Pressure indicating device for indicating clogging condition of a filter

摘要

A differential pressure indicator is provided for detecting and indicating a clogging condition of a filter element and subsequently an opening condition of a by-pass valve. The indicator also indicates when no filter element is installed in a fluid system. A thermal lockout effective even at high internal fluid differential pressure prevents false actuation of the indicating means at low temperatures due to increased viscosity of the system fluid. A positive locking feature prevents resetting of the indicating means after actuation. Servicing of the filter element is required in order to reset the indicator.