Cleaning Cross Flow Filters

We're often asked how to clean cross flow filter systems.  This can often be a challenge.  Cross flow systems remove very fine particles out of wine – and to remove these particles from a filter system can be tricky.  The nature of the organic soils – although still wine – often are more gelatin like, and without some thinking before hand it is easy to turn an organic gelatin in the cross flow system into soap!
Often the two key concerns for cleaning are pressure and flow.  As organic soils and solids build up in the filter there is an increase in pressure on the pump.  While this is building pressure on the pump it is also decreasing the flow rate for the entire machine. 
So the cleaning aims seem simple – remove the solids, reduce the pressure and increase the flow.   With a few variables in play here (ie the filter type) we have some views on this that might help with cleaning.
If we go back to some basic principles of cleaning in wine the steps are;

  1. Reduce the surface tension of any solids to wash the soils off the article being cleaned (detergency, surfactants, wetting agents);
  2. Dissolve (emulsify) any acids/organic soils that can be dissolved.

Once the surface tension of a solid has been reduced (ie that soil can’t hold onto the surface any longer) – it can then be washed off the surface, and if soils can be moved into a solution then they can be washed out of the vessel being cleaned.
This makes sense for tanks – if you can get the soils in the tank into a solution – or get the soils off the wall of the tank you then have a good chance of rinsing out all the organic matter leaving a bright shiny finish.

Where this process comes unstuck for cross flow systems is the type of chemicals that are often used.  Many manufacturers recommend caustic to clean with.  Our view on caustic is that it doesn’t clean effectively.  What we find is that the high pH of caustic products actually increases the surface tension of soils.  This means an organic soil is harder to remove from a surface – it is more attached requiring more force to shift it.  This is happening chemically in tanks, but also in the cross flow filters.

The compounding issue for cross flow filters is that high pH products on gelatin soils can have the effect of creating soap!  The caustic hardens the gelatin, making it extremely difficult to wash from the system.

Another issue we see commonly in bottling lines that can impact cross flow systems is water temperature.  If the water used to clean is too hot (ie above 90 degrees C) it will cause a protein char.  This stain is burnt on (similar to a chemical burn from caustic) and it is actually caused by just hot water.

The two common problems as we see it, are that current chemicals being used aren’t performing adequately, and that very high water temperatures can be creating a further problem in cleaning cross flow systems too.

For cross flow systems we suggest that moving away from caustic is a good first step to a better clean.  A lower pH product, (in our range Cleanskin, Cleanskin K or Oak Restorer) – where the surfactants are food grade, plant based and rinse well, will have a far better impact in reducing surface tension so that soils can be washed from the system.  Using warm water (40-60 degrees C) will help with this too.

Cleaning a cross flow system is tricky, it will take effort.  In our opinion using quality chemicals and water that isn’t too hot will make the job a lot easier.



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