Sheet Filter Setup & Usage: FAQs

Our technical filtration experts have compiled a few of their most frequently asked questions from customers filtering with sheets.

PLANNING & SETUP

Q. How do I setup and run my sheet filter?

A. Check out this short how-to video on our YouTube.

Q: How do I calculate how many sheets to use for a filtration run?

A: By looking at the optimal flux rate for each grade and calculating the surface area needed per run.

Surface Area per Sheet:

• 20 x 20 cm: 0.04 m²
• 40 x 40 cm: 0.143 m²
• 60 x 60 cm: 0.33 m²

*Each sheet has a filtration capacity of approximately 2 hours

**Product should be pre-filtered to a polish to ensure highest efficiency

Q: What is the fewest number of plates I can use in my filter press?

A: This number will depend on how far the spindle can extend to still seal the pack effectively. You might have to add a spindle extension to compress the pack far enough. Depending on your setup, you may need to inquire about a blind plate in a pack with stainless steel plates to limit the amount of plates you’re using.

Q: What pressure can I filter at?

A: We recommend starting filtration <5 dpsi (dpsi = differential pressure drop = inlet-outlet pressure). Once everything looks good, change the pump speed so the differential pressure drop is 5-8 dpsi. Leave the pressure here to build-up by itself. Starting out at higher than 8 dpsi will lead to lower filtration efficiency. You will notice little to no flow when you reach 20 dpsi.

The terminal differential pressure for Seitz filter sheets is 45psi (3 bar) for polishing grades (K100 and coarser) and 21psi (1.5 bar) for sanitizing grades (KS80 and tighter).

Q: What if I see bubbles on the outlet side after filtration begins?

A: If you still see bubbles on the outlet side after filtration begins, it means that the pressure that you are filtering at (the speed/power of the pump) is too low to push out excess air that may be trapped inside the sheets. To get rid of all the bubbles, simply adjust the outlet valve to a slightly closed position while the pump is running so that backpressure is 3 psi. Then vent the filter press at the top sample/vent valve to release the excess gas. If you still see bubbles after this, make sure your connections are tight.

REGENERATION & EFFICIENCY

Q: Can I extend the lifespan of the media and the subsequent filtration run by regenerating the media? How do I do that?

A: There are several ways to improve the capacity of the filter sheets and extend their lifespan; however, backflushing, like with lenticular modules, is not effective with filter sheets. Plates sit in direct contact with the sheet surface and it is difficult to get rid of larger solids. Rinsing filter sheets with water can remove some compounds trapped in the depth of the filter matrix and reduce the load on the filter sheets. This procedure is also known as regeneration. By rinsing with water, the chemical-physical properties of the liquid in the filter sheets are changed and therefore substances which are insoluble in the unfiltered product can dissolve and be removed. Regeneration is most effective if done right before high differential pressure is reached, i.e. below 15-20 psi (1.0-1.5 bar).

Regeneration steps:

1. Rinse for 10 - 15 min with cold water at 1.5-2 times the original filtration speed. The pH will drift to the neutral point, removing some of the bonds between these soluble compounds.
2. Increase the water temperature to 100-125°F and continue rinsing for 10 - 15 min. Proteins and tartrate crystals will be dissolved and the viscosity of the colloids will be reduced. Never use water at this stage warmer than 130 °F. Otherwise proteins will start to denature which makes them insoluble and plug up the filter sheets.
3. If you wish to remove the red color of previously filtered red wine, you may now rinse for 10 more minutes with hot water of 176 – 185 °F. This will enable you to filter a rosé wine through the same filter sheets. With ZD sheets, this step is optional due to the low color adsorption qualities of this media.
4. Continue the preparation of the filter equipment for either sterilization or cooling to room temperature with ambient water.

If you’d like to backwash the filter sheets, then backwash only steps 1 & 2. Never sterilize against the direction of filtration. During backwashing, increase the flow to 1.5 times the filtration speed.

Q: How can I minimize drip loss and dissolved oxygen pickup in my filter press?

A: There are several ways!

Proper maintenance of the plates and H-gaskets can help cut down on drip loss and oxygen pickup by at least 50%. When was the last time you replaced the H-gaskets on your filter press? For wineries, we recommend doing so every two years, for breweries or where the filter is used every week, replace gaskets every 12 months.

