Method of test for determination of openness or fabrication of chrysotile asbestos fibre by air permeability method using Dyckerhoff apparatus

IS 9690: Scope - Key Specifications for Calibrating Standards (Clause 4.3)

The standard defines calibrating standards (low and high) for permeability cells using capillary glass tubes:

Additional Notes:

• Calibrating standards must fill the specimen cavity properly.
• Keep standards in airtight containers or desiccators for accuracy.
• Accessories required (Clause 4.2) include tamper, porous cellulose filters, funnel, handle, and the calibrating standards themselves.

Summary Diagram of Calibrating Standards Setup

flowchart LR
    A[Calibrating Standard Holder] --> B[Capillary Glass Tube]
    B --> C[Specimen Cavity]
    B --> D[Dyckerhoff Time Measurement]
    C --> E[Permeability Cell]

This setup ensures reliable permeability measurement by using precisely dimensioned glass tubes with known flow times.

IS 9690 Key References & Specifications (Summary)

Calibrating Standards (Clause 4.3):

• Purpose: Fill specimen cavity in permeability cell for calibration.
• Handling: Keep in airtight containers or desiccators (Clause 39.5).
• Environmental Control: Maintain barometric pressure, humidity, temperature as during calibration (Clause 9.3 Notes).
• Accessories (Clause 4.2):
  • Tamper, porous cellulose filters, wide-mouth funnel, handle for capillary tubes.

Important Notes:

• Drop formation on electrode tips can cause errors (~2 s for high, 0.25 s for low standards).
• Avoid exposure to dust, heat, or atmospheric changes near apparatus.

Related IS Codes on Asbestos Cement Products:

• IS 459-1970, IS 1592-1970, IS 2096-1966, IS 5913-1970 (test methods), etc.

Diagram: Calibration Setup Overview

flowchart LR
    A[Capillary Glass Tube] --> B[Holder]
    B --> C[Permeability Cell]
    C --> D[Specimen Cavity]
    E[Timer & Electrodes] --> C
    note right of E
      Avoid drop formation on electrodes
      to prevent timing errors
    end

This concise summary provides essential calibration standards, apparatus accessories, and environmental considerations per IS 9690.

Preparation of Test Sample as per IS 9690

• Sampling: Follow IS 4844-1968 for sampling procedure (Clause 2.1).

• Sample Spreading & Quartering (Clause 3.1):

  • Spread the sample in layers on a smooth surface to form a flat pile approx. 13 mm thick.
  • Quarter the pile to obtain a representative sample.

• Test Specimen Preparation (Clause 7.2):

  • Weigh 50 g ± 0.1 g of the test specimen.
  • Divide into four equal parts.
  • Pack each part sequentially into the permeability cell, keeping the bed level uniform.
  • Compress after each addition using the tamping tool, ensuring:
    • Do not compress beyond final plug length.
    • Maintain porosity of 70%.

• Calibrating Standards (Clause 4.3):

  Standard	Dyckerhoff Time (s)	Capillary Bore (mm)	Length (mm)
  Low Standard	20 to 30	0.311 ± 0.012	~13
  High Standard	350 to 450	0.178 ± 0.013	~39.5

This ensures consistent sample preparation for permeability testing.

flowchart TD
    A[Sample Collection] --> B[Spread in 13mm layers]
    B --> C[Quartering]
    C --> D[Weigh 50g ± 0.1g]
    D --> E[Divide into 4 equal parts]
    E --> F[Pack into cell one part at a time]
    F --> G[Compress with tamping tool]
    G --> H[Maintain 70% porosity & final plug length]

IS 9690 - Apparatus for Permeability Test

Key Specifications (Clause 4.3 & 4.2)

Accessories (Clause 4.2)

• Tamper (for compacting specimen)
• Porous cellulose filters (for check valve holder)
• Wide mouth funnel (for loading the cell)
• Calibrating standards (mounted in cell holder)
• Handle (for inserting/extracting capillary tube holders)

Important Notes (Clause 34.5)

• Clean capillary tubes with dry, compressed air before calibration:
  • 138 kPa if permanently mounted
  • 34.5 kPa if temporarily mounted
• Air flow duration: 60 seconds

Preparation Steps (Clause 6.1.1 & 5)

