Here’s a summary, and attached are some photos which I’ll explain further below:

· Initial visual inspection, during your visit, did not indicate any functional or mechanical issue.

· Initial ‘air-test’ seal testing indicated properly installed and functioning seal rings. No air loss was noted, and the unit behaved exactly as designed.

· During the disassembly of the turbo to live-test the unit in the VSR, I noted damage to the turbine wheel inducer and exducer, which I’ll explain below.

The damage to the turbine is indicative of a turbo that has been operated with the CHRA and turbine housing interface seated improperly. As you can see from the photos, this was not the case ‘recently, as the witness marks along the shoulder of the bearing housing are uniform in 360 degrees:

This leads me to believe that the ‘off-center’ running of the unit happened some time ago, and it simply ‘wore the wheel down’ until the housings were squared up, and then it ran without excess wheel clearance. This is a real surprise, because that level of damage to the wheel should have been instant and catastrophic in nature.

The damage to the turbine wheel is catastrophic and not repairable, due to the Gamma Ti alloy, but, even if it were an Inconel turbine, we would not recommend re-use or repair.

The evidence of that off-center operation is found in the turbine housing, as the contact between the wheel and housing took place at only about 180 degrees of the bore and radius:


Just to clarify, I did completely clean the housing prior to the above photos, as it did have a fairly normal layer of carbon-fouling, and I did chuck this into our lathe to confirm that the bore was indeed perfectly circular and not warped or off-center in any way; the bearing housing register ‘step’ and the bore are concentric, and I checked the radius in several positions.

Now, what I did not find was any evidence of seal structure failure or damage. The turbine-end seal area was very, very dry, with no sign of oil loss, and, although the compressor-end area was oily, the seal rings were in new condition, and both the seal bore, and the two ring grooves, were in perfect order as well. I suspect that oil loss is due to an external issue, which is what I’ve suspected from the outset.

Now, that leaves us with the original symptom/complaint unfounded with regard to the turbo, but in doing the inspection, we’ve uncovered a much more serious, immediate issue.

I am, frankly, surprised that the turbine wheel didn’t explode the moment it made contact with the housing, as the GammaTi is very brittle at low temperatures, so the only thing I can say is that you probably got lucky that it held up this long.

I do not think that the damage to the turbine wheel is in any way creating the oil loss issue, but it certainly would have resulted in reduced performance, and possibly some very odd noises when it first happened.

Solutions:
Okay, so all is not lost, although it’s not looking too good. The turbine wheel will need to be replaced, and the seal structure renewed, then the unit overhauled and re-VSR tested and imbalance-corrected. We have not yet experienced an EFR7163 turbine failure that could be repaired with a new turbine shaft/wheel, so we’ve never requested it from BWTS as a loose part, so I’m in the middle of that process now. “If” they release it to us, and I have no reason to believe that they will not, it will be far less expensive than replacing either the CHRA or the Super Core, so I would suggest we sit tight to see what pricing and lead time will be for that item.