I have a question regarding the filters in the lubricating oil station of a centrifugal compressor.
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In the oil circuit system, on the dual oil filters, why are the two filters connected to each other using a cross-connected pipe equipped with a shut-off valve and a flow control orifice plate? What is the purpose of this?
The backup filter is filled with lubricating oil to prevent the oil pump from running dry
The pressure equalizing valve, also known as a balance valve, works in conjunction with the exhaust valve to ensure that the spare filter is filled with oil, allowing for immediate switching.
Its function is to make the oil pressure in the spare filter equal to that in the main filter; generally, it should also be accompanied by a vent valve and an oil sight glass. The lubricating oil enters the backup filter through the main filter pressure equalizing valve (what you mentioned: a cross-connected device with a shut-off valve and a flow control orifice plate). Some of the oil returns to the oil tank via the vent valve (the amount of oil that returns is adjusted using the oil sight glass; it shouldn’t be too much – as long as some oil flows out, that’s sufficient). This ensures that both the main and backup filters have the same oil pressure and temperature, thereby preventing any fluctuations in oil pressure during filter switching and avoiding the presence of air in the oil.