Compressed Air & Gas Filters

CNG Filter

Oil-free, particle-free gas from your compressor to every vehicle you fill, at full station pressure.

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A CNG filter housing with a green head and grey bowl, shown with its differential pressure gauge, brackets, drain fittings and white element

Product overview

Clean gas at every stage of your CNG station

Lubricated reciprocating compressors inject oil into their cylinders and packings, and part of it leaves the final stage as vapour. As the gas cools in the aftercooler, that vapour condenses into sub-micron droplets that no gravity separator can settle out. Our CNG filter captures them in a bed of fine fibres, merges them into drops heavy enough to drain, and collects the liquid for removal.

It stops solids too: rust, mill scale and black powder from steel pipelines, wear debris and ring fragments from compressors, and weld spatter from new pipework. Filters at your station inlet, compressor discharge and dispenser each handle what enters their section of the station.

The filter works at the full working pressure of your station, typically 200–300 bar on the discharge side, and serves online, mother and daughter stations as well as compressed biomethane (bio-CNG) plants.

A CNG filter housing with a green head and grey bowl, shown with its brackets, drain fittings and an orange element
  • 200–300 barTypical discharge-side working pressure
  • About 293Standard m³ of methane in one actual m³ at 250 bar
  • Below 1 µmSize of most compressor oil droplets
  • 12 monthsLongest interval between coalescing element changes

Benefits

The problems it solves

Gas that has passed a lubricated compressor or a long steel pipeline carries oil and solids to small orifices and precision seats. Here is what they do, and how the filters stop them.

  • Unsteady vehicle regulators

    The problem

    Oil collects on the vehicle regulator seat and diaphragm, the coldest point in the fuel system, and alters the regulated pressure.

    How it solves it

    Oil-free gas keeps regulated pressure and injector delivery stable, preserving engine performance and your customers' confidence in the station.

  • Oil slugs from storage

    The problem

    Oil that reaches the cascade collects there and is later dispensed into vehicles in slugs.

    How it solves it

    The discharge filter captures oil before storage, so your cascades stay clean.

  • Worn compressors

    The problem

    Pipeline solids erode compressor valve plates and score cylinder liners.

    How it solves it

    The inlet filter keeps suction gas clean, lengthening the interval between your compressor overhauls.

  • Leaking valve seats

    The problem

    A particle trapped under a valve seat at 250 bar vents gas into a hazardous area and lets stored gas bypass the priority sequence.

    How it solves it

    Particle-free gas keeps high-pressure seats tight, cutting venting losses and gas detector alarms.

  • Inaccurate billing

    The problem

    Deposits in meter tubes affect the quantity of gas billed at the dispenser.

    How it solves it

    Clean gas at the dispenser inlet keeps your meter accurate and protects its valves and breakaway coupling.

  • Hidden compressor wear

    The problem

    Rising oil carry-over from worn rings or an over-set lubricator goes unnoticed until vehicle regulators start to fail.

    How it solves it

    The volume you drain from the filter sump is a record of carry-over, an early sign of compressor wear.

Where it’s used

From the station to the vehicle, and beyond

Wherever natural gas is compressed, stored in cascades and let down again, the filters protect the regulators, meters, injectors and burners downstream.

  • Robots welding a car body on an assembly line

    Vehicles and fleets

    Bus and fleet depots filling CNG vehicles, and workshops filling and testing vehicle CNG systems after fitment or inspection.

  • Glowing glass bottles being formed on a production machine

    Glass and ceramics

    Plants receiving CNG in cascades by virtual pipeline and reducing its pressure for burners.

  • A row of yarn winding machines in a textile mill

    Textiles

    Textile plants supplied with CNG in cascades, away from a pipeline.

  • Wine bottles moving along a bottling line

    Food processing

    Food plants burning cascade-supplied CNG at a reduced, controlled pressure.

  • Electricity pylons and power lines at sunset

    Gas engines and generator sets

    Sites where engines run on CNG supplied from on-site storage.

  • A naval warship at sea

    Marine and rail

    Vessels and locomotives with natural gas fuel systems filled from high-pressure storage.

Also city gas distribution stations, mobile cascade filling, bio-CNG and biomethane plants, compressor packages, engine and emissions test cells, and gas utilities running temporary cascade supply.

How it works

Stop, coalesce, drain, protect

Each filter handles the contaminants formed or picked up in its own section of the station, from pipeline to dispenser.

How CNG filtration works: at a CNG station, the inlet filter stops pipeline dust, rust and black powder before the dryer and compressor. After the aftercooler, the discharge coalescing filter captures the compressor oil aerosol, merges it into drops and drains it to a closed drain vessel, so only filtered gas enters cascade storage. At the dispenser, a final filter stops particles picked up in storage and pipework before the meter and the vehicle. A differential pressure gauge shows the discharge filter element loading. Gas inInlet filterDryer CompressorAfter-cooler Discharge filter200–300 bar Closed drain vessel CascadestorageDispenser filterDispenserVehicle 12345Gas carrying oil or solidsFiltered gasOil and condensate drainedCompressor oil aerosolBlack powder, rust and debris

  1. 1. Inlet filterAt supply pressure, the inlet filter stops pipeline dust, rust and black powder before they erode the compressor's valves, score its liners or foul the dryer's desiccant.

  2. 2. Capture the oilAfter the aftercooler has turned the oil vapour into droplets, the discharge filter passes the gas from the core of its element outward through fine glass microfibres, which capture droplets by impaction, interception and diffusion.

  3. 3. Coalesce and drainCaptured droplets merge into drops that drain down the outer face into the sump. The drain leads to a closed vessel, so gas flashing off the oil vents to a safe location and the oil is kept for disposal.

  4. 4. Dispenser filterAt the dispenser inlet, a final filter stops particles picked up in storage vessels and high-pressure pipework, protecting the meter, dispenser valves and breakaway coupling on the way to the vehicle.

  5. 5. Watch the loadingThe differential pressure gauge shows how loaded the element is. Once it is wetted, a further rise means solids, not liquid, and together with the volume drained it tells you the condition of both filter and compressor.

At a station delivering 1,000 Sm³/h, about 3.4 m³/h of actual gas passes a discharge filter at 250 bar.

Get the full details

Our brochure covers it in detail, and our questionnaire tells us what we need to recommend the right one for your plant.

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