The invention provides systems, methods and apparatus for processing delicate parts within a process tank such as an ultrasonic tank. The lower limit value NinL is greater than a lower limit value set for a normal temperature of operating fluid. The benefits of these systems are higher service lifetime and low thermal conductivity to achieve high operating temperatures. The top plate includes a supporting portion extending from the top plate towards the base wall of the frame and disposed at a periphery portion of the top plate in the longitudinal direction.