How to Size a Basket Strainer

Application Considerations

The nature of the product also has an influence on the strainer size. Soft, gummy materials like tars and resins are more difficult to remove and clog baskets more quickly than hard crystalline materials. In these cases, a larger strainer size is also recommended. The size of a basket strainer, therefore, is a function of the job to be done. It should not automatically be the same size as the pipeline.

There are no industry wide standards on face to face dimensions for flanged basket strainers, such as there are for gate valves. For this reason, the strainer of one manufacturer may not fit in a space designed for a different brand of strainer. If there is doubt on this point, it is best to check the face to face dimensions of the particular unit which is going into the line.

Selection and Sizing of Basket Strainers

When installing basket strainers, it is sometimes a good idea to use two of them in tandem. This is especially true when there is a great deal of material to be taken out of the line and the particles vary in size. If a single strainer with a fine mesh lining were used alone, it would fill quickly and necessitate very frequent cleaning.  By using two strainers in series, the first with larger opening to trap the large particles and the second with a fine mesh lining, the load is spread out and time between cleanings is also spread out.

A Good “Rule of Thumb”

Selecting the proper size basket strainer for a particular application is most important. Most reliable manufacturers have pressure drop information for all sizes. A general rule of thumb is that pressure drop through the strainer should not be greater than 2 psi. If it is, the strainer selected is too small. Factors such as viscosity, specific gravity, and mesh lining size all influence pressure drop through the unit and they must be taken into account.

Don’t Be Misled By Pipeline Size

Thus, the strainer size is not automatically the same as the pipe size. It may be larger. In the case of highly viscous liquids, for instance, where pressure drop through a mesh lined basket can reduce flow considerably it is sometimes necessary to use a strainer several sizes larger than the pipeline in order to insure adequate flow. However, this is often desirable because, aside from the slightly larger initial investment, there are no subsequent added costs. Basket strainers last almost indefinitely and there is almost nothing to wear out. If there is an unusually large amount of material to be taken out of the line, then a larger strainer is almost certainly called for. Too small a unit will fill too quickly for adequate straining and will require frequent basket changing. This can be expensive in the long run. If a basket has to be changed more than once an hour, the strainer is probably too small.