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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

Reducing Coupling weights in Large Motor Driven Pumps

coupling Pump Coupling Assembly
One of the major issues in designing large motor driven pump applications is minimizing the overhung weight on the pump rotor.  Motor or gearbox drives are designed and sized independently of the driven unit.  They are based on motor frame size and/or gearbox frame sizes and the drive component manufacturer has no information on the actual driven unit.  In motors, the design of engineered motors is based on years of experience and rules of thumb.  The motor rotor is significantly heavier than the pump rotor, thus requiring it to be much larger in diameter than the driven unit size to support the rotor weight and give an acceptable bearing surface area.  It is not unusual for the motor output shaft size to be twice the input shaft size of the driven unit shaft. Size Matters The shaft size differences are basically a product of economics.   It cost money for a motor...
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Resolution of Chronic Cooling Tower Fan Vibrations

Resolution of Chronic Cooling Tower Fan Vibrations
Traditional rotating equipment mounted at grade use the mass of a foundation and grout to reduce vibration and provide support and stiffness. However, cooling tower fans must be elevated many feet above a basin of water which sometimes puts them “out of sight and out of mind”. Cost and practicality prohibits concrete and grout, thus most cooling towers are constructed by bolted wood and / or fiberglass elements with a fabricated steel sub base supporting motor, gearbox, and blades. As a result, cooling tower foundations are much less stiff than traditional rotating equipment. This is usually not an issue because the low speed of the fan (usually 60 rpm to 140 rpm) does not usually produce large forces. Motors and gearboxes used are generally made to the same precision levels as other general purpose machinery regarding balance, runout and dimensional tolerances, so the imbalance and forcing functions are usually low.  As...
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Oil System Cleaning - Making Oil Flushing a Predictable Procedure

Oil system cleaning or Oil Flush has humbled many Machinery Guys . What seems like a very simple task often turns out to be to the Achilles' heel and often unpredicted and embarrassing critical path of the machinery overhaul. The purpose of this article is to outline improvements that we have implemented to the old-fashion "Flush and Pray" procedure that will make the planning and execution of your routine oil flushes a predictable and successful part of your machinery overhaul. After finding ourselves in the "Flush and Pray" situation and trying to explain the overhaul start-up delay caused by flushing delays several times, we worked on ways to improve oil flushing procedures and effectiveness. We developed new methods and procedures to assure success in the allotted time. These new methods and procedures were used and constantly improved over time. The "Flush and Pray" procedure has been replaced with improved methods and...
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Randy Passman & Stanley Fussell

Stanley B. Fussell

Sorry for taking so long to respond. I had some health issues that postponed my response. The risk associated with not cleaning th... Read More
Monday, 14 October 2013 17:17
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The Potential Pitfalls of Fabricated Machinery Foundations

A new process unit was designed and built by a petrochemical manufacturer. As part of the project, two 50 horespower blowers were installed. Rotating equipment of this type is traditionally installed at grade on an engineered monolithic concrete foundation with rebar and anchor bolts. A suitable soleplate or baseplate is then grouted to the foundation to rigidly support the motor / blower unit. This insures that alignment between the motor and blower is maintained. Also, since the mass of the foundation is usually designed to be five to seven times the mass of the mounted equipment, residual vibration is reduced as well. During the design phase of the project the piping connection of the vertical vessel from which the blower took suction was located on the fourth floor of the unit. Instead of locating the blower at grade on a foundation as described above and running process piping to the blower...
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2280 Hits
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