Chemical Processing - September 2007 - (Page 51)

2. Reservoir size and usage rate. These data can be used to support calculations of overall system flow rate. In addition, they’re particularly important in applications that recirculate oil through a side-stream (kidney loop) filtration system because the filter must be able to adequately clean the fluid within the required reservoir turnover rate and time. If the filtration system is undersized, the contaminant either will enter the system more quickly than the filter can process it or will linger and settle in the reservoir to create a lasting contamination issue. By specifying a filter that cleans the contents of the reservoir more quickly and more frequently, you can avoid system damage from residual or acute contamination. This attribute is particularly important for systems with smaller, modern reservoirs with higher usage rates. The traditional rule-of-thumb for reservoir turnover is to remove and clean 10% to 20% of the fluid per hour. Today, filtration systems can be specified for an even higher turnover rate. To accurately assess the performance of a filtration system fitted to a re-circulating system, test the purity of the fluid as it enters the reservoir and exits the filtration system. 3. Viscosity. Analysis of the process or lubrication stream’s viscosity also is essential to proper filter fitting because viscosity can affect flow rate. While water and other low-viscosity fluids experience little variation in viscosity, the viscosity of other fluids such as oils can change significantly with the operating temperature (or temperature variations throughout the system). So, a filtration system that processes higher viscosity fluids (Figure 1) requires special attention for a sound specification fit. Viscosity can be an important factor, for instance, in turbine and gear oil applications. >> Diesel filtration skid Figure 1. This unit provides particulate removal to 3 micron and water removal to less than 100 ppm while handling flows from 50 to 800 gal/min. A filtration system that processes higher viscosity fluids requires special attention for a sound specification fit. Ideally, the filter size specification, as well as pump and motor specifications, will be based on the measured or predicted viscosity of the liquid at the time it flows through the filtration system. Equipped with this information, it’s easier to produce a reliable prediction of the fluid’s flow rate and the performance demands on the system. 4. Material compatibility. The filter vessel and element obviously must suit the fluid. Otherwise, filtration system parts could deteriorate and enter the fluid www.chemicalprocessing.com stream — meaning that today’s O-ring could become tomorrow’s contaminant. This parameter is particularly important in applications using synthetic and ester-based lubricants, although compatibility also should be considered with systems using mineralbased fluids. Consider all aspects of the filter, including the vessel, adhesives (if present), seals, filter media, and instrumentation (gauges, flow sights). A compatibility check can be done quickly and easily by comparing filtration system materials with those currently used in the process. If the system has been successfully operating, then a filter fabricated of the same materials should seamlessly integrate with the existing system. The fluid’s supplier, of course, can provide information on compatibility and hazards. 5. Pressure and differential pressure. The system’s operating pressure (pump pressure) determines filter vessel sizing. It’s a good practice to size the filter vessel for a pressure at least 33% higher than the maximum operating pressure to ensure that the vessel is well within the limitations of its pressure rating. Filter element sizing is based on the differential pressure across the filter. To accurately size a filtration system, the supplier will take into account the type of pump (such as positive displacement or centrifugal), existing relief valves and desired flow rate. The supplier also may recommend the installation of a differential pressure gauge on each filter, a pressure gauge on the discharge side of each pump and a vacuum gauge on the suction side. These gauges will greatly enhance the troubleshooting of system problems. 6. Existing pipe line size. It sounds simple, but it’s often September 2007 • 51 http://www.chemicalprocessing.com

Table of Contents Feed for the Digital Edition of Chemical Processing - September 2007

Contents From the Editor Field Notes In Process Energy Saver Compliance Advisor Succeed at Simulation Rethink Your Approach to Process Safety Avoid Blending Blunders Get the Right Cartridge or Bag Filter Wireless Proponents Take HART Membrane Boasts Material Benefits Process Puzzler Plant InSites Chem Show Product Preview ISA Product Preview Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - September 2007

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.