Turbine inspection and component work

Five procedures.

Procedure 0 — Approaching a turbine (R1, R2)

Even on a static article, build the habits now.

1. Know the intake hazard zone and the exhaust hazard zone, and that both are far larger than they appear.
2. Never approach the intake of a running engine, and never assume an idling engine is safe.
3. Nothing loose about your person — badges, pens, hats, tools. Anything you drop, the engine eats (PP-B Concepts §4).
4. Account for every tool before and after (GEN-F Procedures Procedure 1).

Check — count your tools out and back, and say the number.

Procedure 1 — Map airflow through the engine (S4)

This is done on a cutaway illustration of a turbine engine, not at the shop: the element asks you to show and explain the path, and a cutaway shows it better than a closed engine.

1. Identify the sections in order: inlet, compressor, diffuser, combustor, turbine, exhaust.
2. Trace the primary gas path on the cutaway, naming each component the air passes through.
3. At each section, state what happens to pressure, temperature and velocity.
4. Identify the secondary flows: bleed ports, cooling air, sealing air, and where each goes.
5. Identify station numbers and what each corresponds to physically.

Check — narrate the path aloud from inlet to exhaust without notes. If you cannot, you have memorized a diagram rather than understood the engine (PP-B Concepts §1).

Procedure 2 — Inspect compressor blades and inlet guide vanes (S8, S13, S11)

1. Clean the area and arrange lighting — a strong light held at a shallow angle across the blade surface (GEN-K Procedures Procedure 2).
2. Inspect the first two stages most carefully — that is where FOD lands.
3. For each finding, record zone (leading edge, trailing edge, tip, root, mid-span), type and size, measured.
4. Compare against the manual's damage limits for that zone — limits differ sharply between zones.
5. Determine blendable, or not. Cracks are almost never blendable.
6. Where blending is permitted, note the cumulative material removal limit.
7. Rotate the compressor and inspect all blades, not a sample.

Check — state the zone before the size. A 2 mm nick may be acceptable on one part of a blade and rejectable on another, and quoting a size without a zone is meaningless.

Failure — inspecting the blades you can see through the inlet and stopping. Rotate it.

Procedure 3 — Inspect a combustion liner (S6)

1. Access per the manual — frequently by borescope, which is its own technique.
2. Look for cracking — some patterns are acceptable within limits, others are not — plus burning, distortion, missing material and hot streaks.
3. Note the position of any hot streak. It is evidence about a fuel nozzle (PP-I).
4. Compare against the manual's limits and record with position.

Check — a hot streak is a finding about something else. Record where it is; the nozzle opposite it is the next thing to inspect.

Procedure 4 — Remove and install a fuel nozzle (S5)

1. Depressurize and drain the fuel manifold per the manual.
2. Note orientation and any clocking before removal.
3. Remove, capping the line and the port immediately.
4. Inspect the nozzle: carbon build-up, erosion, blocked or distorted orifices.
5. Where the manual requires, check the spray pattern on a test rig — an even, correctly shaped cone (PP-I).
6. Install with new seals, correct orientation, torqued per the manual.
7. Leak check with the system pressurized.

Check — a distorted spray pattern burns the liner. The nozzle and the hot streak in Procedure 3 are the same fault seen from two ends.

The checks, collected

License

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