The quantity of residual air shall be measured during the tear down examination of the thermocouple pouches (post-thermal processing). The amount of residual air shall be recorded as required. The maximum allowable level is listed on the Thermal Process Schedule for each product.
Using one (1) sample pouch, residual air is measured. The pouches will be opened under water into an inverted, water filled 50 ml. buret with a funnel attached to the submerged end. The pouch shall be squeezed while under water to force out all residual air. Test findings shall be recorded on the appropriate form. Specifically, the residual air test is as follows:
- The sink is filled with room temperature water.
- Water is drawn up into an inverted buret with a pipette pump to zero line.
- The pouch is then held under water beneath the inverted funnel attached to the end of the buret.
- The pouch is cut open and squeezed to force out all air in the pouch.
- The reading is taken from the top of the water column in the buret.
- Water is redrawn to zero line with the pipette pump before the next test is performed.
- The sink and buret must be periodically cleaned out to ensure test accuracy.