Condenser Air Inleakage audits are generally conducted with the unit on-line. American Efficiency Services’ technique and experience can identify sources of leakage within the vacuum boundary of the turbine and/or condenser system in one to three shifts. The length of the inspection is dependent upon the unit size, the number of leaks identified, the response and/or clear-out time of the indications, and the station’s desire to repair and re-inspect any of the leaks.
Most condenser air inleakage standards have been developed by research organizations and individual stations. These standards vary from station to station depending on system design and situation. The most common standard used for condenser air inleakage is one cubic foot per minute (CFM) for every 100 megawatts of generator capability. The majority of stations have adopted this standard with a tolerance of between 1 and 2 CFM per 100 megawatts. Other stations rely on their history of backpressure and dissolved oxygen to gauge when an inspection is required. A routine audit program is the best way to determine how effective a condenser can be within a system.
American Efficiency Services is available for routine inspections, outage prep inspections, or emergency inspections that you need for condenser air inleakage testing.
Why Conduct an Air Inleakage Audit to Minimize Air Inleakage Now?
Surface condensers are designed to be a vacuum-tight system with cooling water flowing through tubes. The cold tube surface condenses the steam, creating a reduction in volume inside the condenser which produces the vacuum. Air and non-condensables (air inleakage) that are allowed to enter the steam space from outside the unit can cause a reduction in vacuum, causing operating inefficiencies and impacting the Utility’s bottom line. Condenser air removal systems are designed to remove a certain amount of air inleakage. As the design limitations of the air removal system are approached, the efficiency of the unit decreases. In order for the Utility to maximize the potential of the unit, condenser air inleakage must be minimized. Air inleakage reduction assists with the efficiency of the system.
As condenser air inleakage increases, the backpressure (loss of vacuum) increases. The rate at which the backpressure increases due to air inleakage is dependent on the effectiveness of the air removal system. The air removal system should be able to control small amounts of air inleakage before noticeable effects are observed. Other factors can contribute to an increase of backpressure such as fouled condenser tubes that minimize the amount of heat transfer. An air inleakage audit is an excellent first option for solving a high backpressure problem since the inspections are conducted on-line. A reduction in power or complete unit shutdown must occur to clean the condenser tubes.
Understanding Vacuum Leak Detection Process Regarding Dissolved Oxygen
Dissolved Oxygen is another byproduct of excessive air inleakage and why American Efficiency Services recommends a condenser air inleakage audit. Air that is allowed to enter the steam space and is unable to be removed has the potential of being entrained in the condensate. Although it is thought that the entrained oxygen is passed through the entire system, the condensate pumps are able to separate a percentage of the entrained oxygen and discharge it back to the condenser through the pump vent for final evacuation through the air removal system. The percentage that is sent back to the condenser isthe indications our inspectors are looking for to confirm under the hotwell (water) level leaks.
The percentage of air that is allowed to be passed through the feed water system to the boiler can provide corrosive conditions that will exist throughout the entire path of the system. If the dissolved oxygen levels remain high for a long period of time, the affected components’ life will decrease. This results in longer outages and lost revenue. Vacuum leak detection assists with righting this process, so it functions properly.
Why Do We Use it for condenser air-in leakage testing?
Helium is applied to the various components within the vacuum boundary of a Turbine and/or Condenser system. A leaking component will allow the helium to enter the steam space and from there, the helium will be removed by the unit’s air removal system. AES will have an inspector located at the discharge of the air removal system with a mass spectrometer sensitive to helium.
As the helium is ejected from the system, the mass spectrometer registers an indication. The leak will be recorded and at the completion of the inspection, all leaks will be discussed with plant personnel.
Our helium leak detector results discussion will include the severity of the leak, the location of the leak, and potential repair options. Our staff engages in proper report writing so that our reports are so efficient you might agree they are “almost too good” as other plant managers have commented to us in the past. We pay strict attention to all details during the process in order to provide you the most thorough results possible. Once the helium leak detector is completed, you will understand every step you need to take to correct the problem.
Trust our team with your air leak detector inspection so that you know how to keep everything running efficiently and safely.