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

Building the test rig for each pump requires five people working 16 hours per day for three days. “The environmental conditions of the test field were the most challenging,” Gros said. “The floor stands on springs. This is a special foundation to absorb any vibrations that could affect the other equipment. Also, calculations were made with the help of the University of Applied Sciences Merseburg, which helped determine how the testing would affect the piping system and other systems. It took two weeks to work that out. It was a flowing process. We had to just solve one problem at a time and then begin discussing the next one.”

Pumping Station Special Features

The pump station is divided into two parts and is prepared for three pumps on each side (see Image 5). In addition to the four Super Pumps and two drainage pumps, KSB also designed, fabricated and will install several ancillary features, according to Uwe Hilpmann, KSB’s project manager for the Lee Tunnel project.

KSB designed suction bends on movable devices, which glide about 9.7 meters and serve two purposes:

An illustration of the Lee Tunnel pumping stationImage 5. An illustration of the Lee Tunnel pumping station
  • They provide a connection from the suction bend to the tunnel and are used for access to the tunnel to investigate issues and fix problems.
  • They provide access under the impeller.

A system, which was specially designed for this project by KSB, lubricates the bearings from a reservoir, Hilpmann said. The oil is sprayed directly onto the bearings inside the closed loop.

The Super Pumps are installed on the concrete level on a plinth (28.78 meters) and the motor is installed on the motor floor level above the pumps (35 meters). Two KSB Sewatec K 250-900 drainage pumps will be installed, one on each side of the pumping station. “If the Lee Tunnel is full of water, the water level would be about 85 meters,” Hilpmann explained. “Operating the main pumps lowers the water level by 33 meters, then they stop and the drain-down pumps take over.”

The actual flow rate of the drain-down pumps is 160 l/s (minimum) to 260,000 l/s (maximum) with actual developed head of 86.60 meters to 83.80 meters. The pump efficiency is 59.23 to 71.28 percent with 229.65 kilowatts to 299.93 kilowatts pump power absorbed. These pumps operate at 817 to 827 rpm.

Ready for Heavy Duty

Three of the world’s leading civil engineering contractors—Morgan Sindall, VINCI Construction Grands Projets and Bachy Soletanche (MVB)—are working with Thames Water to build the Lee Tunnel.

Construction began in 2010 and tunneling began in January 2011. Operation of the Lee Tunnel is expected to begin in 2016. The current target completion date for the entire Thames Tideway Scheme is 2023.

The first four pumps are expected to be installed in the third quarter of 2015. After one year of operation, KSB will disassemble and fully-inspect one of the pumps. The pumps will be maintained and serviced by the specialists from the Britain-based KSB Limited.

“These Super Pumps have been challenged a great deal during this project, and so have we,” Ulmschneider said. “Seeing these pumps being pushed to the edge and not fail gives us a lot of confidence for all the challenges to come. We are ready.”

Powering the Super Pumps

Pumping power of this magnitude requires a motor that is customized to handle extremely high temperatures and voltage. Each KSB Super Pump is powered by a Siemens A-modyn vertical motor, which runs at 3.4 MW at 6,600 volts/50 hertz and speeds up to 333 rpm.

“Our challenge was to design a motor that could increase the power factor to 400 amps,” said Torsten Fiedler, Siemen’s sales manager for medium-voltage motors. “We added iron into the design to improve the power factor and the electronic behavior of the motor. This motor has a special electronic package. The stator of the motor consists of iron laminations. The more laminations in the design, the better the power factor and the lower the current.”

Each motor weighs 30.13 tons and measures 2.85 meters long, 2.75 meters high and 3.83 meters wide. The motor features a Rockwell Automation variable frequency drive.

One of the biggest challenges in creating the right motor to power the Super Pumps was the weight of the motor, Fiedler said. “Our competitor offered a motor that weighed 50 tons, but it was rejected by the client. Siemens was able to create a motor with the same power but with a lower weight.”

The Siemens design features a water-cooled motor. The motor has a constant air stream cooling circuit. The heat exchanger serves as the water cooler. Fresh water runs in between the motor casing and the cooling jacket. Water circulates and cools the inner parts. It is cooled by the rising pipe connected to the heat exchanger in the closed circuit. “This is a special design,” Fiedler said. “Usually, the water comes from an open source.”

These motors—manufactured at the Siemens Drasov, Czech Republic, facility—are a special design made for pump applications.

Mechanical Seal Technology

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 (see Image 6). The shaft underseal is 279 mm (11 inches) in diameter. The seal weighs 300 kilograms.

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