Mikropor MOK refrigeration dryers for compressed air

Dew point +3 °C

Mikropor MOK refrigeration dryers dry compressed air to a pressure dew point of +3 °C. The air is cooled in the heat exchanger, water vapour condenses and the drain discharges the water. The circuit is filled with R513A refrigerant with a low global warming potential.

We offer two sizes: MOK-50 for 50 m³/h (833 l/min) and MOK-100 for 100 m³/h (1,667 l/min) at 7 bar, both up to 14 bar. Each comes on its own or with a pair of GO filters on the rear wall: a 1 µm dust filter and a 0.01 µm microfilter.

What the Mikropor MOK dryer offers

• Stable +3 °C dew point even at room temperatures up to +50 °C
• Optionally with a pair of filters mounted on the dryer
• 3-in-1 heat exchanger with a low pressure drop
• Microchannel condenser and temperature-controlled fan
• Hermetic circuit with R513A refrigerant
• Digital controller with alarm and service messages

Sizes and technical data

The code links to the product card. The flow rate applies at 7 bar, +35 °C inlet air and +25 °C room temperature. On the version with filters the connection is on the filters; the pressure drop in the table is that of the dryer.

The version with filters has a pair of GO filters on the rear wall, connected by a manifold that the manufacturer makes specifically for MOK dryers. The air passes through the dryer first, then the 1 µm dust filter and the 0.01 µm microfilter. The set takes up less space and needs no extra piping.

The dryer without filters is connected with a G 3/4" thread. You can install filters separately in the pipework.

How to choose the size

The dryer must handle the full output of the compressor. The flow rate in the table applies to the manufacturer’s nominal conditions. The actual flow rate changes with the inlet air temperature, the room temperature and the pressure. Multiply the nominal flow rate by the manufacturer’s three correction factors:

actual flow rate = nominal flow rate × inlet temperature factor × room temperature factor × pressure factor

Example: the compressor delivers 800 l/min at 8 bar, the inlet air is at +40 °C and the room is at +35 °C. MOK-50 with a nominal flow rate of 833 l/min handles 833 × 0.92 × 0.93 × 1.04 = 741 l/min, which is not enough. MOK-100 handles 1,667 × 0.92 × 0.93 × 1.04 = 1,483 l/min and is suitable.

Inlet air temperature factor

Room temperature factor

Pressure factor

The dryer operates from 4 to 14 bar, with inlet air at +5 to +60 °C and in a room at +5 to +50 °C.

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How the Mikropor MOK dryer works

Warm, humid air from the compressor enters the 3-in-1 heat exchanger. In its first section it is pre-cooled by the dry, cold air leaving the dryer. In the second section the refrigerant cools it to a pressure dew point of +3 °C, water vapour condenses and in the third section the separator captures the droplets. The drain then discharges the condensate.

On its way out, the dry air is reheated in the first section of the exchanger, so no water condenses on the pipework downstream of the dryer. The refrigerant compressor compresses the refrigerant, which cools and liquefies in the condenser and returns to the exchanger through the expansion valve.

In the diagram

• at the top the refrigerant compressor
• on the left the condenser with fan
• the blue line with liquid refrigerant and the expansion valve
• on the right the 3-in-1 exchanger: air/air pre-cooler, air/refrigerant evaporator and water separator, condensate outlet at the bottom

3-in-1 heat exchanger

The exchanger combines the air/air pre-cooler, the air/refrigerant evaporator and the water separator in one aluminium plate block. The air flows through it without unnecessary bends, so the pressure drop is low and the compressor does not have to work at a higher pressure.

Dryer components

The microchannel condenser has a large heat transfer surface and a higher efficiency than a conventional finned condenser. The fan is controlled by temperature, so it runs only when needed. A debris filter protects the condenser against dust from the room.

The piston refrigerant compressor works in a hermetic circuit: all joints are welded and the circuit is sealed from the surroundings. A critical high temperature alarm protects the dryer against overheating.

Pair of GO filters

Mikropor manufactures GO filters according to ISO 8573 and the Pressure Equipment Directive. Each dryer comes with a pair of filters with elements of two grades. Air purity classes are explained under industrial filters according to ISO 8573-1.

The X dust filter removes particles down to 1 µm and reduces oil content to 0.1 mg/m³; the Y microfilter after it removes particles down to 0.01 µm and reduces oil content to 0.01 mg/m³. The elements are replaced at a pressure drop of 700 mbar.

The pore-free aluminium housing is anodised, so it resists corrosion and scratches. The element is supported by a fluted stainless steel tube that does not collapse even when the pressure drops. Elements are replaced without tools and without extra space below the filter.

Digi-Pro controller

The display shows the temperature in the dryer in °C or °F. Indicators show dryer operation, fan operation, energy saving mode, refrigerant compressor stand-by and service. The buttons switch the dryer on, set it up and trigger a manual condensate drain.

The controller reports low and high temperature, high refrigerant suction temperature, high condensation, a fault of the zero-loss drain, filter change and service time.

Condensate drain

The dryer has a time-controlled drain; you can also trigger it manually with a button on the controller. As an option the manufacturer supplies an electronic zero-loss drain that wastes no compressed air.

R513A refrigerant

The manufacturer fills Mikropor MOK dryers with R513A refrigerant. It does not deplete the ozone layer, is non-flammable and suits demanding environments. Its global warming potential is less than half that of the formerly common R134a:

Dew point and air purity

Compressed air carries water, oil and solid particles. Water is expressed by the pressure dew point: the temperature at which the air is saturated with moisture. When the air cools to the dew point or below, water condenses and causes corrosion, rust and leaks in the pipework.

The Mikropor MOK dryer reaches a dew point of +3 °C, i.e. water class 4 according to ISO 8573-1. With the pair of GO filters it also removes solid particles down to 0.01 µm and reduces oil content to 0.01 mg/m³, which corresponds to oil class 1. Larger flow rates are handled by Hankison HDI refrigeration dryers and Omega Air RDS. For a dew point below 0 °C, for example for pipework running outdoors in winter, you need a desiccant dryer.

Technical data of the Mikropor MOK range

How do I choose the dryer size?

By the output of the compressor. Multiply the nominal flow rate from the table by the correction factors for inlet air temperature, room temperature and pressure and choose a dryer that handles the full compressor output.

What dew point does the Mikropor MOK dryer reach?

A pressure dew point of +3 °C, i.e. water class 4 according to ISO 8573-1. For a dew point below 0 °C you need a desiccant dryer.

How does the version with filters differ?

It has a pair of GO filters on the rear wall: a 1 µm dust filter and a 0.01 µm microfilter. It is connected at the filters: MOK-50 with a G 1/2" thread, MOK-100 with a G 3/4" thread. Otherwise the dryer is the same.

When are the filter elements replaced?

At a pressure drop of 700 mbar. The elements are replaced without tools.

Where can the dryer be installed?

In a room at +5 to +50 °C; above +25 °C the flow rate is reduced by the correction factor. The condenser is cooled by room air.

What power supply does the dryer need?

Both sizes are connected to 230 V, single phase, 50 Hz. The rated power consumption of the compressor and fan is 264 W for the MOK-50 and 245 W for the MOK-100.

The technical data of Mikropor MOK dryers are based on documents from the manufacturer Mikropor (MOK series brochure, Compressed Air catalogue 2026 for GO filters).

Other types of dryers are listed under compressed air dryers.