Questions You Should Know about filter press manufacturer

Filter presses have been used for thousands of years to separate liquids from solids.  Some of the earliest uses of filter presses include extracting juices from fruits and oils from nuts and seeds. While there have been many advancements made to filter presses over the years, the idea is still the same. 

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We will go over the basics of a filter press in today&#;s blog, along with three common questions that we hear.

How Does a Filter Press Work?

A filter press works by accepting a liquid slurry fed under pressure thereby causing liquids and solids separation, more commonly known as dewatering.  Modern filter presses use pumps to force a slurry through a stack of cloth covered plates. The pumps ensure that solids are evenly dispersed during the fill cycle.  Every filter press has filter plates with special cloths used to catch the buildup of solids.  The buildup of the solids forms what is called a filter cake.  Once the chamber formed by the plate is full of solids, the cycle is complete, and the plates need to be separated and the cake removed.  

As the filter cakes are forming, the filtrate, or liquid, is discharged from the plates through corner ports to the manifold. The discharged water is clean and filtered and can be recycled in processes or disposed of in an environmentally friendly way.

Now that we know how a filter press works, let&#;s look into common components and some specialty components that could be needed to help your press function at the top level.

What are the Main Components of a Filter Press?

Since filter presses are used over such a wide variety of industries, they must treat a wide range of slurry.  Depending on what slurry is being treated and the amount of liquid passing through the press, some filter presses might need extra components such as scrapers, gaskets, filter cloth washing equipment and air hammers.  

Companies with larger amounts of slurry to treat, or shorter cycle times, might want to purchase a plate shifter to cut down on the time it takes to remove cakes from the plates and clothes.  As the name implies, plate shifters are an efficient and safe plate separation method for filter cake discharge.

Filter presses come in all different sizes but there are four main components to a filter press: the frame, filter cloths, filter plates, and hydraulics.

1. The frame of a filter press typically consists of an overhead or side beam which the plates are supported on.  Whether a filter press has an overhead beam or side beam depends on the pressure that is to be used.  A side beam is typical of a wash system with lower pressure.  Smaller and mobile systems incorporate side beams.

2. Filter cloths are fundamental to the separation of solids and liquids.  As pressure is applied to a slurry, the cloth allows liquids through but traps the solids until eventually the chamber is full and has formed a cake.  

3. A filter plate is typically made of polypropylene or metal.  The type of plate used depends on what is being treated and factors such as temperature and pressure to be used in the process.

4. Lastly, hydraulics are piping and valves that are used to transfer the filtrate to a collection tank.

With knowledge of how a filter press works and the components that comprise a system, let&#;s take a look at the industries where filter presses are used.

What are Common Filter Press Applications?

A filter press can be tailored using different size plates and cloths or by changing the filtration limits to meet your company&#;s specific needs. Due to the versatility of a filter press, they are the equipment of choice for dewatering in the following industries:

·       Municipal Treatment Plants

·       Food and Beverage Processing

·       Aggregates

·       Mining

·       Power Generators

·       Asphalt and Cement Production

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·       Chemical

·       Steel Mills

·       Industrial wastewater

·       Metal finishing

Get Your Filter Press from JMARK Systems

JMARK Systems is a leading provider of filter presses, components, and mobile wastewater treatment systems. With decades of experience in the industry, JMARK Systems has a proven track record of delivering high quality products and exceptional service. 

JMARK Systems offers a water optimization audit to achieve the best results for your industry, enabling us to recommend the best type of wastewater treatment for your application. 

The filter cake will begin to become wet, slimy and not as dry.  This is your indicator that the cloths need to be cleaned.  (see number 5 for cleaning info).  If you have already cleaned your cloths and your process has not changed but you are still getting slimy filter cake, it may be time to replace your cloths.  Cloth life varies from installation to installation and depends on such variables as frequency of cycles, proper cleaning and maintenance and the type of sludge that is generated.  Generally speaking for most installations cloths can last up to 6 months at the most.

Expansion depends on a couple of factors.  First, if your press is already expandable, meaning you&#;re your press has a distance piece for expansion to a larger capacity, all you need to do is unbolt the distance piece and add additional plates in the 1-3 button sequence taking care that you add plates in even numbers.  However, if you have a Met-Chem press or your press has notched and bolted sidebars, then it can also be expanded by removing the sidebars and replacing them with longer sidebars and installing additional plates.  Please note that when adding plates, you must be sure to add them in the 1-3 button sequence in order to provide proper drainage.

There are several possible causes.  You might not have the proper cloths for you application or if you have been using the same cloths for an extended amount of time, you may have holes in the filter cloths.  The gasketed cloth may have slipped out of the grooves.  Or, perhaps, the cloth on the head plate may not  be properly secured.

Precoat and bodyfeed are two related applications.  Both of these special applications use diatomaceous earth (commonly known as D.E.), cellulose, perlite or fly ash, as a filtering aid when the solids in a slurry are extremely fine and free-filtering.  The filter aid helps to trap the fine solids that otherwise might flow through the filter cloths.  The processes of precoat and bodyfeed increase the clarity of the filtrate, provide for higher flow rates, more consistent runs, shorter cycles, dryer cakes, better cake release, and also help to protect and increase the life of the filter cloths.

The precoat process is performed before the slurry is pumped into the press.  A precoat system consists of a tank, mixer and pump.  The filter aid is mixed with water in the precoat tank.  It is then pumped into the press where it coats the filter cloths.  The filter aid rather than the filter cloths becomes your initial filter media.

During a body feed the filter aid mixes with the slurry in the holding tank prior to being fed into the filter press.  The filter aid becomes part of the slurry thereby providing a better filter cake.

If you have not made any recent changes to the plate stack (which is the number one reason this might occur), there are several possibilities.

You could have a build-up of solids on the sealing surfaces which will then need to be cleaned. 

Check to see if the hydraulic pressure is set to the recommended specifications.  If not, make the appropriate adjustment.

Another possibility is that there could be a wrinkle or hole in the filter cloth or the gaskets may be loose.

If you continue to have problems, contact your Met-Chem representative.

It&#;s a good idea to change your gaskets whenever you change your filter cloths.  Also, if you are getting excessive leakage out of the press while maintaining correct hydraulic closure pressure, this may be a sign that it is time to change your gaskets.

Gasket life will depend on many factors, such as length of filtration cycle, temperature, and excessive closing force. Gasket replacement should take place if the gasket appears to be delaminating or shredding.  Also, if excessive temperatures exist and cycles are very long, the standard gasketing material may go into additional cure, causing it to harden slightly.  If  you continue to have a problem, contact your Met-Chem representative for an alternative.

If the press is leaking (around the locknut on the 470mm size or from the bottom leg drain holes on 630mm and larger size presses) during the start-up of the feed process, the problem is usually leakage past the center feed quad ring seal. The quad ring may not seal for several reasons.

First check for the cause:

Did the locknut on the outside of the press head loosen during shipment?  If so, tighten the locknut using a spanner wrench, pliers, or pipe wrench.

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