What Teams Find When the Turbine Casing Opens
During turbine outage maintenance, one of the most consequential inspection points is the casing split line — also called the parting plane or horizontal joint face. Once the casing is opened, the maintenance team frequently encounters surface damage that was not visible during operation.
At that stage, the team must make a practical decision — often under outage pressure, where every additional day carries real cost, schedule and availability implications.
"The question is not machining or compound. The better question is: what is the actual condition of the sealing surface?"
When Machining Remains the Right Answer
In-situ machining remains essential when the parting plane geometry, flatness, alignment or contact condition must be restored mechanically. If surface damage is severe, widespread, distorted or affecting casing geometry, machining is the correct technical route.
Typical in-situ machining work includes turbine casing split-line restoration, HP/IP/LP casing joint repair, portable milling of joint faces, flange face machining, bearing pedestal machining, and local repair after steam leakage or erosion.
However, not every surface defect calls for full machining. In some cases the damage is localised. In others, the sealing surface has minor scratches or imperfections that can be addressed through a controlled sealing surface restoration process — without the time and cost of mobilising a machining contractor.
The FILLING® Sealing Surface Restoration Range
The FILLING® product range is engineered specifically for sealing surface restoration and split-line repair applications in turbines, compressors, generators, pumps and gearboxes. Products are selected based on the condition of the sealing surface and the depth of damage.
Designed for full-surface application where the complete joint face has fine surface imperfections requiring full-coverage sealing support. 1 kg pack, coverage 0.50–0.60 m².
Full-surface application for broader surface wear, minor scratches or general sealing face imperfections across the joint face. 0.75 kg pack, coverage 0.35–0.45 m².
Spot application to isolated damaged areas — deeper local damage, scratches or cavities. Not recommended for full-surface use except in exceptional cases by experienced OEM teams. 0.75 kg pack, coverage 0.25–0.35 m².
FILLING® products are compatible with each other. However, BIRKOSIT® must not be used together with FILLING® products in the same application. If the FILLING® system is selected, the application should be planned accordingly and not mixed with BIRKOSIT® in the same sealing process.
The Two-Step Repair Approach
In many practical cases, a two-step method delivers the most thorough result — addressing both isolated deep damage and broader surface imperfections before final reassembly.
Apply FILLING 2000® only to isolated deeper damage, scratches or cavities up to ≤ 1.0 mm. Spot-repair stage for selected damaged areas of the sealing surface.
Apply FILLING 1000® across the complete sealing surface where damage or scratches are up to ≤ 0.5 mm — addressing both visible imperfections and smaller undetected scratches across the joint face.
Selecting the Right Repair Route
The correct repair path depends on a practical surface assessment. Use the guide below as a starting framework — every case should be evaluated on its own merits.
| Surface Condition | Recommended Route |
|---|---|
| Severe distortion, geometry issue, major unevenness | Machining / OEM repair required |
| Localised deeper scratch, pit or cavity ≤ 1.0 mm | FILLING 2000® spot application |
| Full sealing face with damage ≤ 0.5 mm | FILLING 1000® full surface |
| Fine sealing face scratches ≤ 0.2 mm | FILLING basic® full surface |
| Machined surface before final reassembly | Sealing compound may still be required |
| Unclear damage depth or surface condition | Technical assessment first |
Approximate Coverage per Pack
Coverage depends on surface roughness, application thickness and degree of damage. These values are indicative; actual consumption varies with surface condition.
| Product | Pack Size | Approx. Coverage |
|---|---|---|
| FILLING basic® | 1 kg | 0.50 m² – 0.60 m² |
| FILLING 1000® | 0.75 kg | 0.35 m² – 0.45 m² |
| FILLING 2000® | 0.75 kg | 0.25 m² – 0.35 m² |
Where FILLING® Products Are Used
"Machining and sealing compounds are not competing approaches — in many outages, they are part of the same repair ecosystem."
Both in-situ machining contractors and sealing compound specialists can work together from the same surface assessment. Sealing surface restoration compounds may be relevant before machining (evaluating whether full machining is necessary), instead of machining where damage is within acceptable limits, or after machining during final casing reassembly.
The correct approach is not to replace engineering judgement — it is to give turbine maintenance teams a technically defined option when dealing with casing joint damage, split-line imperfections, steam leakage or surface restoration during outage maintenance.