Why Helium Leak Detection?
Helium Leak Detection has become the standard method for identifying condenser air-inleakage and condenser tube leaks. With the ability to “pinpoint” leakage it takes the guess work out of the older methods such as using smoke, shaving cream and ultrasonic guns. This results in the ability to quickly make repairs creating faster turnarounds for the facility.
For condenser air-inleakage and condenser tube inspections a sample port is connected from the discharge of the air removal system to a helium mass spectrometer. This allows any helium sprayed near or at areas of leakage to be pulled into the condenser’s steam space and recorded by the helium mass spectrometer. The leak rates are transferred to a chart recorder and a final leak list is given to the customer with locations and leak rates.
Condenser Air-Inleakage Inspections
Multiple problems can arise from high air-inleakage, including higher than normal back-pressure, the introduction of dissolved oxygen (which can lead to corrosion inside the condenser), increased heat rates and lost revenue due to the conditions. The increase of back-pressure and heat rates will negatively impact the amount of power able to be produced. Through condenser air-inleakage testing these leaks can be identified allowing for repairs to be made and get your production back to normal.
Under normal conditions even the largest of units can be tested in minimal time, considering that even a slight increase in backpressure can cause hundreds of thousands of dollars in extra operational costs annually. Inspection costs are recovered almost immediately.
The inspection begins on the turbine deck, working from top to bottom at all areas within the vacuum boundary. This includes valves, flanges, rupture diaphragms, pump seals and any other components under vacuum.
Condenser Tube Inspections
Much in the style of condenser air-inleakage inspections, condenser tube leaks are able to be identified through helium leak detection. When hotwell contamination happens, it can cause performance issues, and early system failures in Fossil Boilers and Nuclear Reaction Components and early tube failures in the boiler. The normal process is to remove the suspected tube bundle from service and monitor contaminants.
Once the correct bundle is identified, entry is gained into the waterbox, and the testing process can begin. Plenums of various sizes are used to narrow down areas of suspected leakage down to a single tube. After identifying the leaking tube(s) and plugging, a follow up test is conducted to ensure that the balance of the bundle is free of leakage and the bundle returned to service.