Electrical Generator Hydrogen System Inspections
There are 4 different reasons for conducting an electrical generator hydrogen system survey:
- Safety – to insure excessive pockets of hydrogen are not allowed to build up around the unit.
- Routine inspection to understand where failures have occurred and to maintain an efficiently operating generator.
- Prior to an outage so components in need of repair are addressed and scheduled accordingly and after the outage to insure all repairs were made successfully.
- Emergency inspections because of a catastrophic failure and the hydrogen loss exceeded the machines recommended amount.
How Long Does The Inspection Take?
American Efficiency Services (AES) technique and experience can identify the sources of leakage within the hydrogen system, on average, within one 8 – 12 hour shift.
Why Do We Use Helium?
To date, identifying electrical generator hydrogen system leaks utilizing helium as a tracer gas, coupled with inspection experience, has proven to be the most cost effective method. One or two 219 – 291 cubic foot bottles of helium are introduced to the hydrogen system and the pressure is then increased to the generators operating pressure using additional hydrogen or dry air.
Once there is helium in the system, an AES inspector will inspect the flanges, drains, welds, and vents of the generator with a vacuum probe. If the vacuum probe enters an enriched area of helium created from a leak, an indication will be recorded on the helium mass spectrometer that is used for sampling. Any helium above background will provide an indication that will be isolated to the specific component leaking.
Most leaks can be repaired immediately while the inspection crew remains on-site to insure the repairs have actually reduced the leakage. In some instances, the system must be relieved of the pressure so repairs can be made. In these situations, the inspection crew can remain on-site during the de-pressurization, repair, and re-pressurization of the machine to confirm repairs. In lengthy repair evolutions, the crew can also be released and then re-assigned after the repairs to insure the systems integrity was achieved.
At the conclusion of the inspection, all results, retest results, and repair recommendations will be discussed with plant personnel, leaks photographed, leaks tagged, and a draft report filed.