Standards Development

Scope

This document specifies both test method and test apparatus to determinate resistance of enamelled specimen to impact.

This standard is a destructive test by subjecting enamelled steel specimen to mechanical impact.

This test method is not suitable to determinate the resistance of enamelled articles to impact.

Purpose

The mechanical impact resistance of the vitreous and porcelain enamel layer is a very important parameter of the glass-lined equipment. It is the technical basis for evaluating mechanical impact resistance of vitreous and porcelain enamel and the rationality of the enamelling process of the glasslined equipment. It is utilised frequently while testing performance of vitreous and porcelain enamel and in glass lined equipment researching, manufacturing and testing companies, and most of them use glass-lined specimen as test specimen. 

Current testing method of international standard ISO 4532:1991 “Vitreous and porcelain enamels — Determination of the resistance of enamelled articles to impact — Pistol test” is suitable to test mechanical impact resistance of the glass-lined articles, not suitable to test specimen of vitreous and porcelain enamel. If use the method specified in ISO 4532:1991 to test the mechanical impact resistance of vitreous and porcelain enamel specimens, it will result in large errors and low comparability.

The purpose of this proposal is to state a test method that is more suitable for testing the mechanical impact resistance of vitreous and porcelain enamel specimens, and to improve the accuracy, repeatability and comparability of the mechanical impact resistance testing of glass-lined specimens. There are four reasons for this proposal:

1. The test method specified in the current international standard is more suitable for glass-lined articles, but not for glass-lined test specimens. The test method specified in the new proposal is more suitable for testing the mechanical impact resistance of glass-lined specimens;

2. The impact force specified in current standard ISO 4532:1991 is provided by spring. But the spring force is unstable, inaccurate and varied by the compression, use time, materials and use environment of spring. Also, the spring force value of the spring pistol is also difficult to calibrate. The test method indicated in the new proposal is to impact the glass-lined layer by a steel ball with a certain diameter in free fall at a certain height. The impact force is accurate, stable and does not change by the time of use, environment, and materials. Also, the impact force value is easy to calibrate;

3. The mechanical impact angle has a great influence in test results. The correct impact angle is 90°, and the test method specified in this proposal can more accurately ensure the impact angle to be 90°;

4. The supporting form of the test specimen has a great impact in test results. ISO 4532:1991 does not specify the supporting form.The test method specified in this proposal can greatly reduce the influence caused by the supporting form;

Comparing with the method specified in ISO 4532:1991, the new proposed test method is more accurate, repeatable, and comparable to test impact resistance of glass lined specimens.