Bubble point test
The bubble point test is a commonly used to characterize a membrane integrity. By estimating of the minimum pressure (bubble point) at which a wetting liquid is steadily pushed out of the pore channel forming a bubble chain. Measured pressure with membrane and wetting solution characteristic maximum pore size can be calculated. ASTM F316 - 03.

Chemical resistance
All materials used are stated in product datasheets. Fibers are usually produced from polypropylene (PP), polycarbonate (PC). Housing can be PVC, stainless steel, PC. Fibers are potted with polyurethane or epoxy. Usually polyurethane is most vulnerable to chemical degradation, especially at elevated temperatures. For specific chemical please consult various chemical resistance tables.

engineeringtoolbox polyurethane
engineeringtoolbox epoxy
engineeringtoolbox polypropylene

Cross-flow Filtration mode
In cross-flow filtration, a fluid (feed) stream runs tangential to a membrane, establishing a pressure differential across the membrane. This causes some of the particles to pass through the membrane. Remaining particles continue to flow across the membrane, "cleaning it". wikipedia link

Dead-end filtration mode
In the dead-end filtration technique all the fluid passes through the membrane, and all particles larger than the pore size of the membrane are retained on its surface. Trapped particles will start to build up a "filter cake" on the surface of the membrane, which has an impact on the efficiency of the filtration process. wikipedia link

The fluid/gas that is going to be filtered, will pass through membrane.

Fiber bundle
Potted fibers form a basic heat exchanger element of immersed module. Can be random or ordered.

A process of removing particles of different sizes from feed by passing it through a semi-permeable material - membrane.

The fluid/gas that has been filtered/processed.

Characterizing the flow rate of water/liquid/gas through membrane. This value is usually specified trans membrane pressure, temperature etc.

Food / drinking water / lab applications
For these applications, all parts (housing, hollow fibers, potting) of the module must have at least food certification.

Buildup of solid substances or grown organic material on the surface of the membrane. Fouling decreases flux and the quality of the filtrate. Fouling can be minimized by proper technological process and should be periodically removed by CIP, back-flush and other cleaning procedures.  wikipedia link

Heat exchanger
Heat exchanger is a device used to transfer heat between a solid object and a fluid, or between two or more fluids. wikipedia link

Hollow fiber
Polymer tube with defined outside diameter (OD) and inside diameter (ID). These fibers, depending on the material, are flexible and strong. Ratio of OD / ID will influence the heat transfer coefficient, temperature/pressure rating and kink/physical durability.

Housed filtration module
Membrane module can be pressurized, feed can be pushed through membrane wall to the inner space. No open liquid level is involved.

Membranes characterized as hydrophobic repel water. Water will not pass (unless very high pressure and/or mechanically damaging the membrane) through membrane.Membrane acts as barrier for water only gas/vapours will pass. This is used for contactor and MD applications.

Hydrophilic membranes have an affinity for water. Their surface chemistry allows these materials to be wetted spontaneously. Water filtration is possible as water will wet the pores and flow through membrane under relatively low pressure.

Hydrophilic treatment
Some membrane materials such as PP, PE, PVDF are natively hydrophobic, for most water filtration applications hydrophilicity is desired. Native PP or PE is modified usually surface treated. This newly is not permanent, it wears off chemical cleaning, elevated temperature and other factors.

Inner diameter [ID]
Used in context with hollow fibre membrane, identifies the inner diameter of the membrane. Characterizing the geometry of the membrane together with wall thickness and OD.

Immersed / housed
Immersed heat exchanger requires tank into which is submerged. Circulation and placing inside the tank is crucial. The housed heat exchanger module should have 4 ports, and is ready for use.

Inside/Out filtration mode
Feed is pumped in the membrane hollow fibers and permeates through membrane wall. Retention part of the feed is kept inside of the fiber. Suitable for low feed contamination.