• Assemble apparatus as per Clause 5 instructions.
• Ensure capillary tubes are clean and standards are mounted correctly.

flowchart LR
    A[Start] --> B[Clean Capillary Tubes]
    B --> C{Permanently Mounted?}
    C -- Yes --> D[Use 138 kPa Air Pressure]
    C -- No --> E[Use 34.5 kPa Air Pressure]
    D --> F[Air Flow for 60s]
    E --> F
    F --> G[Assemble Apparatus with Accessories]
    G --> H[Insert Calibrating Standards]
    H --> I[Ready for Permeability Test]

This ensures accurate permeability measurements using IS 9690 standards.

IS 9690: Test Procedure Key Specifications & Tables

1. Calibrating Standards (Clause 4.3)

• These standards fill the specimen cavity in the permeability cell.
• Used to calibrate the permeability apparatus.

2. Accessories (Clause 4.2)

• Tamper (for specimen compaction)
• Porous cellulose filters (at check valve holder top)
• Wide-mouth funnel (for loading)
• Calibrating standards (as above)
• Handle (for inserting/extracting capillary tube holders)

3. Test Accuracy (Clause 8.3)

• Maximum allowed deviation from average reading: ±3.0%
• If exceeded, repeat test with a new specimen.
• Discard first reading if instrument unused for long (may be erratic).

4. Rounding Off (IS 2 - 1960)

• Results rounded to same significant figures as specified values.

Summary Diagram: Test Flow

flowchart TD
    A[Prepare Specimen] --> B[Load Specimen into Cell]
    B --> C[Insert Calibrating Standard]
    C --> D[Take Readings]
    D --> E{Max Diff ≤ ±3%?}
    E -- Yes --> F[Calculate Average & Round Off]
    E -- No --> G[Repeat Test with New Specimen]
    F --> H[Report Result]

This ensures reliable permeability measurement per IS 9690.

IS 9690: Instrument Calibration Key Points

Calibration Tolerance (Clause 9.2)

• Permissible deviation: ±3.0% from the cumulative average value of the calibrating standard.

Cleaning Procedure for Capillary Tubes (Clause 34.5)

• Use dry, compressed air free from contaminants.
• Pressure:
  • 138 kPa if permanently mounted.
  • 34.5 kPa if temporarily mounted.
• Air flow duration: 60 seconds before calibration.

Preparation of Apparatus (Clause 39.5)

• Typical dimension: 39.5 mm approximately.
• Calibration standards must be stored in airtight containers or desiccators to maintain accuracy.

Acceptance Criteria (Clause 6.1.8)

• If the measured value is within ±30% of the cumulative average, the apparatus is considered defect-free.

Summary Table:

flowchart TD
    A[Start Calibration] --> B[Clean Capillary Tube]
    B -->|Permanent| C[Apply 138 kPa air for 60s]
    B -->|Temporary| D[Apply 34.5 kPa air for 60s]
    C --> E[Measure with Calibrating Standard]
    D --> E
    E --> F{Is value within ±3%?}
    F -->|Yes| G[Calibration Passed]
    F -->|No| H[Recalibrate or Repair]
    G --> I{Within ±30% of cumulative average?}
    I -->|Yes| J[Apparatus is defect-free]
    I -->|No| H

This ensures calibration accuracy and apparatus reliability per IS 9690.

IS 9690: Sample Loading and Compression Key Points

Sample Loading (Clause 7.2 & 3.3)

• Sample weight: 50 g ± 0.1 g divided into 4 equal parts.
• Packing: Add each part sequentially, tamp gently to keep bed uniform.
• Avoid: Compressing beyond final plug length or porosity of 70%.
• Specimen prep: Include entire cross-section (pile, grit, fines). Disentangle lumps/knots before loading.

Compression Testing (Clause 7.5)

• Fix hooks on cell to plunger to prevent fibre spring back.
• Clamp cell firmly on apparatus.
• Avoid excessive pressure that causes contact between perforated disc and filter paper.

