Casing hangers are designed with primary and secondary seals. The primary seal combines a square rubber seal with an O-ring, while the secondary seal uses a "BT" seal ring with injected sealant (PTFE).
Leakage at Flange Connection Gaskets
Leakage at flange connection gaskets indicates a failure of either the primary or secondary seal of the casing hanger, or possibly both. Primary seal failure can result from damage to the square seal ring or from casing thermal expansion lifting the casing hanger, rendering the square seal ineffective. Special care must be taken when seating the casing hanger to avoid damaging or scratching the square seal ring. Secondary seal failure occurs when the "BT" seal ring fails to seal properly (it's crucial to inject PTFE into the "BT" seal ring after connecting the tubing head to the casing head cross).
As production time increases, PTFE in the "BT" seal ring gradually depletes, causing the secondary seal to lose effectiveness.
Remedial Procedures
①Addressing Secondary Seal Leakage
Inject PTFE through the grease fitting on the tubing head special cross into the "BT" seal ring. This activates the "BT" seal ring to "grip" the casing hanger, restoring the seal.
②Addressing Primary Seal Leakage
If the primary seal leaks, tighten the set screws on the casing cross flange to move the casing hanger downward, activating the square seal expansion for better sealing. Alternatively, inject a large amount of sealant through a test port on the lower flange of the tubing head special cross to compensate for leak gaps.
After steps a and b, check for resolution of primary and secondary seal leakage through a test port on the lower flange special cross. If resolved, tighten the connecting bolts between the lower flange of the tubing head special cross and the upper flange of the casing cross to eliminate leakage between these flanges.
Leakage at Set Screws
Regularly inject sealant into the "BT" seal ring (every 6 months) to ensure reliable sealing. Periodically check flange connection bolts and set screw caps for looseness, tightening immediately if found loose.
Maintenance and Care
Inject sealant into the "BT" seal ring every 6 months to maintain reliable sealing. Regularly inspect flange connection bolts and set screw caps for looseness, tightening immediately if necessary.
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