ASNT Level III- Visual & Optical Testing
My Level III Self Study Notes Reading 4 Section 4B
My Level III Self Study Notes Reading 4 Section 4B
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6.2 Certification of Temperature Indicators<br />
Temperature indicating sticks are mixtures of organic and inorganic<br />
compounds. The purity of the source materials directly affects the accuracy of<br />
the predicted melting point. There is the possibility of contamination with trace<br />
quantities of other elements, which may be detrimental to the accuracy of the<br />
indicator. In some cases, low melting point materials (lead, tin, sulfur,<br />
halogenated compounds) may be undesirable for the welding procedure.<br />
Most manufacturers can provide certification supported by analyses of typical<br />
batches. Documentation indicates which temperature ratings may contain<br />
contaminants that can be avoided by the user.<br />
In some critical applications (nuclear fabrication, aircraft assembly), actual<br />
chemical analysis of the specific lot number of the temperature indicators may<br />
be required. If the customer supplies a written certification requirement listing<br />
the compounds to be tested for, most manufacturers will send lot numbered<br />
samples for laboratory analysis. The customer is usually expected to pay lab<br />
charges for such specialized requirements.<br />
Charlie Chong/ Fion Zhang
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