Quiz Corner: The most common variable speed drive configuration is…

Select the most common variable speed drive configuration that is typically found in the process industries.    

A. One operating pump and one destination

B. One operating pump and multiple destinations

C. Multiple operating pumps and one destination

D. Multiple operating pumps and multiple destinations

Plant utility systems such as cooling water, hot water, brine and liquid chemical systems provide or recirculate liquids to multiple pieces of equipment that are often in multiple locations. While often highly visible in the plant, these systems are typically limited in number so Answer B and Answer D are not likely correct. 

In process plants, liquids are often pumped from one piece of equipment to one destination. In some applications, multiple pumps running in parallel can be found in process plants to pump large amounts of liquid. However, the majority of flow streams in typical process plants are relatively small and involve operating one pump to transport liquid. Therefore, Answer A would be the best answer. 

Additional complicating factors

Knowing and recognizing the most common variable speed drive configuration provides you with a template to quickly locate potential applications. In particular, one operating pump transporting liquid from one location to one other location throttled with a control valve should reflexively come to the fore as a potential variable speed drive application. 

Potential applications are preferably identified prior to construction when their technical advantages and economic viability can be demonstrated in a straightforward manner before funds are expended. However, many potentially viable variable speed drive applications in operating plants can be easily identified by examining the plant process and instrumentation drawings.