International Appliance Manufacturing 2008 - (Page 17) dropping the product. Because WOB-L pumps do not use liquid lubricants, they can run in any orientation. This gives the product designer leeway in placing the pump inside a product. Low-cost mounting and isolation can be achieved by capturing the pump inside an enclosure with elastomer components and/or springs. This works well when pumps are ordered in a high enough volume to allow the tooling of custom mounting features. For lower production volumes, standard, off-the-shelf isolators are available that can be threaded into mounting feet for most pumps. 4. Operating Life Be straightforward about your expectations for a pump’s service-free life. Because of their application versatility, WOB-L piston pumps may be designed for anywhere from 500 to more than 30,000 hours of service-free life, depending on the ambient temperature, operating speed, type of motor used, and a variety of other factors. Many times, larger WOB-L units are serviceable to further extend unit life. Piston cups and stationary seals are the major wear parts. Be sure to let your pump manufacturer know if serviceability is required so that the pump can be chosen or designed accordingly. 5. Environment Typical ambient temperatures for WOB-L piston pumps are from 50º F to 104º F (10º C to 40º C). However, special designs can operate in temperatures as low as minus 40º F or as high as 212º F (minus 40º C to 100º C). Describe the air surrounding the pump: clean, dusty, gaseous, etc. Also determine the relative humidity. This information will help determine the type of filters required, as well as recommended seal materials. 6. Media to Be Pumped Chemicals, volatile gases and moisture in the air, as well as the media temperature will affect pump sizing and construction, especially of the piston cups, the primary wear component in a WOB-L pump. The cups are compression molded and may include a variety of materials depending on the application. For example, if the application requires exposure to condensed moisture, piston cup materials used for general purpose applications will rapidly disintegrate. Pump manufacturers have conducted extensive life testing under various combinations of temperatures, pressures, strokes and humidity conditions with hundreds of different composite blends, resulting in development of specialized materials for each type of application. Make sure that these environmental factors are communicated to the application specialists when selecting a WOB-L pump to ensure that the appropriate piston cup material is selected for your application. 7. Sound and Vibration Sound and vibration can be a significant challenge when applying a pump. When operating alone, with intake and exhaust piped away, WOB-L pumps in fractional horsepower sizes will typically range in noise level from about 40 dBA to about 60 dBA. Proper application of inlet mufflers and isolation mountings will help limit the noise in the end use application. Noise and vibration transmission through a device can be complex. It often requires specialized skills and tools to determine the best ways to prevent transmission of unwanted vibrations and acoustic noise that can result from gas pulsations, valve action, rolling element bearings, and various flow-path restrictions encountered downstream of the pump. Your WOB-L pump supplier should have the knowledge, skills and tools to provide this service and reduce noise to the low 30 dBA range. Factors as simple as stiff hose connections can transmit vibration that results in noise being emitted from the hoses and components to which they are connected. System resonances can greatly amplify the vibrations and resulting noise level of a device even with a well-balanced compressor. Take advantage of the compressor supplier’s noise and vibration reduction services to ensure that noise and vibration levels are reduced to satisfactory levels. 8. Agency Requirements UL, CSA, TUV, FDA, ISO and other regulatory agencies require that pumps and the motors used with them meet rigorous safety standards. Suppliers with certified labs can test and evaluate their products International Appliance Manufacturing 2008 17
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