# Performance **Spotlight**

**Austin Energy: Pumping System Improvement Project**  **Saves Energy and Improves Performance at a Power Plant**
**Project Summary**
In March 2004, Austin Energy—the electric utility for the city of Austin, Texas— completed an improvement project on the circulating water pumping system that serves a 405-MW steam turbine at its Decker Creek Generating Station. First, a pumping system assessment was performed in part by a U.S. Department of Energy (DOE) Qualifi ed Pumping System Assessment Tool (PSAT) Specialist from Flowserve Corporation; this assessment helped utility personnel create a project that would improve the systemʼs energy effi ciency and output capacity. It involved upgrading several of the pumpsʼ critical components as well as reconfi guring some equipment. When it was completed, the project greatly improved the pumping systemʼs effi ciency and performance. These improvements resulted in signifi cant energy savings and reduced maintenance requirements.



### Plant/Project Background
The Decker Creek Generating Station has two steam turbines and 200 MW of gas turbine peaking units. This project focused on the largest steam turbine, a 405- MW power plant that has been serving the city of Austin, Texas, since 1978. Two 1000-horsepower (hp) circulating water pumps deliver cooling water from a lake to equipment that condenses the steam coming from the turbine. Before the project, these pumps were unable to deliver the amount of cooling water required despite operating at full load.

Both pumps were designed to have a combined fl ow rate of 236,000 gallons per minute (gpm), which was supposed to achieve a turbine back pressure (TBP) of no more than 3.5 inches. During routine, twice-yearly heat rate testing, plant personnel found that the cooling water fl ow was insuffi cient to achieve the rated steam fl ow, and the power plantʼs effi ciency was more than 5% below the design effi ciency level. The assessment revealed that the systemʼs actual fl ow rate when both pumps were running had degraded to 195,000 gpm, that pump effi ciencies were between 50% and 55%, and that the TBP at times increased to as high as 4.1 inches of mercury absolute (HgA), or more than 17.5% above the design TBP. Furthermore, the pumps were vibrating severely, sump vortexes were frequent, and impeller surfaces were severely eroded.

The project involved upgrading the circulating water pumps with new impellers, diffusers, shrouds, and shafts. In addition, the plant personnel and Flowserveʼs pump repair shop reconfi gured the suction bell, sections of the intake sump of both pumps, and the pumping station. Finally, they replaced the suction fl ow splitter below the pumps to better direct the incoming lake water. 

### Benefi ts

• Saves $1.2 million annually

• Reduces annual energy consumption by 220,000 MMBtu

• Reduces maintenance costs

• Achieves 11-month simple payback 

### Industrial Technologies Program 

### Proven Tools and Practices to **Increase Industrial System Energy Effi ciency**



### Applications
Circulating water pumping systems are needed for any application in which cooling water is required to maintain the temperature of a process. In this application, a power plant uses cooling water to condense steam. **Proven Tools and Practices to Increase Industrial System Energy Effi ciency** BestPractices is part of the Industrial Technologies Program, and it supports the Industries of the Future strategy. This strategy helps the country’s most energy-intensive industries improve their competitiveness. BestPractices brings together emerging technologies and energy-management best practices to help companies begin improving energy efficiency, environmental performance, and productivity right now.

BestPractices emphasizes plant systems, where significant efficiency improvements and savings can be achieved. Industry gains easy access to near-term and long-term solutions for improving the performance of motor, steam, compressed air, and process heating systems. In addition, the Industrial Assessment Centers provide comprehensive industrial energy evaluations to small- and medium-size manufacturers.

**A Strong Energy Portfolio for a Strong America** 

Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, and greater energy independence for America. Working with a wide array of state, community, industry, and university partners, the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies.

**F OR**  **A DDITIONAL**  **I NFORMATION**  **, P**  **LEASE C**  **ONTACT :** 

EERE Information Center 1-877-EERE-INF (1-877-337-3463)
www.eere.energy.gov
Visit our home page at www.eere.energy.gov/industry

Industrial Technologies Program Energy Efficiency and Renewable Energy U.S. Department of Energy Washington, DC 20585-0121 

### Results

These improve ments to the plantʼs circulating water-pumping system resulted in an increase in the pumpsʼ combined flow rate to 11.5% above their design rating. This increase sharply reduced the need to operate both pumps concurrently to satisfy the plantʼs cooling water demand. Because of the reduction in the parasitic pump load and in the need for additional cooling water, the plantʼs efficiency increased, yielding annual energy savings of 220,000 MMBtu and energy and maintenance cost savings of $1.2 million per year. With total project costs of $1.1 million, the project had a simple payback of 11 months.



### Lessons Learned
Circulating water-pumping systems should be checked periodically to ensure that they are operating satisfactorily. At the Decker Creek Generating Station, a kink at the low spot in the impulse line from the condenser to the vacuum manometer in the control room caused a water leg (trap), which prevented the vacuum manometer from providing accurate TBP readings. This, in turn, masked the performance of the system. Once the entire system was reviewed, including the pumpsʼ efficiencies, plant personnel were able to discover the suboptimal flow rate of the pumps, determine its cause, and devise an appropriate improvement strategy

. After the project, tests showed that pump efficiency levels had risen to 85%. More importantly, the pumping system flow rate improved significantly. The pumps can now deliver more than 263,000 gpm, an 11.5% increase above the original design flow rate. There has also been a large reduction in vibrational amplitudes, from as high as 3.3 mils down to 0.2 mils, and a TBP improvement of about 3.2 inches HgA. These improvements allow the plant to operate at full capacity using only a single pump, and to do so much later into the summer than it did before the project began—saving both energy and money. The methods applied in this project can be implemented in power plants and at practically all industrial facilities that require water for process cooling.



### Project Partners
**Austin Energy Company** Austin, TX **Flowserve Corporation** Phillipsburg, NJ 

### Partner Profile Alan Flory is a mechanical engineer and a PSAT Qualified Special

ist who has been with Flowserve for 12 years. He has worked with Flowserve’s IT group to develop pump selection software and has authored technical papers on boiler feed water pumps. In his current role as Industry Director, he focuses on upgrading the efficiency and reliability of pumping systems for Flowserve’s industrial customers. 

### Qualified Specialists Qualified Specialistsare industry professionals who identify costcutting and efficiency opportunities in industrial plants. Experienced professionals who complete a qualification training workshop and exam for specifi c DOE-developed software tools receive special designations, and they can use these tools to help plants reduce costs, decrease maintenance and downtime, and improve productivity. The training recognizes and enhances a professional’s expertise in the use of DOE’s AIRMaster+ software tool, Pumping System Assessment Tool, Process Heating Assessment and Survey Tool, and Steam System Tools. For information, visit **www.oit.doe.gov/bestpractices/software_ tools.shtml.**  

### Alan Flory

DOE/GO-102005-2083 June 2005