Corrosion-Resistant Coalescer Cartridges – Four Grades for Light Oil Dehydration

Part 1 – Application Context

Hydraulic power units operate in heavy industries including steel rolling, plastics forming, 

wind power generation, and automated manufacturing lines. The circulating fluid carries

 multiple contaminants: metal particles from pump gears and valve spools, rust from pipe interiors, 

oxidized sludge, and seal wear debris.

Contaminants smaller than 5 microns can damage servo valve surfaces, block small flow passages,

 and cause pressure instability. Original equipment filters are installed on supply lines,

 return circuits, and pressure branches of medium- and large-scale hydraulic systems.

When original parts reach their service limit or are delayed in delivery, replacement elements 

that match the original dimensions and performance are required to keep the system running.

Key requirements for replacement elements include:

· Outer dimensions and thread types matching the original housing

· Bypass valve settings corresponding to the original specifications

· Thermal rating suitable for the system operating temperature

· Ability to withstand repeated pressure cycling

· Stable particle retention under varying flow rates

· Mechanical integrity under pressure surges

· Leak-tight sealing to prevent unfiltered fluid passage

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Part 2 – Filter Media by Temperature Range

All replacement elements use multi-layer borosilicate glass fiber composites. 

This material has been validated by ISO 16889 (filtration performance) and ISO 3724 (flow fatigue)

 testing.

The media has a graded pore structure. The outer layer captures large particles and rust.

 The middle layer holds sludge and colloidal material. The inner layer retains fine abrasive

 particles. This staged design prevents premature surface blocking and balances particle capacity

 with retention efficiency.

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Grade 1 Media – Standard Temperature Service

This grade is used in systems where oil temperature remains at or below 100°C continuously. 

Applications include cold rolling auxiliary circuits and low-load stations without radiant heat

 exposure.

The construction uses three layers of borosilicate fiber with a phenolic resin binder.

 The resin has a thermal deformation temperature of 112°C.

Performance data:

· Operating range: -10°C to +100°C

· Available retention ratings: 1, 3, 5, and 7 micrometres

· Beta ratio at rated size: 2000 or higher

· Particle retention: 99.95% or greater

· Oil cleanliness after filtration: NAS Class 7 or better

· Fiber strength after 500 hours at 100°C: 83% of original

· Efficiency change after same period: 3% or less

· Particle capacity per unit area: 1300 to 1500 grams per square metre

· Effective area: 3 to 4 times that of flat sheet media

Matching components for this grade are NBR seals, a galvanised steel support core, 

and polyurethane end cap adhesive.

Compatible filter types include the 01E series return-line units.

The limitation is that continuous operation above 105°C softens the resin and causes the fiber

 layers to shift.

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Grade 2 Media – High Temperature Service

This grade is specified for systems with oil temperature between 100°C and 120°C.

 These conditions are typical of hot rolling mills and thermal power plant hydraulic stations.

The media consists of four layers of modified borosilicate fiber with a high-crosslink phenolic resin 

containing 14 to 16 percent solid content.

Performance data:

· Operating range: -10°C to +120°C

· Resin thermal deformation: 138°C

· Short-term peak tolerance: 130°C for up to 30 minutes

· Fiber strength after 1000 hours of cycling between 110°C and 130°C: 91% of original

· Efficiency change after same period: 1.8% or less

· Particle capacity per unit area: 1600 to 1900 grams per square metre

· Surface finish: calendered to provide a dense isolating layer

Matching components are FKM seals, a 304 stainless steel core, and fluorine-epoxy end cap

 adhesive.

Compatible filter types include HC series pressure-line units and 3000 series return-line units.

If the daily average oil temperature exceeds 115°C for more than four hours, system flow should

 be reduced by 10 percent.

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Grade 3 Media – Extended High Temperature Service

This grade is used in systems with oil temperature between 120°C and 140°C. 

These are extreme conditions such as furnace-front heavy-load stations and boiler actuator 

circuits where standard elements have short life.

The media is a fluorinated composite glass fiber with a high-temperature binder.

Performance data:

· Operating range: -10°C to +140°C

· Short-term peak: up to 150°C

· Seals: modified full-fluorine FKM

· Support core: 316L stainless steel

Operational measures required:

· Auxiliary oil cooling must be installed

· Daily average temperature kept at or below 130°C

· Replacement interval reduced by 30 percent compared with Grade 2 applications

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Part 3 – Component Matching

For the complete assembly to perform as specified, the media, support core, adhesive, 

and seals must be matched to the same temperature and chemical resistance class.

 If any single component is mismatched, unfiltered fluid can bypass the media.

All elements are manufactured to the same external dimensions, thread specifications, 

and bypass valve settings as the original housings. No housing modifications are required

 for installation.

Seal Selection by Temperature

NBR seals are used only with Grade 1 media for systems up to 100°C. The effective range

 is -40°C to +100°C, with peak tolerance to 110°C. Above 105°C, NBR hardens and swells significantly.

FKM seals are used with Grade 2 media for systems up to 120°C. The range is -20°C to +120°C, 

with peaks to 130°C. Swelling after 1000 hours at 120°C is 3 percent or less.

Modified full-fluorine FKM seals are used with Grade 3 media for systems up to 140°C. 

The range is -20°C to +140°C, with peaks to 150°C. These are specified for high-viscosity aged 

oil and radiant heat exposure.

Adhesive Selection by Temperature

Polyurethane adhesive is used with Grade 1 media. Maximum service temperature is 110°C.

