Capacity

The capacity of a strainer is related to the size of the screen.  The larger the capacity provided, the greater the time between cleaning the screen.  One measure of capacity is the open area ratio.  This is the ratio between the open area of a screen and the cross sectional area of the inlet pipe.  The larger the open area ratio provided, the greater the capacity of the strainer.

Pressure Drop

The pressure drop is also related to the open area of a screen and the selected screen size opening.  The smaller the screen size opening the larger the pressure drop created. As a screen becomes clogged the pressure drop will increase.  Most piping systems permit a clean screen pressure drop of around 15 – 20 kPa.  We typically recommend cleaning the screen when the pressure drop reaches around 70 kPa.

The maximum differential pressure that a screen can withstand is known as the screen burst pressure.  Burst pressures typically exceed 100 kPa.  However it is not recommended to operate a strainer near the burst pressure.  Screens require periodic cleaning to ensure that they continue to perform and to ensure that the pressure drop across them remains low.