A sharp twist or buckling bend of the fiber that is otherwise straight. This, when fiber moves, can cause fatigue strain and in a extreem process condition means problems in a long run.

Lumen/tube side
Space in housed module within lumen of the fibers. In cross flow filtration 2 ports connect to it, in dead end setup only one port. For heat exchanger we use tube side.

Maximum Pore Size
A calculated value gained from the results of the bubble point test. The maximum pore size is theoretically the largest pore within the pore structure of a membrane. Usually estimated by Bubble point test.

Membrane bundle
Quantity of hollow fiber membranes certain length potted in usually plastic pipe for easy connection to lumen side of the fibers. Number of hollow fibers and length can vary. Standard membrane bundle is 1385 membrane fibers potted in d20mm PVC pipe, total length is 750mm.

Membrane contactor
Membrane acts as a barrier between mediums (usually liquid and gas) in controlled manner, without mixing and at large contact surface. Gassing, degassing applications.

Membrane distillation (MD)
Membrane distillation (MD) is a thermally driven separational where hydrophobic membrane acts as a barrier for the liquid phase, allowing the vapour phase (e.g. water vapour) to pass through the membrane pores. wikipedia link

Membrane ponytail
Quantity of hollow fiber membranes certain length loosely fixed together usually with tape at the ends. Membrane ponytails are processed / potted to membrane bundle or membrane module. Number of hollow fibers and length can vary.

Microfiltration is a filtration where 0.1 to 10.0 µm particles are removed from feed.

Outer diameter [OD]
Used in context with hollow fibre membrane, identifies the outer diameter of the membrane.

Outside/In filtration mode
Separation takes place on outside wall of the membrane, inner space is permeate

Pore Size
The pore size, usually stated in micrometers (µm), refers to the theoretical diameter of the pore in the membrane wall. Pore shape is rarely circular or straight. In some cases it is stated as width x length (µm).

Physical connection (inflow, outflow) to the heat exchanger, usually hose barb, push-in connection, inner/outer thread ⅛, ⅜, ½.

Multiple hollow fibers sealed together to form a port through which fiber lumens can be accessed. Boundary between two process mediums.

Random / ordered distribution
For maximal heat exchanger efficiency, fiber distribution is important. In certain cases random-curly distribution is an advantage. Ordered distribution means that individual fibers are evenly distributed in the module.

Shell side
Space in housed module which is between housing shell and membrane. One or more ports connect to it. Lot of dead space, difficult to clean.

Submerged filtration module
Membrane elements/modules are immersed in feed, suction through permeate piping is applied, thus feed is drawn through membrane wall.

Temperature shock
Sudden temperature changes of heat exchangers composed of several different materials is dangerous due to different thermal expansion coefficients. Different materials have different thermal coefficients of expansion which put significant strain on the joints. All temperature changes on heat exchanger modules require slow (low) gradient.

Temperature resistance
The recommended maximum working temperature is mentioned in datasheets. Any excess on those temperatures does not necessarily cause damage the heat exchanger module, but degradation will take place. This will shorten life span of the module.

Trans-membrane flow [TMF]
A measurement of the transmembrane flow is carried out to document the membrane flow characteristics. The TMF is defined as the initial volume of liquid passing through the membrane wall within a given unit of time, related to surface area and pressure, and expressed in ml/min cm² bar.

Trans-membrane pressure [TMP]
Pressure at which feed is forced through membrane wall. Lower TMP means lower flux and lower fouling = longer filtration time between cleaning periods.

Ultrafiltration is a filtration where process similar to microfiltration. The main difference is the "tighter" retention behavior: the ultrafiltration membrane retains much smaller particles from the passage through the membrane than do microfiltration membranes. Typically the particle size is measured by molecular - weight, and ultrafiltration membranes have retention ranges from 1,000 to 1,000,000 molecular weight.

Hudcova 56b, Brno 62100, Czech Republic

Cookies make it easier for us to provide you with our services. With the usage of our services you permit us to use cookies.
More information Ok