Compressed Air & Gas Filters

Ammonia and Refrigerant Filter

Keep compressor oil where it belongs, in the compressor, and out of the condensers and evaporators your cooling depends on.

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Two stainless steel refrigerant filter housings

Product overview

Oil-free refrigerant, cleaner coils, steadier cooling

Every lubricated refrigeration compressor releases oil into the gas it compresses. Your primary oil separator takes out the bulk liquid, but the gas leaving it still carries a fine mist of droplets, mostly below a few micrometres, that gravity cannot settle. Our coalescing filter captures that mist in a fibre bed, merges it into draining liquid, and sends the oil back to the compressor or into an oil collection pot.

Oil that escapes settles where the refrigerant is coldest and moves slowest: in evaporators, low-pressure receivers, surge drums and suction accumulators. There it insulates heat transfer surfaces, and in ammonia plants it has to be drained by hand, exposing operators to ammonia.

The filters work in ammonia (R717), carbon dioxide (R744), hydrocarbons, and HFC and HFO refrigerants. Particulate elements in the same family protect compressor suction, oil return lines and the small orifices of expansion and float valves.

A refrigerant filter housing beside its coalescing element
  • About 42 %Heat transfer lost to a 0.1 mm oil film, in an evaporator example
  • About 2.6 %Ideal-cycle efficiency lost per kelvin lower evaporating temperature
  • About 3.4 %Capacity lost per 0.1 bar suction pressure drop, ammonia at −10 °C
  • R717 and R744Ammonia and carbon dioxide, plus hydrocarbons, HFCs and HFOs

Benefits

The problems it solves

Oil carryover is inherent to lubricated compression. Here is what that oil does once it leaves the compressor, and how the filter stops it.

  • Fouled evaporators

    The problem

    Oil thickens at low temperature and coats evaporator tubes, forcing the plant to run a lower evaporating temperature for the same duty.

    How it solves it

    Clean heat transfer surfaces keep the evaporating temperature at its design value, avoiding the ideal-cycle loss of about 2.6 % per kelvin.

  • Rising head pressure

    The problem

    An oil film on condenser tubes or plates adds heat transfer resistance and raises condensing pressure.

    How it solves it

    Oil-free condenser surfaces keep your head pressure down, reducing compressor power and discharge temperature.

  • Hazardous oil draining

    The problem

    Oil drained from ammonia low-pressure vessels releases dissolved ammonia as it warms, exposing operators at every drain.

    How it solves it

    Less oil reaches the low-pressure side, so your operators spend less time at oil drain points.

  • A compressor short of oil

    The problem

    Oil that leaves the package lowers the charge, starving bearings and the rotor seal, and a low level trips the compressor.

    How it solves it

    Recovered oil returns to the compressor, keeping its charge stable and reducing how often and how much oil you add.

  • Debris in rotors and valves

    The problem

    Weld slag, grinding dust and mill scale can score a rotor, hold a valve off its seat or stop a float mechanism.

    How it solves it

    Suction and liquid line particulate elements keep debris away from rotors, bearings and valves, especially during commissioning.

  • Faults found too late

    The problem

    A failing separator or oil level fault is usually found only when the evaporators foul.

    How it solves it

    The drain sight glass and differential pressure reading show a rise in oil carryover before oil reaches the evaporators.

Where it’s used

Wherever refrigeration keeps the process running

From frozen warehouses to fertiliser terminals, industrial refrigeration relies on clean evaporators and a compressor that keeps its oil.

  • Wine bottles moving along a bottling line

    Food, cold storage and beverages

    Frozen warehouses at −25 to −30 °C, meat, poultry and seafood freezing, dairy, ice cream, and brewery fermentation cooling.

  • Test tubes of coloured chemicals in a laboratory rack

    Chemicals, petrochemicals and fertilisers

    Reactor jacket cooling, crystallisation, propane and propylene refrigeration, and boil-off gas reliquefaction at ammonia storage terminals.

  • A naval warship at sea

    Fishing vessels and marine refrigeration

    Refrigerated seawater systems, onboard freezers and cargo holds.

Also pharmaceutical process cooling, CO₂ recovery plants, supermarket CO₂ transcritical and cascade systems, ice rinks, industrial heat pumps and district heating, HVAC chillers and data centre cooling, and test chambers.

How it works

Catch the mist, return the oil

The filter sits directly after the primary oil separator, in the hot gas line and before the condenser, so one filter protects every component downstream.

How an ammonia and refrigerant filter works: the screw compressor discharges hot gas carrying oil, and the primary oil separator removes the bulk liquid. The coalescing filter in the hot gas line passes the gas from the inside of its element to the outside, capturing the fine oil mist that remains. The oil drains to the sump and returns to the compressor through a sight glass and metering orifice, while the oil-free gas goes on to the condenser, receiver and evaporators. ScrewcompressorPrimary oilseparatorHot gas and oil mist CondenserOil-free gas onTo receiverand evaporators Differential pressure gauge Sight glassMetering orifice Inside the fibresInterception · ≈ 0.3–1 µmImpaction · above ≈ 1 µmDiffusion · below ≈ 0.1 µm 12345Hot gas with oil mistOil-free gasRecovered oilCoalescing mediaRefrigeration plant

  1. 1. Hot gas and oil mistThe screw compressor discharges hot gas carrying oil. The primary oil separator removes the bulk liquid, but a fine mist of droplets follows the gas out.

  2. 2. Capture in the fibresThe gas turns down into the element core and passes from inside to outside through a deep bed of fine fibres. Droplets are caught by impaction above about 1 µm, interception from about 0.3 to 1 µm, and diffusion below about 0.1 µm.

  3. 3. Coalesce and drainCaptured oil joins the oil already on the fibres, is pushed to the outer face, and runs down the drainage layer into the sump in drops of millimetre size.

  4. 4. Oil back to the compressorThe sump drains continuously through a sight glass and metering orifice back to the compressor oil system, or to an oil pot. The sight glass shows the oil is returning.

  5. 5. Oil-free gas onThe oil-free gas goes on to the condenser, receiver and evaporators. The differential pressure gauge shows the element’s condition.

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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