As severe weather events increase, cities need infrastructure that can handle stormwater beyond normal levels. Pump stations play a vital role in defending communities against stormwater, and the proper design of the pump station is critical. Farzad Ferdos, a computational fluid dynamics (CFD) specialist at Xylem, explains how Xylem helps design pump stations that can process larger volumes of water faster and more efficiently, at the lowest operating cost.
What does a pump station design include?
“A pump station design has different components. It includes a hydraulic design, focusing on flow conditions in the sump and at the pump intake. Then there is the monitoring and controls design, including pump controls and electrical parts, the practical design, including accessories and valves, and finally the civil design. A main goal of station design from our side is to make sure that the flow conditions are acceptable for Xylem’s pumps.”
What are some of the challenges customers face with pump stations?
“Most often when a customer says that a pump they have is not working the real issue is with the pump station design and not the pump itself. In these cases, the flow conditions in the sump and how the pumps are positioned and operating lead to the pumps not functioning properly.
What we need for successful functioning, besides a good pump, is a good station design and an appropriate control system. Without any of these components working properly with each other, there will very likely be problems. These can include pumps clogging, excessive pre-swirl, uneven velocity distribution at the pump intake, vortices or persistent floating of debris and sedimentation build-up. This can ultimately result in system failure.
When these elements work well together, however, you can achieve efficient pumping with the lowest operating costs possible and increased product life cycles.”
Are pump station design and pump technology usually well integrated?
“Not necessarily. Usually, we give advice on pumping technology early on. Our customers trust us to give them the correct pump according to preset operational conditions, such as flow, pressure, media type, etc. Unfortunately, for station design, they don’t always do the same.
As station design is part of the civil work, and it is usually performed by consultants. Some consultants have expertise in station design and can provide a specific solution for each project, but some use a standard model, which doesn’t necessarily adapt to the needs of the operation. In these cases, they will most likely have problems.”
How does Xylem help solve these problems?
“When designing pump stations, we do a thorough hydraulic analysis to ensure proper performance at all operating conditions. One way we solve this for customers is provide our standard predesigned station layouts, which are already tested. Another way is through computational fluid dynamics (CFD) software that can run flow simulations for any specific configuration.
We use this methodology to run different scenarios for a specific design. We can use CFD to create a completely new pump station design for a customer or to verify a station design they provide us with. This methodology is becoming more and more relevant and accepted as a station design procedure.”
Why is computational fluid dynamics so important in stormwater applications?
“Stormwater stations are usually large projects and have to be customized. They represent a huge investment for our customers, and at the very least they expect that we can guarantee the performance of our pumps. For stormwater applications, we can use CFD to ensure that the hydraulic conditions are in place for the pumps to perform as required.
Up until now, the only formally recognized tool for station design verification has been scale laboratory modelling. However, CFD is being more and more recognized, and CFD studies are increasingly requested by city leaders looking to ensure optimal operation of their pump stations, both in high and low flow conditions. Digitalization is affecting the whole industry and station design is definitely a part of this transformation, too.”
How do customers benefit from Xylem’s pump station design work?
“There are several benefits, and I would categorize them in terms of investment benefits, operation and maintenance benefits, and reduction in emergency or unplanned servicing.
Our pump station designs often result in reduced station dimensions, which reduces the investment required. For operation and maintenance, we provide the optimal hydraulic conditions for pumps, leading to improved function and reduced sedimentation. Our pumps and pump station designs also reduce clogging and the risk of pump station failure.”