report]
    C -- No --> E[Conduct Third Test]
    E --> F[Average Two Acceptable Tests & Report]

This ensures high accuracy and reproducibility in particle size analysis per IS 9691.

IS 9691: Calculation and Reporting Key Points

1. Calculation (Clause 1.3 & 5.1)

• Mass of fractions passing 75 micron sieve:

[ \text{Mass passing 75 micron} = \text{Total sample mass} - \sum \text{Mass retained on all sieves} ]

Using example data:

[ = 10,g - (0.5 + 1.3 + 1.9 + 1.4) = 4.9,g ]

• Percentage retained on each sieve:

[ % \text{Retained} = \frac{\text{Mass retained on sieve}}{\text{Total sample mass}} \times 100 ]

• Cumulative percentage retained and passing:

(Note: The example shows 49% passing 75 micron; verify based on cumulative sums.)

2. Reporting (Clause 5)

• Report mass retained and passing on each sieve.
• Report cumulative percentages.
• Ensure samples and papers are dried and weighed together after testing (Clause 4.2.13).

Summary Table for Reporting

flowchart TD
    A[Sample Preparation] --> B[Weigh Sample]
    B --> C[Sieve Analysis]
    C --> D[Weigh Retained Fractions]
    D --> E[Calculate % Retained & Passing]

IS 9691: Maintenance and Care of Equipment — Key Points

Accessories Required (Clause 2.2)

• Balance: Sensitivity 0.01 g.
• Beaker: 1000 ml with stirring rod.
• Filter papers: Fit vacuum cups or 45 micron screen cloth filter.
• T-shaped soft rubber scraper: For cleaning screens.
• Rubber pressure hose: 6 mm bore with control valve nozzle for rinsing.
• Drying oven: Convection or mechanical draught type, or infra-red drying unit.
• Automatic overflow alarm and optional automatic clearing device on the 4th tank.

Maintenance Tips

• Wash all material thoroughly into vacuum cups; handle filter papers carefully (Clause 6.2).
• Monitor screens during tests; clean overflow or clogged screens immediately with the rubber scraper (Clause 4.2.8).

Calculation Reference (Clause 1.18 & A-2)

• Mass retained (g) is fundamental for test calculations.
• Use mass retained to determine particle size distribution after sieving.

Summary Table: Essential Equipment and Care

flowchart TD
    A[Sample Preparation] --> B[Sieving in Classifier Tanks]
    B --> C[Screen Cleaning with Rubber Scraper]
    C --> D[Material Washed into Vacuum Cups]
    D --> E[Filtration with Filter Papers]
    E --> F[Drying in Oven or IR Unit]
    F --> G[Mass Retained Measurement]

This flow ensures proper maintenance and accurate

IS 9691: Precautions and Safety - Key Points

1. General Precautions (Clause 6.1 - 6.5)

• Follow all precautions to ensure desired accuracy in sedimentation tests.
• Maintain cleanliness of equipment to avoid contamination.
• Use accessories as specified to ensure consistent results.

2. Required Accessories (Clause 2.2)

• Balance with sensitivity of 0.01 g.
• 1000 ml beaker and stirring rod.
• Filter papers fitting vacuum cups or 45 micron screen cloth.
• T-shaped soft rubber scraper for cleaning.
• Rubber pressure hose (6 mm bore) with control valve for rinsing.
• Drying oven (convection or infra-red type).
• Automatic overflow alarm.
• Optional automatic clearing device on the fourth tank.

3. Equipment Safety Features

• Anti-splash covers to prevent sample loss.
• Constant level tanks to maintain uniform flow.
• Proper sealing and hose assemblies to avoid leaks.

4. Test Procedure (Clause 4.2)

• Follow stepwise procedures ensuring sample preparation, classification, and drying are done under controlled conditions.

Summary Table: Essential Accessories

flowchart TD
    A[Sample Preparation] --> B[Classification Tanks]
    B --> C[Screen Cleaning with Rubber Scraper]
    C --> D[Rinsing with Rubber Hose]
    D --> E[Drying in Oven]
    E --> F[Weighing on Sensitive Balance]
    F --> G[Data Recording & Analysis]

Note: Strict adherence to these precautions and equipment specifications ensures test accuracy and operator safety.

IS 9691 Typical Calculation Summary

Test Data (Clause 5.1)

• Sample group: Group 5 (Q.S. classification)
• Mass of sample: 10 g
• Test duration: 20 min

Calculation (Clause 1.3)

• Mass passing 75 micron sieve:

  [ = 10 - (0.5 + 1.3 + 1.9 + 1.4) = 4.9 \text{ g} ]

• Percentage retained (cumulative):

Accessories Required (Clause 2.2)

• Balance (sensitivity 0.01 g)
• 1000 ml beaker + stirring rod
• Filter papers or 45 micron screen cloth
• T-shaped rubber scraper
• Rubber pressure hose (6 mm bore) with control valve
• Drying oven or infra-red drying unit
• Automatic overflow alarm
• Optional automatic clearing device on 4th tank

Summary Diagram: Particle Size Distribution Flow

flowchart LR
    Sample[Sample 10g] --> Sieve_4_75[4.75 mm sieve]
    Sieve_4_75 --> Sieve_1_18[1.18 mm sieve]
    Sieve_1_18 --> Sieve_425[425 micron sieve]
    Sieve_425 --> Sieve_75[75 micron sieve]
    Sieve_75 --> Passing75[Passing < 75 micron]

This method provides the mass retained on each sieve and calculates cumulative percentages to analyze particle size distribution as per IS 9691.