Temperature Changes (aka: Adiabatic Heat)
- Heat resulting from molecular movement of air during pressurization of the test part or from parts cooled inadequately from thermal operations prior to testing.
- Results from molecular movement during pressurization of the test part
- The higher the test pressure = the faster the air molecule velocity = the more adiabatic heat
- The higher the part volume = the more air molecules moving = the more adiabatic heat
- The Pressure Transducer sees a temperature increase as a pressure increase
- Heating stops when part is fully pressurized
- The air inside the part cools
- The Pressure Transducer sees a temperature drop as a pressure drop
Volume Changes (aka: Elastic Creep)
- Expansion of the part during pressurization reults in an increase in the part volume. As volume increases, pressure trapped inside the part drops.
- Results from expansion of the part during pressurization increases the part volume, dropping the internal pressure of trapped air
- Amount of Creep depends on composition of the part
- Soft plastic parts yield more than rigid plastic parts
- The thinner the wall sections of the part, the more creep
- The higher the pressure, the more potential for creep
- The more creep = the more lost volume = the more lost pressure
- The Electronic Sensor sees this pressure drop as leakage
