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A Common Sense Approach to Separations and Filtration When Oil and Solids Are Present
Learn easy yet effective ways that you can improve the filtration systems in your company to save you time, money and effort.
By Rick Terrien,
Process Cleaning
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Figure 1
Tightly spaced media in a traditional oil separator rapidly plugs up when solids are present. This type is commonly referred to as a tortuous path coalescer.
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Industrial process fluids are engineered for specific beneficial purposes such as cleaning or cooling. The efficiency and benefits of these fluids goes down the longer they are kept in use and as contamination increases.
It is important to take a common sense approach to deploying treatment options for industrial process fluids when oil and solids are present. There are five simple guidelines that can help guide you to a better, more efficient filtration system:
1. Identify and plan for all types of contaminants that need to be removed
2. Deploy the most efficient, lowest cost treatment component at the appropriate location in the treatment system
3. When oil and solids are present, use primary treatment systems designed to remove these contaminants simultaneously and without consumables
4. Make downstream filtration systems much more effective and less costly by first removing oil and larger solids
5. Consider separation options after barrier filters
Traditional approaches to treating industrial process fluids containing oil and solids typically fall back on what has been done previously rather than on analyzing the problem and deploying the most efficient tools. This can sometimes lead to unnecessary expenditures and more labor-intensive work. Therefore, it's important that you continually analyze your company's filtration needs in order to determine if a more efficient process is needed.
Plan for All Contaminants That Need to be RemovedDuring use, industrial fluids become contaminated with oils and solids from the manufacturing process. When solids and oily contaminants need removing, operators typically turn to barrier type filters such as bag and cartridge filters. If these plug up too rapidly due to oil, a traditional oil coalescer is often positioned in front of the filter. Once deployed, these initial ideas tend to stay deployed despite high labor and maintenance costs and high consumables costs.
A more measured, common sense approach to removing contaminants from industrial process fluids can yield significant increases in efficiency, while removing much of the cost of maintenance and consumables.
Deploy the Most Efficient Primary Treatment StepWhen the amount of oily contaminants is high enough that small dragout devices such as rotating belts and disks are no longer effective, most operators opt to try a traditional oil coalescer. These devices are typically packed with closely spaced plastic media meant to attract and remove passing oil. This type of oil removal system is called a tortuous pathway coalescer, named for the tight spaces between the plastic media. Industrial process fluids are pumped through this media at a predetermined flow rate, which determines the amount of retention time the treated fluid has inside the separator and the velocity of the treated fluid through the media. In theory, the oil grows or "coalesces" on the media until the oil droplet is of sufficient size that it floats up and out of the flow being treated.
All-too-often, the problem with this approach is that the fluids being treated contain not only oil, but also a matrix of small solids. This mixture can quickly begin to plug the coalescer media (see Figure 1). As the plugging increases with each use, the velocity of the fluids through the media by necessity must increase. Higher fluid velocities through the remaining unplugged pathways soon exceed the design specifications for retention time. Oil removal efficiency continuously decreases. Soon, the entire package of plastic media blinds over, at which time the tortuous pathway coalescer must be taken out of service and manually cleaned. When deployed in front of a filter, tortuous path oil coalescers can quickly become more like filters in front of filters, adding unnecessary maintenance and labor costs.
A common sense approach to separations and filtration should include the deployment of the treatment components at their most effective and lowest cost positions in the treatment system.
When oil and solids are present, a more appropriate use of "open channel coalescers" is
indicated for use as the primary treatment (see Figures 2a and 2b). Unlike traditional oil
coalescers, these open channel systems allow floating oils and settleable solids to separate from the treatment flow by gravity only. This greatly reduces the use and cost of consumables, while also greatly increasing the efficiency of downstream treatment components such as filters.
Open channel coalescers are designed specifically for removing floating oil and settleable
solids with no plugging and no consumables (Figure 3). These are simple, durable devices
designed to operate in a treatment environment containing both oil and solids. As the treatment flow passes among the open, non-plugging separation channels, oils float up and are diverted from the flow. At the same time, small, settleable solids are dropping out of the flow by gravity. Open channel coalescers are designed to accomplish these gravity separations simultaneously. Because these systems do not plug up, very little maintenance or labor is required to keep them operating at full efficiency.
Solids and oils separate by gravity only inside open channel coalescers. These separators are designed to capture and divert settleable solids from the flow to a capture zone at the bottom of the separator. Similarly, floating oils, which have a lighter specific gravity than the fluids being treated, are captured and diverted to a capture zone at the top of the separator. The diversion plates use no moving parts to coalesce, or cause to come together and enlarge, small oil droplets and small solids into larger, more readily removable particles as they drop out of the flow.
Well designed open channel coalescers provide automatic oil discharge by gravity to a waste oil capture drum or tote. Solids are typically removed as needed, also by a gravity drain, and can be filtered to produce a dry waste rather than wastewater that needs further treatment.
Deploy Barrier Type Filters for Fine FiltrationWith the bulk of the oils and solids removed first by the open channel coalescer, downstream filters can now operate as designed, removing small solids and fines suspended in the treatment flow without needing unnecessary and costly replacements due to plugging by oil and larger solids. Operators can specify an appropriate filter with the desired pore size without fear of these filters quickly plugging up.
Pore size for barrier type filters such as bag filters and cartridge filters are typically rated in the micron size of the openings in the filter. Some industrial process fluids, particularly machine coolants, can not be barrier filtered below specific micron ratings, typically 5 micron, because valuable chemical components within the fluids such as rust inhibitors, etc. are filtered out.
Separation Options After Barrier FiltersWhen ferrous or magnetic contaminants are present, non-barrier filters such as inline magnetic separators can be effectively used on the clean, discharge side of a barrier filter. These components remove magnetic contaminants to the sub-micron level also without any consumables. The treatment flow passes around the magnetic separator and is not barrier filtered, keeping valuable chemical components of the source fluid intact (see Figure 4).
To Sum UpIndustrial process fluids such as cleaners and machine coolants can be treated efficiently and at a reduced cost by first analyzing what type of primary treatment device is to be deployed. Open channel coalescers give operators the ability to remove floating oil and settleable solids using no consumables and requiring very little maintenance or labor. Subsequent downstream treatment devices operate at higher efficiency and lower cost. Simple, effective primary treatment steps can remove the bulk of the contaminants while increasing the efficiency and lifespan of downstream filters.
Rick Terrien is president and co-founder of Universal Separators, Inc. (Madison, WI). Universal Separators holds seven patents in environmental separations and last year was awarded Small Business New Product of the Year for the U.S. by the National Society of Professional Engineers. He can be reached toll free at (800) 663-2167, or visit the Web site at www.smartskim.com.
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