Finding scratches, dents or corrosion pits on a flange face during maintenance is common. The decision lies between three options: close it as it is, repair it, or replace it.
Classify the damage first
- Circumferential scratch: Runs with the machining grooves and is usually tolerable
- Radial scratch: Runs from centre outwards and forms a direct leak path; not tolerable
- Dents and impact marks: Judged by depth
- Corrosion pits: Depend on area and depth; widespread pitting complicates repair
- Erosion: Flow driven thinning; usually calls for replacement
A radial scratch, or damage affecting more than half the gasket seating area, cannot be closed with a gasket.
Repair options
- On-site machining: A portable lathe remachines the face without dismantling the line. The limit is how much material the flange thickness allows; the standard minimum thickness must not be breached.
- Weld build up and machining: Deep pits are filled by welding and the face is remachined. It needs compatible consumables, a qualified procedure and post weld heat treatment where required. Code rules apply on pressure vessels and critical lines.
- Replacement: The safest option once the thickness limit is reached, the damage is widespread or the material is fatigued.
Decision criteria
| Condition | Decision |
|---|---|
| Shallow circumferential scratch | Clean and close with a new gasket |
| Single shallow radial scratch | On-site machining |
| Deep corrosion pits | Weld build up and machining, or replace |
| Close to thickness limit | Replace |
| Damaged RTJ groove | Remachine the groove or replace |
After the repair
The remachined face must fall in the roughness range required by the gasket type; an over polished face lets the gasket creep. See flange face finish and Ra.
If replacement is the answer, send us the dimensions: enquiry form.
FAQ
Can a radial scratch be sealed with a gasket?
No. It forms a direct leak path under the gasket and the face must be remachined.
What limits on-site machining?
The flange must not go below its standard minimum thickness; at that point the part is replaced.
Can any flange be repaired by welding?
It depends on material and service; a qualified procedure, matching consumables and heat treatment where required are essential.
Send us your material list; we reply with price and lead time the same day.
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