Monotube gas dryer for low moisture levels and stable sample conditions
Perma Pure MD series Nafion® dryers are monotube gas dryers that selectively remove water vapour from gas streams. Using a single Nafion™ membrane and an external purge gas flow, these dryers are highly suitable for applications that require a low dew point, high analytical accuracy and reliable gas conditioning, for example in emission measurements (CEMS), process analysis, laboratories and OEM systems.
How does the MD series work?
The MD dryer works with a selectively permeable Nafion™ membrane, through which water molecules from the gas sample diffuse into a counter-current purge gas. This process is driven by the difference in water activity (the partial water vapour pressure) between the sample gas stream and the purge gas stream.
- The gas sample flows through the Nafion™ tube.
- Water molecules migrate through the membrane to the outside.
- A dry purge gas carries the moisture away, drying the sample quickly and effectively.
- Other gas components are retained, without loss of analytes.
With this design, MD dryers can reach dew points down to approx. −40 °C and are ideal for industrial and analytical workflows where moisture control is crucial.
Key features
- Efficient moisture removal with Nafion™ technology: only water vapour is transported.
- Achieves low dew points (down to approx. −40 °C) with the right purge gas configuration.
- No loss of gas components or analytes.
- No moving parts: low-maintenance and highly reliable.
- Supports flows up to approx. 4 L/min depending on model (MD-050/MD-070/MD-110).
- Compatible with various gases, temperatures and pressures for analytical and process environments.
Specifications
| Nafion™ tubing outer diameter options | 0.050″ (MD-050), 0.070″ (MD-070), 0.110″ (MD-110) |
| Max. Flow rate | 0.2 lpm (MD-050), 4 lpm (MD-070), 4 lpm (MD-110) |
| Housing materials available | Polypropylene, Fluorocarbon, or Stainless Steel |
| Max. Operating temperatures | 80 °C for polypropylene housing, 100 °C for fluorocarbon or stainless steel housing |
| Sample gas port – end fitting options | Port 1/16″ compression (MD-050, stainless steel only) |
| Port 1/8″ compression (all models) |
| Port 1/4″ compression (MD-070, MD-110) |
| Purge gas port – end fitting size | Port 1/8″ compression (MD-050) |
| Port 1/4” compression (MD-070, MD-110) |
| Purge gas recommendations | Purge gas must be drier than sample gas |
| Purge gas can be instrument quality air (max -40 °C dew point) or nitrogen |
| Purge gas should flow at 2 or 3 times the sample rate |
| *Alternate methods to using a purge gas are possible, such as recycling the dry sample gas, or pulling vacuum through the purge gas flow path. See website for more information. |
| Coiled configurations | Certain models are shipped coiled based on length. See page 4 for nominal diameters. Contact us for custom coiled solutions. |
Performance per model
Applications
The MD series is particularly suitable for:
- Emission measurements (CEMS) and air quality analysis
- Process gas analysis in chemicals and petrochemicals
- Laboratory and R&D measurements
- OEM integration in analysers and measuring systems
- Protection of moisture-sensitive equipment
Thanks to the monotube construction and Nafion™ membrane technology, these dryers deliver accurate, reproducible, condensation-free sample streams that are essential for reliable measurements.
