Optimizing Power Plant Efficiency with Air-In-Leak Detection and Monitoring

Power generating plants operate with an emphasis to maintain high efficiency in order to ensure reliable power output and profitability. One key parameter for assessing plant efficiency is condenser backpressure. High condenser backpressure can be a result of several issues, including poor exhauster capacity, excessive air-in-leakage, or compromised heat transfer in the condenser. Poor heat transfer is often attributed to tube fouling, which can be quantified as a function of the inlet water temperature, known as the condenser cleanliness factor. However, identifying the source of high condenser backpressure without adequate instrumentation can be a complex task, leaving plant operators with little direction on how to address the problem.

This is where Bionetics comes into play. With over 20 years of experience in power plant efficiency studies, Bionetics has helped numerous plants implement custom monitoring systems, including the innovative RheoVac Condenser Monitoring System. The installation of an effective monitoring system can make all the difference, enabling plants to quickly identify the root cause of increased backpressure and take prompt corrective action.

The RheoVac Condenser Monitoring System: A Game-Changer in Air-In-Leak Detection

Bionetics offers a Condenser Monitoring System, CMS, package that includes the RheoVac multi sensor probe and provides an online condenser cleanliness or performance factor. The CMS includes sensors to measure total circulating water flow rate, circulating water inlet and outlet temperatures and condenser steam temperature and pressure. These measurements allow the actual condenser heat transfer to be compared with the expected heat transfer and provide a condenser cleanliness factor. Bionetics CMS, including the RheoVac multi sensor probe, provides users with the root cause of condenser performance degradation.

At the heart of the RheoVac Condenser Monitoring System is the  RheoVac probe, a powerful diagnostic tool that uses multiple integrated sensors to measure the mass flow rate of water vapor and air in the condenser offtake lines. By monitoring these parameters, plant operators can determine if high condenser backpressure is caused by high air-in-leakage or inadequate exhauster capacity.

• Exhauster Capacity Issues: If the issue stems from the exhauster’s inability to maintain proper vacuum levels, a relatively simple fix—such as scheduling maintenance on the pump or air ejectors—can usually resolve the problem.
• Air-In-Leakage: If the problem is identified as high air-in-leakage, the next step is identifying and repairing the source of the leak. This can be quite challenging because leaks in vacuum systems are not always easy to detect due to the wide variety of components under vacuum.

To pinpoint leaks, Bionetics employs helium leak surveys. These surveys use a helium mass spectrometer to detect small leaks by introducing a small amount of helium to potential leak sites. If there is a leak, the helium is drawn into the system, where it is detected by the mass spectrometer. Common sources of leaks include valve seals, flanged or threaded fittings, steam or water seals, expansion joints, penetrations, and welded joints in high-vibration areas.

Once leaks are detected, the RheoVac probe can be used to quantify the air-in-leakage at each identified location. The team then prepares a detailed report of all the leak locations, allowing the plant to schedule timely repairs.

Case Study 1: Identifying and Sealing Uncapped Pipes

In the first case study, a power plant contacted Bionetics after experiencing high air-in-leakage. The plant had two RheoVac probes installed: one in the west vent line and one in the common vent line. While the east vent line was not accessible, the data from the west and common vent lines allowed Bionetics to calculate the air-in-leakage from the east side of the condenser. The analysis revealed a significant leak on the east side. The data is shown in the multi-axis plot below.

A helium leak survey was scheduled, focusing on the vacuum components on the east side of the condenser. During the survey, Bionetics’ technicians identified several uncapped pipes that had been left exposed. This was traced back to a recent outage, where extraction steam check valves had been replaced with a different type that did not require drain lines. Unfortunately, the old drain lines had not been plugged, leading to the air-in-leakage.

Sealing the drain lines resulted in a significant improvement in the plant’s performance:

• Reduced air-in-leakage by 30 SCFM
• Increased cleanliness factor by 4.08
• Reduced condenser backpressure by 0.46 inHgA

Although additional leaks were found, they were not immediately repaired because the plant was able to achieve an acceptable performance improvement from sealing the drain lines. This case demonstrated the importance of having real-time monitoring and the ability to pinpoint exact sources of inefficiency. For more details please check out the case study video here Case Study – Multiple RheoVac MSP System.

Case Study 2: Uncovering a Broken Joint in a Sight Glass

In the second case study, a plant contacted Bionetics for a routine Air-In-Leak survey. The plant was operating with 18 SCFM of air-in-leak and experiencing slight excess backpressure. Given the pump’s capacity, this level of air-in-leak should not have caused any significant operational issues. However, the system was still not performing optimally.

Bionetics conducted a helium leak survey, which pinpointed several leak locations, including the vacuum pump shaft seals. This was traced back to the seal water supply running dry, causing the seals to malfunction. Near the end of the survey, the team discovered something unexpected: a broken joint on a sight glass. The pipe at the top of the sight glass had sheared off due to vibration, causing air to leak directly into the condenser. Though the break was hard to detect through visual inspection, the helium mass spectrometer readings clearly indicated the leak.,/p>

After the broken joint was sealed off, the air-in-leakage was reduced by 8 SCFM, leading to noticeable improvements in the plant’s efficiency.

The Value of Routine Monitoring and Leak Detection

Both case studies highlight the importance of routine air-in-leak surveys and effective monitoring equipment. Over time, all plants will develop air-in-leaks as part of normal operation, and having a reliable way to monitor and detect these leaks is critical for maintaining optimal performance. By distinguishing whether poor plant performance is due to air-in-leakage or other factors, plant operators can take targeted action to address the root cause of the issue, leading to increased efficiency, reduced backpressure, and, ultimately, improved profitability.

The ability to quickly identify and address air-in-leakage in power plants can result in substantial performance improvements, as demonstrated in the cases above. With advanced monitoring tools like the RheoVac probe and helium leak surveys, Bionetics helps power plants solve complex efficiency problems and achieve long-term operational success.