Deep Tunnel Super Pumps - Pushed to the Edge

Innovative design, engineering and high-performance testing highlight the KSB pumping system to be installed 85 meters beneath the River Thames.

Written by:
Michelle Segrest
Published:
October 1, 2013

“During the early stages, the client often needs help defining solutions for their particular project,” Ulmschneider said. “We can customize the project to meet specific needs. KSB is the only company that has this kind of variety, which is an advantage for us. Every owner, every utility and every location has different requirements and challenges, so this range is critical. A company will invest billions into a project like this, and the pumps have to work.”

Building the Lee Tunnel Super Pumps

In 2011, GIW Industries received an order from KSB, its parent company, to build the four massive pumps for the Lee Tunnel project. Because the scope of this project forced the pumps to be large, it played into GIW’s strength, according to Bob Visintainer, GIW’s VP of Engineering.

GIW builds huge pumps for the mining industry and manufactures large castings. Some of the existing hydraulics were already in place, thanks to the LSA-84 dredge pump that was built by GIW in 1987. This was used as the flagship design for the Super Pump.

“We were challenged with building these hydraulics into a vertical configuration,” Visintainer said. “GIW designed the mechanical end and the vertical configuration. The wet end parts are similar to pumps we have built before, so there were no surprises there.”

The design process took about 16 months with a team of 15 engineers and CAD operators, Visintainer said. For this project, there were two engineering teams—one on the mechanical side and one on the pumping side.

“This project is important for a number of reasons,” Visintainer said. “The pumps alone are a multi-million dollar order. The government of the capital city of an important European country supports the project, which makes it high-visibility. A lot of people are watching it closely. The issue of stormwater storage is a big one for many cities.”

The mechanical seal is complicated and was specially made for this pump by EagleBurgmann design engineers Hans Steigenberger and Peter Haselbacher. The Lee River HGH 300S1/400-E1 seals have split seal faces, which can be replaced without tearing down the pump. The seal weighs 300 kilograms with a shaft underseal that measures 279 millimeters (11 inches) in diameter (see “Mechanical Seal Technology”).

Disassembly of Super Pump No. 2 after hydraulic performance testing.Image 2. Disassembly of Super Pump No. 2 after hydraulic performance testing. Photo courtesy of KSB

“Once these pumps go down into the pit, anything that has to be done to them will become very complicated,” Visintainer said.

“Our focus is on reliability. We have to consider what could potentially go wrong. We worked with the designers at EagleBurgmann to go through every possible scenario so that we would have the best chance of a flawless operation.”

Testing, Part One—Rag Monsters

In wastewater pumping, the easiest thing to pump is water. The hardest thing to pump is rags, Ulmschneider said.

“Wastewater pumping is unpredictable,” he explained. “You never know what you are going to get. When it comes to rags, no one knows how they will behave because there is no data of record for testing rags with a pump of this size.” The rag tests were the most groundbreaking tests performed on the Lee Tunnel Super Pumps. These tests established a basis for all future wastewater pumping.

“Thames Water wanted to be sure to minimize the potential for blockage,” Visintainer said. “This whole system depends on these four pumps running properly, so this test became one of our most critical steps in the entire process.”

For the rag testing, the passing requirements were specific: 2 kilograms dry weight of rags per cubic meter to a maximum length of 1 meter must be pumped for six hours at three different duty points without clogging the pump.

The rag tests were performed at GIW’s Grovetown facility and lasted four months (November 2012 – February 2013).

“We discovered quickly in the test lab that the liquid was recirculating at 350 rpm once every 15 to 30 seconds. In one hour, every rag was going through 100 to 200 times,” Visintainer said. “The fibers of the rags began to tangle and form what we called ‘rag monsters.’ These were clumps bigger than two grown men (nearly 5 meters), which created blockages within 30 minutes (see Image 3).”

One of the Image 3. One of the "rag monsters" generated by the historic four-month rag testing. Photo courtesy of GIW Industries.

KSB and GIW fulfilled the customer’s requirements, but they did not stop there. There was an opportunity for further internal scientific testing to learn what the pump could truly handle.

“We wanted to find out how rags behave in a closed system,” Ulmschneider said. “When do they clog the system? When does the pump start to fail? This test is groundbreaking, not only for KSB but for the wastewater industry as a whole. It is the first comprehensive rag test of this magnitude. We met the contractual requirements of the customer and then really pushed the pump to the edge. We discovered what it could do. We now know at what point the pump will begin to struggle and when it will shut down.”

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).

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