It is often beneficial to monitor the condition of filter elements. One of the most common ways to monitor the condition of filter elements is to measure a pressure drop across a filter element using a differential pressure gauge. A measurable difference in pressure occurs over time because, in a clean filter, a fluid being filtered flows freely without restriction, and in a filter filled with dirt and debris, the fluid flow is restricted. Accordingly, a fluid flowing through a clogged filter will have a higher pressure before entering the filter and a lower pressure after exiting the filter.
Many types of differential pressure gauges are available. For example, a piston-type gauge can be used to measure pressure drop. A piston-type gauge typically includes a piston that is tightly fit into a cylinder, with a spring attached to one end of the piston. A fluid having a higher pressure is directed by tubing to one end of the piston while a fluid having a lower pressure is directed by tubing to an opposite end of the piston. The spring is configured to oppose motion of the piston in a direction from the higher pressure source to the lower pressure source. The pressure from each respective fluid source exerts a force on each respective end of the piston. When the difference in pressure between the two ends of the pistons is zero, the spring does not compress or extend and the piston remains at rest. However, as the difference in pressure becomes greater between the two ends of the piston, the piston is displaced. The spring compresses or extends until the force applied by the spring to the piston is equal to the net force exerted on the piston due to differential pressure. By knowing the relationship between the compression or extension of the spring and the resulting force applied by the spring, the position of the piston can be used to indicate the difference in pressure between the two ends of the piston.
The continued accumulation of debris within the filter element causes the pressure drop experienced across the filter element to continue to increase during extended use of the filter element. The filter element may eventually reach a point wherein the pressure drop experienced across the filter element may cause a fluid system utilizing the filter element to be damaged or to operate less efficiently than desired. It is accordingly beneficial to prevent an occurrence of such a fluid system operating when the pressure drop experienced across such a filter element exceeds a pre-selected maximum value indicating that the filter element is in need of replacement or maintenance.
It would therefore be desirable to provide a differential pressure gauge that determines and communicates to a user when a pre-selected maximum pressure drop is experienced across the filter element associated with the differential pressure gauge.