Which one below is NOT a part of the TXV?

The correct answer identifies an element that does not belong to the components of a Thermostatic Expansion Valve (TXV). In a TXV, the key components include the seat, the pin, and the push rods. These parts work together to control the flow of refrigerant based on the cooling demand determined by the sensing bulb.

The seat functions as a critical part of the valve where the refrigerant flow is controlled, effectively regulating the variable size of the opening based on temperature changes. The pin, which is associated with adjusting the valve’s opening based on pressure differential, works in conjunction with the seat to maintain precise flow rates.

While the push rods serve to transfer force from the diaphragm to the pin, enabling the dynamic operation of the valve, a piston is not a standard component in a TXV. Instead, in some valve designs, a diaphragm is utilized to respond to pressure changes, contributing to the TXV's function without the inclusion of a piston. Thus, the identification of the piston as a non-component is accurate and reflects a deeper understanding of the actual structure and operations of a TXV.