Iron Transport in Condensate Polishing Systems Iron transport reduction is the important function that a Powdex system provides over a deep bed system.  The ability to provide both filtration and ion exchange in a continuous regeneration operation is the hallmark of a Powdex system.

Iron particulate from corrosion (CRUD) ranges from 10 to less than one micron in size. It is important to note that 99% by weight can be removed by capturing particles over 1 micron.  The average size in neutral pH systems is 2-3 microns and in elevated pH systems is 5-7 microns.  With the increased use of amine based systems, particle size is increasingly in the 1-3 micron range.  Graver Technologies recommended precoat (0.2 dry lb/ft2) is designed as a 90% removal tool.  This means that some of these suspended solids, that pass through the precoat, must be captured by the element media.  Because of superior particle capture, pleated media sheets are now preferred.  These polypropylene sheets are made to given pore sizes and pleated and calendared together for various micron ratings.  The user may dictate the pore size dependent upon the amount of iron to be transported.  Graver Technologies uses absolute rated sheets of the named micron rating to make its pleat pack.  Bubble point testing is performed to ensure the media will stop greater than 99% of all insoluble particulate.  There are minor differences in pore sizes between manufacturers and samples should be taken to determine the performance of individual manufacturers.  One filter manufacturer bases its core marketing strategy on being more "absolute". They routinely use smaller micron sheets named with the rated micron size to be sure they are tighter. The DualGuard III is manufactured in 10, 5, 3 and 1 micron sizes. One of the best methods of filtration to separate particulate of different sizes (and prolong backwash interval or media life) is series filtration. Series filtration provides a primary filter or surface to first capture larger particulate and a secondary filter or surface to capture the smaller. Graver Technologies DualGuard III provides series filtration with the precoat maintained on a shroud, allowing the full surface area of the pleated media to capture only the smaller particles. The other manufacturer accumulates precoat directly on the pleats and does not obtain series filtration.

Precoatable Bakwashable Systems System operation must be considered. Graver Powdex systems are increasingly recognized as the most reliable precoatable systems operating. Septa design provides reasons for this:

Precoat Uniformity
Graver Technologies septa precoat evenly from bottom to top. The unique DualGuard III has provided the most consistently even precoats ever. There is an equal differential pressure profile developed along the entire length of the element. Other manufacturer's filters cannot maintain this profile and precoat more heavily on the bottom and are thinner on top. We call this the "Christmas tree effect". Consider a single precoat cycle with the "Christmas tree pattern. While initial flow is mostly drawn to the bottom of the filter, finer particulate filtration is obtained through the thicker layer of powder. As the bottom becomes fouled, flow gradually increases up the element length and less particulate filtration is obtained from the powder barrier. Near the end of the cycle, predominant flow is through the thinly precoated (or nude) top area. The filter media itself is becoming fouled and the higher velocities imbed particulate in the media. Backwashing is not as effective, thus element life is shortened. Graver Technologies elements can operate over 100 cycles because powder and crud are not embedded in the pleat creases.

Uniform Loading and Structural Strength
is important to prevent leakage of resin into the steam generator. Graver Technologies controlled differential pressure profile produces uniform velocities along the length of the element. Without this profile, velocities will initially be higher at the base of the element creating higher thrust vectors at the bottom. As the element becomes fouled, the velocities follow the point of lowest differential pressure as it moves upwards. This non-uniform stress has caused breakage in competitors' filters. Graver Technologies hardware system provides full flow guide rods and Sealfast fasteners to provide element strength and withstand many high velocity backwashes.

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Non-Precoatable Backwashable Systems

The design features of uniform differential pressure profile, ease of backwash and series filtration also benefit non precoatable systems. As discussed above, the differential pressure profile loads the element evenly throughout the cycle without creating higher velocities at different elevations. Backwashing is easier because our surface areas are sized to match the backwash capacity of each system. The DualGuard III offers series filtration; with the shroud capturing larger particulate leaving the pleated area clean for only smaller particles. The smooth surface of the shroud is even easier to backwash than the area between pleats. The success of a Powdex system depends on:

1. Precoat Uniformity and Thickness
2. Precoat Composition
3. Precoat Application Procedure
4. Element Design
5. Element Cleanliness
6. Plant Operating Conditions

While we have discussed only some of these here, we can assist you with all of these. Graver Technologies and our sister company, Graver Water work hard to provide the best and most reliable condensate polishing technology. Any of us listed can help.

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Superior Products & Global Reach

Whether your business is around the corner or around the world, Graver Technologies can support you with superior products and services. Our ion exchange, adsorbent, filtration and membrane products deliver exceptional performance in some of the harshest process environments in North America, Europe, Asia, the Pacific Rim, South America and Africa.

Graver Technologies is a member of The Marmon Group of companies, an international group with more than $6 billion in annual sales. Around the corner or around the world, Graver Technologies is a fast-growing company with the technical resources and financial strength that make us the perfect partner for your business.