During American Efficiency Services (AES) condenser tube inspections and cleaning a tube extraction may be recommended to understand the failure mechanism, confirm eddy current data, and/or to obtain a visual inspection on the condition of the condenser tubes. Since the waterboxes remain in place during these minimal extractions, a procedure is implemented to remove the tube in a controlled manner, so the tube can be placed in the same order once in a controlled area. Once any defects are identified it will be possible to trend if the failures/defects are distributed randomly throughout the tube bundle or if a specific pattern exits.
Once the tube(s) are extracted, a tube sheet plug is inserted into the blank tube sheet holes to ensure there is no cooling water contamination during operation. Since tubes should only be pulled from the condenser off-line, AES can have a helium inspection crew on-site during unit start up to inspect any areas that have had tubes pulled to ensure the plugging is leak free.
AES creates tube bundle maps (see pictured below) of all tubes currently plugged during our tube cleaning projects and can be contracted to provide mapping independently of other projects. Understanding where your failures/defects have occurred and having the ability to trend them can prove to be a valuable tool for efficient and economical outage decisions.
Any system that operates under pressure, positive or negative (vacuum), can be inspected using our helium technique.
For positive pressure systems a small amount of helium, less than 1% in most cases, would need to be added and maintained throughout the inspection. These inspections in the past have included pharmaceutical reactors, petrochemical pipelines (above and below ground) and various food processing systems.
For negative pressure systems AES would need to determine the ideal sampling point which is typically the discharge of the Steam Jet Air Ejector or Vacuum Pump. AES will then identify the systems vacuum boundary and develop a systematic approach for inspecting the system.
On large heat exchangers such as main condensers in electric generating facilities, the most efficient and economic method of inspecting for tube leaks is with the system on line using helium. But when a system is unable to be isolated on line the single tube pressure inspection is the next best method. AES is able to pressure test each independent tube on small to large heat exchangers for tube leakage. AES has inspected heat exchangers with as few as 40 tubes up to those with 15,000 tubes.
Each individual tube is pressurized, usually between 90 – 100 psi, and evaluated for a predetermined time frame based on the specifics of the system. If a pressure loss is indicated two additional qualifying inspections are conducted prior to the tube being permanently plugged. All tubes that are identified as leaking are noted, photographed, and entered into the electronic report.
AES conducts several Boiler Duct Inspections a year identifying sources of leakage that are compromising the unit’s efficiency. After obtaining a sample from the systems discharge AES applies helium to the duct work, expansion joints, manways and all other components under vacuum.
The benefits of the inspection include: reducing the potential for elevated load on the ID fans, reducing the temperature of the SCR’s, and assisting in maintaining an efficient boiler.
AES provides a crew with a boroscope capable of capturing images and video of spaces not accessible to man. Our boroscope is capable of looking inside piping, heater chambers, and other tight areas to conduct visual inspections and assess the need for maintenance or other corrective actions.
AES crews have also been deployed for the specific purpose of evaluating the internals of critical systems for foreign material that could damage a system during start-up and/or operation. The removal of foreign material prior to start-up can save the facility millions of dollars. A complete report of the procedure conducted on the specific system, findings, photographs, and video are all compiled in a final report. The report allows the customer to assess their system so outage planning and proper repairs can be made efficiently.