Home › Knowledge › Why a Coolant Filter Clogs Too Quickly
Filtration technology · Processes
Why does a coolant filter clog so quickly?
Updated: November 2026
Reading time: 3 minutes
In brief
The filter belt keeps advancing, the filter fleece is used up rapidly or the differential pressure rises too soon. The first reaction is often to “use finer filtration”. This can make the problem worse. First, establish which solids are actually reaching the filter and whether coarse chips can be removed upstream.
Coarse chips and fine wear particles require different stages
A chip separator removes coarse solids from the coolant, also known as metalworking fluid, before it reaches the next filtration stage. Depending on the chips and the available space, sedimentation, a slotted screen or magnetic pre-separation for ferromagnetic materials may be suitable. Fine particles are then removed by an appropriate belt filtration system. These stages perform different tasks. Pre-separation does not automatically ensure the required cleanliness after filtration.
How pre-separation can reduce the load on the filter
When fewer solids reach the fine filter, its solids loading decreases. A properly designed pre-separation stage can therefore extend the intervals between filter cleaning or belt indexing cycles and reduce the consumption of filter fleece or filter aids. The actual reduction depends on the particle distribution, the material, the coolant and the flow rate.
The choice of pre-separation stage depends on the properties of the solids. Magnetic separation may be suitable for ferromagnetic particles. For non-magnetic chips, options include a slotted screen or sedimentation. For sedimentation to work, the particles must settle reliably under the existing flow conditions.
One option is a lamella separator. Its inclined plates increase the effective settling area within a limited space and shorten the distance the particles need to settle. The separated solids collect in the lower section and are discharged. Whether this pre-separation method is suitable, and which fine filtration stage is needed afterwards, depends on the fluid properties, the settling behaviour of the particles and the required filtrate quality.
Four questions to ask before changing the filter medium
→
What is on the filter belt: coarse chips, fine wear particles, sludge or a mixture?
→
Does the solids load change with particular machines, materials or shifts?
→
Is the rise in differential pressure caused by solids, or is it related to the operating conditions and filter medium?
→
Which residual particles are permitted in the cleaned coolant, and how is this measured?
Checking the dirty and clean sides of the system, filter fleece consumption and operating data helps avoid premature conclusions. Oily contaminants may also require a different separation approach from metal particles. This should be assessed separately.
To investigate the cause, collect a small set of observations across several shifts. When does the filter regenerate, how much material is discharged and does the filtrate quality change? If problems occur only when machining a particular material, this is more informative than a single daily reading. An unsuitable or damaged filter medium should also be checked in the system concerned.
Match the filtration stages to the process
A pressure belt filter and a vacuum belt filter operate according to different system principles. The appropriate combination with pre-separation depends on the fluid, particle size and quantity, required filtrate quality and available space. KÖBO ECO>PROCESS can integrate these stages into a coolant treatment system. Actual process data will determine whether the pre-separation stage, the filter medium or both should be adjusted.
Frequently asked questions
Why does a coolant filter get clogged so quickly?
A high solids load can cause the filter belt to advance frequently, the filter fleece to be used up rapidly or the differential pressure to rise prematurely. The incoming solids, existing pre-separation stage, filter medium and operating conditions should therefore be checked.
Can pre-separation reduce filter fleece consumption?
A properly designed pre-separation stage reduces the solids load on the downstream filter. This can extend the intervals between belt advances and reduce filter fleece consumption. The actual reduction depends on the particle distribution, material, coolant and flow rate.
What does a lamella separator do?
A lamella separator provides pre-separation by sedimentation. Inclined plates increase the effective settling area within a limited space and shorten the distance the particles need to settle. The solids must be able to settle reliably under the existing conditions.
What information is needed to select the filtration stages?
Key factors are the fluid, the properties, size and quantity of the solids, the flow rate, the required filtrate quality and the available space. Operating data from several shifts helps determine whether the pre-separation stage, the filter medium or both should be adjusted.
Suitable solutions from KÖBO ECO>PROCESS
Filtration Technology
Chip separators
Go to the product →
Filtration Technology
Pressure belt filters
Go to the product →
Filtration Technology
Vacuum belt filters
Go to the product →
Filtration Technology
Coolant treatment systems
Go to the product →
KÖBO ECO>PROCESS Technical editorial team
Questions about this article: Contact us
Contents
Coarse chips and fine abrasion require different steps
Why Pre-Separation Can Reduce the Load on the System
Four Questions to Ask Before Changing the Filter Media
Design the post-process filter train
Related Terms
Pre-separation
Coolant
Filter fleece
Lamellar separator
Sedimentation
Fine filtration
Differential pressure
Design question?
We’ll determine which solution is right for your process—with no obligation.
Request Now