1. High leakage rate & Short service life:

① Excessive valve torque creates elevated sealing surface pressure, significantly increasing risks of galling, creep deformation, overload damage, and adhesive wear. This accelerates sealing surface degradation, heightening internal leakage probability. 

② Poor fitting degree between seat ring and disc ring causes stress concentration.  

2. Repair Limitations:  

① Seat/disc ring interfaces feature irregular conical surfaces with non-replicable eccentric angles. Without precise cone angle and dimensional chain tolerance data, repair integrity cannot be guaranteed.  

② Fixed seat design prevents disassembly for maintenance.  

③ Seal rings and seats lack interchangeability across product lines.  

3. Fail to Achieve True Bi-directional Sealing:

4. Passing Factory Acceptance Tests but Failing In-Service:  

 Blind flange pressure testing yields false positives due to large cavity volume – bubbles cannot traverse conduits within standard test durations, masking leakage.