The XNJ series filters can be installed on the top of the tank and the element is immersed in the oil, so it is easy for installation. During maintenance, you only need to turn off the screws of the connecting flange, and pull-out the connecting flange, the element can be changed or cleaned. A vacuum indicator in the filter gives signals when the pressure drop across the element reaches -0.018 MPa showing that the filter element should be cleaned or changed. If no maintenance is done, as the pressure drop rises to 0.02MPa, the by -pass valve in this filterwill open allowing oilflowing into pump directly, sowhen you select this series suction filter, a vacuum indicator should be necessary for the element clogged by contaminants, you can clean or change it immediately.