3.4.5.1 Property Surveys: In the event an acceptable alternative TUS testing method cannot be
developed employing traversing or insertion of TUS test thermocouples through or into the furnace work
zone(s), property surveys shall be accepted as objective evidence of thermal processing capabilities.
Initial property surveys of the selected product shall analyze those characteristics that are sensitive to
variations in process temperatures and shall establish baseline data against which monthly product
property trends shall be performed. If possible the selected product is processed frequently. The normal
process size range shall be represented in the selected product. When a two-step process is under review,
the second step can be run on the samples independent from the remainder of the lot.
If the furnace qualified operating temperature range is equal to or less than 170ºC (305ºF), the highest and
lowest operating temperatures shall be represented by the product property survey. If the furnace qualified
operating temperature range is greater than 170ºC (305ºF), the product property surveys shall include an
intermediate temperature in addition to the highest and lowest operating temperatures.
At least five product property surveys shall be performed at each survey temperature. Samples for product
property surveys shall be taken from the extremes and center of the load.
Monthly property survey trends shall include selected characteristics of heat-treated product analyzed by
an appropriate statistical technique. Trends shall be examined monthly with defined control limits.
Processing will be halted if any property trend exhibits a shift beyond assigned control limits until the
cause of the shift is corrected.