CRITERIA FOR STRAINER SELECTION:

1.Pressure drop:

Pressure drop across the strainers should be kept to a minimum. An increase in the pressure drop across the strainer will indicate that the strainer screen needs to be cleaned or replaced.

2.Type:

A strainer can be either be Y type for smaller sizes or T type for large sizes. These can also be basket type. Economics of capital investment determines the type of strainer used.

3.Size:

The size of the strainer should be the same as the pipeline size to the component it is supposed to protect. In most cases, the size of the component may be smaller than the pipeline size.

4.Material of construction:

The material of the construction for the strainer will be the body to suit the operating pressure and temperature. The screen used to filter will depend on the particle size allowable as per the design of fitting the strainer.

For steam lines and condensate lines cast Iron, graphite cast iron, or cast steel are used as body material. For the food and drug industry special grades of stainless steel are used.

5.Filter or mesh size:

The screen or the filter has a mesh size of 100 microns as standard. Each manufacturer has a standard mesh size for a particular given application. T-type of strainers are provided with a large screen design.

The selection of the filter is governed by the media that is flowing or the level of contamination of the fluid. The primary factor governing the strainer selection is the equipment that needs to be protected using the strainer.

For example: If a control valve is to be protected by selecting a strainer following parameters should be considered

1.The size of the particle that the control valve can withstand, without damaging the trim and packings.

2.The type of particulate contamination in the flowing fluid, its properties like hardness, dissolved/mixed percentage, etc.

3.The fluid properties like the type of fluid, flow rate, pressure, and temperature.

The above parameters decide the type of the strainer and the size of the filtration element.

There is a wide choice in selecting the strainer like the basket, Y type, T-type, conical, etc. Filtration elements can be perforated sheets, meshes, sintered metal/plastic elements. Due to the variety, there is a need for the right selection.