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Membrane Selection Guide
Finding the right membrane for your existing or potential application can be quickly accomplished by choosing among the options in a few key areas:

1. Material
2. Molecular Weight Cut-Off (MWCO) / Pore Size
3. Cartridge Length / Fluid Path
4. Membrane Area / Processing Volume

To view a complete selection of products, click here.

The following section discusses the importance of key characteristics.

General Guidelines for choosing a WaterSep Hollow Fiber cartridge

1
Material

All WaterSep membranes are based on industry accepted polyethersulfone (PES) materials. PES exhibits exceptional chemical and physical properties and has regulatory properties suitable for food products and biopharmaceutcal processing.

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2
MWCO
(a.k.a Pore Size or “Cut off”)
For a product concentration application the recommended membrane cut-off should be a factor 5-7 smaller than the smallest product molecule that should be retained by the membrane.

Example:
For a product molecule that has a molecular weight of 65,000 Dalton, a 10,000 Dalton membrane is recommended. The molecular cut-off standard for membranes is based on globular shaped molecules. A linear molecule of similar molecular weight typically requires a tighter membrane.

Similarly, for quantitative passage of a molecule through a membrane, the MWCO should be 8-10 times larger than the passing product’s molecular weight.

If a passage >95% is required, an additional diafiltration step is recommended.

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3
Cartridge Length / Fluid Path
Shorter Cartridge Lengths (12” and 24”)
Advantages:
• Used when higher viscosity (>2,000 cps) solutions are processed. Shorter path lengths result in lower pressure drops, lower operating costs, and less product denaturation
• Used when length or height constraints exist or more compact processing is desired.

Disadvantage:
• Less efficient surface area to pumping capacity. Longer path lengths use similar feed flow rates as shorter lengths yet more surface area is employed

Longer Cartridge Lengths (41” and custom configurations)
Advantages:
• Used when low viscosity (<2,000 cps) solutions are processed. Longer path lengths use similar feed flow rates as shorter lengths yet more surface area is employed resulting in higher permeate rates.
• Used when length or height constraints are not a factor. The desired length when large scale processing is desired.

Disadvantage:
• Operating costs increase as a function of pressure drop. High pressure drops also add more heat to the process solution leading to potential product denaturation.

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4
Membrane Area / Processing Volume
For membrane area determination, the average process flow rate and the volumetric throughput need to be considered. For a typical 8- hour work shift, a processing time of 3-5 hours is recommended followed by 1-2 hours of cleaning and sanitization.

Example:
To produce a batch size of 2000 liters in a 4-hour timeframe,
your target rate needs to be 500 liters per hour.

Membrane capacity is measured in liters/m2 and hour (LMH). With a flux of 40 LMH, the required membrane area is 12.5 m2. For this application, we recommend either: 3 Producer 41" cartridges or 6 Producer 24" cartridges.

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