JWI Filter Press Manual & Technical Resource Center

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A filter press separates solids from liquid by pumping slurry into a series of recessed filter plates covered with filter cloths. Solids accumulate inside the chambers while clean filtrate passes through the cloth and exits through filtrate ports.

As filtration continues, solids build into a filter cake while pressure increases inside the press. Eventually the chambers fully fill with solids and the filtration cycle completes.

Many older JWI filter presses were designed using:

• Plate and frame plates 
• Recessed chamber plates 
• Non-gasketed cloth designs 
• Hydraulic closure systems 
• Manual or semi-automatic plate shifting 

Modern filter presses often utilize gasketed recessed plates, upgraded hydraulics, automatic plate shifters, and PLC controls.

Older filter presses commonly experience operational issues due to wear, chemical exposure, aging hydraulics, or improper operating procedures.

Common issues include:

• Cloudy filtrate 
• Wet filter cake 
• Hydraulic pressure loss 
• Leaking filter plates 
• Cloth blowouts 
• Damaged center feed pipes 
• Gasket leaks 
• Slow cycle times 
• Plate shifting problems 
• Air blowdown issues 

Many of these problems can be corrected with replacement parts, operating adjustments, or maintenance procedures.

Cloudy filtrate usually indicates solids are bypassing the filter cloth.

Common causes include:

• Cloth holes or tears 
• Cloth rope improperly seated 
• Incorrect cloth micron rating 
• Starting at excessive feed pressure 
• Damaged gasketing 
• Improper plate sealing 

Operators should gradually build solids inside the chambers before increasing feed pressure. Starting immediately at high pressure can force solids through the cloth before a proper cake layer develops.

Met-Chem can supply replacement cloths with tighter micron ratings, including cloths as tight as approximately 1/2 micron for difficult applications.

Hydraulic systems keep the filter press closed during operation. Loss of hydraulic pressure can cause leaking plates, improper sealing, and unsafe operating conditions.

Common hydraulic problems include:

• Hydraulic oil leaks 
• Cylinder seal wear 
• Low hydraulic pressure 
• Damaged hydraulic hoses 
• Faulty pressure switches 
• Worn hydraulic pumps 
• Incorrect hydraulic oil 

Many filter presses commonly use ISO 46 hydraulic oil.

Older hydraulic systems may eventually require:

• New hydraulic cylinders 
• Power unit replacement 
• Hose replacement 
• Pressure switch replacement 
• Complete hydraulic rebuilds 

Suggested Internal Links

Many facilities struggle identifying the correct filter plate size for replacement parts ordering.

Common JWI filter plate sizes include:

Plate SizeCommon Applications470mmSmall industrial systems630mmPlating & chemical systems800mmIndustrial wastewater1000mmMining & large industrial1200mmMunicipal & heavy industrial 

Correct plate identification is important for:

• Cloth sizing 
• Gasketing 
• Feed pipe sizing 
• Hydraulic closure calculations 
• Replacement plate compatibility

The center feed pipe assembly delivers slurry into the filter press plate pack.

Common JWI center feed pipe sizes include:

Plate SizeFeed Pipe Size470mm1.5" x 7"630mm2" x 12"800mm2" x 12"1000mm3" x 18"1200mm4" x 24" 

Center feed pipe assemblies are sometimes referred to as:

• Threaded tubing 
• Feed manifold pipes 
• Feed tubes 
• Center feed assemblies 
• Threaded feed pipes 

Damaged feed pipes can cause:

• Internal leakage 
• Improper filling 
• Cloth damage 
• Uneven cake formation 

Suggested Internal Links

• JWI Center Feed Pipe 
• Filter Press Manifold 

Many JWI filter presses utilize gasketed filter plates with perimeter gasketing and corner port gasketing.

Common gasketing materials include:

• EPDM 
• Viton / FKM 

Common gasketing cord sizes include:

• 5/16" 
• 3/8" 

Proper gasketing helps prevent:

• Plate leakage 
• Filtrate bypass 
• External dripping 
• Corner port leakage 

Met-Chem stocks replacement filter press gasketing for many older JWI filter press models.

Many JWI filter presses utilize corner feed manifolds and air blowdown systems to help remove liquid from the filter cake and clear the internal piping after filtration.

During filtration:

• Ball valves remain open 
• Slurry fills the chambers 

During air blowdown:

• Certain valves close 
• Air enters through the manifold 
• Remaining liquid is pushed from the chambers 

Proper air blowdown operation helps:

• Reduce cake moisture 
• Clear corner passages 
• Improve discharge performance 

Incorrect valve operation can cause:

• Wet cake 
• Internal flooding 
• Improper blowdown performance

Wet filter cake is one of the most common filter press complaints.

Common causes include:

• Insufficient feed pressure 
• Short filtration cycles 
• Poor air blowdown 
• Incorrect cloth selection 
• Low solids concentration 
• Hydraulic pressure loss 
• Damaged cloths 
• Slurry chemistry issues 

Operators should typically allow feed pumps to continue increasing pressure throughout the filtration cycle until flow significantly slows or stops.