Bypass Pumping Details Often Taken For Granted

By Jeff Griffin, Senior Editor | January 2011 Vol. 66 No. 1

“Temporary bypassing is what we do day-in and day-out. We have experience with a broad range of systems that have already been designed and successfully applied, and we modify those to fit the specific project. It is important not to reinvent what’s already proven technology, so we encourage new engineers to spend time reviewing available installation designs. New engineers benefits from our collective experience, and we benefit from their fresh insight. It is different than designing a permanent structure, so collaboration is critical.”

Askin said when a subcontractor is employed, typically the subcontractor is given the suction point, discharge point and a required flow and with that information the bypass subcontractor designs the system.

Understanding flow is the key to designing a bypass system, Askin believes.

“In addition,” he said, “because end suction centrifugals are affected by suction lift, this needs to be taken into account. When a system isn’t performing to the published curve, it is typically a suction lift issue. We help a lot of owners out after they have had a system installed by a company that didn’t understand this principle.”

Most common problems during the design process, Askin continued, “is not understanding flows and the redundancy.

“If a temporary system is required to handle 1.5 times the peak wet-weather flow and 100 percent redundancy,” he explained, “the system is impractically large. The difference between engineering a system and simply renting a pump to meet flow requirements is that an engineered system provides the exact equipment needed to efficiently meet system demands and potential overburdening without specifying over- or under-powered equipment.”

Noise control has become key in these systems, said Askin. Attenuated units with noise deadening insulation and hospital-grade mufflers to reduce the pump noise are used in areas where noise is an issue. These models are increasingly popular, particularly in residential applications, he added.

Turnkey
“Thompson Pump is a full-service pump company that designs and installs complete bypass pumping systems,” said Kirsten Petersen Stroud, marketing manager. “We have a comprehensive applied products division and numerous bypass specialists. From beginning to end, we provide everything from calculations, set-up, installation, HDPE pipe assembly, on-site support, pump watch, maintenance and tear down. We provide turnkey projects utilizing our years of expert experience and knowledge.”