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Proceedings of the ASME 2021
ASME 2021 Power Conference
July 20-22, 2021, Online, Virtual
Paper ID: POWER2021CONFERENCE-64854
Abstract
Occupational Radiation Exposure must be kept As Low As Reasonably Achievable (ALARA). Operational, economic, and social factors need to be taken into account. Fast purging of a Hydrogen Cooled generator can be achieved through the means of a system that increases the rate of carbon dioxide vaporization. This system has been successfully utilized at two nuclear plants in the USA: Vogtle Electric Generating Plant and Joseph M. Farley Nuclear Generating Plant. The installation reduced the purging procedure by approximately 11 hours from the typical purging time. This was accomplished by increasing the flow of Carbon Dioxide, monitoring the pressure and gas purity monitoring.
The generator was also able to be brought back online more rapidly when the air was replaced with carbon dioxide in 1 hour and 6 minutes. While the Vogtle and Farley Plants are not Boiling Water Nuclear Reactors, this technology clearly demonstrates that exposure meeting the requirements of ALARA can be achieved with the most significant benefit achieved on Boiling Water Nuclear Reactors.
Fast purging operations are described, and test runs from Plant Vogtle are presented and additional benefits of the purging are discussed. These include outage time reduction and risk mitigation.
Proceedings of 2020 28th International Conference on Nuclear Engineering
joint with the ASME 2020 Power Conference
ICONE28-POWER2020 August 2-6, 2020, Anaheim, California, USA
Paper ID: ICONE28-POWER2020-16881
ABSTRACT
This document is designed to explain all aspects of losses associated with operation of a Hydrogen cooled generator when less than pure (100%) Hydrogen is the cooling gas. It will also give a formula which allows the user to calculate the financial impact for the utility when operating at lower purities.
Proceedings of ASME Power 2019
July 15-18, 2019, Salt Lake City, Utah, USA
Paper ID: Power2019-1967
ABSTRACT
Many hydrogen cooled generators operate without a hydrogen dryer. Plant personnel offer a variety of reasons for this including:
– The generator was supplied without a dryer.
– Single Tower Dryer Manual Reactivations are too labor intensive
– The misunderstanding that high purity indicates a dry generator with an acceptable dewpoint.
– A gas turbine with no steam side does not need a dryer.
– The consequences of a high dewpoint are not well understood.
– The use of gas scavenging and bleed and feed practices control purity and dewpoint problems.
– Plants and generators operating in arid or desert environments should not have dewpoint problems.
Generator manufacturers recommend keeping the generator hydrogen dry. Generator dryers are factory set to alarm at dewpoints above +20°F (-7°C). This setpoint is designed to prevent the condensation of water inside the generator. From in plant experience it was suspected that generators operating without dryers were operating with dewpoints above the OEM’s recommendations. To test this and with the permission of plant personnel, the authors took portable dew point analyzers to a number of plants to test the actual dew points of the hydrogen.
This paper presents the results. More than 90% of the generators tested were found to have hydrogen dewpoints higher than the generator manufacturer’s recommendations.
Proceedings of the ASME 2016 Power and Energy Conference
PowerEnergy2016
June 26-30, 2016, Charlotte, North Carolina, USA
Paper ID: PowerEnergy2016-59257
ABSTRACT
Hydrogen cooled generators need to undergo carbon dioxide (CO2) purging before being placed into service and when taken offline. This process typically takes 4 to 12 hours, and can take as long as 36 hours in extreme cases, to fully and safely purge a generator. Reducing the volume of hydrogen gas in these generators is essential for reducing the risks of explosions. If these purge times could be shortened, improvements in safety, shorter outages, and increased production could be realized. This paper describes plant testing of a CO2 Fast Degas purging system for hydrogen cooled generators. Results from eight test runs at two different plants are presented in tabular and graphical form. Mean reduction from pure hydrogen to less than 4% hydrogen was 39.8 minutes, while maintaining CO2 temperatures above 80°F (27°C). This eliminates the possibility of CO2 freeze up, and reduces the stress on the piping and the detrimental effects on the generator from extreme temperature swings that occur when CO2 is de-pressurized. These rapid purge rates were accomplished while maintaining the generator pressure within a set range. In order to achieve the minimum purge time, it is critical that mixing of the two gases be minimized during the purge operation. By utilizing the slope of the graphs provided, the system was optimized to minimize purge times to reach safe levels. Tests were performed on both purging operations, replacing hydrogen with CO2 and replacing air with CO2. Samples to analyze the generator gas purity were taken from the vent line using multiple thermal conductivity purity instruments to assure accurate results. The system was tested in both automatic and semi-automatic modes of operation. The fast degas system was found to significantly reduce generator purge times, reducing down time, and improve operator efficiency, positively affecting the overall safety profile of the plant.
Proceedings of 2020 28th International Conference on Nuclear Engineering
joint with the ASME 2020 Power Conference
August 2-6, 2020, Anaheim, California, USA
Paper ID: ICONE28-POWER2020-16881
OBJECTIVE
This document is designed to explain all aspects of losses associated with operation of a Hydrogen cooled generator when less than pure (100%) Hydrogen is the cooling gas. It will also give a formula which allows the user to calculate the financial impact for the utility when operating at lower purities.
