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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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Your pump's Mean Time Between Repairs (MTBR) is what?...Or what should it be...

Your pump's Mean Time Between Repairs (MTBR) is what?...Or what should it be...
Many of the tourist spots around the world have panhandlers. Some of the more creative ones stand on street corners advertising that they will tell you where you got your shoes, for a dollar. Of course it turns out that “you got your shoes” at the corner of Bourbon and St. Peters - or wherever you happen to be standing at the moment. It’s a play on words. However, being able to predict your pump Mean Time Between Repairs (MTBR) is not a play on words. Indeed it can be done quite accurately. I am often asked to do a facility rotating equipment reliability audit. After all, the plant’s management has heard that top tier plants have pump MTBR’s in excess of 100 months. They would be happy to have half that number. Hence the need to understand the major MTBR influencing factors. The main broad reliability categories that determine what...
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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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Recent Comments
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
Guest — EVELYN SERRANO

What are the potential risks a...

Can you please tell me what are the potential risks that can occur before, during and/or after the process? How do you mitigate s... Read More
Tuesday, 08 October 2013 17:11
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Pump Trips and Check Valve Closure

Pump Trips and Check Valve Closure
Pump Trips and Check Valve Closure Systems running multiple pumps in parallel can undergo serious equipment and piping damage during a pump trip caused by a power outage or pump mechanical failure. Uncontrolled reverse flow in the system can occur and if improperly selected check valves are used it can result in pumps running backwards or transient pressure spikes in the system, i.e., water hammer. Water hammer will occur if reverse flow occurs prior closure of the check valve and the effect increases with higher reverse flow velocity. Becht has worked with clients on analysis of the design of their systems, e.g., a water treating facility running multiple 52,000 gpm pumps in parallel, a seawater pump station pumping cooling water through a several mile pipeline to an inland facility and a boiler feed water circulation system for a 3000 psig forced circulation boiler. In a three pump system (two operating and...
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