1. A system for detecting a plugged impulse line in a process measuring device, the system comprising: a sensor for detecting a pressure in a process line, the sensor providing a pressure signal indicative of the pressure; and one or more processors implementing a first statistical process monitoring (SPM) block, a second SPM block, and a plugged line diagnostic block; the first SPM block configured to calculate mean values from a plurality of pressure signal sample values collected during predefined sample windows, and the second SPM block configured to calculate standard deviation values from a plurality of pressure signal sample values collected during the predefined sample windows; and the plugged line diagnostic block configured to model the standard deviation values as a function of corresponding mean values, to predict standard deviation values based on mean values, compare predicted standard deviation values to corresponding calculated standard deviation values, and detect a plugged impulse line when a predicted standard deviation value differs from a corresponding calculated standard deviation value by more than a predefined amount.