Nafion Gas Dryers – Perma Pure Knowledge Base

What Material Is Used To Bundle Nafion in the Header of PD Dryers or FC Humidifiers?

Gene Bohensky — Thu, 31 Jan 2019 02:42:55 +0000

Perma Pure uses a proprietary epoxy with a high corrosion resistance to bundle the tunes in the “header”. This material has been tested to work well with Nafion and keeps the seal between the sample gas and the purge gas. The same material is used in the FC100 Humidifier. For larger FC humidifiers, a proprietary polyurethane is used to perform the same function. Because this product was designed for fuel cell applications where only clean water is hsed, the enhanced corrosion resistance of the epoxy was not required and a more suitable material was found that would work better with larger bundles (up to 10,000 tubes on the FC800).

How Do the Mechanical Properties of Nafion Change As Water Is Absorbed?

Gene Bohensky — Thu, 31 Jan 2019 02:37:23 +0000

One of the challenges working with Nafion is that it’s dimensions and mechanical properties change depending on the about of water present in the membrane. As the graph shows below, when fully saturated, Nafion can expand up to 18% when fully saturated. Additionally, it looses its strength as well. This makes it a challenge when integrating the membrane into mechanical systems – this high expansion (or contraction) potential must be taken into account when designing your system.

What Are the Particle Losses of Perma Pure Dryers (and Humidifiers)?

Gene Bohensky — Thu, 31 Jan 2019 02:24:07 +0000

Perma Pure dryers are often used in Particle Monitoring and Aerosol Analysis applications. We are often asked about the particle losses of these dryers. There are two ways to look at these losses: first, excess losses when comparing an equivalent bare tube, and net losses. Naturally these losses are dependent on particle size

From our customers, we have learned the following (net losses)

FC 125s and 200s as well as PD 50, 100 and 200s – Net losses of 50%
PD 07018T and MD-110 – Net losses of 15%
MD-700 Large diameter – Net Losses of 2% or roughly equivalent to the same size and diameter bare tube.

These numbers should only be used as a guide, and like we suggest for all customers using our products, they should be tested and characterized for your application.

How Do I Use the Dryer Wheel?

Gene Bohensky — Thu, 31 Jan 2019 02:14:13 +0000

The Perma Pure Dryer Wheel is used to size the dryer. The outside edge shows the flow rates of the various dryer types, and you rotate the wheel according to your flow rate. The inner triangle will show the dew point achievable with the range of dryer lengths available for that series type. This simple tool using flow rate and target moisture level (dew point) contains all of Perma Pure’s published performance data. Bear in mind how that that the data was collected – if your operating conditions differ, the predicted performance may be different. Some notes

Data is base don drying 20 ⁰C saturated air ( 20 ⁰C dew point) – or ambient temperature
-40 ⁰C instrument air was used as the purge gas in 2x flow of the sample gas
Performance ratings are very conservative

How Does the BE Series Braided Exchanger Work?

Gene Bohensky — Mon, 28 Jan 2019 13:09:20 +0000

With the BE Series, Braided Nafion Tubing is exposed to the atmosphere to either extract moisture from the surrounding ambient environment to humidify a gas, or to remove moisture from a sample gas. In both cases, the moisture level is equalized with the surrounding environment. In either application, the continuous moisture transfer properties of the BE series provides long-term and stable performance.

Perma Pure BE Series Highlights:

Simple installation, only requiring the BE series product to be placed in line and exposed to surrounding atmosphere
Consistent performance over time through continuous regeneration
Long service life by maintaining performance through repeated use
Chemically resistant to most gases
Ultimate performance is a function of the dew point of atmosphere where unit is operating
Available in a variety of lengths and tubing diameters
Flow rates to 2 l/m, pressures to 255 psi (17 bar) in the tube when dry

High Pressure Use

The BE Series can also be used in high pressure applications, with some versions able to be used up to 17 bar (250 psi). Using the BE Series in this way makes it possible to effectively dry the gas without needed a purge gas. The sample gas is pressurized – thereby increasing the partial vapor pressure of the water component of the gas, and that pressure is equalized with the ambient water vapor pressure. When the gas is de-pressurized to ambient, the resultant dew point will fall accordingly.

What are the Benefits and Unique Features of the MRD Dryer?

Gene Bohensky — Mon, 28 Jan 2019 12:34:32 +0000

The MRD Dryer is a redesigned version of the MD (Monotube) dryer incorporating a revised end connection design. The “R” stands for rotating, and this redesign has these specific benefits:

1) The rotating ends allow for installation flexibility, as you can rotate the purge gas fitting to where you want it, in contrast to the standard design, where this is fixed. If you try to rotate the standard MD, there is a risk of kinking the tube. The MRD eliminates this risk.