Calibration Standards (Clause 4.3)

Porosity Calculation (for reference):

[ \text{Porosity} = 1 - \frac{\text{Bulk density}}{\text{Fibre density}} \approx 70% ]

flowchart TD
    A[Divide 50g sample into 4 parts] --> B[Add & tamp each part sequentially]
    B --> C{Check porosity < 70%?}
    C -- Yes --> D[Fix hooks & clamp cell]
    C -- No --> E[Adjust compression]
    D --> F[Perform compression test]

This ensures uniform packing and accurate compression results per IS 9690.

IS 9690: Measurement and Recording Key Points

1. Measurement Accuracy (Clause 8.3)

• Maximum allowed difference between any individual reading and the average:
  ± 3.0%
• If exceeded, repeat test with a new specimen.
• Discard first reading if instrument unused for long (may be erratic).

2. Recording Procedure

• Measure vertical position of variable electrode relative to housing when a new working standard is used (Clause 6.2.2).
• Record average reading each time a working standard is tested (Clause 6.1.7).
• Compute cumulative average including nominal and all previous readings.

3. Calibrating Standards (Clause 4.3)

Summary Formula for % Difference:

[ \text{Difference %} = \frac{|R_i - \bar{R}|}{\bar{R}} \times 100 \leq 3% ]

Where:

• (R_i) = individual reading
• (\bar{R}) = average reading

flowchart TD
    A[Start Test] --> B[Take Readings]
    B --> C{Is |Ri - Ravg| ≤ 3%?}
    C -- Yes --> D[Record Average & Cumulative Average]
    C -- No --> E[Repeat Test with New Specimen]
    D --> F[Measure Electrode Position if New Standard]
    F --> G[End]

This ensures precision and repeatability in permeability measurements per IS 9690.

IS 9690: Accuracy and Reproducibility Key Points

• Accuracy Limit:
  Maximum difference between any individual reading and the average = ± 3.0% (Clause 8.3).

• Reproducibility:
  Within ± 3.0% of the average for homogeneous, contaminant-free samples at a fixed instrument setting (Clause 9.1).

• Procedure for Readings:

  • Take two readings (Clause 6.1.6).
  • If the second reading differs significantly from the average, check for errors or contamination.
  • Discard the first reading if the instrument was unused for some time (Clause 8.3 Note).

• If deviation > 3%:

  • Inspect the apparatus for defects (Clause 6.1.9).
  • Repeat test with a new specimen if needed (Clause 8.3).

Summary Table

flowchart TD
    A[Start Test] --> B[Take 1st Reading]
    B --> C{Instrument unused?}
    C -- Yes --> D[Discard 1st Reading]
    C -- No --> E[Take 2nd Reading]
    D --> E
    E --> F[Calculate Average]
    F --> G{Difference > ±3%?}
    G -- No --> H[Accept Results]
    G -- Yes --> I[Inspect Apparatus]
    I --> J{Defect Found?}
    J -- Yes --> K[Rectify & Retest]
    J -- No --> L[Repeat Test with New Specimen]

This ensures compliance with IS 9690 accuracy and reproducibility requirements.

IS 9690: Precautions and Maintenance for Permeability Apparatus

Key Specifications & Formulas

• Capillary Tube Cleaning (Clause 34.5, Note 2):

  • Use dry, contaminant-free compressed air.
  • Pressure:
    • Permanently mounted tubes: 138 kPa
    • Temporarily mounted tubes: 34.5 kPa
  • Flow time: 60 seconds before calibration.

• Accessories (Clause 4.2):

  • Tamper
  • Porous cellulose filters (top of check valve holder)
  • Wide-mouth funnel for loading
  • Calibrating standards (Clause 4.3)
  • Handle for capillary tube holder insertion/extraction

• Calibration Check (Clause 6.1.9):

  • If deviation > 3%, inspect and rectify apparatus defects.

Calibrating Standards (Clause 4.3)

Summary Diagram: Maintenance Flow

flowchart TD
    A[Start: Apparatus Ready] --> B[Clean Capillary Tubes]
    B -->|Permanently Mounted| C[Apply 138 kPa Air for 60s]
    B -->|Temporarily Mounted| D[Apply 34.5 kPa Air for 60s]
    C & D --> E[Calibrate Using Standards]
    E --> F{Deviation > 3%?}
    F -->|Yes| G[Inspect & Repair]
    F -->|No| H[Proceed with Testing]

Note: Regular cleaning and calibration ensure accurate permeability measurements per IS 9690.