Unshaped Refractories standardization

ISO 1927 1984 Prepared unshaped refractory materials (dense and insulating), International Organization for Standardization, Geneva, Switzerland. 

Sand Rammer. The standard rammer for making test-pieces allows a 14 lb (6.25 kg) weight to fall 50 mm on sand contained in a 50 mm diam. mould three blows from the rammer are used in making a standard test-piece. Its use in compaction and workability tests for unshaped refractories is specified in B.S. 1902 Pt. 7.2. 

Initially, when unshaped refractories were first used, the property requirement was kept the same as for shaped refractories, in thatthey mainly replaced linings. Later on, when the use of these refractories became widespread, new standards had to be developed. The first standards on unshaped refractories by the American Society for Testing of Metals (ASTM) were published in 1943 [3]. They were numbered as C 179 and C 181 C 179 covered "drying and firing linear change of plastics and rammings" and C 181 dealt with "workability index of plastic refractories." As noted earlier. World War II saw an increase of about 35% in unshaped refractory production. Specifications were required to obtain the required items from many manufacturers. 

To achieve easier communication and trading within the European community, there was a need to create European standards that was recognized in the mid-1980s. Refractories were also included in these standards. The standard for unshaped refractory products was numbered EN 1402. 

In Europe much more time passed until the first tendencies for starting a standardization of unshaped refractories appeared. In February 1964, the PRE Bulletin No. 65 was published containing a first definition and classification of unshaped refractories and refractory mortars on a modest scale. 

Looking at Tables 1 and 2, it can be stated that during the 1970s, the biggest steps ahead were made in regard to unshaped refractories in Europe and in the United States. On the other side, it must be stated as well that in 1915 it was known how to measure the refractoriness of a product and how to determine the physical properties. But it took 28 years in the United States until the first monolithic standard was published (in Europe, it took more than 60 years). 

In addition to the above-mentioned standards, a number of specifications exist, unfortunately. These specifications come from the petrochemical industry and deviate from EN and ASTM standards especially in regard to the shape of the test pieces. Here, too, harmonization would be in the best interest of all parties involved. Figure 2 demonstrates how many test pieces a producer of unshaped refractories has to prepare. 

The consumer is confronted with a confusing number of manufacturers and products with more or less fancy names. However, names or designations are not always in agreement with the performance capability of the refractory product and what is expected. Consequently, the Verein Deutscher Eisenhiittenleute (VDEh) (Association of the German Iron and Steel Engineers) published a code number key for unshaped refractory products. This code number key is provided in the form of a standard titled Stahl-Eisen-Werkstoffblatt 916 (SEW) and was universally accepted and applied by all concerned German-speaking countries (8). 

The multitude of refractory aggregates (for example, calcined clay, flint clay, andalusite, mulhte, bauxite, fused white or brown alumina, sintered alumina, etc.) and the different grain sizes of these materials—in addition to the big variety of bonding agents, additives, and mixing liquids—enable endless combination possibihties in development work on unshaped refractory products. Therefore, a qualitative standardization is not really possible as it is the case for refractory bricks. As a result of the ENV 1402-1 standard, which now provides a more precise definition of the products, there will probably be adjustments on the market in the long run. If also considering economic aspects, suitable products will obviously be developed on the basis of all the available constituents. 

Krebs R. State of the art of the standardization of unshaped refractories in Europe. CN-Special Refractories. 1999 6(3). 

There are small differences in different classifications of refractory materials among ISO, DIN, and ASTM standards [1 ]. The most common definition is that refractories are shaped and unshaped materials that are durable at high temperature (>1,500 °C). Usually, heat refractory insulation materials have a service temperature of 800-1,100 °C. 

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