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Spin on filter check valve and bypass valve


Usually spin on engine oil The filter is equipped with check valve and bypass valve.

       Function of check valve When the oil filter is set at the top of the engine, it can effectively prevent the loss of oil in the oil filter after the engine stalls, so as to avoid short-term low oil pressure and engine wear when starting again.    


 Oil filter element ore.jpg


The reason why some models of filters do not have check valve is that the installation position of the matching engine oil filter is at the bottom. Even if the engine is shut down, the oil in the oil filter will not be lost. At this moment, the function of the check valve will disappear.

Function of bypass valve In extreme cases, to avoid engine oil loss, so as to prevent engine wear.


 Diesel filter core ore.jpg


     Oil filter core ore blending 1.jpg


    Extreme cases usually refer to:
        1. Extreme low temperature

Low temperature will lead to poor oil flow. Cold oil may not penetrate the filter paper to reach the oil passage, thus affecting the lubrication. In cold state, the oil pressure is usually higher than that in hot state. At this time, the bypass valve can be opened quickly to ensure the oil pressure in the oil passage and reduce the wear during cold start.
       2. When the oil filter paper is full of dirt

        It will increase the pressure difference before and after the oil filter. At this time, if there is a bypass valve, the oil can be short circuited to ensure the oil pressure, but the oil is not filtered at the moment.

The pressure is set by the bypass valve of the main engine. However, if the oil filter is not equipped with a bypass valve, the main engine plant has considered the bypass valve channel when designing the oil base.

The setting of bypass valve is different according to different filter models. Some of the pressure control is spring, some are stainless steel spring, but the purpose is the same, that is, the pressure control must be accurate.
In addition, the environmental protection paper filter body does not have check valve and bypass valve, but there is a perfect system on the oil base, so it does not mean that there is no check valve and bypass valve in the filter seat.


A good filtration must meet the accuracy requirements of check valve and bypass valve. If the check valve cannot be closed, the oil will flow backward, which will lose practical significance. Similarly, if the opening accuracy of the bypass valve is not enough, either the oil often goes short circuit, or it can not be opened in time in extreme cases.

Therefore, in addition to the filter paper's filtering accuracy, flow capacity and pollution capacity, the key is the design of check valve and bypass valve.