Generally, Y-strainers are used with gases such as steam or air. Basket strainers are used with liquids. A Y-strainer will offer more pressure drop than a basket strainer since its free straining area is less. As a strainer becomes clogged to the point where the OAR of the strainer approaches the pipe area, the pressure drop across the strainer increases very rapidly and unpredictably. Pressure gauges on each side of the strainer can be valuable to determine when the strainer requires cleaning. Differential pressure switches can be set up to operate warning lights or alarms if so desired. Most reputable manufacturers of strainers supply all charts for their pressure drop calculations.
The more problem is we didn't know the manufacture and the specification, how do we estimated the pressure drop.
can somenoe have experience to tell the spec of strainer by any method?