The Kadant Blog

My Pressure Liquid Filter is Clogged: What Now?

What does it mean when you hear a process mill technician say a pressure liquid filter is clogged or plugged? It means the filter screen has filled to 100% of its solids loading capacity. The filter no longer has enough flow capacity for the process. Clogged filters are a showstopper for any liquid filtration process if they plug too frequently. The following article explains why pressure liquid filters plug, steps to avoid clogging, and what to do if the filter plugs often.   

Why do pressure liquid filters clog?

Pressure liquid filters have a limited capacity. They collect debris over a certain time interval. If they fill to capacity too frequently, steps must be taken to lengthen the fill time.   There are a couple common reasons why pressure liquid filters clog quickly. First, the process may be unstable and the solids loading becomes high.  Alternatively, the process may have changed, or the filtration equipment isn’t installed in the correct place for the application.

Basic steps to avoid a plugged pressure liquid filter

  1. Avoid a sudden process change. Any type of quick change in the current process can change the makeup of the solids being filtered. Conduct appropriate research and calculations prior to making any process changes.
  2. Conduct a mass balance test prior to installing a new pressure liquid filter. A simple mass balance calculation can determine if a pressure filter will be problematic before installation. The calculation involves taking the flow rate, inlet and solids loading PPM, and sending a sample to a lab to determine the particle size distribution. With that number, we can determine a rough fraction of the material a filter can remove.
  3. If the pressure liquid filter uses an automatic backflush, a good rule of thumb is to make sure the system doesn’t collect and regenerate more than once per hour. More than once per hour can be a sign that the application isn’t appropriate. However, the ideal scenario would be to collect and regenerate every 12 hours or longer.
  4. Some processes use a manual or bag pressure liquid filter. A mill operator must manually shut the filter cartridge offline to clean. If this manual process is being done less than every eight hours, the application may not be appropriate.

What to do if a pressure liquid filter gets clogged too often

There are three common options to consider when a pressure liquid filter gets plugged frequently. First, consider installing additional filtration upstream to reduce the solids going to the filter. Second, add more filtration area to the current equipment location. Finally, try adjusting the screen size.

  • Written by:
    Dave McGowan

    Dave McGowan

    Technical Manager, Kadant Solutions Division

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