2) An improved o-ring seal design allows the dryer to be used more effectively with ultra low vacuum purge gas configurations.

3) Push in tube connections allow for easier set up

4) Optional 6mm connection ends

What Are the Benefits and Unique Features of The MD-H Heated Dryer?

Gene Bohensky — Mon, 28 Jan 2019 12:02:52 +0000

The MDH-Series Nafion gas dryer was designed to dry gas samples with dew points higher than ambient temperature without requiring separate heating elements or insulation. A Nafion dryer is coiled into a plastic enclosure and the first 12″of the dryer are heated to 80 C. The main benefits of this dryer are:

Dry sample gases with dew points up to 70 C (30% water by volume)
The elevated Nafion operating temperature speeds initial moisture transfer when compared with unheated dryers.
All in one package allows faster set-up and/or integration with analuyzers
Flow rates to 1.5 lpm,
Can be incorporated easily into analyzer cabinets or used as a stand-alone device.
Purge gas flow of 10x sample gas recommended

How Do I Know When It’s Time To Replace My Perma Pure Dryer or Humidifier?

Gene Bohensky — Mon, 07 Jan 2019 02:16:37 +0000

How do I know when I should replace my Perma Pure Dryer or Humidifier? Is there any preventative maintenance I can do to extend it’s life in my application?

In general, there is no preventative maintenance on our products. The performance will decline over time only as long as it is subject to contamination by impurities in the water or air in the sample gas, purge gas, or water used for humidification. Our products have seen successful service in excess of 10 years in certain applications. Because the performance you require is dependent on factors beyond our control, we suggest that when developing your product or experiment, it is up to you to size the product accordingly. You will need the right amount of Nafion surface area and to determine at which point the product’s performance will no longer be enough for a successful process or analysis.

Some customers have installed some sort of sensor to determine at which point the unit might need replacement. Again, this trigger point must be defined by you, when the performance decline is sufficient to affect the overall performance of your system or product.

Perma Pure Dryers for Aerosol Analysis

Gene Bohensky — Mon, 07 Jan 2019 00:32:37 +0000

Controlling humidity of the air sample is critical to getting consistent results for aerosol and particle analyses across a wide range of ambient conditions. Gas sample dryers with Nafion membrane technology have been shown to control air sample humidity well in many analysis applications but until now have shown high particle losses due to their small pathway diameters.

The MD-700 Dryer for Aerosol Analysis was developed at the request of our customers specifically for PM particle measurement and aerosol analysis. In order to minimize particle losses, a laminar sample flow is maintained through the flow path of the dryer using special large diameter 17mm (0.700”) Nafion tubing. Users and researchers measuring PM 2.5 or PM1 or performing aerosol research and analysis will have an effective option to control humidity while improving measurement accuracy and limiting particle losses. Some basic features of the dryer are listed below:

Eliminates the need for heating the sample gas stream, preserving the volatile particulate component in the sample
Grounded Stainless Steel Tube and Shell Construction eliminates buildup of static electricity and provides long service life outdoors.
Straight Configuration in 6, 12, 24, and 48 versions minimize turbulent flow that can negatively affect measurements
Dryer is continuously regenerating, eliminating the need to repeatedly replace desiccant
Designed to be used with the vacuum re-flux purge gas method where no dry or instrument air is available.

The MD (Monotube Dryer) Series can also be used for low flow aerosol analysis as for applications under 1 lpm the flow remains linear, with the following construction options:

MD-110 with 0.110″ Tubing for best flow characteristics
Grounded Stainless Steel Tube and Shell Construction will eliminate the buildup of static electricity and provide long service life outdoors.
Straight Configuration standard in 12, 24 versions and optional for 48 and 72 inch versions minimize turbulent flow that can negatively affect measurements

The PD (Polytube Dryer) Series use multiple Nafion tubes in parallel to increase the flow and drying capacity. Choose the following Special Construction Requirements for PM / Aerosol Analysis:

PD-07018T with larger tubes than standard PD Dryers specially developed for PM/Aerosol Monitoring offer the best flow characteristics while minimizing particle losses (15% vs. the standard 50% for standard PDs)
Grounded Stainless Steel Tube and Shell Construction for elimination of the buildup of static electricity and to provide long service life outdoors.
Straight Configurations in 12 ad 24 inch versions minimize turbulent flow that can negatively affect measurements

Is There a Tool to Remove the PD Element?

Gene Bohensky — Sun, 06 Jan 2019 21:06:41 +0000

Yes, there is a special tool that makes removing the element from a PD dryer easier, and it protects the element and/or dryer from damage

The PD element removal tool part number is #GS-2040-03-16 and it is recommended to prevent damage to the dryer when you try to get the element out of the end fittings.