PRM Dual Bag Filter Housing Skid (Duplex) Overview & How to Operate


The PRM Dual Bag Filter Housing Skid allows users to change out filter bags one at a time without stopping flow and minimizing costly downtime.

The system can be configured to your needs depending on the application’s pressure, flow rate, temperature, and chemical compatibility. Our example system shows the most common configuration with two High Pressure 304 Stainless Steel #2 Size Bag Filter Housings, which is rated for up to 200 GPM.

Configuring a custom bag filter housing skid system

The options are nearly endless, but our more popular options consist of the following. If you're considering a custom bag filter housing skid, contact a PRM filtration expert to configure the ideal filtration system for your application.

Bag filter housing size:

  • (2) #2 Size Bag Filter Housings - Up to 200 gpm
  • (2) #2 Size Multi-Bag Filter Housings - Capable of flow rates >200 gpm

Bag filter housing material:

  • Carbon Steel
  • 304 Stainless Steel
  • 316 Stainless Steel

Piping material:

  • Carbon Steel
  • Stainless Steel
  • PVC

Skid material:

  • Carbon Steel
  • Stainless Steel

Valve type and material:

  • Stainless Steel
  • PVC
  • Butterfly Valves
  • Ball Valves

When to change a bag filter on a duplex bag filter housing skid system


When you see the differential pressure between the influent and effluent pressure gauges increasing, it’s time to change the bag filter. There is not a perfect rule-of-thumb to follow in determining the exact differential pressure for when to change a bag filter. If it is time to change one or both bag filters in the system, you will notice a decrease in flow and pressure building at the inlet.

How to change a bag filter on the duplex bag filter housing skid


Follow the steps listed below or watch Luke perform a dry run of changing a bag filter in the PRM Bag Filter Housing Skid at the top of this page. [Back to top]

  1. Cut off the flow at the top (influent) of the housing requiring a bag filter replacement.
    1. Lock the valve into place if using butterfly valves.
      Cut off the flow to the bag filter housing skid

  2. Cut off the flow at the bottom (effluent) of the same housing.
    1. Lock the valve into place if using butterfly valves.
      Cut off the flow at the bottom of the bag filter housing

  3. Drain the housing using the drain port at the bottom of the housing.
    1. Most users attach a hose to direct the drainage flow. Draining the housing will make it easier to pull the bag filter out of the housing, as well as installing the new bag filter.
      Open the bottom drain port to drain remaining liquid out of the filter vessel

    2. Opening the sample port at the top of the housing will allow air flow and assist in draining the housing.
      Open the sample port at the top of the housing to allow air flow for draining

  4. After most of the liquid has drained out of the sample port, loosen the eye bolts at the top of the housing to remove the top plate, and swing the eye bolts downward.
    Loosen the eye bolts at the top of the housing to remove the lid

  5. Remove the top plate and set aside.
    Removing the top plate of the filter housing

  6. Loosen and remove the compression clamp inside of the housing that holds the distributor plate in place.
    Removing the compression clamp inside the filter vessel

  7. Remove the distributor plate from the inside of the housing and set aside.

  8. Remove the dirty bag filter.
    1. After removing the bag filter it’s recommended to inspect the strainer basket and look for any possible buildup. The strainer basket can be pulled directly out of the housing. Clean the strainer basket as needed, and place it back into the housing.
      Removing a dirty bag filter from the housing

  9. Place the new bag filter into the strainer basket. Make sure that the bag filter fully extends down into the strainer basket column.
    Placing a new bag filter into the bag filter housing skid system

  10. Place the distributor plate back into the housing and hand tighten down with the compression clamp.

  11. Inspect the o-ring at the top of the housing for any possible issues, and consider applying a food-grade grease to keep the o-ring from drying out. Be sure to take chemical compatibility into consideration for your application when applying grease to the o-ring.

  12. Place the top-plate lid back on, and hand tighten the eye bolts in a cross-pattern.
    1. Consider applying anti-seize lubricant to the eye bolts.
      Re-install the top plate and tighten the eye bolts

  13. Finish tightening the eye bolts with the tool of your choice (wrench or screwdriver), and do not overtighten.
    Tightening filter housing eye bolts with wrench

  14. Before turning any flow to the housing back on, be sure to close the drain port and sample port.
    Closing the filter housing drain port ball valve Closing the filter housing sample port

  15. Open the effluent valve at the bottom of the housing
    1. Lock the valve into place if using butterfly valves.
      Opening the effluent valve at the bottom of the bag filter housing

  16. Open the influent valve at the top of the housing
    1. Lock the valve into place if using butterfly valves.
      Opening the influent valve to the bag filter housing

  17. Now that there is liquid flowing through the housing, partially open the sample port valve to allow for the housing to degas. As the housing fills with water you will hear a hissing sound. As soon as liquids flow out of the sample port, close the valve immediately.
    Partially opening the sample port at the top of the bag filter housing to let in air for draining

  18. Repeat steps as necessary for the other bag filter housing.


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