Appliance Design - July 2008 - (Page 33)

MOTORS & PUMPS Mounting systems can be as simple or complex as needed to meet the specific needs of an application. When noise and vibration are important issues, careful attention must be paid to both the mounting system and piping or hose connections to ensure that vibrations are not transmitted to surrounding structure inadvertently. In the case of reciprocating pumps, there is inherent vibration due to torque pulsations that result from the motor speeding up and slowing down on each revolution in response to the build up of pressure in each cylinder and the subsequent intake of air at atmospheric pressure. Care has to be taken to isolate the compressor so that minimal vibration is transmitted to the surrounding structures and enclosures to minimize noise and vibration of the device or system. In larger pumps, an isolation system will typically involve elastomeric members. These provide some damping and snubbing capability to prevent impacting of metal parts during shipping and handling or under startup and shutdown conditions. In smaller pumps, standard elastomeric mounts are often used to provide a measure of isolation and to withstand shock loads. Often overlooked are vibration transmission paths created by piping or hose connections to the pump. These need to be flexible enough to provide isolation, just as the mounting system does. In small OEM pumps where cost is critical, isolation systems may consist of simply an elastomer squeezed between recesses on each side of the pump housing and the inner surfaces of the enclosure in which the pump is mounted, thus avoiding the need for fasteners. The elastomeric members must be carefully designed so that they are soft enough to provide adequate isolation and yet strong and stiff enough to withstand shock loading from handling and dropping the product. Pumps, such as the WOB-L, that do not use liquid lubricants, 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, offthe-shelf isolators are available that can be threaded into mounting feet for most pumps. 4. Operating Life. Be straightforward about the expectations for a pump’s service-free life. Custom 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. Often, larger units are serviceable to further extend unit life. Be sure to let the pump manufacturer know if serviceability is required so that the pump can be chosen or designed accordingly. 5. Environment. Typical ambient temperatures for pumps range from 50 DegF to 104 DegF (10 DegC to 40 DegC). However, special designs can operate in temperatures as low as -40 DegF or as high as 212 DegF (-40 DegC to 100 DegC). Describe the air surrounding the pump, whether it is clean, dusty, or 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 sealing materials. For example, the piston cups on the WOB-L are compression molded and may include a variety of materials depending INTRODUCES FANLESS 80+ QUIET Up 10dBA total system noise reduction COOL Cooler vestibule temperatures increase component life LOW PROFILE Smaller cabinet depth means savings on materials SAFE No exposed moving parts For nearly a century, Fasco has been designing and manufacturing what has become the industry’s most respected line of AC motors and Blowers. FASCO OFFERS ENDLESS OEM DESIGN SOLUTIONS for your products in: HVAC MEDICAL EQUIPMENT LAWN & GARDEN PUMPS HOUSEHOLD APPLIANCES POWER TOOLS and MORE FASCO 2401 E. Sunshine Springﬁeld, MO 65804 800-616-8721 www.FASCO.com Solutions. Selection. Support. applianceDESIGN July 2008 33 www.applianceDESIGN.com http://www.FASCO.com http://www.FASCO.com http://www.appliancedesign.com

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Appliance Design - July 2008 Contents Editorial Shipments/Forecasts News Watch Heating Elements Gas Technology Motors & Pumps Controls & Sensors Design Marts Association Report: AHAM Advertiser's Index

Appliance Design - July 2008

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