Method of test for determination of openness or fabrication of chrysotile asbestos fibre by air permeability method using Dyckerhoff apparatus
1980 Edition

This section defines the calibration benchmarks for permeability cells using capillary glass tubes categorized as low and high standards. The key parameters include Dyckerhoff time ranges, capillary bore diameters, and tube lengths. It emphasizes the necessity of proper filling of specimen cavities and storage of standards in airtight containers or desiccators to ensure accuracy. Essential accessories such as tampers, porous cellulose filters, funnels, and handles are detailed to support the calibration process.

Summarizes crucial calibration standards with specifics on Dyckerhoff times, capillary bore sizes, and lengths. Highlights the importance of maintaining environmental controls like barometric pressure, humidity, and temperature during testing. Lists necessary accessories and warns against errors arising from electrode tip drop formation and exposure to dust or heat. References related Indian Standards for asbestos cement products are also provided.

Outlines procedures for sampling chrysotile asbestos fibres according to IS 4844-1968, including spreading the sample to a uniform 13 mm thickness and quartering. Details the preparation of test specimens by weighing 50 g ± 0.1 g, dividing into four equal portions, and sequentially packing them into the permeability cell with controlled compaction to maintain about 70% porosity without exceeding the final plug length.

Describes the specifications of the Dyckerhoff apparatus and related accessories such as tampers, porous filters, wide-mouth funnels, and capillary tube holders. Specifies cleaning protocols for capillary tubes using dry compressed air at designated pressures depending on mounting type, and assembly guidelines to prepare the apparatus for testing.

Explains the stepwise procedure for conducting the permeability test, including use of calibrating standards to fill the specimen cavity, accessory utilization, and accuracy requirements. Specifies acceptable deviations, handling erratic first readings, and rounding conventions for final results to ensure reliable and consistent measurement outcomes.

Details the calibration process emphasizing permissible deviation limits, cleaning methods for capillary tubes using compressed air at specified pressures and durations, and storage of calibration standards. Defines acceptance criteria for defect-free apparatus based on deviation percentages from cumulative averages.

Describes loading the 50 g sample divided into four equal parts into the permeability cell with gentle tamping to maintain uniform bed level and porosity of approximately 70%. Explains use of hooks to prevent fibre rebound during compression and cautions against excessive pressure that might cause contact between internal components.

Covers the accuracy requirements for individual readings relative to averages, procedures for discarding first readings if instruments have been idle, recording electrode positions when using new working standards, and computing cumulative averages. Includes formulas and criteria to maintain measurement precision.

Outlines limits on permissible differences between readings, recommends taking multiple readings, and prescribes actions if deviations exceed thresholds. Details inspection and retesting procedures to uphold test reproducibility within defined tolerance levels.

Focuses on regular cleaning and calibration of the apparatus, specifying air pressures and cleaning durations for capillary tubes. Lists accessory requirements and protocols for inspection and repair if calibration deviations are beyond allowed limits. Emphasizes strict adherence to safety measures while handling chrysotile asbestos fibres.