ABSOLUTE
FILTRATION INDUSTRIES CORPORATION
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ABSOLUTE
FILTRATION INDUSTRIES CORPORATION
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HYDROFLOW
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If
Your Questions Are Not Answered Below
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Answer: Yes, our scrubber pump is designed with special clearances to allow the media to pass through without damage to the media. This pump is the major mechanism for cleaning the media. As the media passes through this pump and comes off the tips of the impeller at a very elevated velocity, a high shear is produced that strips contaminates off of and out of the media. Filters that just fluidize their beds, but do not impact the media or move it at a very high velocity, can not achieve the full cleaning that is accomplished by our pump.
How is a nut shell filter that uses a mixer to clean the media, different than your method of using a pump? Answer:
Nut shell filters that use mixers or agitators are able to stir
& fluidize the media within the space of the vessel; however,
this alone does not provide media impact, nor the high shear,
that is produced within a pump turning at 1800 rpm. It is the
velocity that the media is traveling when it comes off of the
tips of the pump impeller that creates the high shear and therefore,
the media cleaning. The media moving from the pump through the
scrubbing vessel and back into the vessel has a velocity greater
than fifty miles per hour.
How does your filter ensure that all of the media participates in the clean-up? Answer:
After sending the media through the scrubber pump and along the
outside of the scrubber screen, it reenters the filter vessel
near the bottom. As the return water, with the media, reenters
it is turned tangentially to the outside vessel wall, creating
an upward toroidal flow within the vessel to the pump. At the
same time the inlet water enters the bottom head to ensure that
all of the media rises into the toroidal flow path.
What about a filter that puts the media back into the vessel, in the center, just above the media bed; won't this ensure that all media participates in the cleaning? Answer: No, the jetting of the return media down into the center of the bed through a nozzle, will create a rolling effect along the bottom flat screen. This rolling flow path does not get the media located on the bottom outside edges to fluidize and participate with the media going through the pump. Therefore, this part of the bed will "die" and no longer be available during filtration; causing the flux rate of the filter to rise. When part of the bed no longer allows liquid to pass through, the entire volume must then go through the remaining area. This can cause the flux rate to change from a design rate of 13.5 gpm to as high as 18 gpm; this would make their filter efficiency decrease from their stated 95 percent removal rate to a 60 or 70 percent removal rate. Over time they will have to replace the entire bed of media.
What is your expected media attrition rate? Answer: With the Hydroflow's multi media black walnut shells, the attrition rate will be ten (10") inches every eighteen (18) to twenty four (24) months; depending on the number of backwashes set into the system. This is the lowest media attrition rate of any of the nut shell filters.
How does your attrition rate compare with other nut shell filters? Answer: As stated above, our filter will not normally need any media added until after the first year; then every year or so, after that. Most other nut shell filters require that you add 5%, of the entire bed, after the first ninety days and then 7% to 10% every year thereafter.
Do you force set the media bed after backwashing? Answer: Yes, force setting the bed helps maintain a homogeneous pore throat or uniform size of media particles through the entire depth of the bed. If the bed is allowed to settle by gravity, then the large particles ( heavier) will settle at the bottom and the small particles (lighter) on the top. This stratifying means that the media on top will be tighter and therefore do all the filtration and as the water passes down through the large media particles, in the bottom of the bed, no filtration will take place. Therefore, when the first few inches of media get full of dirt the filter will need a backwash, although most of the media has no loading at all. You will see this effect by a lot of short cycles in the backwash time. Back when the first nut shell filters were built, they "force set" the media bed by drawing the water out through their clean water screens and set the media bed in the vessel with the high velocity of the media cleaning pump; this caused the screens to plug. The Hydroflow's, proven design, allows it to "force set" the bed without any plugging of it's clean water outlet screens.
Does your filter require continuous venting during filtration? Answer: No, continuous venting reduces "Through Put Efficiency" and would require oil to be refiltered or an excessive amount of liquid added to the backwash. The Hydroflow vents just prior to starting the scrubber pump and sends all the free oil and gas to the backwash tank, thereby removing it from the system, while keeping backwash fluid at a minimum.
