Perforation:


Depending upon the thickness of the metal, 0.020” thru 1” perforation is available. In the case of metal or stainless steel, the smallest perforation available are usually twice the thickness of the metal. Rather than the use of light gauge sheet metal which would be necessary in obtaining exceptionally small perforations, we suggest heavy gauge perforated metal screens with large perforations lined with wire mesh cloth. This is not necessary for small strainers where lighter gauge metals are satisfactory.

Mesh:

The term “Mesh” applies to woven wire cloth and should not be confused with perforated sheet metal. Mesh screens are satisfactory for small size cast strainers, but are unsuitable for longer strainers except as a liner for perforated metal basket or screen. Mesh screen are primarily furnished for very fine straining with openings so fine they cannot be obtained in Perforated metal. Example: 100 mesh means 100 vertical and 100 horizontal strands of wire to the square inch, resulting in 10,000 openings of 0.0055 sq. inch.



Ratio or Capacity : The 6 to 1 ratio means that the open area of the screen or Basket should be equal to six times the cross-sectional area of the corresponding pipe size.

 
 
 
 

Strainer selection:
Perfectt Engineers have observed that to keep the pressure drop within reasonable limits and to have effective straining it is necessary that the free straining area will be a least three times the pipe cross sectional area in the case of Y - Strainers and six times in the case of Basket type strainers.
Select the anticipated clogging % at the left of the chart. The example shows a basket 75% clogged. Then, follow that until the curve is intersected. From that point follow downward to the scale along the bottom to read the pressure drop multiplying factor, in this case 4. The resulting pressure drop across the basket at 75% clogged is four times as great as that for a clear basket.

Example: How much is the Pressure drop through a 12” Y” strainer for a flow of 1000 GPM of water at ambient temperature with 1/8” perforated basket which is 75% clogged? Find the pressure drop for a clean basket from the curve. At 1000 GPM it is 0.3 psi. As prescribed, the multiplying factor for a 75% clogged basket is 4. The pressure drop is then 03.psi x 4 = 1.2 psi.

Select the anticipated clogging % at the left of the chart. The example shows a basket 75% clogged. Then, follow that until the curve is intersected. From that point follow downward to the scale along the bottom to read the pressure drop multiplying factor, in this case 4. The resulting pressure drop across the basket at 75% clogged is four times as great as that for a clear basket.

Example : How much is the Pressure drop through a 12” Basket strainer for a flow of 2500 GPM of water at ambient temperature with 1/8” perforated basket which is 75% clogged? Find the pressure drop for a clean basket. At 2500 GPM of water the pressure drop is 0.2 psi. As described, the multiplying factor for a 75% clogged basket is 4. The pressure drop is then 02.psi x 4 = 1.8 psi.