ISO 7884-5:1987

Name: ISO 7884-5:1987 — Glass — Viscosity and viscometric fixed points — Part 5: Determination of working point by sinking bar viscometer
SKU: ISO 7884-5:1987
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Glass — Viscosity and viscometric fixed points — Part 5: Determination of working point by sinking bar viscometer

Название (английский):

ISO 7884-5:1987

Glass — Viscosity and viscometric fixed points — Part 5: Determination of working point by sinking bar viscometer

Статус документа:: Действующий
Формат:: Электронный (PDF)
Количество страниц:: 5
Дата публикации:: 26 ноября 1987 г.
Издание:: ISO IS 7884 edition 1 version 1
ICS:: 81.040.01

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Описание (английский):

The specified method is suitable for characterizing the low-viscosity range of glass working: A vertically positioned narrow metal rod, i.e. the bar, is allowed to sink under its own weight into the melt. From the rate of sinking the dynamic viscosity is calculated. The teoretical basis relation and the apparatus including method of measurements are described.

Abstract

Похожие стандарты

Упомянутые в описании и другие стандарты ISO

Overview

ISO 7884-5:1987 - "Glass - Viscosity and viscometric fixed points - Part 5: Determination of working point by sinking bar viscometer" specifies a standardized method to determine the working point of glass using a sinking-bar viscometer. The working point is defined as the temperature at which a glass melt reaches an equilibrium viscosity of 10^4 dPa·s. The method is optimized for the low-viscosity range of glass processing (about 10^3 to 10^4.5 dPa·s) and relates the bar’s sinking rate in a melt to the melt’s dynamic viscosity.

Key topics and technical requirements

Purpose: Rapid, reproducible determination of the glass working point for viscosity–temperature characterization.

Principle: A narrow vertical metal rod (sinking bar) sinks under its own weight into the melt; the sinking rate is used to calculate dynamic viscosity from a calibrated relation.

Specified geometry and materials:

Sinking bar: platinum–rhodium alloy, diameter 0.5 mm, mass 0.902 g (length ≈ 240–245 mm), hemispherical ends.
Depth of sink: nominal I = 20 mm for routine measurements.
Crucible: inner diameter ≥ 23 mm, depth 30–40 mm; platinum or non-porous refractory recommended.
Furnace: electrically heated tube furnace to ~1 200 °C, with ±3 °C uniform zone over the crucible.

Temperature measurement: Type S (platinum–10% rhodium/platinum) thermocouples recommended; measurement thermocouple should dip ~1 mm into the melt.

Calibration: Use a reference glass of similar composition at known viscosity (10^4 dPa·s) to determine the bar constant K; repeat after apparatus changes.

Precision: repeatability ≈ 3 °C (same operator/apparatus); reproducibility ≈ 8 °C (different operators/apparatus).

Practical procedure: hold bar above melt, detect contact (ammeter), release, time sinking to 20 mm (stopwatch 0.1 s), interpolate if necessary over ≤30 °C interval.

Applications and users

Practical applications:

Determining the working point for process control in glass forming and shaping.
Rapid characterization of viscosity–temperature relations during glass R&D.
Quality control and batch comparisons in production environments.
Calibration and validation of viscometric equipment.

Typical users:

Glass manufacturers, process engineers, laboratory technicians, materials scientists, and instrument manufacturers for viscometers and high-temperature furnaces.

Related standards

ISO 7884 series (Parts 1–8) - comprehensive methods and principles for glass viscosity and viscometric fixed points (Part 1: principles; Part 2: rotation viscometers; Part 3: fibre elongation; Part 4: beam bending; Part 6: softening point; Part 7 & 8: annealing/strain and transformation temperatures).

IEC Publication 584-1 - thermocouple type specifications (Type S) referenced for temperature measurement.

Keywords: ISO 7884-5, sinking bar viscometer, working point, glass viscosity, viscometric fixed points, dynamic viscosity, glass processing.

ISO 7884-5:1987

Abstract

Похожие стандарты

Overview

Key topics and technical requirements

Applications and users

Related standards

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