I just remembered something due to NH3LVR's comments on ammonia TVX's. How often do you rebuild or replace ammonia TXV's?

For people who work on ammonia systems this is the result of a very common issue called wire-drawing. Ammonia TXV's are very prone to this and the result is the pin and seat wear away. Eventually the valve orifice is worn out and can't control the liquid flow for superheat control anymore.

Adjusting an NH3 TXV with this problem is a waste of time.