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
