The Challenge of Installing 5 Raw Water Pumps

Water resources are placed under increasing strain as populations expand and industry grows within an area. Municipalities and local government are tasked with planning for the future and making sure that the local population has a safe and reliable source of water. For one city in Texas, the planning for a new water treatment plant had been ongoing for years, to the point that the population had increased by 20 percent while plans were made and the finances secured. After deciding to use a new source of water, the question was raised about the best way to move the water over 390 feet vertically from the lake to the new treatment plant.

Laying the Ground Work

This project presented a challenge in terms of design and installation. The pumping station was located 320 feet above the 9-foot tunnel that carries the water from the intake system in the lake. The position of the pumping station is enclosed, complicating the project by making access difficult for the contractors and the lifting equipment. After the water was raised to the surface, it then had to travel almost a mile uphill to the water treatment plant. So, a considerable amount of civil engineering would also be required to complete this project. The municipality said that the organization responsible for the design and manufacture of the pumps would also take ownership of the installation and commissioning. The plant and the manufacturer agreed on an enclosed line shaft design. This involves the addition of an enclosing tube that surrounds the full length of the line shaft, allowing clean water or an oil-based (NSF International approved) lubricant, to be supplied from the top of the pump before startup. This is important in deeper settings to ensure continued reliability of the line shaft bearings. Once the design requirements for the installation had been established, the manufacturer identified a large vertical turbine pump as the most suitable solution. The pumps were designed as three-stage units equipped with 320 feet of steel column with a 1,500 horsepower electric motor located on top of the above-ground discharge head.

Installation Challenges

Five new pumps were built, but the design and manufacture of the pumps was the easiest part of the project. The challenge came when the pumps needed to be installed. They were designed to be assembled in sections to ensure that the whole process could be completed safely. Field service engineers planned and completed all of the pump installation work on-site. Due to the confined workspace, the delivery of the pump sections had to be planned logistically so they could be organized in the correct sequence for assembly. Each 10-foot pump column section contained the pump line shaft, its support bearings and the enclosing tube, which was gradually lowered into the ground. As the top flange reached ground level, it was held in place while the next section was connected. This process was repeated until all 32 sections had been assembled, and the drive motor and discharge head were in place at ground level. The final step was to apply tension to the enclosing tube, bringing it into alignment using the tension tube nut assembly, which was located in the packing box. This straightened the enclosing tube and brought it into alignment, which should minimize shaft oscillation during operation. The pumps have now been running for a considerable amount of time, and the treatment plant is happy with their performance.