Determining The Minimum Safe Flow Line For A 5 Stage, 350 Hp Variable Speed Centrifugal Pump
An energy survey revealed that two, a main and spare, 5 stage, 3560 rpm, 350 hp, centrifugal pumps were well oversized for their application. The pumps are used to inject waste water into several disposal wells. Due to the excess capacity of these pumps, a spill back line and control valve had to be installed and used continuously to maintain a minimum safe operating flow rate. To reduce the energy consumption, a project was proposed to install a variable speed drive on one of the injection pumps and operate it at reduced speeds as required by demand. To complete the economic analysis we were asked to determine the minimum safe flow operating speed at the rated operating speed and use this information to set a minimum flow line for all potential pump speeds. This minimum flow line was used to determine if the spillback line would still be required at the reduced operating speeds. We will present our methodology for determining the minimum safe operating flow using a simple field test method and API 610 Centrifugal Pump Standard vibration guidelines. This methodology can be readily applied to most types of centrifugal pumps.
Perez, Robert (2007). Determining The Minimum Safe Flow Line For A 5 Stage, 350 Hp Variable Speed Centrifugal Pump. Texas A&M University. Turbomachinery Laboratories. Available electronically from