Compressed Air & Gas Filters

Compressed Air Duplex Filter

Change your filter elements on any shift, while your plant keeps running on fully filtered air.

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A blue duplex filter with its two filter elements beside it

Product overview

Filter maintenance that never stops your process

Our duplex filter places two identical filter paths in parallel between a linked pair of changeover valves. One path carries the full flow while the other stands by. Move the changeover and the flow transfers to the standby path, so the first housing can be isolated, vented, opened and fitted with a new element while your process keeps receiving filtered air at line pressure.

At no point in the valves' travel are both paths closed, and the air never has a route around the filter media. Every cubic metre you receive has passed through an element of the grade you specified, including the air delivered during maintenance.

Each path takes any grade: general-purpose coalescing at 1 µm, high-efficiency coalescing to 0.01 mg/m³ oil aerosol, particulate for dry dust, or activated carbon so total oil can reach 0.003 mg/m³.

A blue duplex filter with its two filter elements beside it
  • 0.01 mg/m³Oil aerosol, high-efficiency coalescing grade
  • 0.003 mg/m³Total oil with activated carbon
  • No stoppageTo change an element
  • About 12,600 kWhA year wasted by one overdue element, in a 75 kW example

Benefits

The problems it solves

Every filter element has to be changed eventually. On a single filter, that means either stopping production or sending unfiltered air downstream. The duplex filter removes that choice.

  • A shutdown for every change

    The problem

    Changing an element on a single filter means isolating it, and a process that cannot stop has to wait for the next planned outage.

    How it solves it

    Element changes take place during normal operation, at any shift, with no production stoppage.

  • Unfiltered air through a bypass

    The problem

    A bypass around a single filter sends unfiltered air downstream for the whole service period, and oil-fouled desiccant does not recover.

    How it solves it

    The changeover moves flow from one filtered path to another, so your dryers, carbon beds and process never see raw air.

  • Energy lost to overdue elements

    The problem

    A postponed change keeps loading the element, and each bar of extra compressor discharge pressure costs about 7 % more compressor energy.

    How it solves it

    Elements are replaced when their pressure drop reaches the limit, not deferred to a shutdown, keeping your compressor discharge pressure down.

  • Gaps in your audit trail

    The problem

    Auditors expect the specified air quality class to hold through maintenance events, not only between services.

    How it solves it

    Continuous filtration supports your ISO 8573-1, BCAS Guideline 102, European Pharmacopoeia and HTM 02-01 records without maintenance exceptions.

  • Rushed, risky maintenance

    The problem

    Working on a filter against the clock of a stopped line invites mistakes on a pressurised housing.

    How it solves it

    The path being serviced is isolated and vented while your process keeps running, so technicians work without time pressure.

  • Upsets that stop the plant

    The problem

    A failed drain, a damaged bowl seal, a blocked element or an oil carryover event would otherwise force a shutdown.

    How it solves it

    Switch paths, and deal with the fault on the isolated housing straight away.

Where it’s used

For processes that cannot stop

Where a filter change must not reduce either the air supply or the air quality, the duplex arrangement keeps both.

  • Test tubes of coloured chemicals in a laboratory rack

    Refining, petrochemicals and chemicals

    Instrument air for control valves, analysers and shutdown systems, and air for reactor blanketing and process supply.

  • Electricity pylons and power lines at sunset

    Power generation

    Instrument and service air for boilers, turbines, ash handling and switchgear that must stay available during unit operation.

  • Yellow tablets spilling from a medicine bottle

    Pharmaceuticals and biotechnology

    Fermenter aeration, tablet coating, filling lines and clean room pneumatics, where a filter shutdown would scrap a batch.

  • Wine bottles moving along a bottling line

    Food and beverage

    Dairy, brewing, bottling and packaging lines holding BCAS Guideline 102 Class 2:2:1 through element changes.

  • Molten metal pouring from a ladle in a foundry

    Steel

    Continuous furnaces that need uninterrupted air for burners, instruments and cooling.

  • Glowing glass bottles being formed on a production machine

    Glass

    Float lines that run for years between rebuilds and need uninterrupted air.

Also hospitals and medical air plant, cement kilns, semiconductors and electronics, nitrogen generators feeding continuous processes, and breathing air for blasting hoods and protective suits.

How it works

Two paths, one flow

Linked valves at the inlet and outlet always move together, so one filter path is always open and the other can be serviced in safety.

How a duplex filter works: two identical filters sit in parallel between linked changeover valves. Filter A carries the full flow while filter B is isolated, vented and fitted with a new element. The equalising valve then fills B slowly to line pressure, and the linked valves move the flow from A to B in one stroke, so filtered air keeps flowing throughout. Air inFiltered air out A · in service, full flow B · standby Linked valves Equalising valve Vent 12453Air to be filteredFiltered airOil and water drainedValve linkageFilter element

  1. 1. One path in serviceThe inlet changeover valve sends the full flow through filter A, and the outlet valve returns it to your line. Filter B is closed at both ends, fully isolated from the pressurised system.

  2. 2. FilterThe element in service removes aerosols, particles or vapour to its grade. In a coalescing path, the captured liquid drains to the bowl, and each housing discharges its own condensate through its own drain.

  3. 3. Service the standbyThe isolated housing is vented to atmosphere and drained. With zero pressure confirmed, the element and O-rings are replaced and the vent closed, and it waits as the standby.

  4. 4. EqualiseBefore a changeover, the equalising valve is opened slowly and fills the standby housing to line pressure over tens of seconds, so no pressure surge reaches your process.

  5. 5. Change overThe linked valves move in one continuous stroke. The opening path starts to open before the closing path shuts, so the flow never stops and no position sends air around the filters.

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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