A Guide to CJC Filter Inserts: Choosing the Right Media for Your Application
Steffen D. Nyman
6 min
25 March 2026
Not all CJC filter inserts are equal. The choice of filter media determines what contaminants are removed, at what efficiency, and over what service interval. This guide walks through the CJC insert range and the selection criteria for each application type.
The Insert as the Heart of the System
In a CJC offline filtration system, the filter insert is the active element that determines performance. The housing, pump, and piping are necessary hardware - the insert is where contamination is actually removed. Selecting the correct insert for your specific oil type, contamination profile, and operating conditions is therefore the most important decision in system specification.
CJC filter inserts are manufactured from specialised cellulose fibres, moulded into bonded discs that form a 3D labyrinth structure. This maze-like accordion geometry forces oil to travel through the full depth of the media, maximising contact time and filtration efficiency. The natural phenols present in the cellulose also help slow down the rate of oil oxidation, giving CJC inserts a unique "4 in 1" capability: simultaneous removal of particles, water, acidity, and varnish.
CJC Insert Types and Their Applications
Different CJC insert types are designed for different contamination challenges and oil systems. The choice of insert affects what is removed, how efficiently it is removed, and where the solution fits best.
Insert Type | Primary Removal | Typical Application |
|---|---|---|
Standard (B-type in HDU) | Particles + water + acidity + varnish | Hydraulic oil, gear oil, lubrication oil with low water ingress |
Water Separation (BLAT-type in PTU) | Particles + free water + varnish | Systems with high water ingress (steam turbines, submersed oil systems e.g. marine applications) |
Varnish Removal (VRi-type in VRU) | Dissolved varnish precursors + particles | Turbine oil, compressor oil, high-temperature systems |
Phosphate Ester (PE-type in PEU) | Particles + acidity | EHC systems using phosphate ester fluid |
Fuel (F- and DFi type in PTU) | Particles + free water + microbial growth | Diesel fuel, marine gas oil |
Key Selection Criteria
When selecting a filter insert, the following criteria should be evaluated systematically: oil type and viscosity, primary contamination type, operating temperature, system volume and contamination rate, and target cleanliness level.
More demanding cleanliness targets may require finer media or higher-efficiency insert types like GFi.
Service Interval Optimisation
A common mistake in offline filtration programmes is changing filter inserts on a fixed pressure rather than on condition. Because contamination type and rates vary significantly with operating conditions, a maximum pressure over the filter insert could either result in premature changes (wasted capacity) or overdue changes (reduced filtration efficiency and a contaminated oil system).
To achieve the highest possible oil cleanliness level, the CJC® Filter Inserts need to be changed at least once a year.
Retained and accumulated oil degradation products (oxidation, acids, and varnish) may not show on the pressure gauge. Leaving filter inserts in service for longer than one year will result in decreased oil filtration efficiency and increased risk of system breakdowns and component wear.
The preferred approach is to monitor differential pressure across the filter and change the insert when pressure reaches the maximum rated value - or at the scheduled interval (max one year), whichever comes first. Some acidity absorbing media may require changes more often depending on system conditions.
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