Why is your multi-grade media better than a filter that uses English walnut shells & pecan shells? Answer: Our multi-grade media is made of two different sizes of "eastern black walnut shells". By having some smaller media particles, the space between all particles is reduced and provides for more uniform openings for the water to travel through; thus providing a higher removal rating. The "eastern black walnut shell" media has a resistance to rupture and modulus elasticity 10 times greater than English walnut or pecan shells. Because of the durability and quality characteristics, of eastern black walnut shells they have proven their ability to stand up and perform. Our media, not only, last longer, but do a better job in removing oil.
Can you use chemicals with this filter? Answer: Although, chemicals are not normally required to achieve fine filtration or media clean-up, they can be used. No special set-up or adjustments are required in order to use chemicals in the Hydroflow filter. However, caution should be used to insure that none of the chemicals contain surfactant, as these can cause the filter to loose efficiency.
What kind of oil & solids effluent will this filter produce? Answer: This will depend upon the amount of oil & solids in the affluent; normally we expect to see a beta rating removal efficiency at 5 microns of 98.9%. In oilfield produced water we would except to see the effluent to have less than 5 m/l of filterable oil and less that 2 m/l of solids greater than 5 microns. This assumes that the affluent is within our normal loading and distribution of particles by size and weight is also normal.
Will the filter recover if it is shut down or has a power loss during the scrubbing cycle? Answer: Yes, the Hydroflow can be shut down during any step of the cleaning cycle and it will restart to complete the entire scrubbing cycle. However, it is recommended that the filter not be shut down during the scrubbing cycle if the vessel is to be drained or service is to be performed.
The water going through my filter can be as high as 90 to 95 degrees C. Will this pose a cavitations problem in the overhead scrubber pump during backwashing? Answer: No, the scrubber pump is always flooded prior to it coming on and has the vessel pressure at its suction; therefore, there is no cavitations problem.
I have some concern over the design of the media support screens. How do they react to thermal expansion? How does it maintain its gap spacing? What is the collapse pressure differential of the screens? Answer: The Hydroflow uses round tubular support screens which are not welded to the vessel and have clearance for outward expansion. This design allows for expansion it all directions. As to the gap between the bars of the screen, we see no problem if some small amount of expansion closed these gaps, because its purpose is only to hold the media and not allow it to exit with the clean water. Since we have a large amount of surface area in our support screens, no reduction in water flow would occur. Our support screens are designed to withstand a differential pressure greater than the maximum pressure that the feed pump can produce when shut-in. However, our screens will always be designed to withstand a differential pressure greater than the coded stamp working pressure of the vessel.
Do you ever dead-head the feed pump, if so how long? Answer: No, the feed pumps are never shut-in with the Hydroflow filter. In fact, the feed pump is not only never shut-in (dead-headed), but is never turned off. It runs all the time and takes the same flow rate when filtering or when backwashing.
We would like to have 50% capability on stand-by; could we use three filters, with two providing 100% of the required flow? Answer: Having a filter on stand-by may not be the best solution for the following reasons: First, the Hydroflow requires the same flow rate all the time. Since the same dirty water rate is needed to backwash or clean the filter, there may not be any additional water to switch to the offline filter. For the short time that two are providing the 100% down stream requirements, the filter being backwashed will need 50% inlet flow, thus a 150% inlet flow will be necessary. If the inlet water supply is over sized by 10%, then a small storage tank, or an increase in the inlet tank size, could handle this problem. If no additional inlet water is available, then the water for the backwash must come from the filtered water. This would add an additional tank and a pump or some valves. Secondly, leaving a filter offline for a long period of time may cause additional problems that are not encountered with filters that are operating 100% of the time, such as bacteria growth etc. However,
if having an extra filter is needed to ensure no change in the
thru-put because of maintenance or repairs, then having a spare
may be the only solution.
How often does the Hydroflow filter backwash? Answer:
The Hydroflow filter will normally backwash once every day (every
24 hours).
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STAGE™
Skim Tank Augmented by Gas Eductor System |
FLOWGUARD
™
Automatic Backwashable Filter (ABC) |
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