 Above this, hydrolysis and delamination occur.

Fluorine-epoxy hot-melt adhesive is used with Grades 2 and 3. 

Maximum service temperature is 145°C. Peel strength is 50 Newtons per centimetre or greater.

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Part 4 – Selection by Operating Condition

Condition A – Cold Rolling Auxiliary Station

Oil temperature: 100°C continuous or less, peak up to 105°C.

Configuration: Grade 1 media, NBR seals, galvanised steel core.

Compatible with 01E series return filters.

Additional measures: heat shields installed, water drained from tank bottom weekly.

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Condition B – Hot Rolling Mill or Power Station EH System

Oil temperature: 100°C to 120°C continuous, peaks of 125°C to 130°C lasting under 30 minutes.

Configuration: Grade 2 media, FKM seals, 304 stainless steel core.

Compatible with HC series pressure filters and 3000 series return filters.

This configuration covers more than 90 percent of steel and power industry main hydraulic stations.

Additional measures: cooling system performance monitored, 

differential pressure recorded each shift.

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Condition C – Furnace-Front or Boiler Actuator Station

Oil temperature: 120°C to 140°C continuous, peaks of 140°C to 150°C.

Configuration: Grade 3 media, modified FKM seals, 316L core.

This is a custom configuration for extreme thermal loads.

Additional measures: auxiliary coolers installed, daily average temperature kept at or below 130°C,

 replacement interval shortened by 30 percent.

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Part 5 – Operating Limits

Deviations from specified flow velocity, backwash air quality, or differential pressure thresholds

 reduce service life by 30 to 50 percent.

Maximum Oil Velocity

For Grade 1 media, the maximum velocity is 0.8 metres per minute with a 20 percent margin.

 For Grade 2, the limit is 0.7 metres per minute with a 25 percent margin. For Grade 3,

 the limit is 0.6 metres per minute with a 30 percent margin.

If instantaneous flow exceeds 115 percent of the housing rating, the bypass valve should be opened.

Backwash Air Quality

For housings equipped with online backwash, the compressed air must be treated with

 a refrigerated dryer and two-stage oil-water separator. Dew point must be below -20°C. 

Residual oil content must not exceed 0.1 parts per million. Backwash pressure should be 

between 0.4 and 0.5 megapascals.

Oil or water vapour in the backwash air deposits as sludge on the media surface, 

permanently blocking pores and reducing service life by more than 40 percent.

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Part 6 – Failure Modes

End Cap Leakage

If oil seeps around the end cap, the adhesive grade is below the operating temperature. 

The correction is to use adhesive matching the actual oil temperature.

If the end cap separates from the media, the adhesive has been exposed beyond its limit

 for an extended period. The correction is to reduce oil temperature or select a higher-grade 

assembly.

Rapid Pressure Rise with New Element

If differential pressure reaches the alarm within days of installation, there is no upstream

 coarse pre-filter. Large particles are impacting the media directly. The correction is to install 

an 80 to 100 micrometre pre-filter at the inlet.

If pressure spikes immediately after installation, the oil is degraded with high acid value. 

Sludge is blocking the surface. The correction is to replace the oil, flush the tank,

 and remove accumulated sediment.

Efficiency Below Specification

If downstream cleanliness deteriorates, bypass is occurring due to seal swelling or shrinkage. 

The correction is to replace seals with material matching the temperature grade.

If downstream particle count increases, the media has ruptured from a pressure spike or flow 

excess. The correction is to verify flow velocity, inspect for pressure surges, and use a

 reinforced core.

Thermal Degradation in High-Temperature Service

If media discolouration or brittleness is observed, the element has been operating above its 

rated temperature. The correction is to add cooling capacity or reduce thermal load.

If fibre shedding is detected downstream, the resin has broken down at extreme temperature. 

The correction is to upgrade to Grade 3 media with fluorinated binder.

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Part 7 – Installation and Maintenance

Pre-installation checks: verify the model number, inspect the seal groove and media for damage.

Seals: install new seals matching the temperature grade. Do not reuse old seals.

Housing preparation: clean sealing surfaces before installation.

Differential pressure: record each shift. Replace the element when the alarm threshold is reached.

Oil analysis: test acid value, water content, and particle count monthly.

Storage: keep elements in a dry, dustproof location away from sunlight.

Cleaning: do not clean used elements with solvent, water, or compressed air. 

The gradient structure is permanently damaged by these methods.

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Part 8 – Frequently Asked Questions

What is the retention efficiency of these replacement elements?

Beta ratio is 2000 or higher by ISO 16889 testing. Retention efficiency at the rated size is 99.95 

percent or greater.

Can Grade 1 media be used at 110°C?

No. Continuous operation above 105°C softens the resin binder and reduces efficiency. 

Grade 2 is required for temperatures above 100°C.

When should the element be replaced?

Replace when differential pressure reaches the alarm value specified for the housing. 

Fixed-interval replacement is not recommended.

Can new and old elements be used together in the same housing?

No. All elements in a single housing should be replaced simultaneously to maintain uniform 

flow distribution.

What documentation is supplied with each order?

EN 10204 material certificates, ISO 16889 test reports, and dimensional inspection records 

are provided.

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Part 9 – Summary

Selection of replacement elements is based on three operating parameters: oil temperature, 

system flow rate, and upstream contamination load.

Correct matching of media grade, sealing materials, and structural components to actual 

operating conditions maintains oil cleanliness at NAS Class 7 or better, achieves specified 

service intervals, and provides direct interchangeability with original housings without 

modifications.