When an exhaust valve body is seized in the cylinder head and its internal threads for the bellows connection are damaged, the removal becomes a complex "over-limit" maintenance task. The following procedure combines mechanical extraction techniques with heat-based and structural solutions:

1. Preparation and Safety

• Isolate the Engine: Ensure the main engine is properly "blocked" (stopped, starting air isolated, turning gear engaged, and "Work in Progress" tags posted).
• Drain Cooling Water: Drain the cylinder head cooling water to avoid thermal shock or contamination during heating operations.
• Clear the Area: Remove the exhaust bellows (if possible) and all peripheral piping to provide maximum workspace.

2. Initial Extraction Attempts (Non-Destructive)

• Penetrating Oil: Apply high-quality penetrating oil or "freeze-off" spray to the seating area and let it soak for several hours.
• Thermal Expansion (Differential Heating):
  • Carefully apply heat (using a rosebud torch) to the cylinder head surrounding the valve body to expand the bore.
  • Simultaneously, apply cooling (CO2 or ice) to the valve body itself to shrink it.
• Impact Loading: Use a heavy-duty slide hammer or a pneumatic hammer with a flat bit to create vibrations that may break the rust/carbon bond.

3. Addressing Damaged Internal Threads

Since the internal threads for the bellows connection are stripped, standard lifting tools cannot be used.

• Fabricate a Custom Puller: Use a "stud-and-bridge" arrangement. If the threads are gone, you may need to weld a heavy-duty lifting eye or a threaded stud directly onto the top of the seized exhaust valve body.
• Hydraulic Jacking: Set up a bridge over the cylinder head and use a high-capacity hydraulic jack (10–30 tons) pulling on the welded stud. Apply steady pressure while tapping the valve body to encourage movement.

4. Destructive Removal (Last Resort)

If the valve remains seized after hydraulic and thermal attempts:

• Drilling/Milling: Use a portable magnetic drill to drill out the valve body's core or mill away the seating flange to relieve the compression.
• Gouging: Carefully use an oxy-acetylene torch or carbon-arc gouging to cut a vertical slit inside the valve body. Caution: Extreme care must be taken not to damage the cylinder head bore.
• Collapsing: Once a slit is cut, use a heavy drift and hammer to collapse the valve body inward, breaking its grip on the head.

5. Post-Removal Inspection and Repair

• Cylinder Head Bore: Inspect the head bore for scoring or cracks. Use emery cloth or a hone to clean the landing surface.
• Thread Restoration: Since the valve body is being replaced, the damaged threads are a non-issue for the old part. However, ensure the exhaust bellows and studs on the cylinder head are inspected for collateral damage.
• Pressure Test: After fitting the new valve assembly, perform a cooling water pressure test to ensure the seals are watertight.