MD-R Series Gas Sample / Membrane Air Dryers

Perma Pure MD-R™-Series Membrane Air Dryers use exclusive Nafion™ selectively permeable membrane tubing to continuously dry gas streams removing only water vapor. These Air Dryers operate over a wide range of temperatures, pressures and flow rates, and dry to dew points as low as -60°C.

Product Features:

  • Flow rates up to 4 l/m
  • Operating temperatures to max. 120° C
  • Operating pressures to 100 psi (absolute)
  • Straight or coiled configuration
  • Corrosion resistant
  • Standard dew points to – 25° C, with – 60° C possible in special cases (contact factory)
  • No loss of analytes
  • No moving parts

Principle of Operation

The MD-R Series Membrane Air Dryers transfer moisture from one gas stream to a counter-flowing purge gas stream, much like a shell-and-tube heat exchanger transfers heat. Water molecules permeate through the Nafion™ tube wall, evaporating into the purge gas stream. The water concentration differential between the two gas streams drives the reaction, quickly drying the air or gas. Purge gas should be dry (-40°C dew point) air or other gas. If no dry gas is available, a portion of the gas dried by the MD-Series dryer can act as the purge gas in a split-stream or reflux method. Visit the Purge Gas Configurations page to learn more about the purge methods Perma Pure customers deploy in their equipment.

Intelligent Product Numbering System

Perma Pure offers the MD-R Series Membrane Air Dryer with two sizes of Nafion™ tubing and in a variety of lengths and connection types. Choose the size based on your flow rate and dryness requirement and build your MD dryer according to the selection guide and the part number table below:


1 – Series
MD-R (Monotube Dryer) Series MRD
2 – Tubing Size
0.070″ Nafion™ Tubing 070
0.110″ Nafion™ Tubing 110
3 – Dryer Lengths
12″ (30 cm) 012
24″ (60 cm) 024
48″ (120 cm) 048
72″ (180 cm) 072
96″ (240 cm) 096
144″ (360 cm) 144
4 – Shell Material
Fluorocarbon (FEP / PVDF) T
Polypropylene (PP)
5 – Fitting Material
Kynar K
6 – Ferrule Material
Viton V
7 – Connector 1-4
1 Left Sample 2 Left Purge
3 Right Purge 4 Right Sample
1/4″ Quick Connect 1
1/8″ Quick Connect 2
6mm Quick Connect 4

Recommended Sample Gas Flow Rates:
0.1-2 lpm: MDR-070 Series
1-4 lpm: MDR-110 Series

Selection Guide Notes – 2MDR-070 and MDR-110 offer approximately the same drying performance. Specify MD-110 when pressure drop is a concern, MD-070 to minimize dead volume. For higher flow rates, please see our PD-Series dryers.

Select your dryer based on model line, flow and length



Support Materials / Documents