Alliant Energy doing steam blows at Marshalltown gas plant

Alliant Energy (NYSE:LNT) has started a “steam blow” cleaning process at the 650-MW gas-fired Marshalltown power plant, the company said recently.

The process is one of the final steps necessary to complete the installation of a new heat recovery steam generator (HRSG) at the facility. The company expected the cleaning process to begin around Nov. 28 and continue around-the-clock until roughly Dec. 20.

The Marshalltown Generating Station is approximately 95% complete. Performance testing is scheduled for completion in mid-February with substantial completion of the facility expected in early April, Alliant said in a Nov. 16 news release.

Steam blows are critical to ensuring the reliability and safety of the HRSG system, as well as the quality of the steam. The process cleans the lines and the HRSG prior to admitting steam to the turbine. This removes any foreign matter or debris remaining in the equipment and steam piping after the installation is completed.

Dirt and rust can reside in steam lines from initial construction and manufacturing and can result in serious equipment damage if not “blown” away.

“We appreciate the cooperation and patience of our Marshalltown neighbors and residents in the area during the cleaning process,” said Craig Crawford, plant manager at the Marshalltown Generating Station. “These steam blows are part of the initial startup procedures we need to follow. They are a one-time occurrence that will not need to be repeated.”

During the cleaning process, it is possible that those in the area will hear periodic low rumbles from the release of steam and see steam coming from the nearly completed generating station. Alliant Energy has taken several proactive steps to reduce noise from the steam blow.

Mufflers have been put on the steam exhaust piping and have been located on the east side of the building, farthest away from the Marshalltown city limits, homes and businesses. In addition, the combined use of water spray and the temporary expansion of the steam pipes will help to keep the noise volume down.

The company expects the steam blow noise level to reach approximately 85 decibels within 15 feet of the exit of the building; dissipating steadily the farther it travels. According to the American Speech-Language-Hearing Association, an 85-decibel sound level is comparable to that of a blow dryer, kitchen blender or food processor.

“We recognize that unusual increases in noise levels at the facility’s construction site can cause concern that something is not going as it should be,” added Crawford. “However, the cleaning process is an important step to ensure that the new steam system is operating normally when the generating station goes into service next year.”

The project is being developed in Marshall County, Iowa by Alliant utility Interstate Power & Light (IPL).

About Wayne Barber 4201 Articles
Wayne Barber, Chief Analyst for the GenerationHub, has been covering power generation, energy and natural resources issues at national publications for more than 20 years. Prior to joining PennWell he was editor of Generation Markets Week at SNL Financial for nine years. He has also worked as a business journalist at both McGraw-Hill and Financial Times Energy. Wayne also worked as a newspaper reporter for several years. During his career has visited nuclear reactors and coal mines as well as coal and natural gas power plants. Wayne can be reached at