Properly care for Noryl plates. Do not steam sanitize Noryl plates. Do not cool them down too quickly after a hot water sanitization. This will cause warping and hairline cracks. Noryl plates are also not suitable for high-solids filtration as solids will build on plates and lead to internal turbulence. When filtering high solids, choose a different filtration method or prepare the product properly through fining and clarification techniques before filtration. Alternatively, place a bag filter before the sheet filter to help catch plant material like hops, or fine coffee grounds from cold brew coffee filtration.

Spindle Care.

• Lubricate the center spindle to prevent loss of compression. Lubrication of the center spindle where it makes contact with the moving head has to be checked regularly and maintained.
• All surfaces on the spindle must be particle-free and clean.
• Backing beam and spindle must be straight and undamaged.
• The spindle lens needs to be checked regularly.
• Surfaces need to be corrosion-free and smooth. If required, use fine sandpaper and lubricate with food grade grease.

Control sliding shoes. When sliding shoes are new, filter plates are positioned in 90 degree angle to the beam. Make sure that the plates are positioned without staggering.

Wet sheets properly. Cellulose fibers are the only material in a filter sheet that has sealing capabilities. By wetting the sheets properly, and giving the cellulose fibers a chance to absorb the water and expand before closing the filter press, helps to improve sealing characteristics.

Q: Can I store my filter sheets between uses?

A: It is not uncommon for distilleries to use their filter sheets for weeks or months at a time and just keep the filter press full of product between runs or even for breweries or wineries to pack the filter press overnight in a sanitizing solution. We do not recommend that you remove the sheets between uses as many of the grades do not have adequate wet strength and microscopic tearing during handling in this state, can create large areas of potential bypass, resulting in inconsistent filtrate quality. The ZD grades of sheets have a very high wet strength compared to the K-Series and it is possible to remove these between uses, but for sanitation reasons, minimal handling is recommended.

CLEANING & SANITIZATION

Q: How do you clean a filter press between uses?

A: Periodically, you should take out all the plates and their H-gaskets and clean them individually with a soft brush and a compatible cleaner. Inspect the plates for any hairline cracks or signs of biofilm buildup before placing the H-gaskets back in place. In the picture below, the inlet chamber side of the plates were clogged and the material had dried out between uses, causing uneven flow in the plates and leading to premature clogging of the media. Each inlet chamber on these plates had to be cleaned separately. A CIP (Clean-In-Place) step with filter sheets installed did very little to unclog the plates.

Q: Can you steam sanitize a filter press?

A: You should only steam sanitize a filter press that has 100% stainless steel plates. For Noryl plastic plates, a hot water or chemical sanitization is acceptable. Noryl plastic tends to warp thermally at steam sanitizing temperatures and the damage is usually permanent. Such damage will cause uneven sealing of the plat, leakage, and elevated dissolved oxygen pickup.

Q: What are some of the compatible chemical sanitizers I can use on my filter sheets and can I use these to remove the paper taste in the media if I don’t have access to warm water?

A: Filter aids on sheets can cause a papery taste. A hot water sanitization will remove this, but if you don't have access to hot water you may use an acidified sanitizing solution instead. Rinse with water afterwards to remove traces of the acid, before introducing your beverage. Alternatively, you can use ZD sheet media which is 100% cellulose and contains no filter aid (paper taste source). Here is a list of compatible acid-based sanitizers to use on your media when filtering lower alcohol beverages:

Q: Can I run caustic through my filters to strip color or try and clean the sheets?

A: It is possible to run a low concentration of caustic (< 1%) through your filter sheets but please note that it is very difficult to rinse out. The filter aid tends to hold onto to caustic and it may get dissolved into the product that you are filtering.

To remove color from sheets, a better option is an acidified SO₂ solution. Start with 200ppm of SO₂ and 1-2% citric acid. You can add up to 1000 ppm of SO₂ but then it becomes challenging to remove the SO2 flavor from the sheets afterwards. Circulate this solution and let sit overnight. Alternatively, use ZD sheets which are much easier to regenerate without having to use chemicals.

Q: Can I sanitize the sheets with ozone?

A: No. Ozone will instantly destroy the internal structure of any filter media. You will end up with cellulose fibers in your final product and ultimately, the media will break down quickly into a pulpy mess.

Q: What about Iodine-based sanitizers. Can I use these on my sheets?

A: No. The Iodine in these formulations will permanently stain the media and end up in your final product.