Frequently Asked Questions

Cleaning Filter Cloths, Reducing Cycle Time and More!

  1. What is a filter press?
  2. What is an air-over-oil filter press?
  3. Can I wash filter cloths with a portable high pressure washer?
  4. Can I chemically clean my filter cloth?
  5. Why does my filter leak around the edges?
  6. Can I reduce my cycle time?
  7. What is the highest pressure I can pump to my filter press?
  8. What is the best pump for a filter press?
  9. Can I try samples to see if they work?
  10. How do I extend my cloth life?
  11. How long may I store filter cloth?
  12. Do you provide a micron rating for your filter cloths?
  13. How can I buy spare filter plates for my filter press?
  14. How can I tell if my filter cloth needs replacing?
  15. Can I change the type of filter plate I have?
  16. Can I arrange for a service call to refurbish my filter at my facility?
  17. Can I easily replace my existing hydraulic power pack?


1. What is a filter press?
A filter press is a piece of equipment used in liquid/solid separation. Specifically, the Filter Press separates the liquids and solids using pressure filtration, wherein a slurry is pumped into the Filter Press and is dewatered under pressure. Micronics, Inc. is a trusted expert in liquid/solid separation and offers a wide range of Filter Press types to suit your application needs for trouble-free, economical dewatering including: Sidebar Automatic, Manual Overhead, Automatic Dual Overhead Beam, Stainless Steel Clad, Explosion-proof Filter Presses, Vacuum Filter Presses, and Hand Filter Presses.

The four main components of a Filter Press include the frame, filter plates, manifold (piping and valves), and filter cloth, the key ingredient for optimizing Filter Press operations.

To learn more about “What Is a Filter Press?,” please view our informative video here. If you have any questions, please contact us and our expert team of Sales, Service and Applications Engineers will assist you with optimizing your existing Filter Press operation or help you with sizing new filtration equipment.


2. What is an air-over-oil filter press?
As you probably know, most filter presses use a hydraulic cylinder for closing, clamping, and opening of the plates in the plate stack. Hydraulic cylinders may be powered manually, air-assisted, or powered electrically. The hydraulic solution used depends upon the specific application as well as the size of the filter press required. An Air-Over-Oil Filter Press relies upon an air-assisted hydraulic cylinder. Air-assisted hydraulic cylinders use an air-operated intensifier pump to build hydraulic pressure for closing and clamping of the filter press. Air is directed to the opposite end of the cylinder for opening the filter press. This is in contrast to Electro-Hydraulic powered cylinders that use an electric motor and pump to close and open the filter press. Contact us to learn more about various hydraulic power pack solutions and how to troubleshoot problems.


3. Can I wash filter cloths with a portable high pressure washer?
Yes, provided the hose has a fan and not a needle tip. The wand should be moved over the filter cloth consistently and not held in one position. 800 to 900 psi is probably an adequate pressure to clean cloths. If cleaning is not efficient, then consider chemically removing embedded particulates. (See Question #3)


4. Can I chemically clean my filter cloth?
Chemical cleaning of filter cloth is a very effective way of rejuvenating filtration performance. Polypropylene cloths will accept both caustic and acid cleaning whereas nylon and polyester fibers require more careful selection of the cleaning medium – contact us for help. REMEMBER – Precautions must always be taken when handling chemical cleaning solutions.


5. Why does my filter press leak around the edges of the plates?
The filtration characteristics of specific slurries will affect filtration efficiency and having too much back pressure will result in edge leaking. Poorly-designed filtrate discharge piping, higher than recommended pumping volumes, or incorrectly selected filter cloths may all cause or contribute to this problem.


6. Can I reduce my cycle time?
Normally the slurry characteristics determine cycle time. Conditioning of the slurry can improve the dewatering time. Thinner cakes will also reduce cycle times and are more easily washed.


7. What is the highest pressure I can pump to my filter press?

Filter presses are designed generally for two pressures, 7 and 15 bar (100 and 225 psi), although special machines are made for higher pressures. Check the equipment manual to ensure you do not exceed the pressure your filter framework was designed for. If you need assistance, measure your cylinder ram size, note the hydraulic pressure and contact us for help.


8. What is the best pump for a filter press?

Many pump types are used with good results, depending upon the characteristics of the material being processed. Air diaphragm pumps do not shear flocculated slurries and are the most common type of pump used. An added advantage to this type of pump is that the air drive stalls when filtration is complete. Positive displacement pumps are used on high pressure filters.


9. Can I try cloth samples to see if they work?

We will provide a small number of filter cloth samples at no charge for initial evaluation. It is usual for us to require some information on the operating conditions and your goals prior to making filter cloth recommendations.


10. How do I extend my filter cloth life?

Cloth life is shortened by mechanical damage, which may be caused by chemical attack, mechanical abrasion, or both. Life is also shortened when cloth becomes blinded. Write down all the filter press operating conditions, and in particular changes that you have made, and forward them to us for evaluation and recommendations. We have a questionnaire for this purpose.


11. How long may I store filter cloth?
Micronics’ synthetic cloths may be stored indefinitely; they are not affected by mildew or insects. Ultraviolet light will weaken polypropylene and these cloths should be stored inside.


12. Do you provide a micron rating for your filter cloths?
No, filter cloth specs are not provided with a specific micron rating. The terminology in the fabric manufacturers & filter cloth world is the material’s permeability. The unit of measure for these specifications is “CFM” or cubic feet per minute, which refers to cloth permeability. CFM numbers vary considerably depending upon textile type (woven vs. felt), material of construction, filament type, fabric weight, and other parameters. Our specifications include a permeability number (in CFM).

Here’s a useful tip if you are concerned about micron ratings: Once you develop a thin layer of filter cake in your filtration application, the filter cake actually becomes the true filter, often filtering down to one micron at that point. Please contact us to discuss cloth specifications for your particular filtration application.


13. How can I buy spare filter plates for my filter press?
A questionnaire is available to help fill in the correct dimensions. Filter plates are custom made for the particular brand of filter you have. We can manufacture plates to the correct specification for any brand, make or model of filter press.


14. How can I tell if my filter cloth needs replacing?
Filter cloth that has performed well – indicating that it was the correct design for your conditions – will eventually have to be replaced. Usually, when filter cloth needs replacing, you will observe that the filter cycle times will be longer and the filter cake will become progressively wetter. If your cloth has not performed well from the start, then you need to modify the design. Contact us so that we may assist you in selecting the right filter cloths for your operating conditions.


15. Can I change the type of filter plate I have?
Yes, any type of filter plate may be retrofitted to any filter press. You must only adhere to the maximum operating pressure of the filter press frame.


16. Can I arrange for a service call to refurbish my filter at my facility?
Yes, we can arrange for technicians to visit to conduct the refurbishment work on site. In many cases, it is possible for Micronics to supply parts that may easily be installed by your personnel, saving you money. Examples of this include replacement polypropylene filter plates, hydraulic systems, control panels, and automatic and semi-automatic plate shifters.


17. Can I easily replace my existing hydraulic power pack?
Yes, we manufacture modular power packs for both air/oil and electro/hydraulic closure. These are easily installed in any brand of filter press and are capable of running simple and automatic machines. In some cases, it may be required for an additional control panel to be included.