Differences in testing practice

Descriptions of 21 test facilities and operating procedures were received. AU the required information was not available on eveiy facility but sufficient information was forthcoming to allow conclusions to be drawn. The data supplied were analysed for differences in main parameters listed above, and 

The first aspect to consider is the overall layout of the cyclic oxidation facility. The results are summarised in Table 17.1. There is an approximately even split between vertical and horizontal arrangements of furnace and cooling chamber. The other category included a burner rig, a muffle furnace and a direct resistance heating facility for ultra-short cycle testing. 

The choice of open or closed system is summarised in Table 17.2. Most facilities are closed an arrangement that prevents any influence of local environment, such as chloride contamination at coastal sites or variations in laboratory humidity, affecting the test data. An open system is one in which the laboratory atmosphere is also the atmosphere inside the furnace. 

In most of the facilities, temperature was controlled and monitored by thermocouple. One piece of equipment, a direct heating system for ultra-short cycle testing, was controlled by pyrometer. Type R (Pt Ptl3%Rh) and S (Pt PtlO%Rh) thermocouples were the most commonly used, although types K (NiCr NiAl) and B (Pt6%Rh Pt30%Rh) were also used. This information is summarised in Table 17.3. 

The positioning of thermocouples is summarised in Table 17.4. One facility attached a thermocouple to a dummy specimen in the assembly, which is the most accurate way of measuring the surface temperature of specimens and it is perhaps surprising that more laboratories do not employ this practice. The 

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