INTRODUCTION
The losses that are associated with the friction between the rotor and the cooling gas are commonly described as windage losses. While generators are synchronous operating at fixed RPM’s the amount of energy they produce and the amount of energy they consume to produce that energy varies. Optimally in a thermal power plant every BTU of fuel burned would produce an equivalent kW of electrical energy. This is not the case since the best coal and gas fired thermal power plants operate at efficiencies of around 60%. This paper will help the reader understand where a significant loss occurs that is frequently overlooked and that can be easily remedied for a nominal investment.
Proceedings of the ASME Power 2014
July 28-31, 2014, Baltimore, Maryland, USA
Paper ID: Power2014-32296
ABSTRACT
Much has been done in recent years to upgrade turbines and improve plant efficiency. Recent years have also seen improvements and upgrades in the hydrogen cooled generator auxiliaries which also can improve plant efficiency and safety. A summary of upgrades and new products that are available and that have been implemented are presented in this paper.
HYDROGEN COOLED GENERATOR UPGRADE RAPID PURGING OF HYDROGEN COOLED GENERATORS TO MITIGATE RISKS AND SHORTEN OUTAGE TIMES
Track 4: Operation, Optimization & Servicing
Power Gen Asia
Conference October 2-4, 2013 | Bangkok, Thailand
ABSTRACT
Two reasons exist for the rapid degassing of Hydrogen cooled generators. The first is an upset condition which could cause an unsafe condition or generator failure if the Hydrogen is not removed. The second is the time savings that can be recognized by reducing the time required to fully purge the generator and refill during either an unplanned or planned outage. A seismic event, extreme weather event (typhoon or hurricane) or generator bearing fire are examples of the first condition where the ability to remove the Hydrogen and purge with Carbon Dioxide rapidly would result in a significant reduction in the risk of a catastrophic situation, fire or explosion. Current purge operations typically require hours for the gas change from Hydrogen to Carbon Dioxide during outages. The cost of an unplanned outage during peak generating periods can be very high. A system which reduces the time required for this step to less than 30 minutes is explained. Times for refilling can also be reduced by similar amounts. This time can be extremely valuable during peak generation periods. Carbon Dioxide vaporizer systems provided by generator OEM’s that have been installed previously have been limited by the rate they can vaporize the Carbon Dioxide and feed the gas to the generator without freezing. The system described uses flow controls, a large heater and backup CO2 storage to perform the necessary operations quickly while minimizing the impact to the generator. The system can be operated or fully automatic. Automatic operation is preferred for the safety concerns since any fire or other upset would likely occur in the area of the equipment. The system described has been installed and tested in a number of operating plants and is performing satisfactorily.
Power Gen International 2010, Plant Performance I Track
Orlando, Florida, December 14, 2010
ABSTRACT
A method is presented for improving the generator purity data provided by the current instrumentation available. The improved data can be used to reduce Hydrogen consumption by eliminating unnecessary purging for safety or to improve generator efficiency by reducing windage losses.
Current purity instruments use gas density, thermal conductivity or some gas property to calculate purity. All however are binary gas systems that calibrate to two gases, and are limited to display purity as two gas mixtures. During normal generator operation this would be Air in Hydrogen. Unfortunately this method does not consider the impact of water vapor, the most common contaminant in the generator. As a result poor decisions may be made about generator operation. Purging done to improve purity for safety is often unnecessary or ineffective.
This method utilizes the data available from the generator dryer dew point instrument to provide the impact of the water vapor on the purity reading and provide a corrected purity, or gas composition, which lists three gases, Air, Water Vapor and Hydrogen. Actual data has been compared to theoretical data to confirm accuracy of the system. While other more expensive methods exist for analyzing multiple gas mixtures this method utilizes equipment and instruments already available in the power plant to provide real time data to identify the source of the impurity, water or air infiltration. This then allows the proper action to insure the generator operates safely and in the most efficient manner.
Proceedings of the EP09 Session 12A: Reliability Centered Maintenance Strategies
Electric Power Conference
May 12-14, 2009, Chicago, Illinios, USA
Abstract ID # 70089
Abstract
Two reasons exist for the rapid degassing of Hydrogen cooled generators. The first is an upset condition which could cause an unsafe condition or generator failure if the Hydrogen is not removed. The second is the time savings that can be recognized by reducing the time required to fully purge the generator and refill during an unplanned or planned outage.
A generator bearing fire is an example of the first condition where the ability to remove the Hydrogen and purge with Carbon Dioxide rapidly would result in a significant reduction in the risk of a catastrophic situation.
Current purge operations typically require many hours for the gas change from Hydrogen to Carbon Dioxide during maintenance outages. This new system reduces the time required for this step to less than 20 minutes. Times for refilling can also be reduced by similar amounts. This time can be extremely valuable during peak generation periods.
The Carbon Dioxide vaporizer systems that have been installed previously have been limited by the rate they can vaporize the Carbon Dioxide and feed the gas to the generator without freezing. The system described uses flow controls, a large heater and backup Carbon Dioxide storage to perform the necessary operations quickly. The system can be operated manually or fully automatic. Automatic operation is preferred for the safety concerns since any fire or other upset would likely occur in the area of the equipment and time would be of the essence.
The system described has been installed and tested in a number of operating plants and is performing satisfactorily.
Requesting a quote from Lectrodryer is easy – simply fill out the RFQ form to the right. However, to help us give you the most accurate quote, please provide as much information as possible including:
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In general, the more information you put in the RFQ Message section, the better we can address your inquiry.
You can also download our Application Questionnaire and email it to info@lectrodryer.com
Requesting a quote from Lectrodryer is easy – simply fill out the RFQ form. However, to help us give you the most accurate quote, please provide as much information as possible.
