Testing, Part Two—Performance Tests
Complete hydraulic performance tests were performed on each of the four Super Pumps and each of the four motors at KSB Halle’s Q-Loop Test Field, one of six state-of-the-art test fields at this location. Performance testing included the pump running continuously at four different duty points for two hours, explained Dr. Thomas Hennig, KSB’s test field engineer. The maximum speed (critical point) is a flow rate of 3,000 l/s with total head of 87 meters. At this point, the pump should absorb the power of 3,000 kilowatts (3 MW).
The highest absorbed power ever tested at the Halle facility is 3.4 MW, Hennig said. This test field has the capability to test up to 10 MW.
It was a goal to come as close as possible to a real-life situation in the pumping station. The total height of the Lee Tunnel test rig is 10.4 meters, including the original carbon cardan shafts of 1.2 meters.
Another challenge was that the clear height on this test field was limited to just 10.6 meters because of the maximum height of the cranes. Only 203 mm (8 inches) were available to maneuver, which is not a lot of space when it comes to moving such heavy equipment (see Image 4).
Each test lasted about five hours and required an additional cooling system, which KSB was prepared to handle.
“Within KSB, we have several test fields all over the world,” Ulmschneider said. “This test field in Halle is the only KSB test field that can allow for the electrical power, dimensions and functionality that can comply with all the testing requirements for this project. But even this test field needed extra cooling for the continuous two-hour test.”
KSB invested 18 million Euros in 2009 to build a testing facility that would accommodate pumps of this size. This included the test field, test field hall and XXL machining centers. Two cooling towers were built at that time, but space was made to accommodate six.
Two more cooling towers were added specifically for this project. “We doubled our cooling capacity to accommodate the long-term, two-hour permanent tests for this project.” Ulmschneider said. “When we built this test field, we made provisions—from cooling size and electrical power input size—that maybe we would need to test even larger pumps one day. Today, we don’t build many pumps that need 10 MW of power, but we are prepared for when we do.”
The first part of the performance tests involved two hours of continuous running at the specified 3,000 l/s. KSB measured the time gaps in 10-minute intervals. For the test to be successful, the average flow rate/total head should remain constant for two hours. The winding and bearing temperatures of the motor and bearing temperatures of the pump were measured. During the two hours, the temperatures rise. The temperature time test determines the estimate of the temperature values after a long period of constant running. Maximum limits were measured, not overloads.
The second part of the performance test measured one complete performance curve by changing the flow rates. This was measured four times at four different speeds: 326 rpm, 315 rpm, 166 rpm and 150 rpm. Four performance curves were determined. These tests also measured vibration, bearing temperatures and noises.
The final part of the testing involved measuring net positive suction head at a speed of 326 rpm.
“A performance test is normally a standard test of each pump, and we have a contract with the client for the guaranteed points,” Hennig said. “We give the client information about how the pump will run at these conditions. These tests show whether the specified tolerances can be fulfilled.”
The client was present to witness all the testing in every stage of the process.
Each of the four pumps could run differently. “We run it until we get it right,” Hennig said. “Sometimes, the pumps have to be adjusted or reworked to meet the client’s requirements.”
This test field includes a complete closed-loop system. Water travels through large tubes to reach the pump instead of other test fields that use open basins.
This Q-Loop Test Field runs approximately 100 tests per year and can test pumps with a capacity of up to 5,043 l/s with a maximum head of 600 meters.
Andrea Gros is an industrial engineer and is KSB’s head of production for large pumps. She was responsible for coordinating the schedule for the performance testing, a process that took a year and a team of five engineers to accomplish. Gros coordinated all the experts, designed the setup for testing, scheduled the six-week testing process, verified all the technical specifications and was the primary problem solver.
The most challenging aspects, she said, were the weight of the pump, the size of the pump, the electrical power needed and the vertical installation for a wastewater application. Every tool and accessory for the tests had to be specially designed.
Gros created a detailed schedule, which included a setup simulation to determine how long assembly and disassembly of the pump and test rig would take. The pumps were delivered in parts, and the setup had stages. The pump was assembled on the test field, and then the test rig support frame (tower) was built around the pump. After this, the impeller was installed. Then the bearing bracket was added, followed by the remainder of the tower and the motor.