Problems with hydraulic check valves in hydraulic oil systems
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Dear sea friends and experts, in hydraulic oil systems, there is a set of filter and directional valve assemblies, among which the fluid-controlled check valve 2 does not make sense from a conventional perspective. Generally, in this case it is necessary to force the hydraulic check valve to close in order to keep Filter Group B available as a backup. However, with the normal control of a hydraulic check valve, when control oil P-B is supplied, the valve opens, which is the opposite of what is desired. How can the controls on this graph be explained? ? Is there a hydraulic check valve that is closed by hydraulic control? ?
According to the diagram, CV and PCV operate on different principles; is it that CV has a control hydraulic signal to shut it off, while PCV has a signal to turn it on?
CV is a regular check valve, while PCV is a fluid-controlled check valve
Following the process shown in the diagram, the oil from the pump outlet flows through P-B to the check valve located within the red circle; when this valve opens, the system on the right side operates normally. After passing through the filter, the oil returns to the tank via the check valve on the right side in an A-T manner. Since this is a direct return flow, no pressure is generated; as a result, the PCV on the left side cannot function, and the filter on the left side serves as a backup. When a filter replacement is needed, manually switching to HCV activates the left filter, while the right one remains in standby or is taken for maintenance. I’m not sure if this understanding is correct?
The normal process is as follows: The hydraulic oil exits the pump and splits into three paths. Path one: The oil flows through filter A normally. Path two: The P-B ports of the manual directional control valve HCV act to press against the check valve at the outlet of filter A, preventing backflow of oil; the PB ports also control the PCV valve at the inlet of filter B, causing that valve to close. Path three: Filter B has its flow blocked by the oil controlled by HCV, so it remains in a standby state. In summary, a hydraulic check valve should not be used here; instead, a 2-position 2-way valve should be used. Control the opening and closing of the 2 inlet valves of the filter. It uses a pressure-operated latch, which resets and opens when the pressure is released.